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J M Cobcroft - One of the best experts on this subject based on the ideXlab platform.
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Advances in the culture of striped trumpeter larvae: A review
Aquaculture, 2020Co-Authors: S C Battaglene, J M CobcroftAbstract:Striped trumpeter, Latris lineata, was chosen as the best new candidate for sea cage culture in Tasmania in the late 1980s. It has\ud a complex and extended post-larval or ‘paperfish’ stage lasting up to 9 months and has historically proven difficult to culture.\ud Excellent progress has been made in understanding and controlling reproduction and broodstock are spawned year-round through\ud photothermal control. Problems with early larval rearing have been overcome and egg incubation and early larval rearing protocols\ud have been established. A mortality peak associated with first feeding has been reduced using better live feed production techniques\ud and improved water quality. Using antibiotics showed that high bacterial loads were an important factor in larval mortality. A new\ud water filtration and ozonation system has removed the need for antibiotics. Larval nutrition research focused on the link between\ud potential deficiencies or imbalances in the three essential PUFA in live feeds: docosahexaenoic acid, eicosapentaenoic acid and\ud arachidonic acid. Novel experimental emulsions were applied with dose response experimental designs to identify the dietary\ud requirement for selected PUFA and vitamins. Despite the advances in live feed enrichments, the live feeds, particularly Artemia,\ud were found to have sub-optimal lipid profiles. Copepods were cultured, as a supplement to traditional live feeds, and improved\ud larval rearing success. Costs to scale-up production and to control extensive cultures presently restrict the usefulness of copepods.\ud Important breakthroughs have occurred in health with the detection and control of nodavirus, myxozoan and bacterial disease.\ud Ozone disinfection of eggs and sterilisation of hatchery seawater have been important control measures. Another bottleneck to\ud production has been mortality of larvae from notochord flexion to metamorphosis. System changes to reduce nocturnal movements\ud and a better understanding of optimal live feed densities, and weaning onto formulated diets, have improved survival and growth.\ud High rates of Jaw Malformation remain a challenge and no definitive cause has been established. Reduced rates of Malformations\ud have been associated with one or a combination of high feed rates, lower larval densities and temperatures, and reductions in\ud ‘walling’ behaviour. Future research is aimed at finding ways to reduce Malformations, develop probiotics and early weaning\ud strategies, control parasites and scale-up production to assess performance of juveniles in sea cages
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the effects of tank colour live food enrichment and greenwater on the early onset of Jaw Malformation in striped trumpeter larvae
Aquaculture, 2012Co-Authors: J M Cobcroft, Alexander Chong Shuchien, Mengkiat Kuah, Annette Jayaram, S C BattagleneAbstract:A high incidence of Jaw Malformation has hindered the production of quality striped trumpeter Latris lineata juveniles and has been correlated with walling behaviour in Artemia-fed larvae. In this study, striped trumpeter were reared from first feeding to 29 days post-hatching (dph) in different coloured tanks (black or white), culture conditions (clear or greenwater) and fed different diets (enriched or non-enriched rotifers and Artemia), to examine behaviour, retinoid receptor gene expression and Jaw Malformation. The highest incidence and severity of Jaw Malformations occurred in clearwater and enriched diet treatments and were significantly more common in white (70 ± 15%, mean ± SD) than in black tanks (26 ± 15%). In black tanks, Jaw Malformation was significantly more common in larvae fed enriched diets (18 ± 14%) than in those fed non-enriched diets (8 ± 8%) and in clearwater (19 ± 14%) versus greenwater (7 ± 6%). At the end of the rotifer feeding phase, larvae were significantly larger in black than white tanks, and longer in greenwater than in clearwater. In the Artemia feeding phase, larval growth was slowest and mortality was highest in non-enriched diet treatments. Larval length and survival were higher in black tanks and in enriched diet treatments, whilst survival was almost twice as high in greenwater (46 ± 18%) than clearwater (26 ± 13%). The average proportion of larvae walling over the duration of the experiment was higher in white than black tanks, and higher in enriched than non-enriched treatments, with lowest walling in greenwater. There was no consistent relationship between feed intake and Jaw Malformation. However, there was a significant positive correlation between walling and the incidence of Jaw Malformation at 29 dph in larvae fed enriched diets. The expression pattern of three retinoid receptor genes indicated that live feed enrichment and stress could potentially perturb retinoic acid-associated pathways leading to skeletal abnormality. We found that the use of greenwater, black tanks and enriched live feeds is required for good growth, development, survival and final yield of striped trumpeter. The study emphasises the importance of reducing walling in the culture of oceanic larvae and may have direct application in the rearing of other marine fish with similar Malformations.
