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Hasna Akther - One of the best experts on this subject based on the ideXlab platform.
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naupliar and metanaupliar development of thysanoessa raschii malacostraca euphausiacea from godthabsfjord greenland with a reinstatement of the ancestral status of the free living nauplius in malacostracan evolution
PLOS ONE, 2015Co-Authors: Mette Dalgaard Agersted, Hasna Akther, Jorgen OlesenAbstract:The presence of a characteristic crustacean larval type, the nauplius, in many crustacean taxa has often been considered one of the few uniting characters of the Crustacea. Within Malacostraca, the largest crustacean group, nauplii are only present in two taxa, Euphauciacea (krill) and Decapoda Dendrobranchiata. The presence of nauplii in these two taxa has traditionally been considered a retained primitive characteristic, but free-living nauplii have also been suggested to have reappeared a couple of times from direct developing ancestors during malacostracan evolution. Based on a re-study of Thysanoessa raschii (Euphausiacea) using preserved material collected in Greenland, we readdress this important controversy in crustacean evolution, and, in the process, redescribe the naupliar and metanaupliar development of T. raschii. In contrast to most previous studies of euphausiid development, we recognize three (not two) naupliar (= ortho-naupliar) stages (N1-N3) followed by a Metanauplius (MN). While there are many morphological changes between nauplius 1 and 2 (e.g., appearance of long caudal setae), the changes between nauplius 2 and 3 are few but distinct. They involve the size of some caudal spines (largest in N3) and the setation of the antennal endopod (an extra seta in N3). A wider comparison between free-living nauplii of both Malacostraca and non-Malacostraca revealed similarities between nauplii in many taxa both at the general level (e.g., the gradual development and number of appendages) and at the more detailed level (e.g., unclear segmentation of naupliar appendages, caudal setation, presence of frontal filaments). We recognize these similarities as homologies and therefore suggest that free-living nauplii were part of the ancestral malacostracan type of development. The derived morphology (e.g., lack of feeding structures, no fully formed gut, high content of yolk) of both euphausiid and dendrobranchiate nauplii is evidently related to their non-feeding (lecithotrophic) status.
Jorgen Olesen - One of the best experts on this subject based on the ideXlab platform.
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naupliar and metanaupliar development of thysanoessa raschii malacostraca euphausiacea from godthabsfjord greenland with a reinstatement of the ancestral status of the free living nauplius in malacostracan evolution
PLOS ONE, 2015Co-Authors: Mette Dalgaard Agersted, Hasna Akther, Jorgen OlesenAbstract:The presence of a characteristic crustacean larval type, the nauplius, in many crustacean taxa has often been considered one of the few uniting characters of the Crustacea. Within Malacostraca, the largest crustacean group, nauplii are only present in two taxa, Euphauciacea (krill) and Decapoda Dendrobranchiata. The presence of nauplii in these two taxa has traditionally been considered a retained primitive characteristic, but free-living nauplii have also been suggested to have reappeared a couple of times from direct developing ancestors during malacostracan evolution. Based on a re-study of Thysanoessa raschii (Euphausiacea) using preserved material collected in Greenland, we readdress this important controversy in crustacean evolution, and, in the process, redescribe the naupliar and metanaupliar development of T. raschii. In contrast to most previous studies of euphausiid development, we recognize three (not two) naupliar (= ortho-naupliar) stages (N1-N3) followed by a Metanauplius (MN). While there are many morphological changes between nauplius 1 and 2 (e.g., appearance of long caudal setae), the changes between nauplius 2 and 3 are few but distinct. They involve the size of some caudal spines (largest in N3) and the setation of the antennal endopod (an extra seta in N3). A wider comparison between free-living nauplii of both Malacostraca and non-Malacostraca revealed similarities between nauplii in many taxa both at the general level (e.g., the gradual development and number of appendages) and at the more detailed level (e.g., unclear segmentation of naupliar appendages, caudal setation, presence of frontal filaments). We recognize these similarities as homologies and therefore suggest that free-living nauplii were part of the ancestral malacostracan type of development. The derived morphology (e.g., lack of feeding structures, no fully formed gut, high content of yolk) of both euphausiid and dendrobranchiate nauplii is evidently related to their non-feeding (lecithotrophic) status.
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Swimming and cleaning in the free-swimming phase of Argulus larvae (crustacea, branchiura)--appendage adaptation and functional morphology.
