Jm Cobcroft

Jaw development and malformation in cultured striped trumpeter Latris lineata

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.

Jaw malformation in cultured yellowtail kingfish (Seriola lalandi) larvae

Abstract 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.

Sensory organ development in cultured striped trumpeter larvae Latris lineata: implications for feeding behaviour

Teleost larvae are reliant on sensory organs for feeding, in particular for the detection and subsequent capture of prey. The present study describes the development of sensory organs in cultured striped trumpeter larvae, Latris lineata. In addition, a short-term feeding trial was conducted to examine the feeding response of larvae with different senses available; streptomycin sulfate was used to ablate the superficial neuromasts, and testing larvae in the dark prevented visually mediated feeding. Some non-visual senses are available to striped trumpeter larvae from an early age, as indicated by the presence of superficial neuromasts at hatching, and innervated olfactory organs and a developed inner ear from Day 3 post hatching. The neuromasts proliferated on the head and body with increasing larval age, and formation of the lateral line canal had commenced by Day 26 post hatching. Oral taste buds were not present in any of the larvae examined, up to Day 26 post hatching. At hatching, the retina was at an early stage in development, but differentiated rapidly and was presumed functional coincident with the onset of feeding on Day 7 post hatching. The ventro-temporal retina was the last to differentiate, and was distorted by the embryonic fissure, such that larval vision in the forward and upward visual field would be compromised. In contrast, the dorso-temporal retina was the first area to differentiate, and presumptive rod and double-cone development occurred in this area from Days 11 and 16, respectively, indicating that the forward and downward directed visual field is most suited for acute image formation. Larvae on Day 18 post hatching demonstrated increased feeding with an increase in the senses available, with 8 ± 3% of streptomycin-treated larvae feeding in the dark (chemoreception and inner ear mechanoreception only) and 27 ± 5% of untreated larvae feeding in the light (all senses available). It remains to be demonstrated whether there is an advantage to larval growth and survival by providing live feed during the dark phase in culture, facilitating feeding 24 hours per day.

Host response to the chondracanthid copepod Chondracanthus goldsmidi, a gill parasite of the striped trumpeter, Latris lineata (Forster), in Tasmania

The chondracanthid copepod, Chondracanthus goldsmidi is an ectoparasite of gills, inner opercula and nasal cavities of cultured striped trumpeter, Latris lineata (Forster). Whilst often present in high numbers (up to 60 parasites per host), little is known about its effect on striped trumpeter. In this study C. goldsmidi was associated with extensive epithelial hyperplasia and necrosis. Pathological changes were most pronounced near the parasites attachment site, with papilloma-like growths surrounding the entire parasite resulting in deformation of the filament. The number of mucous cells increased near the parasite attachment sites on both the opercula and gills. Mast cells were absent in healthy gills; in contrast numerous mast cells were identified in the papilloma-like growths. Immunostaining identified piscidin-positive mast cells in the papilloma-like growths, presenting the first evidence of piscidin in the family Latridae.

Influences of dietary n-3 long-chain PUFA on body concentrations of 20 : 5n-3, 22 : 5n-3, and 22 : 6n-3 in the larvae of a marine teleost fish from Australian waters, the striped trumpeter (Latris lineata)

We determined the effect of dietary long-chain (≥C20) PUFA (LC-PUFA), 20∶5n−3 and 22∶6n−3, on larval striped trumpeter (Latris lineata) biochemistry through early development and during live feeding with rotifers (Brachionus plicatilis). Rotifers were enriched using seven experimental emulsions formulated with increasing concentrations of n−3 LC-PUFA, mainly 20∶5n−3 and 22∶6n−3. Enriched rotifer n−3 LC-PUFA concentrations ranged from 10–30 mg/g dry matter. Enriched rotifers were fed to striped trumpeter larvae from 5 to 18 d post-hatch (dph) in a short-term experiment to minimize gross deficiency symptoms such as poor survival that could confound results. No relationships were observed between larval growth or survival with dietary n−3 LC-PUFA at 18 dph. The larval FA profiles generally reflected those of the rotifer diet, and significant positive regressions were observed between most dietary and larval FA at 10, 14, and 18 dph. The major exception observed was an inverse relationship between dietary and larval 22∶5n−3. The presence of 22∶5n−3 in elevated amounts when dietary 22∶5n−3. The presence of 22∶5n−3 in elevated amounts when dietary 22∶6n−3 was depressed suggests that elongation of 20∶5n−3 may be occurring in an attempt to raise body concentrations of 22∶6n−3. We hypothesize that accumulation of 22∶5n−3 might be an early indicator of 22∶6n−3 deficiency in larval fish that precedes a reduction in growth or survival. A possible role of 22∶5n−3 as a biochemical surrogate for 22∶6n−3 is discussed.

Ultraviolet irradiation is an effective alternative to ozonation as a sea water treatment to prevent Kudoa neurophila (Myxozoa: Myxosporea) infection of striped trumpeter, Latris lineata (Forster)

Myxozoan parasites are known pathogens of cultured finfish. Kudoa neurophila n. comb. (Grossel, Dyková, Handlinger & Munday) has historically infected hatchery-produced striped trumpeter, Latris lineata (Forster in Bloch and Schneider), a candidate species for seacage aquaculture in Australia. We examined the efficacy of four water treatment methods to prevent K. neurophila infection in post-larval (paperfish) and juvenile striped trumpeter. Treatments included dose-controlled ultraviolet irradiation [hydro-optic disinfection (HOD)], ozone with conventional UV (ozone), mechanical filtration at 25 μm and then foam fractionation (primary filtration), and 50-μm-filtered sea water (control). In post-larvae (initially 10.3 ± 2.7 g, mean ± SD, 259 days post-hatching, dph), the infection prevalence (PCR test) after 51 days was 93 ± 12% in the control, 100 ± 0% in primary filtration and 0 ± 0% in both ozone and HOD. Likewise, in juveniles (initially 114 ± 18 g, 428 dph), prevalence was 100 ± 0% in the control and primary filtration treatments with no infection detected in ozone and HOD. Concurrently, there was a 50-100% reduction in heterotrophic bacteria and 100% reduction in presumptive Vibrio sp. in sea water HOD and ozone treatments. HOD with a dose of ≥44 mJ cm(-2) UV was as effective as ozonation at >700 mV ORP for 10 min, in preventing K. neurophila infection.

