Haemagglutination as a low-cost detection method for gill-associated virus and by inference, yellowhead virus in Penaeus monodon Fabricius, 1798

A quantitative, low‐cost test based on haemagglutination (HA) using chicken erythrocytes was developed to indicate the viral load of Australian yellowhead‐like virus, gill‐associated virus (GAV), in Penaeus monodon. The study tested the haemolymph, gill, lymphoid organ, heart, sub‐cutaneous tissue, eye stalk, pleopods, uropods and the central nerve cord for agglutination activity in 100 prawns, with the haemolymph and gill tissue giving the highest end‐point titres of 1:1370 and 1:361 respectively. The sensitivity of the test was demonstrated by testing two different populations of P. monodon, which showed a highly significant difference (P<0.001) in HA activity, indicating a difference in viral load. By testing three other penaeid prawn species (n=20), Penaeus esculentus, Penaeus merguiensis and Penaeus longistylis, and the crayfish Cherax quadricarinatus, it was demonstrated that natural agglutinins were not causing the high agglutination in the population of P. monodon being tested. It was also demonstrated that there was no effect of freezing and thawing of samples on HA activity. The speed and low cost of this test makes it a very useful tool, particularly in the developing world, for on‐farm testing of penaeid prawns to indicate yellowhead virus and GAV loads which can contribute to management practices with respect to harvesting of ponds.     

Histological examination of final oocyte maturation and atresia in wild and domesticated Penaeus monodon (Fabricius) broodstock

Oocyte maturation and gonadosomatic index (GSI) of eyestalk ablated Penaeus monodon females collected from the wild and from two first‐generation domesticated lines were assessed. Frequency and diameter of the different oocytes, and the intensity of oocyte atresia, were compared among groups through histological assessments of the sections of the middle ovarian lobe. Digitized images from ovary sections were used to record the frequency and diameter of different oocyte types. Spawning performance of the three groups were expressed in terms of the percentage of females that spawned at least once (productive females), time from eyestalk ablation to first spawning (latency period) and the number of spawnings per female stocked. Final ovarian maturation was attained in all groups, as indicated by the presence of mature oocytes with cortical rods (cortical oocytes), dark‐green ovarian colour and high GSI values (5.83–6.86%). However, domesticated groups presented significant larger immature oocyte types (previtellogenic and yolky oocytes) and smaller cortical oocytes compared with wild females, indicating a reduced vitellogenic activity during final oocyte maturation. Additionally, the frequency of atresia was comparatively higher for both domesticated groups, which could be related to their inferior spawning performance. The implications of these results on the reproductive potential and development of domesticated P. monodon are discussed.     

CONSUMPTION OF FROZEN AND LIVE Artemia BY PROTOZOEA OF Penaeus setiferus

The role of an animal component in the diet of protozoeal penaeid shrimp larvae is not known. Short-term experiments were performed on the larvae of Penaeus setiferus (L.) to determine the ability of each protozoeal substage to consume frozen and live Artemia nauplii. Significant consumption of frozen Artemia took place during the protozoea 2 and 3 substages at rates of 1.0 and 1.6 Artemia nauplii/penaeid larva/hour respectively. Consumption of live Artemia occurred in the protozoea 3 substage, at a rate of 0.7 Artemia nauplii/penaeid larva/hour. Data suggesting that there is a beneficial role of an animal component in the diet of protozoeal penaeid shrimp larvae are discussed.     

Profitability evaluation of resource allocation for growing redtail and Chinese shrimp

A farming survey was conducted to evaluate the profitability of resource allocation for producing redtail shrimp, Penaeus penicillatus (Alock) and Chinese shrimp, P. chinensis (Osbeck). Data on production costs and total revenue according to different harvest sizes of shrimp species were collected based on 108 individual ponds operated by 25 surveyed shrimp farmers. The results indicated that growing Chinese shrimp to a marketable size of 12 g was the most profitable management strategy. The profits could be maximized by integrating small-scale farms to a 12.41 ha optimal farming area when the available resources remained the same as those for a 10 ha farm.     