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Jaw Malformation in striped trumpeter latris lineata larvae linked to walling behaviour and tank colour
Aquaculture, 2009Co-Authors: J M Cobcroft, S C BattagleneAbstract:Abstract Jaw Malformations are a recurrent obstacle in the hatchery production of high quality juveniles of many marine finfish species. Whilst nutrition and temperature are often cited as the most likely causes, this study investigated manipulation of the physical culture environment and larval behaviour to reduce Jaw Malformations. The onset of Jaw Malformation after metamorphosis in striped trumpeter, Latris lineata , follows changes in larval behaviour from an even distribution throughout the water column to close association with the tank walls, often with vigorous swimming into the walls known as ‘walling’ behaviour. Larvae were reared through metamorphosis, 16 to 44 days post-hatching (dph), in twenty four 300-l hemispherical tanks with six different wall colours, black, blue, green, marble (a black, grey and white mottled pattern), red and white. Walling behaviour and Jaw Malformation were assessed. The highest proportion of severely malformed Jaws at 44 dph occurred in red tanks, followed by green, white, blue, black and marble. More fish walled in coloured tanks (25–44%) than in black and marble tanks (9.6 and 3.4%, respectively). The proportion of fish with Jaw Malformations at 44 dph was positively correlated with fish walling behaviour. Both black and marble tanks had more than 50% of fish with normal Jaws at 44 dph, and close to 80% with no or very minor Malformations. Growth and survival to 44 dph were highest in the black (15.7 ± 1.3 mm fork length, 7.9 ± 0.9 mg dry weight, 71 ± 6%) and marble (15.6 ± 1.2 mm, 7.6 ± 0.5 mg, 58 ± 17%) tanks, compared with the lowest values in red tanks (14.2 ± 1.1 mm, 6.4 ± 0.4 mg, 11 ± 6%). Potential mechanisms for the influence of walling behaviour on Jaw Malformation are mechanical damage and poor nutrition, via reduced feed intake and increased energy expenditure. The study highlights the often overlooked importance of hard-surface interactions in the growth and survival of some cultured marine fish and demonstrates a cheap and effective technique for assessing tank background colour as a means of reducing Malformations in cultured fish.
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Jaw Malformation in cultured yellowtail kingfish seriola lalandi larvae
New Zealand Journal of Marine and Freshwater Research, 2004Co-Authors: J M Cobcroft, Patricia M Pankhurst, C W Poortenaar, Bob Hickman, Mike TaitAbstract:Several Jaw Malformations are common in cultured finfish larvae. Hatchery-reared yellowtail kingfish (Seriola lalandi) larvae were cleared and stained to examine cartilage and bone structure of the Jaw. One Malformation, characterised by a lowered hyoid arch, was present in kingfish larvae on days 4 and 8 post-hatching, but not on day 12. A different Malformation was present in larvae on day 16, typified by abnormal positioning of the lower Jaw and hyoid arch, and breakage of the Meckel's cartilage. Evidence of Jaw Malformations as early as day 4 suggests that broodstock nutrition may be a factor in the Jaw Malformation of kingfish larvae, but other potential causes are environmental factors in culture and larval nutrition.
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Jaw development and Malformation in cultured striped trumpeter latris lineata
Aquaculture, 2001Co-Authors: J M Cobcroft, P M Pankhurst, J Sadler, P R HartAbstract:Intensive culture of striped trumpeter (Latris lineata) has resulted in a high incidence of Jaw Malformation in juveniles. In this study, cranial and Jaw development in striped trumpeter was described in cultured larvae reared in greenwater on rotifers and Artemia. Jaw Malformation was only evident in post-flexion larvae greater than the standard length of 10 mm and was characterised by an open Jaw in which the maxilla and premaxilla were aligned dorso-ventrally, and the anterior hyoid arch elements were in an abnormal ventral position. X-radiography of the heads of juvenile and adult cultured striped trumpeter revealed ventro-lateral distortion of the Jaw elements in comparison with wild-caught fish. The possible role of physical environmental factors and nutrition during culture are discussed in relation to Jaw Malformation in this and other species.
