Australian Freshwater Crayfish Research Articles

Free amino acids in claw muscle and haemolymph from Australian freshwater crayfish at different stages of the moult cycle

Amino acids were measured in claw muscle and haemolymph in the freshwater decapod crustacean, Cherax destructor, at different stages of the moult cycle. The total pool of amino acids in muscles from animals in intermoult (97±13 mmol kg −1 muscle), premoult (80±20 mmol kg −1) and postmoult (97±19 mmol kg −1) were not significantly different. Despite the relatively stable total pool of amino acids, there were changes in the concentrations of alanine, glutamine and proline over the moult cycle. Compared to intermoult, claw muscles from animals in premoult had a lower concentration of proline, and animals in postmoult had higher concentrations of alanine and glutamine, but lower concentrations of proline. Concentrations of alanine and glutamine in claw muscle of animals in postmoult were higher and proline concentrations lower than in the same animals during the premoult stage. The concentration of proline in haemolymph was lower in animals in premoult and postmoult compared to intermoult. The total amino acid pool in the claw muscle of Cherax destructor did not change significantly over the moult which is distinctly different to the changes in amino acids reported in the claw muscles of marine decapod crustaceans.

Production of Australian freshwater crayfish in earthen-based systems using pelleted diets and forage crops as food

Juvenile Cherax destructor (commonly called theyabby) were cultured in earthen-based ponds and tanks for 70–105d, and were fed pellets and/or a forage crop of the perennialwhiteclover, Trifolium repens. Three supplementary feedingstrategies were evaluated. Yabby growth on pellets consistently exceeded (by67–159%) that obtained on clover. Base-line yields for extensiveproduction systems are around 400 kg ha−1. Thesupplementary addition of T. repens produced yields of 635kg ha−1 (in ponds) to 1086 kgha−1 (in tanks). The sequential addition of cut-cloverto tanks stimulated growth to levels approaching those achieved on pellets.Yabbies stocked into ponds at 17 m−2 and fed 33%protein pellets for 100 d, resulted in a yield of 1117 kgha−1.Pellet inputs at a rate of 129–249 g m−2(dry matter) and 38–83 g m−2 (protein) over70–100 d resulted in acceptable growth and feed utilisationindices. Clover inputs of 534–682 g m−2 (asdry matter) or 84–177 g m−2 (as protein)produced reasonable growth rates but poor feed utilisation indices. Aconsiderable quantity of the dry matter and protein content of clover waseitherinefficiently utilised or directed into other production pathways. In tanks,clover inputs from 113–296 g m−2 (drymatter) and 24–54 g m−2 (protein) weresufficient to maintain high growth rates for 4 weeks, while in ponds, inputs of21 g m−2 (dry matter) and 4.3 gm−2 (protein) were sufficient for 3 weeks. During theearly weeks of production no growth advantage was gained by providing pelletstoanimals cultured in forage-based systems. Forage depletion occurred after3–4 weeks and was probably a major growth limiting factor.

Comparison of Brood Size and Juvenile Weight between a Blue Strain and Normal-Coloured Strains of the Australian Freshwater Crayfish Cherax Destructor Clark (Decapoda: Parastacidae)

A blue strain of the yabby Cherax destructor albidus was compared to two normal-coloured strains of C. d. destructor and C. d. albidus for brood size and juvenile weight. Reproductive performance of the blue strain was found to be significantly poorer than the two normal-coloured strains. Similarly, the weight of newly independent juveniles was also found to be significantly lower for the blue strain. No differences were detected between the two normal-coloured strains in either reproductive performance or size of newly independent juveniles. The phenotypic differences between the blue strain and normal-coloured strains are most likely genetic. However, further studies are needed to investigate whether these differences are due to pleiotropy or inbreeding effects.

Physiological compensation in unilateral eyestalk ablated crayfish,Cherax quadricarinatus

The eyestalks of crustaceans contain neurosecretory cells involved in the regulation of molting. In crayfish, bilateral ablation results in increased molting frequency and weight gain whereas unilateral ablation typically has no effect on molting frequency and weight gain. The effects of unilateral ablation were examined in juvenile Australian freshwater crayfish, Cherax quadricarinatus. As observed for other crayfish species, molting frequency and weight gain of unilateral ablated crayfish were not significantly different from control (intact) crayfish. Survival of unilateral ablated crayfish, however, was reduced compared to controls and was likely due to stress associated with the surgical procedure itself. Using radiolabeling techniques, protein synthesis was determined for neural tissues from the remaining eyestalk of ablated crayfish and compared to protein synthesis of neural tissues from eyestalks of control, non-ablated crayfish. Protein synthesis of ablated crayfish neural tissues was significantly higher (ca. 45%) than protein synthesis of control neural tissues. Electrophoretic analysis (SDS-PAGE and autoradiography) further demonstrated that protein synthesis increased linearly for all proteins in the remaining eyestalk of ablated crayfish. Together, these results suggest that a compensatory response occurred in unilateral ablated crayfish allowing normal physiological functions, particularly those involved in regulating growth cycles, to be maintained. J. Exp. Zool. 289:184-189, 2001.