Journal of Morphology, 2006Co-Authors: Ole Sten Møller, Jorgen Olesen, Dieter WaloszekAbstract:The free-swimming early larval stages of Argulus foliaceus (Linneaus) (Branchiura) are studied using digital video, light microscopy, and SEM. We analyze and document the mode of swimming in the hatching stage of A. foliaceus and the subsequent juvenile stages with fully developed thoracopods. We present new observations and an analysis of the functional morphology of a cleaning behavior in the first stage. This stage swims very effi- ciently using the large exopods of the second antennae in concert with the mandibular palp (naupliar limbs), while the subsequent stages use the now developed thoracopods for propulsion. This posterior shift in propulsion is similar to—but independent from—what is seen in other crusta- ceans. The hatching stage has previously been referred as a ''Metanauplius'' but as the first and second maxillae are developed and active, and buds of all four thoracopods are present, it is too advanced to be included in the naupliar phase. The hooks of the first antennae and the distal hooks of the maxillae are demonstrated to function not only as attachment organs (to the host), but also to play a signifi- cant role in the cleaning of the naupliar swimming ap- pendages. A digital video-based analysis of the swimming mode is provided. The larval swimming pattern is generally similar to that of other crustaceans such as Branchiopoda and Cirripedia, but autapomorphies of the Branchiura include the following: 1) While actively swimming, the nau- pliar appendages are almost straight during the recovery stroke and 2) they have a relatively small deflection during movement (� 258 or � 358 for mandible and second antenna respectively), 3) the larval mandible has a uniramous palp which is the retained exopod. The morphological implica- tions of the transition from the possibly nonfeeding pelagic, or free-swimming, first larval stage to the feeding, parasitic second stage are discussed and compared with other crus-
Dieter Waloszek - One of the best experts on this subject based on the ideXlab platform.
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a eucrustacean Metanauplius from the lower cambrian
Current Biology, 2010Co-Authors: Xiguang Zhang, Andreas Maas, Joachim T Haug, David J Siveter, Dieter WaloszekAbstract:Summary A new eucrustacean arthropod, Wujicaris muelleri gen. et sp. nov, is represented by a Lower Cambrian early Metanauplius of strikingly modern morphology despite being the oldest known fossil of such an early immature crustacean larva. The morphology of the Metanauplius closely mirrors that of corresponding developmental stages of living barnacles and copepods [1, 2], and it is likely that its appendages had a similar function for feeding and locomotion. The Metanauplius larva demonstrates remarkable stasis in morphology, life history, and lifestyle of (small) eucrustaceans over 525 million years, probably as a result of adaptation to a long-lasting physical niche and regime involving low Reynolds numbers and laminar current flow [3].
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Swimming and cleaning in the free-swimming phase of Argulus larvae (crustacea, branchiura)--appendage adaptation and functional morphology.
Journal of Morphology, 2006Co-Authors: Ole Sten Møller, Jorgen Olesen, Dieter WaloszekAbstract:The free-swimming early larval stages of Argulus foliaceus (Linneaus) (Branchiura) are studied using digital video, light microscopy, and SEM. We analyze and document the mode of swimming in the hatching stage of A. foliaceus and the subsequent juvenile stages with fully developed thoracopods. We present new observations and an analysis of the functional morphology of a cleaning behavior in the first stage. This stage swims very effi- ciently using the large exopods of the second antennae in concert with the mandibular palp (naupliar limbs), while the subsequent stages use the now developed thoracopods for propulsion. This posterior shift in propulsion is similar to—but independent from—what is seen in other crusta- ceans. The hatching stage has previously been referred as a ''Metanauplius'' but as the first and second maxillae are developed and active, and buds of all four thoracopods are present, it is too advanced to be included in the naupliar phase. The hooks of the first antennae and the distal hooks of the maxillae are demonstrated to function not only as attachment organs (to the host), but also to play a signifi- cant role in the cleaning of the naupliar swimming ap- pendages. A digital video-based analysis of the swimming mode is provided. The larval swimming pattern is generally similar to that of other crustaceans such as Branchiopoda and Cirripedia, but autapomorphies of the Branchiura include the following: 1) While actively swimming, the nau- pliar appendages are almost straight during the recovery stroke and 2) they have a relatively small deflection during movement (� 258 or � 358 for mandible and second antenna respectively), 3) the larval mandible has a uniramous palp which is the retained exopod. The morphological implica- tions of the transition from the possibly nonfeeding pelagic, or free-swimming, first larval stage to the feeding, parasitic second stage are discussed and compared with other crus-
So Kawaguchi - One of the best experts on this subject based on the ideXlab platform.
