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Laudien Jürgen - One of the best experts on this subject based on the ideXlab platform.
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Population dynamics, feeding ecology, and larval biology of the Surf Clam, Donax hanleyanus
2005Co-Authors: Herrmann Marko, Laudien Jürgen, Arntz Wolf, Carstensen Daniel, Schiel Sigrid, Penchaszadeh P. E.Abstract:Exposed intertidal sandy beaches are often dominated by bivalves of the family Donacidae (super family Tellinacea), constituted by the genera Donax, Egeria and Iphigeni. On a worldwide basis, Donacidae form by far the largest group inhabiting such highly dynamic environments. The Surf Clam Donax hanleyanus, also known as berberecho, can be found along the Atlantic coast of South America, from Rio de Janeiro (Brazil) to northern Argentina. Along the coast of the Buenos Aires Province (Argentina), D. hanleyanus is abundant from San Clemente to Punta Mogotes, south of Mar del Plata. The beaches represent the southernmost habitats of a Donax species in the south western Atlantic. D. hanleyanus has a maximum adult size of 4.2 mm and rarely lives for more than 4 yr. In order to study the gametogenic cycle, recruitment patterns, growth, production, and mortality, monthly sampling has been carried out in Santa Teresita, Villa Gesell and Faro Querandi. First results on growth based on cohort analysis are presented. For microgrowth analysis fluorescent stains (Alizarine, Calcein, Strontium chloride) are used. To estimate the economically optimal bivalve and food densities in aquaculture systems, nutrition experiments with the algaes Isochrysis galbana, Chaetoceros sp. and Tetraselmis sp. has been carried out. For the observation of the embryonic and larval development under controlled conditions, induction of spawning was necessary by thermal shocks and injection of Serotonin
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Population structure, growth and production of the Surf Clam Donax serra (Bivalvia, Donacidae) on two Namibian sandy beaches
'Elsevier BV', 2003Co-Authors: Laudien Jürgen, Brey Thomas, Arntz WolfAbstract:Population structure, growth and production of the Surf Clam Donax serra (Bivalvia, Donacidae) inhabiting highly exposed sandy beaches of Namibia, were investigated between November 1997 and December 1999. From length-frequency distribution and tagging-recapture data a von Bertalanffy growth function with an asymptotic length (L*) of 82 mm and a growth constant (K) of 0.274 y-1 was established. Regarding growth performance of Donacidae, D. serra fits in a group of species inhabiting cold-temperate and upwelling regions. The intertidal biomass of the studied population ranged between 141 g ash free dry mass (AFDM) m-2 y-1 and 546 g AFDM m-2 y-1. Individual production was maximal at 56.5 mm shell length (0.83 g AFDM ind.1 y1) and annual production ranged between 167 g AFDM m-2 y-1 and 637 g AFDM m-2 y-1, resulting in productivity values (P/B) between 1.167 y-1 and 1.589 y-1. This data underlines the importance of D. serra for the beach/Surf ecosystem. Further the findings of this study are crucial to support future aquaculture or exploitation activities and management
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Genetic and morphological variation in four populations of the Surf Clam Donax serra (Röding) from southern African sandy beaches
'Elsevier BV', 2003Co-Authors: Laudien Jürgen, Flint N. S., Van Der Bank F. H., Brey ThomasAbstract:The Surf Clam Donax serra (Bivalvia, Donacidae) dominates sandy beach communities of two southern African biogeographical regions, a cold (Benguela current) and warm province (Agulhas current). Morphometric and behavioural differences led to a controversial discussion of whether or not populations from the two provinces belong to the same species. Shell size measurements confirmed morphological differences: Clams from the cold province were significantly rounder, flatter and less wedge-shaped than Clams from the warm province. In this study a genetic approach was used to relate phenotypic differences to genetic variability of four populations of D. serra separated by up to 2 500 km of shoreline. Genetic analysis of twenty-two protein-coding loci was carried out by starch-gel electrophoresis. Populations studied are conspecific (genetic distances range from 0.003 to 0.044) and possess genetic variation (alleles per locus: 1.73 - 1.91; mean heterozygosity: 18 - 22%; percentage polymorphism: 45.5 - 59.1%) in the range of most other marine bivalves, which allows for potential adaptation to environmental changes. Wrights fixation indices show little to moderate genetic divergence among the subpopulations relative to the limiting amount under complete fixation (FST = 0.016 - 0.089), moderate divergence of individuals relative to the total population (FIS = 0.265 - 0.452), and comparably high divergence of individuals relative to the compound population (FIT = 0.300 - 0.473). The effective number of individuals exchanged between populations in each generation is high enough (1.44 - 8.65) to counteract genetic drift. We propose that the observed differences represent phenotypic plasticity enabling this species to inhabit different biogeographic regions. Gene flow, balanced selective pressure and evolutionary inertia are discussed as explanations for similarities of the two outlying populations. The substantial subdivision of the two Namibian populations indicates a potential biotic barrier and requires separate studies of the population dynamics
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Population dynamics and ecology of the Surf Clam Donax serra (Bivalvia, Donacidae) inhabiting beaches of the Benguela upwelling system
2002Co-Authors: Laudien JürgenAbstract:The Surf Clam Donax serra (Röding, 1798) dominates macrobenthic communities of extended and exposed sandy beaches of those southern African biogeographical regions where phytoplankton production is high: the cold Benguela upwelling system and areas of the warm Agulhas current system, which experience occasional upwelling and estuarine input. It feeds on phytoplankton and detritus, serves as food item for marine and terrestrial predators and is exploited by recreational anglers. The overall aim of this study was to investigate the population dynamics and ecology of Namibian D. serra in order to contribute essential knowledge for the understanding of its role in the Benguela upwelling ecosystem as well as for its potential use in aquaculture and exploitation activities. In particular two populations of the central Namibian coast were studied during November 1997 and December 1999.Histological examinations of D. serra gonads and the condition index indicated a seasonal reproductive cycle, coupled to the annual mean sea Surface temperature cycle. Spawning started in August/September and lasted until February. Recruits, however, were present for only three months in the intertidal zone. The period when these juveniles are abundant is decoupled from the spawning period and therefore cannot be