Mating behaviour in the penaeid shrimp Penaeus vannamei

Mating behaviour of Penaeus vannamei was observed during January, 1986. Mating behaviour was divided into four phases: (1) approach, (2) crawling, (3) chasing, and (4) mating. Male mating and spermatophore transfer to the mature female take place at intermolt stage C₄. The glutinous spermatophore emitted from the male can be transferred onto the female open thelycum during the ventralto-ventral position in mating in P. vannamei. Though male P. vannamei often chase males or immature females with undeveloped ovaries, no males were ever mated and mating only occurred in females with ripe ovaries.     

External synchronizers of tidal activity rhythms in the prawns Penaeus indicus and P. monodon

Phasing of persistent circatidal rhythmicity to an artificial tidal cycle was assessed in the prawns Penaeus indicus Milne Edwards and P. monodon (Fabricius) collected from the Vellar estuary, South India, in the period between June and December 1984. Simulated 6 h cycles of 20 and 30 S, and 6 h cycles of 20° and 30°C induced a persistent tidal rhythmicity after 20 cycles. The imposed 6 h cycles of 25 and 30 S, and 25° and 30°C induced tidal rhythms after 30 cycles. In both cases, re-established tidal activity rhythms were evident for at least 48 h — higher activity occurring during the higher salinity and lower temperature phases of the simulated tidal cycles. Artificial tidal cycles of still water and running water synchronized the tidal rhythm after 20 cycles. Combined 30 S, 20°C, for 6 h and 20 S and 30°C for 6 h established a persistent tidal rhythm after 10 cycles, whereas wave action had no influence on tidal synchronization. The influence of possible interactions of tidal rhythms and in situ tidal variables on circatidal activity is discussed.     

Biochemical responses during starvation and subsequent recovery in postlarval Pacific white shrimp,Penaeus vannamei

Postlarval shrimp, Penaeus vannamei Boone, 1931, were held individually in cages and exposed to two feeding regimes. One group was starved for 12 d and then fed during the following 12 d. A second group was fed throughout the 24 d study. Four individuals were sampled from each of the two groups on Days 0, 1, 2, 4, 8, 12, 13, 14, 16, 20, and 24. Molting and growth among the starved-fed postlarvae stopped after 2 d starvation, while fed postlarvae increased significantly in size throughout the 24 d study. Among the starved-fed postlarvae, water content increased rapidly in response to starvation. DNA and sterol concentrations increased significantly during starvation due to selective catabolism of cellular components. After 12 d, RNA concentration was not significantly different between the fed and starved-fed postlarvae, but became significantly higher in the starved-fed postlarvae 48 h after feeding resumed. Triacylglycerol reserves were severely depleted during the first day of starvation, while protein concentrations began to decrease after the second day of starvation. RNA, protein, and the polyamines spermidine and spermine, when expressed as a ratio to DNA, decreased in response to starvation. Concentrations of all measured parameters in the starved-fed postlarvae returned to levels similar to those in the fed group 8 to 12 d after feeding resumed. Results of this study suggest that triacylglycerol provides energy during short periods of starvation, while protein is utilized during prolonged starvation. The ratios of RNA:DNA, protein:DNA, spermidine:DNA, spermine:DNA, two unidentified amine compounds, and percent water content are all useful indicators of prolonged nutritional stress in postlarval P. vannamei.     

Use of nucleic acids as indicators of growth in juvenile white shrimp,Penaeus vannamei

The use of nucleic acids to estimate crustacean growth is not well documented, and may be complicated by biochemical changes associated with their molt cycle. The objectives of this study were to assess the effects of molt stage on nucleic acid concentrations in abdominal muscle tissue of juvenile white shrimp,Penaeus vannamei, and to examine the relationship between nucleic acid concentrations and growth rates of shrimp exposed to different feeding regimes throughout a 12 d feeding experiment. RNA and DNA concentrations and RNA:DNA ratios were not significantly different among the five major molt stages early postmolt, late postmolt, intermolt, early premolt, and late premolt. In the feeding experiment, RNA concentrations and RNA:DNA ratios accounted for >70% of the variation in shrimp growth on three different sampling days. In addition, RNA concentrations and RNA:DNA ratios were used successfully to discriminate between unfed, moderately-fed, and well-fed shrimp. These variables exhibited significant treatment differences in <24 h after the initiation of the different feeding regimes, whereas significant changes in whole-body weight took longer to detect. Rapid detection of significant treatment effects can be useful in ecological studes, especially those concerned with food-web interactions.     