S C Battaglene - One of the best experts on this subject based on the ideXlab platform.
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Advances in the culture of striped trumpeter larvae: A review
Aquaculture, 2020Co-Authors: S C Battaglene, J M CobcroftAbstract:Striped trumpeter, Latris lineata, was chosen as the best new candidate for sea cage culture in Tasmania in the late 1980s. It has\ud a complex and extended post-larval or ‘paperfish’ stage lasting up to 9 months and has historically proven difficult to culture.\ud Excellent progress has been made in understanding and controlling reproduction and broodstock are spawned year-round through\ud photothermal control. Problems with early larval rearing have been overcome and egg incubation and early larval rearing protocols\ud have been established. A mortality peak associated with first feeding has been reduced using better live feed production techniques\ud and improved water quality. Using antibiotics showed that high bacterial loads were an important factor in larval mortality. A new\ud water filtration and ozonation system has removed the need for antibiotics. Larval nutrition research focused on the link between\ud potential deficiencies or imbalances in the three essential PUFA in live feeds: docosahexaenoic acid, eicosapentaenoic acid and\ud arachidonic acid. Novel experimental emulsions were applied with dose response experimental designs to identify the dietary\ud requirement for selected PUFA and vitamins. Despite the advances in live feed enrichments, the live feeds, particularly Artemia,\ud were found to have sub-optimal lipid profiles. Copepods were cultured, as a supplement to traditional live feeds, and improved\ud larval rearing success. Costs to scale-up production and to control extensive cultures presently restrict the usefulness of copepods.\ud Important breakthroughs have occurred in health with the detection and control of nodavirus, myxozoan and bacterial disease.\ud Ozone disinfection of eggs and sterilisation of hatchery seawater have been important control measures. Another bottleneck to\ud production has been mortality of larvae from notochord flexion to metamorphosis. System changes to reduce nocturnal movements\ud and a better understanding of optimal live feed densities, and weaning onto formulated diets, have improved survival and growth.\ud High rates of Jaw Malformation remain a challenge and no definitive cause has been established. Reduced rates of Malformations\ud have been associated with one or a combination of high feed rates, lower larval densities and temperatures, and reductions in\ud ‘walling’ behaviour. Future research is aimed at finding ways to reduce Malformations, develop probiotics and early weaning\ud strategies, control parasites and scale-up production to assess performance of juveniles in sea cages
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the effects of tank colour live food enrichment and greenwater on the early onset of Jaw Malformation in striped trumpeter larvae
Aquaculture, 2012Co-Authors: J M Cobcroft, Alexander Chong Shuchien, Mengkiat Kuah, Annette Jayaram, S C BattagleneAbstract:A high incidence of Jaw Malformation has hindered the production of quality striped trumpeter Latris lineata juveniles and has been correlated with walling behaviour in Artemia-fed larvae. In this study, striped trumpeter were reared from first feeding to 29 days post-hatching (dph) in different coloured tanks (black or white), culture conditions (clear or greenwater) and fed different diets (enriched or non-enriched rotifers and Artemia), to examine behaviour, retinoid receptor gene expression and Jaw Malformation. The highest incidence and severity of Jaw Malformations occurred in clearwater and enriched diet treatments and were significantly more common in white (70 ± 15%, mean ± SD) than in black tanks (26 ± 15%). In black tanks, Jaw Malformation was significantly more common in larvae fed enriched diets (18 ± 14%) than in those fed non-enriched diets (8 ± 8%) and in clearwater (19 ± 14%) versus greenwater (7 ± 6%). At the end of the rotifer feeding phase, larvae were significantly larger in black than white tanks, and longer in greenwater than in clearwater. In the Artemia feeding phase, larval growth was slowest and mortality was highest in non-enriched diet treatments. Larval length and survival were higher in black tanks and in enriched diet treatments, whilst survival was almost twice as high in greenwater (46 ± 18%) than clearwater (26 ± 13%). The average proportion of larvae walling over the duration of the experiment was higher in white than black tanks, and higher in enriched than non-enriched treatments, with lowest walling in greenwater. There was no consistent relationship between feed intake and Jaw Malformation. However, there was a significant positive correlation between walling and the incidence of Jaw Malformation at 29 dph in larvae fed enriched diets. The expression pattern of three retinoid receptor genes indicated that live feed enrichment and stress could potentially perturb retinoic acid-associated pathways leading to skeletal abnormality. We found that the use of greenwater, black tanks and enriched live feeds is required for good growth, development, survival and final yield of striped trumpeter. The study emphasises the importance of reducing walling in the culture of oceanic larvae and may have direct application in the rearing of other marine fish with similar Malformations.