predicted. Starvation, hydrodynamic processes, chemical parameters and different release times during the spawning period are likely to cause spatial and temporal differ-ences in settlement time and recruitment strength.Individual growth is best described by a Von Bertalanffy growth function with an asymptotic length (L*) of 82 mm and a growth constant (K) of 0.274 y-1 in both intertidal populations. Growth performance of D. serra agrees with values of cold-temperate and upwelling donacids while temperate Donax-species have intermittent and tropical/subtropical congeners show lowest values. The intertidal biomass of the studied populations ranged between 141 g ash free dry mass (AFDM) m-2 and 546 g AFDM m-2, which is much higher that in D. serra populations at warm temperate beaches and distinctly surmounts the range for several non-upwelling Donax-species. In line, annual production exceeds values calculated from populations of habitats without permanent upwelling as well as those of non-upwelling donacids. The present values ranged between 167 g AFDM m-2 y-1 and 637 g AFDM m-2 y-1, resulting in productivity values between 1.167 y-1 and 1.589 y-1. Individual production was maximal at 56.5 mm shell length (0.83 g AFDM ind.-1 y-1).To investigate whether toxic hydrogen sulphide affects survivorship of juvenile D. serra and thus is a potential community structuring factor, the reaction of these Clams to low oxygen concentrations and sulphide presence was examined. In vitro exposure experiments were conducted using an innovative gas-tight continuous flow system. Hydrogen sulphide was adjusted to a concentration (0.1 mmol l-1) as regularly found during native "sulphide eruptions", which occur sporadically in the highly productive inshore regions of the central Namibian Benguela. During the first 2 h of hypoxic and hypoxic-sulphidic exposure test Clams emerged to the sediment Surface, which might support the drift to locations with more favourable conditions. Juvenile Clams possess a high sulphide detoxification capacity and are adapted to sulphur events by their ability to oxidise the penetrating hydrogen sulphide to non-toxic thiosulphate. In addition, they are able to switch to anaerobic energy production, indicated by a significant accumulation of succinate and alanine. However, tested Clams were not able to withstand long periods of exposure, the median survival time (LT50) under hypoxic sulphide incubation was 80 h. Spatial and temporal extended sulphur events are assumed to be a potential community-structuring factor, owing to their negative impact on recruitment.Shell size measurements confirmed that Clams from the cold Benguela were significantly rounder, flatter and less wedge-shaped than Clams from the warm Agulhas. A genetic comparison of four D. serra populations inhabiting both regimes aimed to clarify if populations are separate (sub-) species reflected in allelic variation. Genetic analysis of twenty-two protein-coding loci was carried out by starch-gel electrophoresis. Populations studied are conspecific and possess genetic variation in the range of most other marine bivalves, which allows for potential adaptation to environmental changes. Little to moderate genetic divergence among sub-populations relative to the maximal divergence under complete fixation (FST = 0.016 - 0.089), moderate divergence of individuals relative to their sub-population (FIS = 0.265 - 0.452), and comparably high divergence of individuals relative to the compound population (FIT = 0.300 - 0.473) were found. The effective number of individuals exchanged between populations in each generation is high enough (1.44 - 8.65) to counteract genetic drift. Therefore it is proposed that observed morphological differences represent phenotypic plasticity enabling this species to inhabit different biogeographic regions. Gene flow, balanced selective pressure and evolutionary inertia are proposed as explanations for similarities of the geographically most distant populations. The substantial differentiation of the two Namibian populations indicates a potential biotic barrier and requires separate studies of the population dynamics.The results of this investigation, especially the high growth and production rates as well as the ability to inhabit substrates in high abundances are encouraging for future aquacultural use of this species. Work perspectives are identified for further support of culturing activities of D. serra, which will moreover contribute to a broader understanding of sandy beach ecology
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Population dynamics and ecology of the Surf Clam Donax serra (Bivalvia, Donacidae) inhabiting beaches of the Benguela upwelling system
2002Co-Authors: Laudien JürgenAbstract:The Surf Clam Donax serra (Röding, 1798) dominates macrobenthic communities of extended and exposed sandy beaches of those southern African biogeographical re-gions where phytoplankton production is high: the cold Benguela upwelling system and areas of the warm Agulhas current system, which experience occasional upwelling and estuarine input. It feeds on phytoplankton and detritus, serves as food item for marine and terrestrial predators and is exploited by recreational anglers. The overall aim of this study was to investigate the population dynamics and ecology of Namibian D. serra in order to contribute essential knowledge for the understanding of its role in the Benguela upwelling ecosystem as well as for its potential use in aquaculture and exploitation activities. In particular two populations of the central Namibian coast were studied during November 1997 and December 1999.Histological examinations of D. serra gonads and the condition index indicated a sea-sonal reproductive cycle, coupled to the annual mean sea Surface temperature cycle. Spawning started in August/September and lasted until February. Recruits, however, were present for only three months in the intertidal zone. The period when these juve-niles are abundant is decoupled from the spawning period and therefore cannot be predicted. Starvation, hydrodynamic processes, chemical parameters and different re-lease times during the spawning period are likely to cause spatial and temporal differ-ences in settlement time and recruitment strength.Individual growth is best described by a Von Bertalanffy growth function with an asymp-totic length (L∞) of 82 mm and a growth constant (K) of 0.274 y -1 in both intertidal populations. Growth performance of D. serra agrees with values of cold-temperate and upwelling donacids while temperate Donax-species have intermittent and tropi-cal/subtropical congeners show lowest values. The intertidal biomass of the studied populations ranged between 141 g ash free dry mass (AFDM) m-2 and 546 g AFDM m-2, which is much higher that in D. serra populations at warm temperate beaches and dis-tinctly surmounts the range for several non-upwelling Donax-species. In line, annual production exceeds values calculated from populations of habitats without permanent upwelling as well as those of non-upwelling donacids. The present values ranged be-tween 167 g AFDM m-2 y-1 and 637 g AFDM m-2 y-1, resulting in productivity values be-tween 1.167 y-1 and 1.589 y-1. Individual production was maximal at 56.5 mm shell length (0.83 g AFDM ind.