Hybridization in Australian Freshwater Crayfish—Production of All‐Male Progeny

Abstract.— In freshwater crayfish aquaculture high densities can result from uncontrolled reproduction. Hence some farmers manually sex yabbies Cherax albidus and stock only mate crayfish in farm dams or ponds. Although male‐only yabby populations produce an estimated 70% increase in gross income, hand sexing is time consuming and prone to error. A hybridization experiment using freshwater crayfish from the yabby species complex, collected from geographically isolated regions throughout Australia, revealed a hybrid between Cherax rotundus females and C. albidus males which consistently produces only male progeny. This has been confirmed in nine crosses of the same two species. The reciprocal cross of C. albidus females ×C. rotundus males produces both male and female progeny. The consistent production of only male progeny by hybridization has not been recorded previously for a crustacean.

Amino acids in haemolymph, single fibres and whole muscle from the claw of freshwater crayfish acclimated to different osmotic environments

The concentrations of free amino acids were measured in whole claw muscle, single fibres and haemolymph of Australian freshwater crayfish, Cherax destructor, during the intermoult stage. The average total pool of amino acids in short-sarcomere fibres (179 mmol kg −1) was 60% greater than in long-sarcomere fibres, due to higher concentrations of alanine, cysteine, glutamate, leucine and proline. The two fibre types exhibited differences in the banding pattern of the isoforms of troponin using gel electrophoresis. The average pool of amino acids in haemolymph was 2.7 mmol kg −1. Cherax has symmetrical claws and the total pool of amino acids from whole muscles (approx. 79 mmol kg −1) was similar in left and right claw muscles. In animals acclimated to osmotic environments between 0 and 220 mOsm, the osmotic pressure of the haemolymph increased from 356 to 496 mOsm, but no systematic changes were observed in the amino acid profiles of muscles or haemolymph. The major findings were that (a) concentrations of amino acids differed between the two major fibre types in claw muscle and (b) amino acids in the muscle fibres did not play a major part in intracellular osmoregulation in Cherax, suggesting this species is an anisosmotic regulator.

Effects of Dietary Copper on the Australian Freshwater Crayfish Cherax destructor

Little information is available on the effects of metals in the diet of parastacids, despite the importance of the freshwater crayfish industry worldwide. There have been no published studies on the effect of either dissolved or dietary copper on the Australian freshwater crayfish Cherax destructor. Herein is reported a study on the bioaccumulation of copper through a simple food chain. The copper was first absorbed by the floating aquatic macrophyte Lemna minor to an average concentration of 74 μg/g, before being fed to C. destructor. In the crayfish, the highest copper concentrations were found in the muscle (56.4–1299.6 μg/g), gills (86.8–714.3 μg/g) and hemolymph (14.8–293.5 μg/g). There was no bioaccumulation or bioconcentration of copper from contaminated dietary material. A general linear model indicated that such treatment had no effect on copper concentrations in the crayfish. The results are consistent with the regulation of copper by C. destructor, with the gills being the main site for absorption and depuration of copper to and from the water column. C. destructor does not appear to be sensitive to dietary copper.

Central complex in the brain of crayfish and its possible homology with that of insects

A small, medial heterolateral neuropil in the brain of crustaceans has long been regarded as the central body of the crustacean brain. Its simplicity and the absence of clear layers within its neuropil have led to the question of its homology with the more complex central body that occupies an approximately equivalent position in the brain of insects. We have labelled neurons in the central body of the Australian freshwater crayfish Cherax destructor by the extracellular application of dextrans and by treating the brain with antibodies to anti-CCAP, anti-locustatachykinin, anti-perisulfakinin, anti-proctolin, anti-dip-allatostatin AI, anti-PEA-head-peptide, anti-serotonin, and anti-rabbit anti-substance P, all of which label neurons in the insect brain. The dextran and immunocytochemical labelling have revealed a neural complex associated with the crayfish central body that is very similar in overall anatomical architecture to the subset of neuropils that are incorporated in the central complex of the insects, and in particular to that of the locust. Similarities between the crayfish and locust central complexes extend to the number and position of the neuropils, the location of the cell body clusters of the neurons that belong to the central complex, the numbers of tracts that link some of the constituent neuropils together, and the form and immunoreactivity of many of the individual neuron classes. These similarities are taken as evidence to support a possible homology between the crustacean central complex and that of the insects. J. Comp. Neurol. 416:245–261, 2000. © 2000 Wiley-Liss, Inc.