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Jaw Malformation in striped trumpeter latris lineata larvae linked to walling behaviour and tank colour
Aquaculture, 2009Co-Authors: J M Cobcroft, S C BattagleneAbstract:Abstract Jaw Malformations are a recurrent obstacle in the hatchery production of high quality juveniles of many marine finfish species. Whilst nutrition and temperature are often cited as the most likely causes, this study investigated manipulation of the physical culture environment and larval behaviour to reduce Jaw Malformations. The onset of Jaw Malformation after metamorphosis in striped trumpeter, Latris lineata , follows changes in larval behaviour from an even distribution throughout the water column to close association with the tank walls, often with vigorous swimming into the walls known as ‘walling’ behaviour. Larvae were reared through metamorphosis, 16 to 44 days post-hatching (dph), in twenty four 300-l hemispherical tanks with six different wall colours, black, blue, green, marble (a black, grey and white mottled pattern), red and white. Walling behaviour and Jaw Malformation were assessed. The highest proportion of severely malformed Jaws at 44 dph occurred in red tanks, followed by green, white, blue, black and marble. More fish walled in coloured tanks (25–44%) than in black and marble tanks (9.6 and 3.4%, respectively). The proportion of fish with Jaw Malformations at 44 dph was positively correlated with fish walling behaviour. Both black and marble tanks had more than 50% of fish with normal Jaws at 44 dph, and close to 80% with no or very minor Malformations. Growth and survival to 44 dph were highest in the black (15.7 ± 1.3 mm fork length, 7.9 ± 0.9 mg dry weight, 71 ± 6%) and marble (15.6 ± 1.2 mm, 7.6 ± 0.5 mg, 58 ± 17%) tanks, compared with the lowest values in red tanks (14.2 ± 1.1 mm, 6.4 ± 0.4 mg, 11 ± 6%). Potential mechanisms for the influence of walling behaviour on Jaw Malformation are mechanical damage and poor nutrition, via reduced feed intake and increased energy expenditure. The study highlights the often overlooked importance of hard-surface interactions in the growth and survival of some cultured marine fish and demonstrates a cheap and effective technique for assessing tank background colour as a means of reducing Malformations in cultured fish.
P R Hart - One of the best experts on this subject based on the ideXlab platform.
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Jaw development and Malformation in cultured striped trumpeter latris lineata
Aquaculture, 2001Co-Authors: J M Cobcroft, P M Pankhurst, J Sadler, P R HartAbstract:Intensive culture of striped trumpeter (Latris lineata) has resulted in a high incidence of Jaw Malformation in juveniles. In this study, cranial and Jaw development in striped trumpeter was described in cultured larvae reared in greenwater on rotifers and Artemia. Jaw Malformation was only evident in post-flexion larvae greater than the standard length of 10 mm and was characterised by an open Jaw in which the maxilla and premaxilla were aligned dorso-ventrally, and the anterior hyoid arch elements were in an abnormal ventral position. X-radiography of the heads of juvenile and adult cultured striped trumpeter revealed ventro-lateral distortion of the Jaw elements in comparison with wild-caught fish. The possible role of physical environmental factors and nutrition during culture are discussed in relation to Jaw Malformation in this and other species.
Zhenhua Ma - One of the best experts on this subject based on the ideXlab platform.
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Water temperature induces Jaw deformity and bone morphogenetic proteins (BMPs) gene expression in golden pompano Trachinotus ovatus larvae.