-1 y-1).To investigate whether toxic hydrogen sulphide affects survivorship of juvenile D. serra and thus is a potential community structuring factor, the reaction of these Clams to low oxygen concentrations and sulphide presence was examined. In vitro exposure ex-periments were conducted using an innovative gas-tight continuous flow system. Hy-drogen sulphide was adjusted to a concentration (0.1 mmol l-1) as regularly found during native "sulphide eruptions", which occur sporadically in the highly productive inshore regions of the central Namibian Benguela. During the first 2 h of hypoxic and hypoxic-sulphidic exposure test Clams emerged to the sediment Surface, which might support the drift to locations with more favourable conditions. Juvenile Clams possess a high sulphide detoxification capacity and are adapted to sulphur events by their ability to oxidise the penetrating hydrogen sulphide to non-toxic thiosulphate. In addition, they are able to switch to anaerobic energy production, indicated by a significant accumulation of succinate and alanine. However, tested Clams were not able to withstand long periods of exposure, the median survival time (LT50) under hypoxic sulphide incubation was 80 h. Spatial and temporal extended sulphur events are assumed to be a potential community-structuring factor, owing to their negative impact on recruitment.Shell size measurements confirmed that Clams from the cold Benguela were significantly rounder, flatter and less wedge-shaped than Clams from the warm Agulhas. A genetic comparison of four D. serra populations inhabiting both regimes aimed to clarify if populations are separate (sub-) species reflected in allelic variation. Genetic analysis of twenty-two protein-coding loci was carried out by starch-gel electrophoresis. Popula-tions studied are conspecific and possess genetic variation in the range of most other marine bivalves, which allows for potential adaptation to environmental changes. Little to moderate genetic differentiation among sub-populations relative to the maximal dif-ferentiation under complete fixation (FST = 0.016 - 0.089), moderate differentiation of individuals relative to their sub-population (FIS = 0.265 - 0.452), and comparably high differentiation of individuals relative to the compound population (FIT = 0.300 - 0.473) were found. The effective number of individuals exchanged between populations in each generation is high enough (1.44 - 8.65) to counteract genetic drift. Therefore it is proposed that observed morphological differences represent phenotypic plasticity ena-bling this species to inhabit different biogeographic regions. Gene flow, balanced se-lective pressure and evolutionary inertia are proposed as explanations for similarities of the geographically most distant populations. The substantial differentiation of the two Namibian populations indicates a potential biotic barrier and requires separate studies of the population dynamics.The results of this investigation, especially the high growth and production rates as well as the ability to inhabit substrates in high abundances are encouraging for future aquacultural use of this species. Work perspectives are identified for further support of culturing activities of D. serra, which will moreover contribute to a broader understanding of sandy beach ecology
Jose M Riascos - One of the best experts on this subject based on the ideXlab platform.
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regulatory factors and structure of a component population of the spionid polydora bioccipitalis infesting the Surf Clam mesodesma donacium
Journal of Aquatic Animal Health, 2011Co-Authors: Jose M Riascos, Miguel Cuturrufo, Aldo S Pacheco, Marcelo E. OlivaAbstract:Abstract Spionidae, particularly polydorids, are common polychaete parasites of edible mollusks around the world. However, our understanding of the regulatory factors and population structure of these parasites is scant. In this study involving Polydora bioccipitalis and the Surf Clam Mesodesma donacium we evaluated (1) the environmental correlates of the prevalence and mean intensity of the infestation, (2) the relationship between the number of egg capsules and juvenile and adult parasites and the time elapsed since infestation, and (3) the spatial patterns of juveniles and adults within the host. Environmental factors showed no significant correlations with prevalence and mean intensity, suggesting that these factors do not act directly as regulators. Rather, storm surges seemingly induced Clam stranding, which in turn affected both the prevalence and intensity of the infestation. The numbers of juveniles and egg capsules in blisters were significantly related to the time since infestation, suggesting ...
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infestation of the Surf Clam mesodesma donacium by the spionid polychaete polydora bioccipitalis
Journal of Sea Research, 2008Co-Authors: Jose M Riascos, Olaf Heilmayer, Jurgen Laudien, Marcelo E. Oliva, Wolf E ArntzAbstract:The Surf Clam Mesodesma donacium is an economically important species for Chilean and Peruvian shellfisheries. This Clam is often infested by Polydora bioccipitalis, a species belonging to the Spionidae, the most common parasitic polychaete group. To study this association, Clams were sampled monthly over a one-year period in northern Chile. Collected Clams covered the entire available size range and were classified into four infestation levels in order to study: (1) the relationship between prevalence of infestation (PI) and host size, (2) the temporal pattern of infestation events related to seasonal temperature changes, and (3) the relationship between infestation, body condition index (BCI) and gonado-somatic index (GSI). Additionally, growth rate and digging ability of Clams with different infestation levels was studied. A logistic regression model best explained the relationship between PI and host size, with the smallest infested Clam being 34 mm long and PI increasing steeply thereafter. Ontogenetic shifts in the habitat of the Clam and ontogenetic changes, mainly in shell morphology, seem to explain the sigmoid pattern. Periods of increased shell blistering after infestation by P. bioccipitalis showed a similar seasonal pattern with GSI and BCI of non-infested Clams, suggesting either an association between infestation ability and low condition of the Clam or common environmental triggers for those factors. Heavily infested Clams showed a significant lower BCI, growth rate and digging ability; however, given its low number, they are unlikely to be significant in terms of the local population survival. However, the infestation could play a key role in explaining mass mortality of northern populations during El Nino events, given the latitudinal differences in PI and the fact that infestation ability could be enhanced by increased temperature and facilitated in stressed Clams.