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Behavioural changes observed in Antarctic krill (Euphausia superba) exposed to p,p'-DDE
2020Co-Authors: Anita H. Poulsen, So Kawaguchi, Robert King, Catherine K. King, S. M. Bengtson NashAbstract:Euphausia superba is an Antarctic keystone species and its health has importance for the condition of the entire Antarctic ecosystem. Persistent organic pollutants (POPs) are transported to remote areas such as the polar regions by long range environmental transport. One such toxin is the notorious insecticide DDT, which use has been re-introduced in some southern hemisphere countries. p,p’-DDE is the most stable metabolite of DDT and was a dominant organohalogen contaminant in E. superba sampled across the Eastern Antarctic in 2006. Recently, the behavioural effects of aqueous exposure to p,p’-DDE were demonstrated in adult krill. Behavioural fitness is crucial for the survival of the early life stages of Antarctic krill. Eggs are laid in the surface layer and sink down to about 1km depth where they hatch out, then start ascending, and must reach the surface as they develop into their fourth larval stage calyptopis 1 when they finally start feeding. In this study, larvae of E. superba were exposed to aqueous p,p’-DDE (1-20ug/L nominal) for 10 days post hatching, from nauplius 1 through nauplius 2 to Metanauplius. An increased proportion of unresponsive larvae was observed at concentrations as low as 1ug/L, and there was an indication of higher mortality in exposed larvae. Interestingly, upon termination of the experiment, surviving exposed larvae had reached the same larval stage as the controls, although developmental aspects need further examination. These preliminary findings are fundamental for understanding the toxic implications of early life stage exposure of an Antarctic keystone species to one of its main anthropogenic contaminant threats. This study further highlights the need to continue to explore the toxicity of POPs to all life stages of Antarctic krill.
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Krill-Parasite Interactions
Global Diversity and Ecological Function of Parasites of Euphausiids, 2017Co-Authors: Jaime Gómez-gutiérrez, José Raúl Morales-Ávila, So KawaguchiAbstract:We review all the available, worldwide reports of epibionts and parasites of species of the Order Euphausiacea published between 1885 and 2015 (126 publications, 346 records). We add our own observations carried out on euphausiids from waters off Oregon (USA), Tasmania (Australia), Concepcion (Chile), and Mexico. This information provides us a relatively broad and coherent perspective about interespecific interactions inferred in the bases of diversity, prevalence patterns, intensity, parasite–host size ratios, and availability of microhabitats for parasites on and inside euphausiid bodies, as well as the association of parasitism with the hosts’ reproductive strategies. Currently, there are 18 different types of epibionts, pathogens, parasites, and parasitoids infecting krill (107 known taxa reported from 49 of the 86 euphausiid species). Symbionts affect almost all stages of the life cycle of euphausiids (except nauplius-to-Metanauplius stages). They increase in diversity, prevalence, and parasitic intensity with euphausiid age. Epibionts and ectoparasites generally do not affect the fitness of their hosts, but several pathogens, mesoparasites, and endoparasites can decrease the host fitness to zero by castration or death. Currently known parasites do not transmit vertically from parent to offspring and all the endoparasites seem to infect euphausiids by trophic transmission. All symbionts interact indistinctly with euphausiid species with broadcast spawning species or sac-spawning reproductive strategies. Species of the genera Euphausia, Meganyctiphanes, Nematoscelis, Nyctiphanes, and Thysanoessa possesses the most diverse and better-known parasitic fauna. In contrast few parasites are known for krill species of the genus Nematobrachion, Pseudeuphausia, and Stylocheiron. No symbionts are known at present from species of Bentheuphausia, Tessarabrachion, or Thysanopoda.
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Factors determining the hatching success of Antarctic krill Euphausia superba embryo: lipid and fatty acid composition
Marine Biology, 2011Co-Authors: Toshihiro Yoshida, Patti Virtue, So Kawaguchi, Peter D. NicholsAbstract:The present study addresses the effect of maternal diet on hatching success and condition of embryos and larvae of Antarctic krill Euphausia superba. Lipid and fatty acid content and composition were determined in field and laboratory samples. Developmental stages analyzed in embryos included: multiple-cell, gastrula, and limb-bud stages. Larval stages analyzed included: nauplius I, nauplius II, and Metanauplius. Laboratory-reared embryos were spawned by gravid females incubated under three feeding groups: (1) phytoplankton mixture, (2) phytoplankton mixture and minced clam, and (3) phytoplankton mixture, minced clam, and commercial larval food. Hatching success was highest in group 3 (100%), lowest in group 1 (0%), and highly variable in field samples (0–48%). Lipid decreased slightly in embryos during embryonic development, while large decreases in lipid were found during nauplius development. High levels of 18:2(n-6), 20:4(n-6), and 22:6(n-3) observed with group 3 samples coincided with high hatching success in krill embryos. The ratio of 22:6(n-3)/20:5(n-3) also correlated to hatching success of embryos. The fatty acid profile of embryos in group 3 was similar to that of the field-collected embryos, reflecting the contribution of the commercial larval food in the maternal diet. In our study, the maternal diet was found to influence the fatty acid composition of embryos and in turn affects the hatching success of krill. Specific polyunsaturated fatty acids appeared to play important roles in embryogenesis in krill.