THE FIRST CHONDRACANTHID (COPEPODA: CYCLOPOIDA) REPORTED FROM CULTURED FINFISH, WITH A REVISED KEY TO THE SPECIES OF CHONDRACANTHUS

A new species of the Chondracanthidae (Copepoda: Cyclopoida), Chondracanthus goldsmidi, is described based on material collected from the nasobranchial region of striped trumpeter (Latris lineata [Forster]) cultured at the Tasmanian Aquaculture and Fisheries Institute, Marine Research Laboratories, Australia. This represents the first report of a chondracanthid copepod infecting cultured finfish and the first metazoan parasite from cultured striped trumpeter. Chondracanthus goldsmidi n. sp. can be distinguished from its female congeners by the absence of lateral processes on the head and the presence of 3 pairs of lateral trunk outgrowths, 3 middorsal body outgrowths (of which the first 2 are rounded), a small and subcylindrical antennule, and unornamented legs 1 and 2. A revised key to the 39 valid species of Chondracanthus is provided.

Skeletal anomaly assessment in diploid and triploid juvenile Atlantic salmon ( Salmo salar L.) and the effect of temperature in freshwater

Triploid Atlantic salmon tend to develop a higher prevalence of skeletal anomalies. This tendency may be exacerbated by an inadequate rearing temperature. Early juvenile all-female diploid and triploid Atlantic salmon were screened for skeletal anomalies in consecutive experiments to include two size ranges: the first tested the effect of ploidy (0.2-8 g) and the second the effect of ploidy, temperature (14 °C and 18 °C) and their interaction (8-60 g). The first experiment showed that ploidy had no effect on skeletal anomaly prevalence. A high prevalence of opercular shortening was observed (average prevalence in both ploidies 85.8%) and short lower jaws were common (highest prevalence observed 11.3%). In the second experiment, ploidy, but not temperature, affected the prevalence of short lower jaw (diploids > triploids) and lower jaw deformity (triploids > diploids, highest prevalence observed 11.1% triploids and 2.7% diploids) with a trend indicating a possible developmental link between the two jaw anomalies in triploids. A radiological assessment (n = 240 individuals) showed that at both temperatures triploids had a significantly (P < 0.05) lower number of vertebrae and higher prevalence of deformed individuals. These findings (second experiment) suggest ploidy was more influential than temperature in this study.

Visual field of cultured striped trumpeter Latris lineata (Teleostei) larvae feeding on rotifer prey

The visual field of striped trumpeter Latris lineata larvae fed rotifer prey was determined from analysis of feeding behaviour in the horizontal plane. The visual field was forward and laterally directed, characterised by maximum reactive distances (distance at which the predator first detects and reacts to the prey) of 5.07 mm and 5.25 mm on days 13 and 17 post-hatching, respectively, 97% of mean larval length. This confirmed the predicted horizontal visual field, forward and laterally directed, derived from higher cone cell densities in the dorso-temporal and medial regions of the retina compared with ventral regions. The visual field of prey detection expanded laterally with ontogeny as a wider range of reactive angles was used by 17 day-old than 13 day-old larvae. Larvae displayed a saltatory searching pattern, periodically stopping to scan for prey throughout the visual field, and exhibited a side-to-side movement of the head as they approached and stopped, prior to striking at a detected prey item. Larvae on day 17 post-hatching terminated 35% of feeding sequences at the pre-strike position, at a mean distance from prey of 0.58 mm.

Triploid Atlantic salmon shows similar performance, fatty acid composition and proteome response to diploids during early freshwater rearing

There is currently renewed interest in farming triploid Atlantic salmon. Improving farming requires identifying triploid specific phenotypic and physiological traits that are uniquely derived from ploidy per se and developed under optimal growing conditions. This study investigated firstly, the impact of ploidy on growth performance and whole body composition of Atlantic salmon at different early freshwater stages [34dph (days post-hatching) alevin, 109dph fry, and 162dph parr] and secondly, whether phenotypic differences at these stages were reflected in protein samples collected from whole fish, white muscle or liver tissue. Female diploid and triploid Atlantic salmon (n=3) were first fed at 35dph and then maintained by feeding to satiation on commercial feeds. Triploids were significantly lower in weight at the late alevin and fry stages but matched diploid weight at the parr stage. The whole-body lipid content was significantly higher for triploids at the parr stage, while the whole-body lipid class profile was broadly similar and was largely not affected by ploidy. Comparative label-free shotgun proteomic analysis did not detect significant alterations in protein expression between diploids and triploids at any growth stage. The present results indicate that ploidy under optimal growing conditions and during early freshwater stages only result in small phenotypic differences in weight and whole body lipid content that were not reflected at the proteome level. These findings suggest that optimal husbandry conditions for freshwater Atlantic salmon are similar between ploidies, at least for all-female populations.