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The infestation of the Surf Clam Mesodesma donacium by the spionid polychaete Polydora bioccipitalis: patterns, effects and ecological implications
2006Co-Authors: Jose M Riascos, Olaf Heilmayer, Jurgen Laudien, Marcelo E. Oliva, Wolf E ArntzAbstract:The Surf Clam Mesodesma donacium is one of the most valuable commercial species in Chile and Peru. Populations of the northern and central area of the geographic range can be decimated during El Nino events (Arntz et al. 1987). Although boring polychaetes represent a threat to native and commercial molluscs (Moreno et al. 2006), the effects of the association between Polydora bioccipitalis and M. donacium has not been studied yet. Clams covering the whole size range were sampled monthly at Hornitos (northern Chile) and classified into four infestation levels (0 to III) to study: i) the relationship between the prevalence of infestation and host size, ii) timing of infestation events and iii) effects on body condition (BCI) and reproduction (GSI). Additionally, different staining chemicals (alizarin red, calcein and strontium chloride) were tested for suitability of growth analyses, resulting in calcein to be the best stain. This method enabled comparisons of short-term growth differences between reared Clams at different infestation levels. Furthermore, effects of the infestation on digging ability were tested as well in reared Clams. The relationship between prevalence and host-size was well described (r2 = 0.959) by a logistic regression model: Clams under 34 mm in shell length where never infested, which could be related to habitat segregation between juvenile and adult Clams. A rapid increase of prevalence in medium-size Clams was explained by gaping in shell closure. Main infestation events were coupled with BCI and GSI drops. Hence, infestation takes place during energy-demanding periods of the host after spawining events. As previously observed by Lleonart et al. (2003), effects of infestation depend on the severity of infestation and the host size: significant negative effects on body condition, growth and digging time were found only in heavily infested adult Clams. No differences in GSI where observed between Clams with distinct infestation levels, which suggests that even if infestations affect body conditions, the gametogenic cycle apparently is not affected and follows the natural rhythm. As the percentage of heavily infested animals of this population was low (7.6% of all infested Clams) it seems to be capable of sustaining the thresholds of stress induced by this symbiosis. This, however, could significantly change under environmental stress and play a role in mass mortality events commonly observed in this species, given previous observations on the Polydora spp. infestation ability (Tinoco-Orta & Caceres-Martinez 2003) and the traits of M. donacium populations (Arntz et al. 1987).
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infestation of the Surf Clam mesodesma donacium by the worm polydora bioccipitalis in northern chile
EPIC3International Congress of Parasitology 2006 p., 2006Co-Authors: Jose M Riascos, Olaf Heilmayer, Marcelo E. Oliva, Jurgen LaudienAbstract:The Surf Clam Mesodesma donacium is one of the most valuable shellfish species in Chile. It exhibits a high prevalence of infestation (31.4 %) by the shell-inhabiting polychaete Polydora bioccipitalis. 80 specimens covering the whole size range were collected monthly from Hornitos (Northern Chile) to determine (i) the shell size of first infestation and (ii) the effect of infestation on body condition index (BCI = dry tissue mass/internal cavity volume*100). The duration of the symbiosis was determined by measuring the thickness of the blister walls formed inside the bivalveŽs shell. Preliminary results indicate that the growth rate and BCI of the host was significantly different (t-test, P < 0.05) between infected and non-infected animals. Although the internal shell cavity was smaller in infected Clams, thus affecting considerably the BCI, the proportion of dry tissue mass was not significantly different. In addition, the symbiosis can only be found in Clams larger than 33 mm. M. donacium undergoes a migration from the intertidal (up to 30 mm juveniles) to the lower subtidal (post-juveniles and adults) during its life cycle, therefore the symbiosis only occurs during a later ontogenetic stage when individuals inhabit the subtidal level. This suggests that M. donacium is well adapted to the presence of the commensal. Thickness of blister walls showed differences (F= 2.834, P < 0.05) between months: average notch thickness decreases from August to December, suggesting a seasonal pattern of the infection. The economic consequences of the infection are discussed based on our results.
Francois Dube - One of the best experts on this subject based on the ideXlab platform.
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characterization of a novel octopamine receptor expressed in the Surf Clam spisula solidissima
General and Comparative Endocrinology, 2010Co-Authors: Veronique Blais, Nassim Bounif, Francois DubeAbstract:We have cloned and sequenced a cDNA from the Surf Clam (Spisula solidissima, a pelecypod mollusc) that encodes an octopamine receptor which we have named Spi-OAR. The sequence of Spi-OAR shares many similarities with two Aplysia and three Drosophila octopamine receptors belonging to a sub-group of beta-adrenergic-like octopamine receptors. Using an expression vector and transient transfections of Spi-OAR into HEK 293 cells, we observed an increase of cAMP upon addition of octopamine and, to a lesser extent, of tyramine, but not after addition of dopamine, serotonin, or histamine. Using a battery of known agonists and antagonists for octopamine receptors, we observed a rather unique pharmacological profile for Spi-OAR through measurements of cAMP. Spi-OAR exhibited some constitutive activity in HEK 293 cells and no Ca(2+) responses could be detected following addition of octopamine to Spi-OAR-transfected cells. RT-PCR analysis revealed ubiquitous expression of Spi-OAR mRNA in all adult tissues, oocytes and early embryos examined. While addition of serotonin to isolated Clam oocytes resulted in meiotic activation, similar additions of octopamine had no effect, suggesting that its potential role in Clam reproductive physiology differs significantly from that of serotonin. This work identifies Spi-OAR as a novel mollusc octopamine receptor closely related to other invertebrate beta-adrenergic-like octopamine receptors, with possible reproductive and other physiological functions. This initial characterization of Spi-OAR makes possible further investigations and comparisons with more studied and familiar insect or gastropod mollusc octopamine receptors.