Mineral concentration in tissues during ovarian development of the white shrimp Penaeus vannamei (Decapoda: Penaeidae)

Levels of calcium, magnesium, zinc, copper, iron, and manganese were examined in the muscle, hepatopancreas, and gonad of white shrimp, Penaeus vannamei, females at different stages of ovary maturation. Eyestalk-ablated shrimp were sampled during the intermolt stage and classified using the following maturation stages evaluated histologically: cortical stage, vitellogenesis, previtellogenesis, and without gonadic development. In muscle, the copper concentration was significantly lower in the vitellogenic stage than in other stages of ovary development. In the hepatopancreas, manganese levels were higher in the cortical and vitellogenic stages than in animals in previtellogenesis and without gonadic development. No other influence of ovary maturation on muscle and hepatopancreas mineral content was found. In contrast, in the ovary, significant differences of some mineral concentrations were detected. Zinc, iron, and magnesium concentrations were significantly increased in the cortical stage compared to the vitellogenic and previtellogenic stages. Our results indicate that these elements are selectively accumulated during ovary development, especially when the ovaries reach the cortical stage. Received: 14 March 2000 / Accepted: 30 November 2000     

Delivery of dietary components to larval shrimp (Penaeus vannamei) by means of complex microcapsules

Efficient delivery of nutrients is necessary for the successful study of aquatic larval nutrition. Conventional artificial food particles for larval shrimp (Penaeus vannamei) have poor water stability and poor nutrient retention or both. We developed a novel food particle type that retained low-molecular weight, water-soluble nutrients (vitamins and glucose) within lipid-wall microcapsules embedded with dietary ingredients in particles of gelled alginate-gelatin. The combination of lipid-wall microcapsules (LWMs) embedded in gelled food particles was termed complex microcapsules (CXMs). Eighty-five percent of ¹⁴C-activity associated with encapsulated ¹⁴C-glucose was retained by CXMs (after 18 h of suspension in seawater). Bioavailability of CXM-encapsulated molecules was demonstrated by release of encapsulated dye marker into the gut lumen of larval shrimp, and by uptake of ¹⁴C from encapsulated ¹⁴C-glucose. Minimum ingestion rates, calculated from ¹⁴C-uptake for larval shrimp (Mysis-1 through Postlarva-2) fed CXMs, ranged from 48 to 99 g dry wt larva^-1 d^-1, and were similar to literature values reported for ingestion of live rotifers by penaeid larvae. Complex microcapsules described in this study will be a valuable new tool for studying nutrition of suspension-feeders in that both micro-and macronutrients can be delivered to these animals by one particle type.     

Persistent locomotor rhythmicity in the prawns Penaeus indicus and P. monodon

The locomotory activity of adult Penaeus indicus Milne Edwards and P. monodon (Fabricius) collected from the Vellar estuary, South India, in 1983 was monitored continuously for a period of 40 d in the laboratory. Both species exhibited persistent circatidal and circadian rhythmicity, the former displayed peak activity during predicated times of high water in their original habitat. The latter exhibited peak activity during periods corresponding to in situ night-time, with almost no activity during the day, except at the time of high tide. The tidal and daily rhythms were evident for only 3 to 4 d and 5 to 6 d, respectively, under laboratory conditions. The amplitude of the rhythms displayed variations in each semilunar period, reflecting the synchrony and dissynchrony of the tidal and daily rhythms. Activity was correlated with phases of the moon, peaking at times of new and full moon, and showing a scattered pattern with smaller peaks during the first and third quarters.     

Toxicity and distribution of Aroclor® 1254 in the pink shrimp Penaeus duorarum

The polychlorinated biphenyl Aroclor^® 1254 was released in an accidental leakage of heat-exchange fluid from an industrial plant, into the Escambia River, near Pensacola, Florida, USA. This material was carried downstream, and is now found in the fauna of Escambia Bay and its contiguous waters, prime nursery areas for fishes and invertebrates such as penaeid shrimp. The significance of pollution by this chemical was assessed by establishing toxicity levels, determining routes of entry, and investigating its movement and distribution in various tissues of shrimp under controlled conditions in the laboratory. Aroclor 1254 added to the water was toxic to the juvenile pink shrimp Penaeus duorarum at a concentration of 1.0 part per billion within 15 days, but was less® Registered trademark, Monsanto Company, St. Louis, Missouri, Mention of commercial products does not constitute endorsement by the Environmental Protection Agency.Contribution No. 128, Gulf Breeze Laboratory.     