Central complex in the brain of crayfish and its possible homology with that of insects

A small, medial heterolateral neuropil in the brain of crustaceans has long been regarded as the central body of the crustacean brain. Its simplicity and the absence of clear layers within its neuropil have led to the question of its homology with the more complex central body that occupies an approximately equivalent position in the brain of insects. We have labelled neurons in the central body of the Australian freshwater crayfish Cherax destructor by the extracellular application of dextrans and by treating the brain with antibodies to anti-CCAP, anti-locustatachykinin, anti-perisulfakinin, anti-proctolin, anti-dip-allatostatin AI, anti-PEA-head-peptide, anti-serotonin, and anti-rabbit anti-substance P, all of which label neurons in the insect brain. The dextran and immunocytochemical labelling have revealed a neural complex associated with the crayfish central body that is very similar in overall anatomical architecture to the subset of neuropils that are incorporated in the central complex of the insects, and in particular to that of the locust. Similarities between the crayfish and locust central complexes extend to the number and position of the neuropils, the location of the cell body clusters of the neurons that belong to the central complex, the numbers of tracts that link some of the constituent neuropils together, and the form and immunoreactivity of many of the individual neuron classes. These similarities are taken as evidence to support a possible homology between the crustacean central complex and that of the insects.

Evidence for the Inheritance of a Blue Variant of the Australian Fresh-Water Crayfish Cherax Destructor (Decapoda: Parastacidae) as an Autosomal Recessive

Abstract The inheritance of a blue body color phenotype found in Cherax destructor (the yabby) was investigated in a series of experimental crosses including both F2 and backcrosses. The blue phenotype, which can be easily distinguished from the normal color phenotype in newly released juvenile yabbies, was found to be inherited as an autosomal recessive trait. Color phenotype was independent of age for juveniles maintained over a 12-week period, and no association was found between color and sex. The potential for the use of this blue trait as a genetic marker in growth comparisons of yabby strains is discussed.

Effect of Temperature on Molt Increment and Intermolt Period of a Juvenile Australian Fresh-Water Crayfish, Cherax destructor

The effect of 3 temperatures (22, 25, and 28?C) on molt increment and intermolt period in juvenile C. destructor (the yabby) was investigated under laboratory conditions. Newly independent juveniles were grown individually in 1-1 polyethylene containers for 6 molts from molt stages 3-9. Both the intermolt period and molt increment decreased with increasing temperature. The mean intermolt periods were 6.7, 5.5, and 5.0 days and mean molt increments were 102, 98, and 93% at 22, 25, and 28?C, respectively. Regression models derived by combining molt increment and intermolt period data indicated that overall growth increased with increasing temperature. Pairwise comparisons of regression coefficients indicated that the growth rate of juvenile C. destructor at the two higher temperatures (25 and 28?C) did not differ, but was significantly reduced at 22?C. Thus, a shorter intermolt period, in spite of a reduced molt increment, is responsible for superior growth of juveniles of this species at elevated temperatures.

Growth-Related and Antennular Amputation-Induced Changes in the Olfactory Centers of Crayfish Brain

Freshwater crayfish increase in size throughout their lives, and this growth is accompanied by an increase in the length of the appendages and number of mechanoreceptive and chemoreceptive sensilla on them. We find that in the Australian freshwater crayfish Cherax destructor, neuropil volumes of the olfactory centers increase linearly with body size over the entire size range of animals found in their natural habitat. The number of cell somata of two groups of interneurons associated with the olfactory centers (projection neurons and small local neurons) also increases linearly with the size of the animals. In contrast, axon counts of interneurons that represent a nonolfactory input to the olfactory centers show that these reach a total number in the very early adult stages that then remains constant regardless of the size of the animal. Only the axon diameter of these interneurons increases linearly with body size. Amputation of the antennule and olfactory sensilla reduces the number of projection and local interneurons on the amputated side. No change in the size of the olfactory centers occurs on the unamputated side. Amputation of the olfactory receptor neurons in crayfish therefore leads not only to a degeneration of the receptor cell endings in the olfactory lobe but also to a trans-synaptic response in which the number of higher order neurons decreases. Reconstitution of the antennule and olfactory receptor neurons in small adult crayfish is accompanied by the reestablishment of the normal number of interneurons and neuropil volume in the olfactory centers.