SpringerPlus, 2016Co-Authors: Zhenhua Ma, Nan Zhang, Mingjun Fu, Shigui JiangAbstract:Golden pompano Trachinotus ovatus larvae were kept at 26, 29 and 33 °C for 15 days from 3-day post hatching (DPH) to 18 DPH to test temperature-dependent growth and Jaw Malformation. The growth, survival, Jaw deformity and the gene expressions of bone morphogenetic proteins (BMPs) were used as criteria to examine the fish response to temperature manipulation. The growth rate of fish at 29 or 33 °C was significantly faster than fish at 26 °C, while fish survival at 29 °C was significantly higher than fish at 33 °C. Jaw deformity was significantly affected by water temperature. The highest Jaw deformity occurred on fish at 33 °C, and the lowest Jaw deformity was at 26 °C. The expressions of all BMP genes except BMP10 were significantly affected by water temperature. The highest gene expression of BMP2 was on fish at 29 °C, and the lowest expression was at 33 °C. For the BMP4 gene, the highest and lowest expressions were found on fish at 33 and 26 °C, respectively. The present study indicates that Jaw deformity of golden pompano larvae increases with increasing temperature, and the gene expression of BMP4 proteins coincides with high Jaw deformity and water temperature elevation.
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Molecular cloning and expression analysis of the retinoid X receptor (RXR) gene in golden pompano Trachinotus ovatus fed Artemia nauplii with different enrichments.
Fish Physiology and Biochemistry, 2015Co-Authors: Qibin Yang, Panlong Zheng, Zhenhua Ma, Tao Li, Shigui JiangAbstract:The retinoid X receptors (RXRs) are involved in the skeletal development and other biological process such as blood vessel formation and metabolism. Partial sequences of RXRα and β genes were obtained, and their expressions were quantified on golden pompano Trachinotus ovatus at 28 days post hatching (DPH) to explore the molecular response to nutritional manipulation in fish larvae. As live food, Artemia nauplii were separately enriched with Nannochloropsis and Algamac 3080 and non-enriched Artemia nauplii (control) for fish feeding. The expressions of RXRs were detected in the embryos and fish larvae at early stages, suggesting that the skeletal development in golden pompano initiated before yolk re-sorption completion. Fish fed non-enriched Artemia nauplii ended up with higher Jaw Malformation. The highest specific growth rate was obtained when fish were fed with the Artemia nauplii enriched with Algamac 3080, and the lowest growth rate was observed when fish were fed with unenriched Artemia nauplii. The highest survival was obtained when fish were fed with non-enriched or Nannochloropsis-enriched Artemia nauplii. This study indicates that the use of enriched formula for Artemia nauplii can significantly affect the expression levels of RXRs and Jaw Malformation of golden pompano larvae, but there is no clear correlation between RXRs expressions and Malformation rates when fish are subjected to nutrient challenge.
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Jaw deformities in the larvae of yellowtail kingfish (Seriola lalandi Valenciennes, 1833) from two groups of broodstock
Indian Journal of Fisheries, 2014Co-Authors: Zhenhua MaAbstract:Jaw Malformation is a major bottleneck in hatchery development of marine finfish. This study compared the occurrence of Jaw deformities in larvae produced from two sets of broodstock of yellowtail kingfish ( Seriola lalandi , Valenciennes 1833). Fish eggs from two groups of broodstock (B1 and B2) were separately hatched and the fish larvae were reared up to 25 days under similar conditions. No significant differences were found in specific growth rate and overall Jaw deformities between these two groups. However, a clear pattern was observed in occurence of Jaw deformities at different lengths groups. In population B1, minor deformities occurred in larvae of 9.80-11.60 mm standard length (SL) with maximum in fish of 10.89-11.11 mm SL. In B2, minor Jaw deformities occurred in larvae of 8.69-12.21 mm SL with maximum deformities observed in fish of 9.35-9.52 mm SL and 10.18-10.34 mm SL. No severe Jaw deformities were found in either of the two groups of larvae in this study. The study clearly showed that the sizes at which Jaw deformities occur vary between two groups of larvae of the same species, under the same environmental and nutritional conditions. which indicated the need for selective breeding to reduce occurrence of deformity in the larvae.
Jennifer M. Cobcroft - One of the best experts on this subject based on the ideXlab platform.
