Production of triploid Kuruma shrimp, Marsupenaeus (Penaeus) japonicus (Bate) nauplii through inhibition of polar body I, or polar body I and II extrusion using 6-dimethylaminopurine

This study investigated the chromosome ploidy level of Marsupenaeus (Penaeus) japonicus (Bate) non-viable (unhatched) embryos and nauplii after exposure to 6-dimethylaminopurine (6-DMAP), timed to stop either polar body (PB) I, or PBI and II extrusion. Embryos from eight separate families or spawnings were exposed to 150 or 200 mu M 6-DMAP from 1- to 3-min post-spawning detection (psd) for a 4- to 5-min duration (timed to stop PBI extrusion). Separate aliquots of embryos from five of the same spawnings were also exposed to 200 mu M of 6-DMAP from 1- to 3-min psd for a 16-min duration (timed to stop both PBI and II extrusion). For one spawning, a third aliquot of embryos was exposed to 400 p M of 6-DMAP from 1- to 3-min psd for a 16-min duration (timed to stop both PBI and II extrusion). At 18-h psd, non-viable embryo and nauplii samples were taken separately for fluorescent activated cell sorting (FACS). FACS revealed that there were diploids and triploids among all treated non-viable embryos and nauplii. All control non-viable embryos and nauplii were diploid. Percentages of triploid induction for the 4- to 5-min and 16-min durations were not significantly different (P > 0.05). Additionally, no difference was found in the triploidy level of nonviable embryos compared to nauplii in these treatments. The percentage of triploid embryos and nauplii when exposed to 6-DMAP for a 4- to 5-min duration ranged from 29.57% to 99.23% (average 55.28 +/- 5.45%) and from 5.60% to 98.85% (average 46.70 +/- 7.20%), respectively. The percentage of triploid embryos and nauplii when exposed to 6-DMAP for a 16-min duration ranged from 11.71% to 98.96% (average 52.49 +/- 11.00%) and from 47.5% to 99.24% (average 79.38 +/- 5.24%), respectively. To our knowledge, this is the first documentation of successful PBI or PBI and II inhibition in shrimp. This study conclusively shows that treatment of M. japonicus embryos with 6-DMAP at 1- to 3-min pscl for either a 4- to 5-min duration (timed to stop PBl extrusion) or 16-min duration (timed to stop both PBI and II extrusion) results in viable triploid nauplii. (c) 2006 Elsevier B.V. All rights reserved.

Isolation and molecular identification of planctomycete bacteria from postlarvae of the giant tiger prawn, Penaeus monodon

Bacteria phenotypically resembling members of the phylogenetically distinct planctomycete group of the domain Bacteria were isolated from postlarvae of the giant tiger prawn, Penaeus monodon. A selective medium designed in the light of planctomycete antibiotic resistance characteristics was used for this isolation. Planctomycetes were isolated from both healthy and monodon baculovirus-infected prawn postlarvae, The predominant colony type recovered from postlarvae regardless of viral infection status was nonpigmented. Other, less commonly observed types were pink or orange pigmented, A planctomycete-specific 16S rRNA-directed probe was designed and used to screen the isolates for their identity as planctomycetes prior to molecular phylogenetic characterization. 16S rRNA genes from nine prawn isolates together with two planctomycete reference strains (Planctomyces brasiliensis and Gemmata obscuriglobus) were sequenced and compared with reference sequences from the planctomycetes and other members of the domain Bacteria, Phylogenetic analyses and sequence signatures of the 16S rRNA genes demonstrated that the prawn isolates were members of the planctomycete group, Five representatives of the predominant nonpigmented colony type were members of the Pirellula group within the planctomycetes, as were three pink-pigmented colony type representatives. Homology values and tree topology indicated that representatives of the nonpigmented and pink-pigmented colony types formed two discrete clusters within the Pirellula group, not identical to any known Pirellula species, A sole representative of the orange colony type was a member of the Planctomyces group, virtually identical in 16S rDNA sequence to P. brasiliensis, and exhibited distinctive morphology.