Maturation and spawning performance of pond-reared Penaeus merguiensis in different combinations of temperature, light intensity and photoperiod

The combined effects of temperature (23 and 27 °C), light intensity (1100 and 2 lux or ≈ 21.5 and 0.04 μEinst m^?2 s respectively) and photoperiod (10 h light/14 h dark and 14 h light/10 h dark) on ovarian maturation and spawning performance of ablated pond‐reared Penaeus merguiensis were investigated in a 51‐day experiment. The results showed that temperature was the most influential factor, followed by light intensity, whereas the effect of photoperiod was minor. As the maturation process progressed, the effects of temperature and light intensity became stronger while that of photoperiod became less significant. Temperature significantly affected all the reproductive parameters assessed. Prawns in the 27 °C treatments outperformed those in the 23 °C treatments (P < 0.05). The effect of light intensity was found to have a significant effect (P < 0.05) only on the proportion of spawners (prawns that spawned) and spawning rate. More prawns spawned at a higher rate under dim light (2 lux) than under strong light (1100 lux). Photoperiod affected only the proportion of prawns reaching stage III of ovarian development (P < 0.05). There were interactions between temperature and light intensity affecting the proportion of prawns reaching stage III and, although not significantly, the proportion of spawners (P = 0.177), fecundity (P = 0.134) and survival (P = 0.061). Overall, it is recommended that a combination of 27 °C, 2 lux and 10 h light/14 h dark is suitable for the maturation of pond‐reared P. merguiensis. There were indications that temperature can be used to control the rate of ovarian maturation. Also, it is possible to increase light intensity up to 1100 lux in P. merguiensis hatcheries if prawns are ablated.     

Penaeus monodon (Fabricius) and Penaeus merguiensis (de Man) biculture in East Java, Indonesia

Shrimp farmers in South-East Java have recently observed a decline in Penaeus monodon (Fabricius) production. To stabilize overall production, some farms have switched partially to biculture of P. monodon and P. merguiensis (de Man). The production from 33 ponds in two of these farms was analysed. In addition, the water quality in 10 ponds was monitored over the entire culture period. Information was also available on the post-larvae (PL) source and feed used per pond. Water quality remained stable during the culture period and there was no accumulation of organic material during the second half of the culture period. Stocking P. merguiensis 2 months after P. monodon partially compensated for the low production of P. monodon, thereby stabilizing overall production. When the production of P. monodon is low, the production of P. merguiensis is high and vice versa (P<0.001). Feed source had no effect on production when stocking density was included as a covariable in the analysis (P > 0.05), while P. monodon PL source caused production to differ by a factor of three (P<0.001). It was concluded that biculture of P. monodon and P. merguiensis is an effective way to stabilize overall shrimp production.     

Spawning behaviour of Penaeus (Fenneropenaeus) merguiensis de Man and the effect of light intensity on spawning

An experiment was conducted to investigate the effect of light intensity just prior to and during spawning of Penaeus (Fenneropenaeus) merguiensis de Man in the laboratory. Neither the presence of light nor light intensity (0, 10 and 1100 lux) had a significant effect on the spawning process or hatching rate in P. merguiensis. Difference in the percentage of spawners, percentage of incomplete spawning, fecundity and hatching rate were all insignificant (P > 0.05) among the three light treatments. However, spawning was delayed (up to 21 min on average) under 1100 lux with a high percentage of incomplete spawning, compared with the Control (0 lux). For the first time, spawning behaviour of P. merguiensis was observed and fully described. The spawning process can be divided into four phases: dormant, pre‐spawning, spawning and post‐spawning by distinct behaviour of prawn broodstock. The dormant phase was characterized by a quiescent and non‐feeding period, whereas movement of prawn broodstock was active during the pre‐spawning and post‐spawning phases. Depending on the individual, spawning was completed within 3–5 min. Prawns often stayed still on the water surface during spawning with occasional manoeuvres to change the position. After a short rest at the termination of the spawning phase, prawn broodstock re‐exhibited active movement as in the pre‐spawning phase, but showing conspicuous care to the deposited eggs. The role of light in controlling ovarian development and spawning, and the behaviour of prawn broodstock in relation to maximizing fertilization rate are discussed.     

Morphogenesis of the membranous labyrinth in penaeid shrimp cells infected with Penaeus monodon bacuiovirus (MBV)

The morphogenesis of a highly organized cellular membrane structure, a membranous labyrinth (ML), in the cells of penaeid shrimp infected with Penaeus monodon baculovirus (MBV) is described. The ML possibly originates from dilated Golgi apparatus, endoplasmic reticulum (ER) or the outer nuclear membrane. The ML apparently grows by proliferation of the cellular membranes of these systems. In addition, its degree of development was correlated with stages of MBV reproduction.     