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Improvements in yellowtail kingfish larval survival and juvenile quality
2020Co-Authors: Stephen C. Battaglene, Jennifer M. CobcroftAbstract:Jaw Malformation assessment was completed by IMAS (formerly TAFI) for all Yellowtail Kingfish (YTK) larval tanks for five Clean Seas Tuna (CST) hatchery runs (from the Arno Bay and Port Augusta hatcheries) in 2008, and for most larval rearing tanks in five hatchery runs at CST in 2009. The overall proportions of fish with commercially significant Jaw Malformations at the end of the larval stage in each of the hatchery runs were 27 to 29% in 2008, and 32 to 35% in 2009. These values correlated with IMAS assessments using the same Jaw Malformation classification system at the end of the nursery phase of 17 to 35% and 25 to 38% in 2008 and 2009, respectively. As in 2007, there was considerable variation in Malformation rates between larval tanks (7 to 64%), even when they were stocked with larvae from the same batch of eggs. In 2008 and 2009, fertilised YTK eggs were transported from CST to the Darwin Aquaculture Centre (DAC) and South Australian Research and Development Institute (SARDI) for rearing trials. Samples of larvae (from 1, 5, 10, 15, 20 DPH, and at transfer to the nursery and at handsorting) were sent to IMAS for assessment of Jaw and other Malformations. There was a high incidence of Jaw (44%) and spinal (>30%) Malformations in the YTK cultured at DAC in Jan-Feb 2009. Significant notochord (spinal) Malformations were observed from Day 1, supporting other evidence such as low hatching rate, that the batch was compromised before larval rearing commenced. There was no effect of the Artemia feeding regimes tested at SARDI in 2008 on Jaw Malformation (25-41%) which was similar to the incidence in commercial hatcheries. Bacteriology methods were demonstrated to CST staff for diluted plate counts of water and homogenised rotifers, and serial dilution was recommended for ongoing testing. Biochemical analyses were completed for 20 fertilised egg samples and 36 samples of live feeds, with lipid composition, lipid class and vitamin content analysed. There were indications of variability between different batches of fertilized eggs and enriched live feed profiles, although it is not known how much these may have been due to differences in the way and duration for which the samples were stored prior to analysis. The implications (if any) of differences in these parameters to YTK culture are unknown without further experimentation. Histopathology of over 2,000 larvae and juveniles from commercial production did not indicate any significant pathologies, with the most notable finding being non-inflated swimbladders.
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Skeletal Malformations in Australian marine finfish hatcheries
Aquaculture, 2020Co-Authors: Jennifer M. Cobcroft, Stephen C. BattagleneAbstract:The Australian finfish aquaculture industry has a target to more than treble production from 2005 to 100,000 t p.a. by 2015. Most of the current production is from sea cage culture of Salmo salar and Thunnus maccoyii but new and emerging species are predicted to have a faster increase in production and were the focus of this study. The quantity and quality of hatchery-produced fingerlings is an impediment to achieving growth in the marine finfish sector. A survey of 18 hatcheries revealed that 44% indicated skeletal Malformations were a significant issue in hatchery production, and 89% reported variability in Malformation rates between production batches. Samples of fish from selected hatcheries were cleared and stained for assessment of abnormal bone development. Two hatcheries that had indicated Malformations were not a significant problem submitted samples with > 5% severe Malformations. Jaw and spinal Malformations occurred in Lates calcarifer, Seriola lalandi, Epinephelus fuscoguttatus, E. coioides, and Latris lineata. To the best of our knowledge, causative factors of Malformations in Australian hatcheries have only been identified for Jaw Malformation in Lates calcarifer and Latris lineata, and further research is either needed or underway with other species and Malformation types in order to improve culture protocols and increase fingerling quality. Improved monitoring techniques for skeletal Malformations would substantially enhance the comparison of production methods at a commercial scale and enhance research efforts
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Aspects of the morphological development and feeding performance of larval striped trumpeter (Latris lineata) in culture