In vitro fertilization with non-motile spermatozoa of the brown shrimp Penaeus aztecus

The sperm of the brown shrimp Penaeus aztecus are nonflagellated and non-motile. In vitro fertilization can be obtained when mature eggs removed from female shrimp are added to dense sperm suspensions in seawater and agitated in a manner simulating natural spawning.     

Expression of foreign genes in primary cultured cells of the blue shrimp Penaeus stylirostris

 The ability to introduce and express foreign genes can greatly facilitate in vitro studies of the molecular biology of an organism. We report here the first use of modified retroviral vectors to achieve foreign gene expression in primary cultured cells from the Oka organ and ovary of the blue shrimp Penaeus stylirostris (Litopenaeus) stylirostris (Holthuis 1980). Of the heterologous promoters tested, the Moloney murine leukemia virus and Rous sarcoma virus promoters mediated the highest levels of reporter gene expression. Firefly luciferase and Escherichia coliβ-galactosidase were successfully used as reporter genes in cultured cells from both Oka organ and ovary. These in vitro systems can be exploited for the study of shrimp cellular biology and regulation of gene expression. Received: 16 January 2000 / Accepted: 21 June 2000     

Body increases during molt and molting cycle of the oriental brown shrimp Penaeus japonicus

Individuals of the oriental brown shrimp Penaeus japonicus Bate, were raised separately (1 shrimp per rearing cage) with surplus food, in almost dark, non-sediment conditions. Results were obtained regarding growth of each part of the body in conjunction with exuviation and molting cycle. Increases in carapace, body length and body weight conformed to the general pattern discribed by Hiatt (1948), with no difference in growth resulting from sex, or inflexion point in juvenile stage. The molting cycle of shrimp weighing 1.5 to 15 g was 6 to 17 days at a water temperature of 20° to 28°C. The molting cycle was prolonged in proportion to the size of the shrimp; shortened as the water temperature increased.     

Identification and quantitative analysis of the amino acids present in protein of the brown shrimp Penaeus aztecus

In order to better formulate an artificial shrimp diet, the protein composition of shrimp was assessed and the essential amino acids determined. Penaeus aztecus were treated to remove lipids, carbohydrates and other interfering substances, and the protein was hydrolyzed to its constituent amino acids. The amino acids were then quantitatively analyzed by gasliquid chromatography as their trimethylsilyl derivatives. The essential amino acids were then determined. Shrimp were injected with ¹⁴C-labeled glucose and analyses performed to determine which amino acids then exhibited radioactivity, i.e., were synthesized from the labeled glucose. Those amino acids which were not manufactured from the glucose were categorized as essential.     

Effects of ammonia on survival and osmoregulation of various development stages of the shrimp Penaeus japonicus

In Penaeus japonicus, the tolerance to ammonia increased with the development from nauplius to late juvenile. The 48-h LC₅₀ of ammonia in nauplii (III–V), 96-h LC₅₀ in zoeae (I–III), mysis (I–III), post-larvae (PL1) and late juveniles (10.4±1.1 g) were respectively 5.0, 6.1 to 8.1, 9.4 to 10.9, 15.5 and 52.7 mg Nl^-1 (0.5, 0.6 to 0.7, 0.9, 1.3 and 3.1 mg NH₃–Nl^-1). In a chronic experiment (20 d), the LC₅₀ in post-larvae (PL1) was 19.1 (1.4) at 96 h and 16.2 mg Nl^-1 (1.3 mg NH₃–Nl^-1) at 480 h. Osmoregulatory capacity (OC) was calculated as the osmotic gradient between the hemolymph and the external medium at given salinities. The effects of ammonia on OC, Na⁺ and Cl^- regulation and gill Na⁺–K⁺ ATPase activity in late juveniles were examined in fullstrength seawater, SW (1050 mosm kg^-1, 36 S) and in dilute SW (450 mosm kg^-1, 15%.), after 48 or 96 h exposure to various concentrations of ammonia. Ambient ammonia disrupted both hypo- and hyper-osmoregulation; decreased OC resulted from impaired Na⁺ and Cl^- regulation. Gill Na⁺–K⁺ ATPase activity increased in SW and was not affected in dilute SW. The decrease of OC was ammonia-dose-dependent. The threshold ammonia concentrations affecting hypo-OC and hyper-OC were, respectively, 16 (1.3) and 32 mg Nl^-1 (2.3 NH₃–Nl^-1) for a 48 h exposure; these concentrations were lower than the 48-h LC₅₀ value, 65.3 mg Nl^-1 (3.5 NH₃–Nl^-1). The time course of exposure to sublethal ammonia (48 mg Nl^-1) demonstrated that the effect on osmoregulation was time-dependent. This effect was also temporary, and the exposed shrimps recovered control OC values after removal of excessive ambient ammonia. The possibility of using OC as an indicator of physiological condition in osmoregulating crustaceans and the acting mode of ammonia on osmotic and ionic regulation are discussed.     