Observations on growth, sexual maturity and spawning performance of pond-reared Penaeus merguiensis

This 12‐month preliminary study investigated the development of sexual characters, primary sexual maturity, ovarian maturity and spawning performance of pond‐reared Penaeus merguiensis in relation to culture conditions in south‐east Queensland, Australia. Post‐larvae of P. merguiensis were produced and cultured in two 60‐m³ tanks during the first 14 weeks. Before winter, they were harvested and stocked in three different overwintering facilities: a 200‐m² covered pond, two 60‐m³ outdoor tanks and a 15‐m³ indoor, recirculated tank at a stocking density of 10 individuals m^?2. The development of sexual characters was found to be similar to that reported previously in wild P. merguiensis. Males matured at younger ages and smaller sizes than females. Overall, the average size at primary sexual maturity of pond‐reared P. merguiensis was 23.1 mm carapace length for males (possessed spermatophores) and 29.3 mm for females (being impregnated). Water temperature and the availability of natural food strongly influenced prawn growth, maturity rate and their subsequent spawning performance. Growth, maturity rate and spawning performance of prawns in the covered pond were significantly higher than in the other overwintering facilities. Prawns started mating at 6–7 months, reached full ovarian maturation and spawned as early as about 8 (peaked at 9–11) months from hatching, producing high fecundity and viable larvae. There was a strong relationship (P < 0.001) between prawn size and fecundity. The results of this study suggest a potential for using pond‐reared broodstock P. merguiensis for hatchery production and for domestication or selective breeding programmes.     

High allozyme variation and genetic similarity of two populations of commercial penaeids, Penaeus brevirostris (Kingsley) and P. vannamei (Boone), from the Gulf of California

Genetic resources assessment is considered as the starting point for population management in both fisheries and aquaculture. In this study, we have obtained genetic variability measures of two commercial penaeid shrimp species, Penaeus brevirostris (Kingsley) and P. vannamei (Boone), from the Gulf of California by means of starch electrophoresis analysis of 16 enzymatic systems, plus total protein. Thirty-two loci were resolved, which revealed polymorphism values (P₉₅) of 15.63% in P. brevirostris and 25.00% in P. vannamei. Unbiased expected heterozygosity (H_e) was 0.076 and 0.105 respectively. These are high genetic variability figures, taking into account the previously low genetic variability, assessed by means of allozyme variation, reported in several penaeid species around the world. Nei’s genetic similarity between the two species is 0.891.     

Patterns of oocyte development in natural habitat and captive <Emphasis Type="Italic">Salminus hilarii</Emphasis> Valenciennes, 1850 (Teleostei: Characidae)

Fecundity and oocyte development in Salminus hilarii female brood stock were analyzed with the aim of investigating the impact of migration impediment on oogenesis. Histological analyses of the ovaries were performed in adult females caught in two different environments—the Tietê River (natural) and captivity—and the gonadossomatic index, oocyte diameter and fecundity determined. Five germ cell development stages (oogonium, perinucleolar, cortical alveoli, vitellogenic, ripe) and two other structures (postovulatory follicles and atretic oocytes) were observed in females caught in the river. Captive animals lacked the ripe oocytes and postovulatory follicles and had a relatively higher number of atretic oocytes. Females in captivity are known to produce larger oocytes, and they release fewer eggs in each spawn (absolute fecundity) when compared with animals that are able to migrate. Our results suggest that the Tietê River is undergoing alterations which are being reflected in the reproductive performance of S. hilarii, mainly due to the presence of atretic oocytes in females caught in the river. The lack of postovulatory follicles and ripe oocytes in captive animals reveals that migratory impediment negatively impacts final oocyte maturation. However, the stage of maturation reached is adequate for ovulation induction with hormone manipulation.     

