Genetic and morphological identification of formalin fixed, preserved larval fishes; can we have the best of both worlds?

Surveys of larval fishes require accurate identifications of larvae which are essential to understand early life history of fish fish ecology and fisheries However the identification of larval fishes requires microscopic examination that is substantially more difficult than that of juvenile and adult fishes as many larval stages remain undescribed Furthermore the traditional formalin fixation of larval fishes were previously thought to prevent genetic sequencing compared to ethanol preserved larvae In this study we used an integrative taxonomic approach based on morphology imaging and DNA barcoding of the mitochondrial mtDNA cytochrome c oxidase subunit COI gene We used this approach in both cultured yellowtail kingfish Seriola lalandi and wild sourced fish larvae that had been fixed in 5 formalin Based on controlled and in field formalin treatments DNA barcoding and genetic species identification was 100 successful in cultured yellowtail kingfish fixed in formalin for up to 6 months while barcoding of wild caught fish larvae enabled species identification of 93 of up to 8 weeks formalin fixed specimens Furthermore we demonstrated the viability of using either whole larval individuals or a single eyeball remove

Investigating the Potential Utility of Environmental DNA to Provide a Relative Abundance Index for the Depleted Teleost, Mulloway, Argyrosomus japonicus

Non-invasive, low-cost methods for censusing depleted fish populations are being prioritised among many jurisdictions worldwide. Collecting environmental DNA (eDNA) could offer one such option for augmenting fish population assessments. However, candidate species need to be carefully selected because species-specific DNA shedding and decay rates are affected by many biotic and abiotic factors that may influence relative abundance estimates. In this study, we sought to ascertain if the eDNA of a depleted Australian teleost, mulloway, Argyrosomus japonicus, reflects its weight under controlled aquaria conditions. With four experiments, we investigated the relationships between mulloway eDNA concentrations and their weight tank−1 as a function of: (1) time post-tank establishment; (2) water temperatures (within the species’ tolerance range); (3) stocking densities; and (4) among individual, similar-sized fish. The concentrations of eDNA in tanks stabilised after six days, and a positive relationship was found between fish weight and eDNA concentration, despite some variability in shedding rates by similar-sized fish. There was also a positive effect of water temperature on eDNA concentrations, which reinforces the need to control for such abiotic factors. We conclude that there is strong utility in applying eDNA concentrations as an index of relative abundance for mulloway under controlled conditions, which justifies future field-based investigations

Correlating corneal arcus with atherosclerosis in familial hypercholesterolemia

Abstract Background A relationship between corneal arcus and atherosclerosis has long been suspected but is controversial. The homozygous familial hypercholesterolemia patients in this study present a unique opportunity to assess this issue. They have both advanced atherosclerosis and corneal arcus. Methods This is a cross-sectional study of 17 patients homozygous for familial hypercholesterolemia presenting to the Clinical Center of the National Institutes of Health. Plasma lipoproteins, circumferential extent of arcus, thoracic aorta and coronary calcific atherosclerosis score, and Achilles tendon width were measured at the National Institutes of Health. Results Patients with corneal arcus had higher scores for calcific atherosclerosis (mean 2865 compared to 412), cholesterol-year score (mean 11830 mg-yr/dl compared to 5707 mg-yr/dl), and Achilles tendon width (mean 2.54 cm compared to 1.41 cm) than those without. Corneal arcus and Achilles tendon width were strongly correlated and predictive of each other. Although corneal arcus was correlated with calcific atherosclerosis (r = 0.67; p = 0.004), it was not as highly correlated as was the Achilles tendon width (r = 0.855; p Conclusion Corneal arcus reflects widespread tissue lipid deposition and is correlated with both calcific atherosclerosis and xanthomatosis in these patients. Patients with more severe arcus tend to have more severe calcific atherosclerosis. Corneal arcus is not as good an indicator of calcific atherosclerosis as Achilles tendon thickness, but its presence suggests increased atherosclerosis in these hypercholesterolemic patients.</p