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localization and quantification of gonad serotonin during gametogenesis of the Surf Clam spisula solidissima
The Biological Bulletin, 2002Co-Authors: Isabfjllf Masseau, Pierre Bannon, Michel Anctil, Francois DubeAbstract:In the Surf Clam, Spisula solidissima, serotonin was reported to induce spawning when injected into the gonads. At nanomolar concentrations, it facilitates the fer- tilizability of oocyte by sperm, at micromolar concentration, it triggers the meiotic maturation of prophase 1-arrested oocytes, thus mimicking the effect of sperm. To further understand the role of serotonin in the gametogenic and spawning processes, we used both immunohistochemistry and high-pressure liquid chromatography linked with elec- trochemical detection to detect serotonin in the gonads of the Surf Clam. We found serotonin-containing varicose fi- bers covering the Surface of the germinal epithelium in both sexes. The area occupied by the serotonergic innervation field encircling gonad acini varied according to the gonadal stages (active phase, ripe phase, partially spawned phase, spent phase). We also found large variations in the serotonin concentration between specimens during the gametogenic cycle. The serotonin concentration was correlated with go- nad growth: it decreased in the ripe phase in comparison with the previous phase, the active phase. We attribute the decrease to the increase of total gonad mass in this stage. In contrast, as spawning begins, the total gonad mass declines while the gonad serotonin concentration increases to a level similar to that found in active phase. The finding that prior to spawning, serotonin is present in the gonads within fibers exhibiting distinct varicosities suggests that it is implicated in spawning.
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mechanisms of activation of Surf Clam spisula solidissima oocytes
Invertebrate Reproduction & Development, 1996Co-Authors: Francois DubeAbstract:Summary Surf Clam (Spisula solidissima) oocytes, when shed, are at prophase I of meiotic maturation. Fertilization is the normal activation process leading to germinal vesicle breakdown (GVBD) and further steps of meiosis, followed by successive embryonic mitoses. We review here work suggesting that early rises in intracellular Ca2+ and pH (pHi) are normally associated with oocyte activation. Experimental evidence suggesting a pivotal role for the Ca2+ response and a more modest contribution of pHi are presented. The mechanisms of activation of Spisula oocytes by various artificial agents mimicking sperm are discussed in relation to their potential relevance to the physiological process of fertilization. We emphasize that serotonin-induced activation of Spisula oocytes is probably the best available model system to gain knowledge on the signal transducing systems stimulated by both serotonin or sperm. The potential physiological role of serotonin receptors present on oocytes is critically considered. Futu...
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studies on the chromosomes of the giant scallop placopecten magellanicus gmelin and the Surf Clam spisula solidissima dillwyn
Cytologia, 1993Co-Authors: Jianhai Xiang, Richard R Desrosiers, Francois DubeAbstract:The karyotypes of two bivalve molluscs, the giant scallop Placopecten magellanicus and the Surf Clam Spisula solidissima, were examined in unfertilized eggs and embryos. In both bivalves, a haploid number of 19 and a diploid number of 38 were determined in well-spread metaphase chromosomes of meiotic and mitotic cells respectively. Moreover, karyological analysis of induced triploid embryos in Placopecten magellanicus indicates a chromosome number of 57 and thus corroborates the haploid and diploid counts. The chromosomes of Spisula solidissima are shorter than those of Placopecten magellanicus. Their sizes vary from 1.5 to 4.4μm in Surf Clam while those in giant scallop range from 3.3 to 8.5μm. Both bivalve species have submetacentric, subtelocentric and telocentric chromosomes but only Spisula solidissima has metacentric chromosomes.
Wolf E Arntz - One of the best experts on this subject based on the ideXlab platform.
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infestation of the Surf Clam mesodesma donacium by the spionid polychaete polydora bioccipitalis
Journal of Sea Research, 2008Co-Authors: Jose M Riascos, Olaf Heilmayer, Jurgen Laudien, Marcelo E. Oliva, Wolf E ArntzAbstract:The Surf Clam Mesodesma donacium is an economically important species for Chilean and Peruvian shellfisheries. This Clam is often infested by Polydora bioccipitalis, a species belonging to the Spionidae, the most common parasitic polychaete group. To study this association, Clams were sampled monthly over a one-year period in northern Chile. Collected Clams covered the entire available size range and were classified into four infestation levels in order to study: (1) the relationship between prevalence of infestation (PI) and host size, (2) the temporal pattern of infestation events related to seasonal temperature changes, and (3) the relationship between infestation, body condition index (BCI) and gonado-somatic index (GSI). Additionally, growth rate and digging ability of Clams with different infestation levels was studied. A logistic regression model best explained the relationship between PI and host size, with the smallest infested Clam being 34 mm long and PI increasing steeply thereafter. Ontogenetic shifts in the habitat of the Clam and ontogenetic changes, mainly in shell morphology, seem to explain the sigmoid pattern. Periods of increased shell blistering after infestation by P. bioccipitalis showed a similar seasonal pattern with GSI and BCI of non-infested Clams, suggesting either an association between infestation ability and low condition of the Clam or common environmental triggers for those factors. Heavily infested Clams showed a significant lower BCI, growth rate and digging ability; however, given its low number, they are unlikely to be significant in terms of the local population survival. However, the infestation could play a key role in explaining mass mortality of northern populations during El Nino events, given the latitudinal differences in PI and the fact that infestation ability could be enhanced by increased temperature and facilitated in stressed Clams.