Impact of mineral deposition on shrimp, Penaeus monodon in a high alkaline water

This study compares water quality parameters, shrimp growth and mortality rates, and biomass at harvest in two ponds of equal size, seeded with the same density (7 m2) of White Spot Syndrome Virus (WSSV) and Monodon Baculo Virus (MBV) negative post-larvae (PL)-20 of shrimp, Penaeus monodon in the Vellar estuary of South India. The primary difference between the ponds was the water source; one was filled from the estuary and the second with water from bore wells with high alkalinity. Temperature in both ponds was similar and reached 320C after 185 days of culture. Dissolved oxygen (DO) levels were within the acceptable range although levels in the alkaline pond were near the lower limit for the last 90 days before harvest. Salinity levels were similar in both ponds, above optimal levels, and increased over the 185 days. Alkalinity in the estuarine water was typically <50 ppm and again 200-320 ppm in the alkaline pond. In the alkaline pond, beginning on the 75th day mineral deposits was observed covering all parts of the shrimp including the eye and the inner gill chambers, and by harvest, 42% of the shrimp showed this coating. Elemental analysis identified the major constituents as calcium, phosphorus and manganese. Survival rates in the estuarine-water-fed pond was 92% with a total pond biomass at harvest of 1.65 tons ha-1 compared to survival of 79% in the alkaline pond and a biomass at harvest of 1.020 tons ha-1. When well water must be used, its alkalinity should be monitored and diluted with water from other sources.     

RFLP analysis of the mtDNA control region in white shrimp (Litopenaeus vannamei) populations from the eastern Pacific

White shrimp (Litopenaeus vannamei) population genetic structure from the eastern Pacific was determined by restriction fragment length polymorphism analysis of the mitochondrial DNA control region. Four localities were surveyed with four endonucleases (Alu I, Taq I, Spe I, Ssp I) yielding 48 composite haplotypes. White shrimp showed high average within-locality haplotype (0.823) and nucleotide (5.41%) diversities and also high average nucleotide divergence between all pairs of localities (0.73%). A mismatch analysis of pairwise differences between haplotypes indicated that white shrimp does not fit the sudden population expansion model. An analysis of molecular variance showed significant geographic variation in the frequencies of haplotypes (Φ_ST=0.1382, P<0.0001). Population differentiation may be maintained by a combination of physical, oceanographic, and biological factors acting as barriers to gene flow among localities. Because of its high polymorphism, the control region might be useful as a genetic marker for monitoring genetic diversity in aquaculture stocks.     

Effect of mercury on the survival,respiration, and growth of postlarval white shrimp,Penaeus setiferus

The results of toxicity experiments have shown that a level of 17 ppb ionic mercury is acutely toxic (96-h LC₅₀) to postlarval white shrimp (Penaeus setiferus). In addition, the size of the shrimp, within the range tested (7 to 35 mm) did not significantly alter the toxicity values of mercury to this species. Fifty-seven days pre-exposure to low levels of mercury (0.5 and 1.0 ppb) had no effect on the acute toxicity (96-h LC₅₀) of mercury to the shrimp. The effect of chronic exposure to low levels of mercury on the respiratory rate, growth, and molting rate of postlarval P. setiferus was studied, and the results showed that 60 days exposure to 0.5 and 1.0 ppb mercury did not significantly affect any of these parameters for the postlarvae.     