Comparison of low temperature adaptation ability in three native and two hybrid strains of the rotifer Brachionus plicatilis species complex

The low temperature adaptation ability of five selected strains of the Brachionus plicatilis species complex, i.e., three native strains [ Japanese (NH1L), Australian, German] and two hybrid strains [♀NH1L and ♂Australian (N × A) and ♀NH1L and ♂German (N × G),was investigated in terms of life history traits, reproductive characteristics, and mobility under different thermal conditions (12 and 25 °C). The life history traits of these five strains included a longer lifespan, reproduction period and generation times at 12 °C than at 25 °C, combined with reduced lifetime egg and offspring production. At 12 °C, the intrinsic rate of natural increase was higher in NH1L and N × A strains. Reproductive characteristics determined at 12 °C by batch culture showed active population growth for NH1L and N × G strains, while no resting egg production was observed in all of the strains tested. The ratio of swimming rotifers at 12 °C was monitored every hour for 6 h (short term) and every day for 10 days (long term). In the short-term study there was a 81% ratio of swimming rotifers of the NH1L strain, while other strains exhibited low swimming ratios (75% swimming ratio from the initial day of the study. These results suggest that outcrossing of rotifer strains is useful to obtain live food resources for the larviculture of cold water fish

Improvement of intensive larval rearing and evaluation of inland saline groundwater for aquaculture of snapper, Pagrus auratus

No description availabl

Effect of rapid changes in temperature and salinity on availability of the rotifers Brachionus rotundiformis and Brachionus plicatilis.

Euryhaline rotifers are an important food for rearing marine fish larvae. Their availability to fish larvae in the water column may be reduced if they are transferred to fish larval rearing tanks with different temperatures and salinities. The rotifers, Brachionus rotundiformis (formerly called S-type) and Brachionus plicatilis (formerly called L-type), were mass-cultured at 23°C and 35‰ salinity, and then abruptly transfered into tanks at different temperatures (18°C, 23°C, 28°C) and salinities (10‰, 15‰, 20‰, 25‰, 30‰, 35‰). Their availability in the water column was then measured in non-turbulent beakers over time. Both species showed initial transfer shock. The number of rotifers 1 h after stocking was approximately 50% of that potentially available, but increased to approximately 75% after 6 h. Availability was reduced when rotifers were transferred from 23°C to 18°C, but was not affected by transfer from 23°C to 28°C and remained relatively constant over time. B. rotundiformis was slightly more tolerant at higher temperatures than B. plicatilis. Salinity had a greater effect on availability than temperature. Availability of rotifers decreased as salinity was reduced. The availability of rotifers increased over time indicating that some rotifers had acclimated to the transfer conditions. B. plicatilis was slightly more tolerant at lower salinity than B. rotundiformis. Rotifers should be cultured at lower temperatures and similar salinities to the fish larval rearing tanks or acclimated for at least 6 h to larval rearing conditions before transfer. (C) 2000 Elsevier Science B.V

Effects of photoperiod and feeding frequency on performance of newly weaned Australian snapper Pagrus auratus