2020Co-Authors: Jennifer M. CobcroftAbstract:Striped trumpeter (Latris lineata) is a new candidate species for aquaculture in temperate Australia. Survival of larvae prior to flexion has proven a bottleneck in the production of this species for culture. In addition, almost all juveniles cultured to date exhibit Malformations of the Jaw that may impede larval feeding success. Body size and morphology impose constraints upon feeding success in larvae of broadcast spawning fishes. Furthermore, larvae have an absolute reliance upon sense organs for the detection and subsequent capture of prey. In this study, aspects of morphological development and feeding performance were described in larval striped trumpeter. Chemosensory and mechanosensory organs were present and presumed functional soon after hatching, while the eye was functional coincident with first-feeding on day 7 post-hatching. The structure of the photoreceptors in different regions of the retina of the larvae suggested the area specialised for the most acute image formation corresponded to a visual field in the fronto-ventral region. Analysis of videocinematography of feeding larvae in the horizontal plane confirmed a forward-directed functional visual field. The area of the visual field increased with larval ontogeny from day 13 to day 17 post-hatching, due to the wider range of reactive angles used by older larvae. Maximum reactive distances of larvae to rotifer prey (~5.1mm) were 97% of larval standard length, while the distance at which larvae initiated a strike at the prey was much lower (~0.45mm) at 8% of larval standard length. Visual angles determined from larval feeding behaviour were higher than the minimum separable angles predicted by histology, such that the functional acuity of the larvae was not as good as that predicted by retinal structure. Jaw Malformation was only evident in post-flexion larvae greater than 10 mm standard length and was characterised by an open Jaw in which cartilage and bone elements appeared structurally normal but were in abnormal positions. The effects of light intensity and microalgal cell density (turbidity) on larval feeding behaviour were assessed in short-term feeding trials. None of the pre-flexion larvae used to investigate optimal light conditions for feeding exhibited Jaw Malformations. Larvae fed equally well in clearwater (no microalgal cells present) in a light intensity range of 1-10 umol.s-1.m-2. An ontogenetic improvement in photopic visual sensitivity of larvae was indicated by improved feeding at 0.1 umol.s-1.m-2 between day 8 and day 23 post-hatching. Algae-induced turbidity had different effects on larval feeding response dependent upon the previous visual environment of the larvae. Young larvae, day 9 post-hatching, reared in clearwater showed decreased feeding capabilities with increasing turbidity, while older clearwater reared larvae fed well at all turbidities tested. Likewise, greenwater (with microalgal cells present) reared larvae had increased feeding capabilities in the highest algal cell densities tested compared with those in low algal cell density, and clearwater to which they were naive. This study demonstrated that striped trumpeter larvae are primarily visual feeders with a small visual field relative to larval body size, that Jaw Malformation is unlikely to impede feeding in pre-flexion larvae, and that greenwater may provide a benefit to larval feeding although the previous visual environment of larvae affected subsequent feeding responses.
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Performance and skeletal abnormality of striped trumpeter Latris lineata larvae and post larvae fed vitamin A enriched Artemia
Aquaculture, 2014Co-Authors: Reham K. Negm, Jennifer M. Cobcroft, Malcolm R. Brown, Barbara F. Nowak, Stephen C. BattagleneAbstract:Several nutritional studies have found that excess or reduced dietary vitamin A (VA) causes skeletal Malformations in marine fish larvae. Feeding VA enriched rotifers to striped trumpeter (Latris lineata) from 6 to 18 days post hatch (dph) has been shown to affect vertebral column Malformations but not Jaw Malformation. Our study examined the effect of dietary VA during the later Artemia feeding period on the prevalence of Malformations. Larvae were initially reared in a 3000 l tank and fed a diet of Algamac-3050 enriched rotifers from 2 to 16 dph. At 16 dph, larvae were transferred to 24 × 300 l tanks and fed Artemia enriched with one of six doses of retinyl palmitate (VA) four times per day from 19 to 44 dph. Enrichment with emulsions containing 0 (control), 795, 1558, 3174, 4911 and 10,518 ng retinyl palmitate mg− 1 emulsion resulted in an average VA in Artemia of 0, 6, 7, 27, 30 and 55 ng retinyl palmitate mg− 1 dry weight (DW). The retinoid content of L. lineata at 44 dph was positively correlated with the enriched Artemia they fed on. Growth in length (15.91 ± 0.31 mm, mean ± SD) and dry weight (5.08 ± 0.32 mg), and survival (26.1 ± 2.9%), were not significantly affected at 44 dph by increasing dietary doses of retinyl palmitate. Retinyl palmitate enrichment in Artemia did not affect Jaw Malformation in L. lineata, which is contrary to other studies on a range of marine fish species treated with increased doses of dietary VA. By the end of the study, 54 ± 10% and 18 ± 6% of the post larvae across treatments had short lower and open Jaws, respectively. Severe Jaw Malformations affected 50 ± 11% of the post larvae. Early culture of larvae in a larger tank was likely to reduce overall prevalence of Jaw Malformations compared to previous studies as interaction with tank walls was reduced. The prevalence of vertebral column Malformations in 44 dph post larvae (58 ± 4%) were also not affected by dietary VA. The study suggests that the window of influence for dietary VA is during earlier development of bone structures in L. lineata.