Comparison of internal and external markers in digestibility studies involving the Australian freshwater crayfish, Cherax destructor Clark (Decapoda, Parastacidae)

Apparent dry matter and protein digestibility coefficients (DMD and PD, respectively) were determined using several different marker compounds [Cr2O3, ash, crude fibre (CF), hydrolysis resistant ash (HRA) and hydrolysis resistant organic matter (HROM)] for nine different pelleted diets fed to adult Australian freshwater crayfish, Cherax destructor Clark. For a soybean-meal-based diet (Soy-60), HRA resulted in the highest DMD and PD coefficients (98.6 and 99.6%, respectively), while the lowest values were obtained by using CF (DMD, 74.3%; PD, 91.6%). For the series of diets tested, digestibility coefficients determined using Cr2O3 were significantly higher than those obtained using ash or CF, and lower than those obtained using HRA and HROM. Using ash as the marker resulted in a mean reduction in DMD and PD of 12.4% and 5.5%, respectively, compared to Cr2O3. On average, coefficients obtained using CF were 11.8% and 4.2% lower, respectively, than the values obtained using Cr2O3- Despite an overall reduction in the digestibility coefficients estimated using ash, the ash-ratio technique provided a reasonable estimate of nutrient digestibility for some diets. Based on the ease and speed of determination, it is proposed that dietary ash is suitable for use as a digestibility marker in field situations.

Comparison of internal and external markers in digestibility studies involving the Australian freshwater crayfish, Cherax destructor Clark (Decapoda, Parastacidae)

Comparison of internal and external markers in digestibility studies involving the Australian freshwater crayfish, Cherax destructor Clark (Decapoda, Parastacidae)

A Comparison of Natural and Artificial Diets for Juveniles of the Australian Freshwater Crayfish Cherax destructor

Abstract Growth rates of juvenile yabbies Cherax destructor fed a variety of natural and an artificial diet were compared under controlled conditions. Newly independent (stage 3) juveniles were reared individually in 1‐L pomades for 35 d. The best survival and growth were obtained on live zooplankton, frozen zooplankton, shrimp meal pellets and tubifex worms (survival, 100%; mean weights, 608, 444, 380 and 338 mg, respectively). Intermediate growth and survival was exhibited by crayfish fed chironomid larvae, snails and mussels (survival, 80–100%; mean weight, 138–169 mg). Juveniles fed trout muscle, beef heart and yabby tail gave very poor growth and survival (survival, 50–80%; mean weight, 50–55 mg). The use of shrimp meal pellets as a reference diet for juvenile yabbies is discussed.

The ontogeny of GABA- and glutamate-like immunoreactivity in the embryonic Australian freshwater crayfish, Cherax destructor

The distribution and ontogeny of GABA- and glutamate-like immunoreactivity in embryos of the Australian freshwater crayfish Cherax destructor were investigated over the period from 30% development until hatching. GABA-like immunoreactive cells and fibres appeared first in the brain at 40–45% development. By 70% development, GABA-like immunoreactive cells were present in almost all ganglia, and GABA-like immunoreactive fibres were distributed extensively throughout the neuropil, commissures and connectives of the central nervous system, and were also found in peripheral nerve roots supplying the appendages and the abdominal musculature. In contrast, glutamate-like immunoreactivity did not appear in the central nervous system until 60–65% development. By the time of hatching, the distribution of glutamate-like immunoreactivity was restricted to discrete regions of neuropil and fibre staining in the thoracic and abdominal nerve cord, the abdominal musculature and the appendages. The precocious establishment of the extensive distribution of GABA-like immunoreactive neurons in the developing crayfish embryo is consistent with the possibility that these neurons play a trophic role in controlling or modulating the development of the nervous system.