Identification of genetic populations of the Pacific blue shrimp Penaeus stylirostris of the Gulf of California, Mexico

Species are often composed of discrete breeding units (i.e. populations or stocks) which, while not reproductively isolated from other such groups, may have limited opportunities to exchange genetic material because of geographic distance, barriers to migration, or spawning asynchrony. Low levels of gene flow between stocks may result, over time, in their genetic divergence, and species that are subdivided into morphologic or genetically distinct stocks are said to be structured. The aim of our investigation was to test whether or not Penaeus stylirostris from the Gulf of California (Mexico) was structured into genetically distinct populations. Shrimp samples were collected in 1996 from six regions of the Gulf where specimens with distinct morphologic characteristics had previously been identified. Statistical analysis of 324 RAPD loci (randomly amplified polymorphic DNA), resolved through polyacrylamide gels and scored for each of 78 specimens, permitted the quantification and comparison of between-stock genetic differences. The finding that genetically discrete stocks of P. stylirostris can be found in a small portion of the geographic distribution range of the species, disagrees with the long-held perception that this resource is panmictic in nature. This new evidence is not only of interest for selective breeding programs in the shrimp aquaculture industry, but is also relevant to the management of the Mexican shrimp fishery which, at present, is perceived and managed as a single stock. Received: 10 May 1999 / Accepted: 27 July 2000     

Growth and reproductive biology of the small penaeid shrimp Trachysalambria curvirostris in Tokyo Bay

We investigated the growth and reproductive biology of the penaeid shrimp Trachysalambria curvirostris in Tokyo Bay, Japan, by monthly bottom-trawl surveys from May 2002 to December 2004. We also examined oogenesis in T. curvirostris by histological observation of the ovary. Females grew faster and attained a larger body size for age than males. The growth rate was high in summer and low in winter and was likely to be associated with seasonal changes in water temperature. The carapace length (CL) at which 50% of females contained vitellogenic oocytes was estimated to be 17.0 mm. The reproductive season extended from May to October. Young-of-the-year appeared in October and could be traced across the months on CL histograms to the following September or October, indicating a 1-year life cycle. This extended reproductive season, together with our observation of asynchronous development of oocytes in the ovary, suggests that multiple spawning by individual females may occur during the reproductive season. Postovulated oocytes were not found among the samples we collected during the daytime, suggesting that final oocyte maturation and spawning occur at night. Cortical crypts in the cytoplasm of the oocyte, considered to be a general feature of oogenesis in penaeid shrimps, were not found in T. curvirostris, even in oocytes undergoing germinal vesicle breakdown. This result implies that the cortical reaction after spawning of T. curvirostris may be different from that of other penaeid shrimps.     

Diel,lunar and seasonal rhythms in the reproduction of two tropical damselfishes: Pomacentrus flavicauda and P. wardi

It has been hypothesized that site-attached coral reef fishes breed during periods when their offspring will be rapidly flushed from the reef environment, but within the season when these propagules are least likely to be forever lost from the local populations. Daily, monthly and annual rhythms were observed in the reproduction between November 1978 and February 1980 of two tropical damselfishes, Pomacentrus flavicauda and P. wardi, from the southern Great Barrier Reef, Australia. These data support the first part of the hypothesis, but not the explanation for seasonality. When breeding, females of both species spawned demersal eggs into the care of males during a brief period at first light. After several days, larvae hatched from these eggs during another brief period after sunset. An experiment confirmed that the change from light to dark triggered the hatchings and that the emerging larvae were photopositive. Eggs of P. flavicauda usually hatched on the evening of their fourth day in the nest; eggs of P. wardi hatched on their fifth day. A small proportion of eggs required longer incubation. Hatching success was 90%. When breeding, both species spawned in bi-weekly cycles synchronised with the phases of the moon. The largest clutches, as well as the most clutches, were laid at the peaks of these cycles. In the case of P. flavicauda, maximum hatchings occurred on days during which spring high tides fell near sunset (the cue for hatching to begin). It is likely that these hatchlings were rapidly flushed off the reef by the ebbing tides. The hatching cycles of P. wardi consistently peaked 4 d earlier in the lunar month. Consequently, hatchlings of this species remained in shallow water at least one tidal cycle longer than those of P. flavicauda. This difference may be a consequence of the different habitat specialisations of the two species. Both species bred seasonally during the warmest, calmest months of the year. This is not the period of least current flow on the Great Barrier Reef. The observed seasonality may reflect the best times for larval survival in the open sea rather than an adaptation that limits the loss of offspring from the parent populations.     

Effect of salinity on oxygen consumption in postlarvae of the penaeid shrimps Penaeus monodon and P. stylirostris without and with acclimation

The effects of salinity on oxygen consumption was investigated in cultured Penaeus monodon Fabricius and P. stylirostris Stimpson postlarvae (32 and 35 d after metamorphosis, respectively). In both species, no difference appeared between non-acclimated and fully-acclimated individuals. The metabolic rate was unaffected by salinity variations, but P. stylirostris displayed a tendency (non-significant at P<0.05) to increase respiration at lower salinities. These observations are discussed in reference to the ecology of the young prawns.