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Growth estimates of the Argentinean Surf Clam Donax hanleyanus (Bivalvia: Donacidae) derived from fluorescent marking
PoLAR, 2007Co-Authors: Marko Herrmann, Wolf E Arntz, Jurgen Laudien, Pablo E. PenchaszadehAbstract:RESUMEN Micro-growth increments of the Argentinean Surf Clam Donax hanleyanus were measured at the exposed sandy beach Mar Azul. After marking the shells with the fluorescence marker Calcein, animals were allowed to grow in situ for 36 days. The majority of the marked specimens showed a distinct fluorescent band reflecting the calcein staining time and allowing for growth estimates. Palabras llaves: growth rate, fluorescent marking, Calcein, Surf Clam, Donax hanleyanus INTRODUCCIÓN Growth rate is one of the basic parameters to describe population dynamics; from a fisheries point of view growth, as well as recruitment determines the sustainable yield, which can be exploited from a stock. Growth rates of bivalves have been well studied, since many species are important for the fishing industry. A variety of methods, including length-frequency analysis, tagging-recapture experiments and readings of shell growth rings were used. Among these, marking methods are efficient in estimating bivalve growth rates because they are inexpensive and relatively easy to apply. However, it is difficult to detect micro-growth increments in shells on a scale of less than tens of micrometers, since such increases must be measured with a vernier caliper or by optical microscopy. The aim of the current study is to determine in situ growth rates of the bivalve Donax hanleyanus inhabiting an Argentinean exposed sandy beach. MATERIAL Y MÉTODOS Fig. 1: Left: Experimental cage (40 cm 40 cm 40 cm) bonded with a 1-mm mesh, right: Installed cubes in the intertidal (Donax-belt) of the beach at Mar Azul (duration of experiment: 36 days). 260 specimens of the Argentinean Surf Clam Donax hanleyanus (anterior-posterior shell length SL: 13.47 to 34.95 mm) were collected alive at the exposed sandy beach Mar Azul, Province of Buenos Aires (3720S, 5701WO) in March 2006. To avoid high mortality rates during staining test bivalves were placed immediately in aerated tanks (circulating seawater). The water temperature was set to resemble the ambient temperature (17-20C). 195 specimens were stained with Calcein (Sigma, CAS 1461-15-0; 50 mg/l for 3 h) in a dark tank to prevent light degradation of the fluorescent chemical during the immersion period. Additionally a non-treated control group of 65 specimens was maintained in resembling tanks. The concentration and immersion period were chosen in accordance to our previous studies for marking Donax hanleyanus in controlled systems. After immersion test animals were reared in situ in three experimental cages (40 cm 40 cm 40 cm) bonded with a 1-mm mesh for 36 days (Fig. 1). Every seventh day samples were taken. Test bivalves were scarified, empty shells were cleaned and dried at room temperature. For the detection of incorporated growth marks produced during the immersion in the Calcein solution, a transverse shell section was cut across the longest growth axis with a Buehler diamond saw (model Isomet) before embedding in Epoxicure resin (Araldit GY 257) and Endurecedor (HY 5083). Thereafter the cuts were successively polished on glass slides with different grades of SiC powder (125-68-30-12), and finally with 1 µm Al2O3 suspension (Brot). Marks were detected by examination and photographing under a fluorescence microscope (Zeiss Axio Imager Z1) using blue light (460 to 490 nm, filter 9: 488009-0000-000). The growth of Donax hanleyanus was determined with a micrometer measuring the distance (µm) between the staining mark and the growth edge. Absolute growth rate was measured as shell growth along time: absolute growth rate = where, SL1 is the shell length before staining (t1) and SL2 the shell length at the end of the rearing period (t2). RESULTADOS Y DISCUSIÓN The distinct green fluorescence band of Calcein was visible in 81 % of the marked specimens. In 40 % of the spells growth increments were determined (Fig. 2). Maximal growth (362.86 µm) was found in juvenile shells (SL = 15.89 mm 18.98 mm). Fig. 2: Photomicrograph under blue light: transverse shell section of Donax hanleyanus, 14 days after (t2) Calcein staining (t1), the increment between t1 and t2 represents shell growth. CONCLUSIONES Calcein was found to be a useful growth marker for the Surf Clam Donax hanleyanus. Once incorporated into the shell, it emitted a bright green fluorescence under blue light, which was clearly distinguishable from natural autofluorescence. The distinct and narrow fluorescent band incorporated into the growing edge of the shells at the time of the Calcein staining could be successfully used as a distict starting point for the time interval and thus for very exact growth measurements (µm scale) related to time. For better insights of growth from the whole Donax hanleyanus population at Mar Azul it would be necessary to run the experiment for a longer time, which however proved to be very difficult due to the conditions of the exposed habitat. In addition, Calcein marking did not affect survivorship or growth of Donax hanleyanus and thus is considered to be a useful non-lethal marker for in situ growth experiments with Clams. REFERENCIAS Bashey, F. (2004). A comparison of the suitability of Alizarin Red S and Calcein for inducing a nonlethally detectable mark in juvenile guppies. Trans. Am. Fish. Soc. 133: 1516-1523. Fujikura, K., Okoshi, K. & Naganuma, T. (2003). Strontium as a marker for estimation of microscopic growth rates in a bivalve. Mar. Ecol. Prog. Ser. 257: 295-301. Gosselin, M.J., Fernandez, E., Guzmán, N., Lazareth, C.E. & Ortlieb, L. (2006). Preliminary study of growth increments of the Peruvian mollusc shell Trachycardium procerum (Bivalvia) throughout