An experiment was done to investigate the interactive effects of photoperiod (12L:12D or 18L:6D) and feeding frequency on the growth of newly weaned Australian snapper (mean weight = 0.14 g fish- 1). Feeding frequency was investigated over 4 levels with 2 feeds delivered during the first half of the daylight period (2FE), 2 feeds during the latter half of the daylight period (2FL), 4 (4F) or 8 (8F) evenly spaced feeds per daylight period. Each treatment combination was replicated in 6 tanks and each tank was stocked with a biomass of 15 g tank- 1 (i.e. approximately 108 fish tank- 1). Snapper were fed a constant ration of 10% BW day- 1 for 32 days, which was adjusted during the experiment according to frequent weight check procedures. Fish that died were counted but not replaced. Photoperiod, feeding frequency and the interaction of these factors significantly affected the individual harvest weight and thermal growth coefficient (TGC) of snapper. Interactions were driven by an increase in the magnitude of individual weight and TGC in snapper fed the 4F and 8F treatments and reared under the 18L:6D photoperiod, compared to snapper fed at the same frequencies but reared under the 12L:12D regime. Weight gain and TGC were best in snapper reared under a 18L:6D photoperiod regime and fed 8 feeds day- 1, however, weight gain did not plateau, suggesting further increases in weight gain may be possible if feeding frequencies greater then 8F are employed. Survival and apparent feed conversion ratio (AFCR) were significantly affected by feeding frequency alone, with significant improvements in snapper fed more frequently and in snapper fed twice daily but later in the same photoperiod (2FE < 2FL < 4F < 8F). Size heterogeneity (measured by the coefficient of variation for individual harvest weight, CVhw) was affected by photoperiod, and decreased significantly in snapper reared under the 18L:6D regime. Size heterogeneity was also affected by feeding frequency, however, only the CVhw for snapper reared under the 8F feeding frequency was significantly lower than snapper fed at other rates (i.e. 2FE = 2FL = 4F < 8F). Snapper fed later in a photoperiod regime generally performed better than snapper fed earlier. Results from this study indicate that in order to maximize weight gain, survival and AFCR and to reduce size heterogeneity, newly weaned snapper should be reared under a 18L:6D photoperiod and, for fish fed 10% BW day- 1, fed 8 times day- 1. © 2006 Elsevier B.V. All rights reserved

Ontogenetic milestones of chemotactic behaviour reflect innate species-specific response to habitat cues in larval fish

© 2017 The Association for the Study of Animal Behaviour The distribution and connectivity of marine populations are largely dependent on biophysical factors affecting pelagic larval dispersal between spawning at adult spawning sites and settlement to juvenile nursery habitats. Behaviour and swimming ability of pelagic larvae are increasingly understood to influence patterns of dispersal, but it is unclear which sensory cues are involved and when during ontogeny these abilities first develop. Here we studied the early ontogenetic development of responses to olfactory cues from coastal and estuarine waters in larvae of two temperate estuarine-associated fish species, Australian bass, Macquaria novemaculeata, and mulloway, Argyrosomus japonicus, to determine when olfaction begins to influence dispersal. Olfactory responses to habitat-associated cues were not present when larvae first transitioned from nonswimming to swimming (indicated by flexion of the notochord), but emerged after ca. 7 days in a species-specific manner that was consistent across different cohorts. Based on general additive models (GAMs), age (in days posthatch) best explained the ontogenetic pattern in both species. The emergence of chemotactic responses coincides with an exponential increase in swimming endurance reported for these species. This suggests the existence of ontogenetic milestones during larval development that, once reached, trigger active influence on dispersal. Salinity and pH did not influence choice behaviour after these ontogenetic milestones; however, the presence of cues generated by seagrass harvested from the estuary habitat elicited strong responses in fish larvae consistent with species-specific habitat preferences, indicating an important role for aquatic vegetation in driving these behaviours