Artificial substratum consisting of poly‐β‐hydroxybutyrate‐based biodegradable plastic improved the survival and overall performance of postlarval tiger shrimp Penaeus monodon

The use of artificial substratum consisting of poly‐β‐hydroxybutyrate (PHB)‐based biodegradable plastic for penaeid shrimp culture was investigated in the present study. The survival of postlarval tiger shrimp Penaeus monodon (30 ± 5 mg) provided with PHB substratum made out of PHB type DP9002 (Metabolix GmbH, Köln, Germany) was 88.7 ± 3.4% and this was significantly higher as compared to postlarvae provided conventional substratum consisting of polyvinylchloride (PVC) pipes (67.3 ± 6.5%). However, no significant weight improvement was observed for the postlarval tiger shrimp indicating that PHB could not be used as growth promoter. Nevertheless, a trend of improved robustness against adverse environmental conditions (lethal ammonium chloride concentration) and increased resistance to pathogenic Vibrio was observed in postlarval tiger shrimp provided with PHB substratum as compared to postlarvae provided with PVC substratum. Results indicate higher preference by postlarvae on PHB substratum over PVC substratum. Overall, this study indicates the potential of artificial substratum consisting of PHB‐based biodegradable plastic as replacement for conventional substratum consisting of PVC pipes in enhancing the survival of postlarval tiger shrimp and improving its performance against adverse environmental conditions and disease resistance.     

Tissue distribution of hepatopancreatic parvo‐like virus of shrimp in freshwater rice‐field crab,Paratelphusa hydrodomous (Herbst)

An attempt was made to determine the replication efficiency of hepatopancreatic parvo‐like virus (HPV) of shrimp in different organs of freshwater rice‐field crab Paratelphusa hydrodomous (Herbst) using bioassay, PCR, RT‐PCR, ELISA, Western blot and q‐PCR analyses. Another attempt was made to use this crab as an alternative to penaeid shrimp for the large‐scale production of HPV. This crab was found to be highly susceptible to HPV by intramuscular injection. The systemic HPV infection was confirmed by PCR and Western blot analyses in freshwater crab. The expression of capsid protein gene in different organs of infected crab was revealed by RT‐PCR analysis. Indirect ELISA was used to quantify the capsid protein in different organs of the crab. The copy number of HPV in different organs of the infected crab was quantified by q‐PCR. The results revealed a steady decrease in C_T values in different organs of the infected crab during the course of infection. The viral inoculum that was prepared from different organs of the infected crab caused significant mortality in post‐larvae of tiger prawn, Penaeus monodon (Fabricius). The results revealed that this rice‐field crab could be used as an alternative host for HPV replication and also for large‐scale production of HPV.     

Hollow sperm syndrome during spermatogenesis in the giant tiger shrimp Penaeus monodon (Fabricius 1798) from eastern Australia

During spermatogenesis, giant tiger shrimp (Penaeus monodon) from Queensland, eastern Australia had a high proportion of testicular spermatids that appeared ‘hollow’ because their nuclei were not visible with the haematoxylin and eosin stain. When examined by transmission electron microscopy, the nuclei of hollow spermatids contained highly decondensed chromatin, with large areas missing fibrillar chromatin. Together with hollow spermatids, testicular pale enlarged (PE) spermatids with weakly staining and marginated chromatin were observed. Degenerate‐eosinophilic‐clumped (DEC) spermatids that appeared as aggregated clumps were also present in testes tubules. Among 171 sub‐adult and adult P. monodon examined from several origins, 43% displayed evidence of hollow spermatids in the testes, 33% displayed PE spermatids and 15% displayed DEC spermatids. These abnormal sperm were also found at lower prevalence in the vas deferens and spermatophore. We propose ‘Hollow Sperm Syndrome (HSS)’ to describe this abnormal sperm condition as these morphological aberrations have yet to be described in penaeid shrimp. No specific cause of HSS was confirmed by examining either tank or pond cultured shrimp exposed to various stocking densities, temperatures, salinities, dietary and seasonal factors. Compared with wild broodstock, HSS occurred at higher prevalence and severity among sub‐adults originating from farms, research ponds and tanks. Further studies are required to establish what physiological, hormonal or metabolic processes may cause HSS and whether it compromises the fertility of male P. monodon.     

Production of second generation penaeid shrimp,Penaeus stylirostris,from Mexico

The life cycle of the penaeid shrimp, Penaeus stylirostris, was completed in captivity with the production of F₂ generation nauplii. Over one million F₂ generation nauplii were harvested from the F₁ generation represented by laboratory-reared adult shrimp. The studies were completed in a laboratory simulated, tropical environment for maturation and spawning, and in pond systems located in a temperate environment for growout of the F₁ generation.     