the last half-million years. International Congress on Bivalvia, 22-27 July 2006, Universitat Autònoma de Barcelona, Spain. Guzmán, N.G. (2004). Validation d'une approche scléroclimatologique sur la côte du Chili et du Pérou par l'analyse microstructurale et biogéochimique des coquilles du gastéropode Concholepas concholepas Bruguière, 1789. phd thesis 220 p. Herrmann, M., Laudien, J., Arntz, W.E. & Penchaszadeh, P.E. (2006a). Applicability of three fluorescent markers for growth estimations of the Surf Clam Donax hanleyanus. International Congress on Bivalvia, 22-27 July 2006, Universitat Autònoma de Barcelona, Spain. Kaehler, S. & McQuaid, C.D. (1999). Use of the fluorochrome calcein as an in situ growth marker in the brown mussel Perna perna. Mar. Biol. 133: 455-460. Lamare, M.D. & Mladenov, P.V. (2000). Modelling somatic growth in the sea urchin Evechinus chloroticus (Echinoidea: Echinometridae). J. Exp. Mar. Biol. Ecol. 243: 17-43. Leips, J., Baril, C.T., Rodd, F.H., Reznick, D.N., Bashey, F., Visser, G.J. & Travis, J. (2001). The suitability of calcein to mark pocilid fish and a new method of detection. Am. Fish. Soc. 130 (3): 501-507. Marschal, C., Garrabou, J., Harmelin, J.G. & Pichon, M. (2004). A new method for measuring growth and age in the precious red coral Corallium rubrum (L.). Coral Reefs 23 (3): 423-432. Medeiros-Bergen, D.E. & Ebert, T.A. (1995). Growth, fecundity and mortality rates of two intertidal brittlestars (Echinodermata: Ophiuroidea) with contrasting modes of development. J. Exp. Mar. Biol. Ecol. 189 (1-2): 47-64. Monaghan, J.P. (1993). Comparison of Calcein and Tetracycline as chemical markers in summer flounder. Trans. Am. Fish. Soc. 122: 298-301. Moran, A.L. (2000). Calcein as a marker in experimental studies newly-hatched gastropods. Mar. Biol. 137: 893-898. Peck, L.S., Baker, A.C. & Conway, L.Z. (1996). Strontium labelling of the shell of the Antarctic limpet Nacella concinna (Strebe 1908). J. Moll. Stud. 62: 315-325. Riascos, J.M., Guzman, N., Laudien, J., Heilmayer, O. & Oliva, M. (2006). Suitability of three stains to mark shells of Concholepas concholepas (Gastrpopda) and Mesodesma donacium (Bivalvia). J. Shellfish Res. 26 (1): 1-7. Rousseau, M., Plouguerne, E., Wan, G., Wan, R., Lopez, E. & Fouchereau-Peron, M. (2003). Biomineralisation markers during a phase of active growth in Pinctada margaritifera. Comp. Biochem. Physiol. A 135 (Part A): 271-278. Rowley, R.J. & Mackinnon, D.I. (1995). Use of the fluorescent marker calcein in biomineralisation studies of brachiopods and other marine organisms. Bulletin de l'Institut Océanographique (Monaco) Spec. Issue 14 part 2: 111-120. Schöne, B.R., Tanabe, K., Dettman, D.L. & Sato, S. (2003). Environmental controls on shell growth rates and 18O of the shallow-marine bivalve mollusk Phascosoma japonicum in Japan. Mar. Biol. 142 (3): 473-485.
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The infestation of the Surf Clam Mesodesma donacium by the spionid polychaete Polydora bioccipitalis: patterns, effects and ecological implications
2006Co-Authors: Jose M Riascos, Olaf Heilmayer, Jurgen Laudien, Marcelo E. Oliva, Wolf E ArntzAbstract:The Surf Clam Mesodesma donacium is one of the most valuable commercial species in Chile and Peru. Populations of the northern and central area of the geographic range can be decimated during El Nino events (Arntz et al. 1987). Although boring polychaetes represent a threat to native and commercial molluscs (Moreno et al. 2006), the effects of the association between Polydora bioccipitalis and M. donacium has not been studied yet. Clams covering the whole size range were sampled monthly at Hornitos (northern Chile) and classified into four infestation levels (0 to III) to study: i) the relationship between the prevalence of infestation and host size, ii) timing of infestation events and iii) effects on body condition (BCI) and reproduction (GSI). Additionally, different staining chemicals (alizarin red, calcein and strontium chloride) were tested for suitability of growth analyses, resulting in calcein to be the best stain. This method enabled comparisons of short-term growth differences between reared Clams at different infestation levels. Furthermore, effects of the infestation on digging ability were tested as well in reared Clams. The relationship between prevalence and host-size was well described (r2 = 0.959) by a logistic regression model: Clams under 34 mm in shell length where never infested, which could be related to habitat segregation between juvenile and adult Clams. A rapid increase of prevalence in medium-size Clams was explained by gaping in shell closure. Main infestation events were coupled with BCI and GSI drops. Hence, infestation takes place during energy-demanding periods of the host after spawining events. As previously observed by Lleonart et al. (2003), effects of infestation depend on the severity of infestation and the host size: significant negative effects on body condition, growth and digging time were found only in heavily infested adult Clams. No differences in GSI where observed between Clams with distinct infestation levels, which suggests that even if infestations affect body conditions, the gametogenic cycle apparently is not affected and follows the natural rhythm. As the percentage of heavily infested animals of this population was low (7.6% of all infested Clams) it seems to be capable of sustaining the thresholds of stress induced by this symbiosis. This, however, could significantly change under environmental stress and play a role in mass mortality events commonly observed in this species, given previous observations on the Polydora spp. infestation ability (Tinoco-Orta & Caceres-Martinez 2003) and the traits of M. donacium populations (Arntz et al. 1987).
Robert E. Palazzo - One of the best experts on this subject based on the ideXlab platform.