Effect of photoperiod on growth and survival of snapper Pagrus auratus larvae

Experiments were done in 100-1 recirculation tanks to determine the effects of photoperiod on (1) first-feeding and (2) post-swimbladder inflated snapper, Pagrus auratus, larvae. In Experiment 1, feeding onset, growth, initial swimbladder inflation, and tail flexion were assessed at five photoperiod treatments (0L:24D, 6L:18D, 12L:12D, 18L:6D, and 24L:0D) in larvae from 3 to 15 days after hatching (dah). Growth and development of first-feeding larvae increased with increasing photoperiod duration in the 12L:12D to 24L:0D treatments. Larvae did not start feeding in 0L:24D and onset of feeding was delayed by up to 3 days in 6L:18D. All larvae held in 0L:24D and 6L:18D died within 6 or 9 dah, respectively. Initial swimbladder inflation was best (80-100%) in an intermediate photoperiod of 12L:12D at 9 dah. By 15 dah, although the percentage of larvae with inflated swimbladders had increased in all treatments, swimbladder inflation in 12L:12D was 1.3 and 2.0 times greater than that of larvae in 18L:6D and 24L:0D, respectively. In the second experiment, growth and survival of snapper after the initial swimbladder inflation period (11-32 dah) were assessed at three photoperiod treatments (12L:12D, 18L:6D, and 24L:0D). Growth was greatest in 18L:6D in which wet weights (16.3±0.5 mg; mean±S.E.) and dry weights (2.8±0.1 mg; mean±S.E.) of larvae were approximately 1.3 and 1.9 times heavier than the larvae held in 24L:0D and 12L:12D, respectively. Survival of snapper larvae to 32 dah was not significantly different between the three photoperiod treatments, but power of the experiment to detect effects on survival was small due to large variability within treatments. Further research is needed to determine optimal photoperiods for the survival of the snapper larvae. Because of the potential for large larval mortality, if initial swimbladder inflation is not achieved, the optimal photoperiod for the period from feeding onset to swimbladder inflation (3-15 dah) was deemed to be 12L:12D, whereas on the basis of growth parameters that were measured (total length, wet and dry weights), 18L:6D was determined to be the optimal photoperiod for the culture of snapper from the post-swimbladder window to metamorphosis (11-32 dah). © 2002 Elsevier Science B.V. All rights reserved

The effects of salinity and temperature on growth and survival of Australian snapper, Pagrus auratus larvae

The effects of salinity and temperature on performance were determined for Australian snapper, Pagrus auratus first-feeding to pre-metamorphosis larvae held in 100-l recirculation tanks. In the first experiment, performance was assessed after transfer from 35‰ at eight salinity treatments (5‰, 10‰, 15‰, 20‰, 25‰ 30‰, 35‰ and 45‰) in larvae from 3 to 21 days after hatching (dah). Survival of larvae was best within the range of 20-35‰. Final size of larvae was similar within the range of 10-35‰ (6.8 ± 0.1 to 7.1 ± 0.2 mm total length [TL]; 3.0 ± 0.3 to 3.3 ± 0.3 mg wet weight) but larvae were 15% shorter at 45‰. Final swimbladder inflation and feeding onset of larvae was not affected by salinity in the range of 10-45‰. The presence of calculi in the urinary bladder of larvae was correlated positively with increasing salinity but no relationship between urinary calculi and larval survival was observed. In a second experiment, performance was assessed after transfer from 21°C at seven temperature treatments (15, 18, 21, 24, 27, 30 and 33°C) in larvae from 3-21 dah. All larvae transferred from 21°C to 30°C and 33°C died after 3 days and from 21°C to 27°C died after 9 days. Survival was not significantly different between 15°C and 24°C. Larval growth increased as temperature was increased; larvae at 24°C (4.8 ± 0.2 mg wet weight) were 6-fold heavier than larvae at 15°C. Swimbladder inflation of larvae grown at 18°C, 21°C and 24°C was high (65.2 ± 18.0% to 86.7 ± 8.8%) and similar but inflation was lower in 15°C and 27°C. The incidence of urinary calculi occurred earlier and in a greater number of larvae when temperature was increased. Feeding onset was not affected by temperature. In a third experiment, performance was assessed at combinations of two salinities (20‰ and 35‰) and three temperatures (18°C, 21°C, and 24°C) in larvae from 3 to 24 dah. Survival of snapper larvae was not significantly different between these treatments. Growth was not affected by salinity but larvae increased in size as temperature was increased and there was no interaction of salinity and temperature. The percentage of larvae that commenced feeding and inflated their swimbladders was similar in all treatments. Salinity and temperature influenced the incidence of urinary calculi and there was an interaction between the parameters. Based on our results in terms of larval performance (growth), development and survival, we conclude that the optimal conditions for larval rearing of snapper from first-feeding (3 dah) to pre-metamorphosis (24 dah) are combinations of salinity from 20‰ to 35‰ and a temperature of 24°C. © 2005 Elsevier B.V. All rights reserved