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Altered developmental timing in early life stages of Antarctic krill (Euphausia superba) exposed to p,p'-DDE.
Science of The Total Environment, 2011Co-Authors: Anita H. Poulsen, So Kawaguchi, Matti T. Leppänen, Jussi V. K. Kukkonen, Susan Bengtson NashAbstract:Abstract Persistent organic pollutants (POPs) are persistent, toxic and bioaccumulative anthropogenic organic chemicals, capable of undergoing long range environmental transport to remote areas including the Antarctic. p,p′-dichlorodiphenyl dichloroethylene (p,p′-DDE) has been identified as a dominant POP accumulating in Antarctic krill ( Euphausia superba ), which is a key Southern Ocean species. This study examined the developmental toxicity of p,p′-DDE via aqueous exposure to Antarctic krill larvae. p,p′-DDE exposure was found to stimulate developmental timing in the first three larval stages of Antarctic krill, while extended monitoring of larvae after a five day exposure period had ended, revealed delayed inhibitory responses during development to the fourth larval stage. Stimulatory responses were observed from the lowest p,p′-DDE body residue tested of 10.1 ± 3.0 μmol/kg (3.2 ± 0.95 mg/kg) preserved wet weight, which is comparable to findings for temperate species and an order of magnitude lower than the exposure level found to cause sublethal behavioural effects in Antarctic krill. The delayed responses included increased mortality, which had doubled in the highest p,p′-DDE treatment (95 ± 8.9% mortality at 20 μg/L p,p′-DDE) compared to the solvent control (44 ± 11% mortality) 2 weeks after end of exposure. Development of surviving Metanauplius larvae to calyptopis 1 larvae was delayed by 2 days in p,p′-DDE exposed larvae compared with untreated larvae. Finally, the developmental success of surviving p,p′-DDE exposed larvae was reduced by 50 to 75% compared to the solvent control (100% developmental success). The lowest observed effect concentration for all delayed effects was 1 μg/L, the lowest exposure concentration tested. These findings demonstrate the importance of delayed and indirect effects of toxicant exposure. Further, the findings of this study are important for environmental risk assessment of POPs in the Southern Ocean ecosystem and strongly highlight the significance of developmental endpoints for ecotoxicological testing.
Volker Storch - One of the best experts on this subject based on the ideXlab platform.
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development of the stomach in euphausia superba dana euphausiacea
Journal of Crustacean Biology, 1993Co-Authors: Bernd Ullrich, Volker StorchAbstract:ABSTRACT Development of the stomach, with emphasis on the filter system, was investigated in the Metanauplius, calyptopis, and furcilia stages of the Antarctic krill Euphausia superba. The Metanauplius lacks an elaborated stomach as well as a connection between the esophagus and the midgut. In calyptopis I, the stomach becomes functional. The armature of the cardiac stomach consists of basic components such as lateral and ventral projections and stout spines, but not a primary filter. The latter develops before molt beneath the cuticle and is seen in the exuvial space of calyptopis II. With molting to calyptopis III, the primary filter is elaborated and becomes capable of sorting food particles and of separating a dorsal food from a ventral filtration channel. Although in furcilia IV the spacing of spines in the primary filter is nearly identical to that in the adult specimens, the filter spines in calyptopis III are more widely separated. In all larval stages examined (except furcilia IV), the development of the pyloric stomach is delayed with respect to that of the cardiac stomach. Residues of a pyloric secondary filter system were not found in developing stages of Euphausia superba.
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DEVELOPMENT OF THE STOMACH IN EUPHA USIA SUPERBA DANA (EUPHAUSIACEA)
1993Co-Authors: Bernd Ullrich, Volker StorchAbstract:Development of the stomach, with emphasis on the filter system, was investigated in the Metanauplius, calyptopis, and furcilia stages of the Antarctic krill Euphausia superba. The Metanauplius lacks an elaborated stomach as well as a connection between the esophagus and the midgut. In calyptopis I, the stomach becomes functional. The armature of the cardiac stomach consists of basic components such as lateral and ventral projections and stout spines, but not a primary filter. The latter develops before molt beneath the cuticle and is seen in the exuvial space of calyptopis II. With molting to calyptopis III, the primary filter is elaborated and becomes capable of sorting food particles and of separating a dorsal food from a ventral filtration channel. Although in furcilia IV the spacing of spines in the primary filter is nearly identical to that in the adult specimens, the filter spines in calyptopis III are more widely separated. In all larval stages examined (except furcilia IV), the development of the pyloric stomach is delayed with respect to that of the cardiac stomach. Residues of a pyloric secondary filter system were not found in developing stages of Euphausia superba.