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Centrosome-associated RNA in Surf Clam oocytes
Proceedings of the National Academy of Sciences, 2006Co-Authors: Mark C. Alliegro, Robert E. PalazzoAbstract:Centrosomes are the major microtubule-organizing center in animal cells. They are composed of a pair of [9(3) + 0] centrioles surrounded by a relatively ill-defined pericentriolar matrix, provide the ciliary centriole-kinetosome (basal body) progenitor, and organize the assembly of microtubules into the mitotic spindle during cell division. Despite >100 years of microscopic observation and their obvious significance, our understanding of centrosome composition, dynamic organization, and mechanism of action is limited when compared with that of other cellular organelles. Centrosomes duplicate only once per cell cycle to ensure development of a normal bipolar spindle. The initial event in centrosome duplication is centriole replication, which is generative, semiconservative, and independent of the nucleus. Such observations led to the proposal that centrosomes contain their own complement of nucleic acids, possibly representative of an organellar genome comparable with those described for mitochondria and chloroplasts. The consensus in the field is that centrosomes lack DNA but may contain RNA. We isolated centrosomes from oocytes of the Surf Clam, Spisula solidissima, and purified from them a unique set of RNAs. We show here by biochemical means and subcellular in situ hybridization that the first transcript we analyzed is intimately associated with centrosomes. Sequence analysis reveals that this centrosome-associated RNA encodes a conserved RNA-directed polymerase domain. The hypothesis that centrosomes contain an intrinsic complement of specific RNAs suggests new opportunities to address the century-old problem of centrosome function, heredity, and evolution.
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sperm nuclear transformations in cytoplasmic extracts from Surf Clam spisula solidissima oocytes
Developmental Biology, 1994Co-Authors: Frank J Longo, Lori Mathews, Robert E. PalazzoAbstract:Abstract Following their incorporation into oocytes, sperm nuclei (SN) of the Surf Clam, Spisula solidissima, undergo an initial expansion, followed by condensation and then a dramatic enlargement during their development into male pronuclei. These changes are temporally correlated with alterations in the maternal chromatin: germinal vesicle breakdown (GVBD), meiotic maturation, and female pronuclear development, respectively. To analyze possible changes occurring in SN at fertilization, Surf Clam oocyte extracts; prepared before and after parthenogenetic activation, were examined for their ability to affect SN in vitro. Sperm heads were incubated in extracts for variable periods up to 5 hr. Extracts prepared from oocytes following GVBD (15 min postactivation) induced an expansion in ∼90% of SN by 60 min incubation. However, when SN were incubated in extracts from unactivated or 4-min-activated oocytes only ∼30% underwent expansion. Ultrastructural examination of specimens taken at increasing periods of incubation in oocyte extracts revealed that SN expansion in vitro resembled chromatin decondensation in vivo. SN incubated 1 to 5 hr in extracts prepared from oocytes following GVBD consisted of decondensed chromatin surrounded to varying degrees by membranous cisternae. Staining with anti-lamin antibody was variable: some specimens (60-70%) were positive while others (30-40%) were weak to negative. In contrast, all decondensed SN incubated in extracts from postmeiotic oocytes (65 min postactivation) were delimited by an intact nuclear envelope possessing nuclear pores and reactive to anti-lamin antibody. Decondensation of SN in 15- or 65-min extracts was blocked by EDTA, 2,6-dimethylami-nopurine, histone, and protamine. The presence (65-min extract) and absence (unactivated, 4- and 15-min extracts) of sperm nuclear envelope assembly in vitro is consistent with events in vivo, where such a structure forms after meiotic maturation in concert with the development of the female pronucleus.
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sperm nuclear transformations in cytoplasmic extracts from Surf Clam spisula solidissima oocytes
Developmental Biology, 1994Co-Authors: Frank J Longo, Lori Mathews, Robert E. PalazzoAbstract:Abstract Following their incorporation into oocytes, sperm nuclei (SN) of the Surf Clam, Spisula solidissima, undergo an initial expansion, followed by condensation and then a dramatic enlargement during their development into male pronuclei. These changes are temporally correlated with alterations in the maternal chromatin: germinal vesicle breakdown (GVBD), meiotic maturation, and female pronuclear development, respectively. To analyze possible changes occurring in SN at fertilization, Surf Clam oocyte extracts; prepared before and after parthenogenetic activation, were examined for their ability to affect SN in vitro. Sperm heads were incubated in extracts for variable periods up to 5 hr. Extracts prepared from oocytes following GVBD (15 min postactivation) induced an expansion in ∼90% of SN by 60 min incubation. However, when SN were incubated in extracts from unactivated or 4-min-activated oocytes only ∼30% underwent expansion. Ultrastructural examination of specimens taken at increasing periods of incubation in oocyte extracts revealed that SN expansion in vitro resembled chromatin decondensation in vivo. SN incubated 1 to 5 hr in extracts prepared from oocytes following GVBD consisted of decondensed chromatin surrounded to varying degrees by membranous cisternae. Staining with anti-lamin antibody was variable: some specimens (60-70%) were positive while others (30-40%) were weak to negative. In contrast, all decondensed SN incubated in extracts from postmeiotic oocytes (65 min postactivation) were delimited by an intact nuclear envelope possessing nuclear pores and reactive to anti-lamin antibody. Decondensation of SN in 15- or 65-min extracts was blocked by EDTA, 2,6-dimethylami-nopurine, histone, and protamine. The presence (65-min extract) and absence (unactivated, 4- and 15-min extracts) of sperm nuclear envelope assembly in vitro is consistent with events in vivo, where such a structure forms after meiotic maturation in concert with the development of the female pronucleus.
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centriole duplication in lysates of spisula solidissima oocytes
Science, 1992Co-Authors: Robert E. Palazzo, Eugeni A Vaisberg, Richard W ColeAbstract:A cell-free system has been developed that executes centriole duplication. Surf Clam (Spisula solidissima) oocytes, arrested at late prophase of meiosis I, do not contain centrioles, centrosomes, or asters. Serial section high-voltage electron microscopy (HVEM) of asters and spindles isolated from potassium chloride-activated oocytes indicates that within 4 minutes oocytes assemble a single centriole that is duplicated by 15 minutes when assembly of the first meiotic spindle is complete. A mixture of lysates from unactivated oocytes and potassium chloride-activated oocytes induces centriole formation and duplication. Astral microtubule content in these lysate mixtures increases with time.