The effects of temperature on the growth, survival and biomass of different families of juvenile Penaeus japonicus Bate

Variation in the growth, survival and change in total biomass (termed biomass increase) of different families of juvenile Penaeus japonicus was investigated over a range of temperatures in controlled laboratory experiments. In the first experiment, the effects of temperature on six families of juveniles were examined over a broad range of temperatures (24 to 30 degreesC). In the second experiment, the effects of temperature on six more families of juveniles were examined over a narrower range of temperatures (27.5 to 31.2 degreesC). Over the broad temperature range, mean growth and biomass increase were highest at 27 degreesC and mean survival was highest at 24 degreesC. Mean growth was lowest at 24 degreesC, whilst survival and biomass increase were lowest at 30 degreesC. However, there was a significant interaction between family and temperature, with some families tolerating a broader range of temperatures than others. As a result, the ranking of families in relation to growth, survival and biomass increase changed at each temperature. This effect was more pronounced for survival than for growth. Over the narrower range, temperature significantly affected growth, survival and biomass increase, but there was no significant interaction between family and temperature. Growth, survival and biomass increase were significantly lower at 31.2 than at 27.5 and 29.2 degreesC. These results suggest that if grow-out conditions for P. japonicus vary by more than a few degrees, interactions between family and temperature could affect the efficiency of selection. The results also suggest that the family x temperature interaction may have a more pronounced effect on survival than on growth. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.

The effects of density on the growth and survival of different families of juvenile Penaeus japonicus Bate

Variations in the growth and survival of six families of juvenile (initial mean weight = 4.16 g) Penaeus japonicus were examined at two densities (48 and 144 individuals m(-2)) in a controlled laboratory experiment. Survival was very high throughout the experiment (95.4%), but differed significantly between densities and rearing tanks. Family, sex and family x density interaction did not significantly affect survival. Mean specific growth rate (SGR) of the shrimp was 18% faster at the low density (1.93 +/- 0.05% day(-1)) than at high density (1.64 +/- 0.03% day(-1)). However, there was a small but significant interaction between family and density indicating that growth of the families was not consistent at both densities. The inconsistent growth of the families across the two densities resulted in a change in the relative performance (ranking) of families at each density. Sex, rearing tank and rearing cage also affected growth of the shrimp. Mean SGR of the females (1.79 +/- 0.03% day(-1)) was 5% faster than males (1.70 +/- 0.03% day(-1)) when averaged across both densities. Shrimp grew significantly faster in rearing tank 3 than rearing tank 1 or 2 at both densities. Results of the present study suggest that family x density interaction could affect the efficiency of selection for growth if shrimp stocks produced from shrimp breeding programs are to be grown across a wide range of densities. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved.

Application of DNA parentage analyses for determining relative growth rates of Penaeus japonicus families reared in commercial ponds

The ability to track large numbers of individuals and families is a key determinant of the power and precision of breeding programs, including the capacity to quantify interactions between genotypes and their environment. Until recently, most family based selective breeding programs for shrimp, and other highly fecund aquaculture species, have been restricted by the number of animals that can be physically tagged and individually selected. Advances in the development of molecular markers, such as microsatellite loci, are now providing the means to track large numbers of individuals and families in commercial production systems. In this study microsatellites, coupled with DNA parentage analyses, were used to determine the relative performance of 22 families of R japonicus reared in commercial production ponds. In the experimental design 6000 post-larvae from each of 22 families, whose maternal parents had been genotyped at 8 microsatellite loci, were stocked into each of four I ha ponds. After 6 months the ponds were harvested and a total of 6000 individuals were randomly weighed from each pond. Mean wet weight of the shrimp from one pond was significantly lower than that of the other three ponds demonstrating a possible pond effect on growth rate. The representation of families in the top 10% of each pond's weight distribution was then determined by randomly genotyping up to 300 individuals from this upper weight class. Parentage analyses based on individual genotypic data demonstrated that some families were over-represented in the top 10% in all ponds, while others were under-represented due to slower growth rates. The results also revealed some weak, but significant, male genotype x environment (G x E) interactions in the expression of shrimp growth for some families. This indicates that G x E effects may need to be factored into future R japonicus selective breeding programs. This study demonstrated the utility of DNA parentage analyses for tracking individual family performance in communally stocked shrimp pond populations and, its application to examining G x E effects on trait expression under commercial culture conditions. Crown Copyright (c) 2005 Published by Elsevier B.V. All rights reserved.