Apparent nutrient digestibility of formulated diets by the Australian freshwater crayfish Cherax destructor Clark (Decapoda, Parastacidae)

Apparent nutrient digestibility of formulated diets by the Australian freshwater crayfish Cherax destructor Clark (Decapoda, Parastacidae)

Apparent nutrient digestibility of formulated diets by the Australian freshwater crayfish Cherax destructor Clark (Decapoda, Parastacidae)

Dry matter (DMD), protein (PD), ash (AD) and crude fibre (CFD) digestibility coefficients were determined for nine different diets fed to the Australian freshwater crayfish Cherax destructor Clark. Diets differed principally in the type and quantity of ingredients used to supply the protein component with fish, meat, soybean, snail, yabby and zooplankton meals comprising the main protein-based ingredients. DMD ranged from 71.8% (soybean meal 40%, Soy-40 diet) to a maximum of 91.4% (zooplankton-based diet). Protein digestibility coefficients were all high and ranged from 88.4% (Soy-0) to 96.0% (Soy-60). Protein digestibility did not appear to be influenced by the principal protein source. Diets that contained a high level of animal or plant-based protein were all highly digestible (PD, 94.1% for the yabby meal-based diet, 80.4% animal protein; PD, 95.2% for the Soy-60 diet, 80.2% plant protein). AD coefficients were highly variable and ranged from 17.3% (snail-based diet) to 73.2% (yabby meal diet). Crude fibre digestibility coefficients were as high as 57% (diet A30: fish/yabby/soybean meal-based diet). No apparent trend occurred in dry matter digestibility in relation to the ash or crude fibre components of the diets. The high digestibility coefficients obtained for a wide variety of diet-types suggests that C. destructor has a versatile digestive system which may reflect its natural polytrophic omnivorous feeding behaviour.

Influence of differential movement of the marker chromic oxide and nutrients on digestibility estimations in the Australian freshwater crayfish Cherax destructor

Faeces were obtained from the Australian freshwater crayfish C. destructor (commonly called the yabby) using a faecal collection system. Daily samples were obtained using 2 different protocols: an 8 h feed immediately followed by a single 4 h collection period, and a 2 h feed followed by 2 separate faecal collections at 10 and 14 h thereafter. Faecal samples using the latter protocol were either analysed separately (as early and late collections) or pooled prior to analysis. The composition of the faeces varied according to the time of deposition. The faecal chromium, protein and ash content were 788, 133 and 244% higher, respectively, in early deposited material compared to faeces collected 4 h later. In contrast the late faecal sample contained about 46% more fibre. The faecal collection period (early versus late) and the collection protocol (single versus pooled) strongly influenced the digestibility estimations. Dry matter (DMD) and protein (PD) digestibility coefficients were 14.1 and 61.1% higher, respectively, for the early deposited faeces compared to the late samples. Ash (AD) and crude fibre (CFD) digestibility coefficients were negative for the late deposited faeces and highly positive for the early samples. The chromium and nutrient content of pooled (early + late) samples, and the resultant digestibility coefficients, were arithmetically located between those values for the early and late collections. The single collection protocol resulted in significantly lower dry matter, protein, ash and crude fibre digestibility coefficients (10.1. 2.8, 13.1, and 54.1%, respectively), than for the pooled collection protocol. C. destructor may be capable of selectively processing certain dietary components whereby low nutrient value foods are rapidly transported through the gut. Despite the limitations of using Cr 2O 3 it is proposed that the errors associated with its use are small providing the majority of the deposited faecal matter is collected.

The effect of dietary protein source on growth and carcass composition in juvenile Australian freshwater crayfish

A feed trial was conducted for 12 weeks on juvenile Australian freshwater crayfish (Cherax destructor) (mean weight (SE) 0.82 (0.02)g) maintained on five isoenergetic diets with a protein content of 30%. Diets differed in the primary source of protein used, with meat, snail, soybean, yabby, and zooplankton meals comprising the major protein ingredient, varying from 56–60% of total protein. Mean percentage weight gain per day ranged from 7.57% (yabby meal diet), to 9.42% (snail meal diet). No significant difference occurred in mean weight, percentage weight gain, specific growth rate (%), or survival among diets. A maximum size of 16.44g was attained on the yabby meal diet. Largest mean weight was 8.27g on the snail-based diet. Food conversion ratios were all good, with a minimum value of 0.95 recorded for the snail-based diet. Initial food consumption per day was approximately 5% of mean animal weight, decreasing to around 2.4%, and is collectively described by a power curve. Protein retention ranged from 29.57% in the zooplankton meal diet to 41.15% in the snail-based diet. Carcass composition was influenced by feed type, with the most marked difference occurring in carapace colour. Animals fed the zooplankton-based pellets developed the strongest pigmentation. Recommendations are made for including certain protein-based ingredients in manufactured yabby diets.