Bioprospection of Microalgae and Cyanobacteria as Biocontrol Agents Against Vibrio campbellii and Their Use in White Shrimp Litopenaeus vannamei Culture

Vibrio spp. are the most common and harmful shrimp pathogenic bacteria; however, microalgae and cyanobacteria have the ability to produce antimicrobial substances against these species. In this study, the organic and aqueous extracts of 28 species of marine microalgae and cyanobacteria were screened against Vibrio campbellii M1. Two of these phytoplankton species with antibacterial activity in aqueous extracts (Dunaliella tertiolecta and Skeletonema costatum) and nontoxic to brine shrimp Artemia franciscana nauplii were used to evaluate their anti‐Vibrio effect when used as green‐water cultures in Vibrio‐challenged white shrimp Litopenaeus vannamei cultures. No differences in mortality of juvenile L. vannamei were observed between treatments tested, suggesting that the pathogenicity of V. campbellii could be related to the growth stage of shrimp. The proximal composition of D. tertiolecta and S. costatum was in the recommended range for penaeid shrimp nutrition, allowing shrimp supplemented with these microalgae to have significantly greater total length and weight than control shrimp. Shrimp supplemented with S. costatum presented the highest values of organic mass (11.48 mg/organism) and growth rate (0.31 mg/d) in comparison to D. tertiolecta. These results indicate that microalgae are not only capable of producing antibacterial compounds against Vibrio but can also help shrimp nutrition.     

中国对虾卵子激活过程的形态学研究

报道了对中国对虾卵子激活反应的形态学研究。中国对虾卵子皮层中有由卵黄膜下陷形成的与卵表垂直的皮层囊,内有棒状结构称棒状周边体,其内物质为凝胶前体。对虾卵子的激活并不需要精子的发动,而是在卵子与海水接触后即开始进行。在卵子激活过程中,棒状周边体向外放出形成花冠状的凝胶层,然后从基部开始逐渐消失并向远端扩展,最后完全消失,同时卵子进行成熟分裂放出第一、第二极体,并举起受精膜,完成激活反应。还对中国对虾卵子激活的作用进行了讨论。     

Ovarian maturation stages of the mud crab Scylla serrata

Ovarian maturation in adult wild‐sourced and pond‐grown Scylla serrata (Forsskål) was determined based on gross morphology and histological appearance. There were no significant differences noted in the histological features of both wild and pond‐reared S. serrata females. Ovarian maturation was classified into five stages: immature, early maturing, late maturing, fully mature and spent. The immature ovaries are thin and translucent to off white and contain oogonia, primary oocytes with large nuclei. The follicle cells were found around the periphery of the lobes and an area among groups of oogonia and oocytes. The follicle cells gradually enclosed the oocytes. The early‐maturing ovaries were yellow and small yolk globules started to appear in larger oocytes. In late‐maturing ovaries, the colour became light orange and lobules were apparent. Yolk globules occurred in the cytoplasm with larger globular inclusions towards the periphery, while follicle cells were hardly recognizable. Fully mature ovaries were orange to deep orange and had swollen lobules. Large yolk globules were apparent in the entire cytoplasm. Follicle cells were hardly seen. Spent ovaries were similar to the early‐maturing and late‐maturing stage in partially spawned females. The ovarian development was correlated closely to the gonadosomatic index, oocyte diameter, and ovarian histology. The classification of ovarian maturation provides baseline information for further studies on reproductive biology. Likewise, the information provides a guide for broodstock management in the hatchery.     

An hypothesis on the light requirements for spawning penaeid shrimp,with emphasis on Penaeus setiferus

Using standard equations, we have concluded that the light intensities which have been used by investigators attempting to induce maturation and spawning are up to 4000 times higher than would occur over the spawning grounds of Penaeus setiferus, a species for which successful controlled spawning has yet to be achieved. We recommend that future attempts at captive maturation and spawning with that species be conducted at light levels of no more than 12 μW cm^?2 and that the intensity at which other species of shrimp are matured and spawned be examined relative to natural light levels on their spawning grounds. It is further recommended that the need for light of blue or green color be evaluated for its role as a promotor of maturation and spawning. The intent of these modifications in current spawning procedures is to eliminate the need for eyestalk ablation in captively spawned penaeid shrimp.