Quantifying the effects of bycatch reduction devices in Queensland's (Australia) shallow water eastern king prawn (Penaeus plebejus) trawl fishery

This study presents results from an experimental 10-day research charter that was designed to quantify the effects of (a) a turtle excluder device (TED), (b) a radial escape section bycatch reduction device (BRD) and (c) both devices together, on bycatch and prawn catch rates in the Queensland shallow water eastern king prawn (Penaeus plebejus) trawl fishery. The bycatch was comprised of 250 taxa, mainly gurnards, whiting, lizard fish, flathead, dragonets, portunid crabs, turretfish and flounders. The observed mean catch rates of bycatch and marketable eastern king prawns from the standard trawl net (i.e., net with no TED or BRD) used during the charter were 11.06 kg/hectare (ha(-1)) (S.E. 0.90) swept by the trawl gear and 0.94 kg ha(-1), respectively. For the range of depths sampled (20.1-90.7 m), bycatch rates declined significantly at a rate of 0.14 kg ha-1 for every 1 m increase in depth, while prawn catch rates were unaffected. When both the TED and radial escape section BRD were used together, the bycatch rate declined by 24% compared to a standard net, but at a 20% reduction in marketable prawn catch rate. The largest reductions were achieved for stout whiting Sillago robusta (57% reduction) and yellowtail scad Trachurus novaezelandiae (32% reduction). Multidimensional scaling and analysis of similarities revealed that bycatch assemblages differed significantly between depths and latitude, but not between the different combinations of bycatch reduction devices. Despite the lowered prawn catch rates, the reduced bycatch rates are promising, particularly for S. robusta, which is targeted in another fishery. Prawn trawl operators are not permitted to retain S. robusta and the devices examined herein offer the potential to significantly reduce the incidental fishing mortality that this species experiences. (c) 2006 Elsevier B.V. All rights reserved.

Esterified astaxanthin levels in lobster epithelia correlate with shell colour intensity: Potential role in crustacean shell colour formation

Carotenoids, particularly astaxanthin, are the primary pigment in crustacean shell colour. Sub-adults of the western rock lobster, Panulirus cygnus, moult from a deep red colour (termed the red phase) to a much paler colour (the white phase) at sexual maturation. We observe a 2.4-fold difference in the amount of total carotenoid present in the shell extracts of reds compared to whites, as might be expected. However, analysis of the underlying epithelium shows that there is no correlation with shell colour and the amount of free (unesterified) astaxanthin-the level of free astaxanthin in reds and whites is not significantly different. Instead, we observe a correlated two-fold difference in the amount of esterified astaxanthin present in the epithelium of red versus white individuals. These data suggest a role for esterified astaxanthin in regulating shell colour formation and suggest that esterification may promote secretion and eventual incorporation of unesterified astaxanthin into the exoskeleton. (c) 2005 Elsevier Inc. All rights reserved.

The effectiveness of heat, cold and 6-dimethylaminopurine shocks for inducing tetraploidy in the Kuruma shrimp, Marsupenaeus japonicus (Bate)

In this study tetraploid Marsupenaeus japonicus (Bate) embryos were produced by preventing the first division in mitosis. The effectiveness of temperature and chemical shocks for producing tetraploid M. japonicus were assessed when applied at different times postspawning and for different durations. Tetraploid M. japonicus embryos (spawned at 27 degrees C) were produced by heat shocks at 35 degrees C and 36 degrees C in three and eight spawning samples respectively, and a cold shock at 5 degrees C in a single spawning sample. All temperature shocks inducing tetraploidy were applied 18-23 min postspawning for a 5-10 min duration. The percentage of spawnings successfully inducing tetraploid embryos (i.e., frequency of induction) ranged from 33.33% to 66.67% for the 21, 22 and 23 min postspawning heat shock treatment regimes. The percentage of tetraploid embryos within an induction (i.e., induction rate), as determined by flow cytometry, ranged from 8.82% to 98.12% (ave. S.E.) (34.4 +/- 21.4%) for the 35 degrees C shock treatments, from 13.12% to 61.02% (35.0 +/- 5.0%) for the 36 degrees C shock treatments and was 15% for the 5 degrees C cold shock treatment. No tetraploids were produced for spawnings that received heat shocks above 36 degrees C or below 35 degrees C, or for cold shocks above 5 degrees C for any of the tested postspawning treatment and duration times. Chemical shock with 150 mu M 6-dimethylaminopurine did not result in tetraploid M. japonicus embryos at any of the tested postspawning treatment times and durations. Tetraploid M. japonicus embryos were nonviable, with no tetraploid larvae being detected by flow cytometry. Based on our results heat shocking of M. japonicus embryos at 36 degrees C, 23 min postspawning for a 5-10 min duration is the most effective means to produce tetraploids through inhibition of the first mitotic division (taking into consideration the importance of frequency and induction rate equally).

Reproductive dynamics of endeavour prawns, Metapenaeus endeavouri and M-ensis, in Albatross Bay, Gulf of Carpentaria, Australia

The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort, and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths < 50 m and was concentrated particularly in inshore waters ( 50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (

The efficiency and condition of oysters and macroalgae used as biological filters of shrimp pond effluent

Current shrimp pond management practices generally result in elevated concentrations of nutrients, suspended solids, bacteria and phytoplankton compared with the influent water. Concerns about adverse environmental impacts caused by discharging pond effluent directly into adjacent waterways have prompted the search for cost-effective methods of effluent treatment. One potential method of effluent treatment is the use of ponds or raceways stocked with plants or animals that act as natural biofilters by removing waste nutrients. In addition to improving effluent water quality prior to discharge, the use of natural biofilters provides a method for capturing otherwise wasted nutrients. This study examined the potential of the native oyster, Saccostrea commercialis (Iredale and Roughley) and macroalgae, Gracilaria edulis (Gmelin) Silva to improve effluent water quality from a commercial Penaeus japonicus (Bate) shrimp farm, A system of raceways was constructed to permit recirculation of the effluent through the oysters to maximize the filtration of bacteria, phytoplankton and total suspended solids. A series of experiments was conducted to test the ability of oysters and macroalgae to improve effluent water quality in a flow-through system compared with a recirculating system. In the flow-through system, oysters reduced the concentration of bacteria to 35% of the initial concentration, chlorophyll a to 39%, total particulates (2.28-35.2 mum) to 29%, total nitrogen to 66% and total phosphorus to 56%. Under the recirculating flow regime, the ability of the oysters to improve water quality was significantly enhanced. After four circuits, total bacterial numbers were reduced to 12%, chlorophyll a to 4%, and total suspended solids to 16%. Efforts to increase biofiltration by adding additional layers of oyster trays and macroalgae-filled mesh bags resulted in fouling of the lower layers causing the death of oysters and senescence of macroalgae. Supplementary laboratory experiments were designed to examine the effects of high effluent concentrations of suspended particulates on the growth and condition of oysters and macroalgae. The results demonstrated that high concentrations of particulates inhibited growth and reduced the condition of oysters and macroalgae. Allowing the effluent to settle before biofiltration improved growth and reduced signs of stress in the oysters and macroalgae. A settling time of 6 h reduced particulates to a level that prevented fouling of the oysters and macroalgae.

The effects of ionizing radiation on the reproductive capacity of adult Penaeus (Marsupenaeus) japonicus (Bate)

The reproductive capacity of adult Penaeus (Marsupenaeus) japonicus (Bate) was assessed after exposure to ionizing gamma radiation from a cobalt-60 source. Males and females were each exposed to 0, 10 and 20 Gray (Gy) of ionizing radiation (IR) and reciprocally crossed to give nine mating combinations. Fecundity and hatch rate of resulting spawnings were used as measures of reproductive capacity. IR significantly (P