Female Shrimp Research Articles

Studies on contact sex pheromones of the caridean shrimp Palaemonetes pugio: II. The role of glucosamine in mate recognition

The role of surface glycoproteins in mate recognition of the shrimp Palaemonetes pugio was studied using mating bioassays and fluorescence microscopy. Our data indicate that a glycoprotein associated with female shrimp functions in mate recognition in P. pugio. This glycoprotein is likely to be a glucosamine or an N-acetylglucosamine-containing glycoprotein complemented by a lectinlike receptor on males. Significantly fewer copulations occurred in seawater augmented with glucosamine as compared to seawater augmented with glucose. Thus, it is likely that glucosamine competitively inhibits mate recognition by binding male receptors and significantly reducing recognition of parturial females. The antennal lagellum of decapod crustaceans has long been considered to be chemotactile with bimodal, touch/taste receptors. The fluorescent dye, Lucifer Yellow, is incorporated into antennal setae from the surrounding seawater. Furthermore, the fluorescent dye, DiI, stained neural tissues at the base of the antennal setae. Taken together, these results are consistent with a bimodal, sensory function. When fluo-treated male antennal setae were exposed to the carapace of postmolt, parturial females, an immediate and significant increase in fluorescence intensity was observed, suggesting that Ca2+ likely acts as a second messenger for the receptor system. Fluo-labeled antennal setae of both males and females showed larger increases in intracellular Ca2+ levels when exposed to glucosamine as compared to glucose. The effects produced by glucosamine were sexually dimorphic, with male setae displaying a significantly greater mean overall change in fluorescence intensity than female setae. The dimorphic response observed suggests that glucosamine or a related compound serves as a female signal (i.e., contact sex pheromone) in mate recognition.

Catch, survey and life-history data for shrimp (Pandalus borealis) off Jan Mayen

Abstract The Jan Mayen area has an extreme environment with low temperatures and infrequent, but abrupt temperature changes. The shrimp population here is considered to be on its edge of distribution. The life-history parameters are in the same range as in other high-latitude shrimp populations and are characterized by slow growth, large size at maturation and extended longevity. Irregular and sporadic commercial exploitation limit fishing mortality and give the population life-history parameters not previously seen in other areas. The Jan Mayen shrimp are large compared to, e.g., the Barents Sea shrimp and can reach a maximum carapace length (Lmax) of 37 mm and an age of 10–11 years. The large size at sex transformation (L50, >24 mm) and analyses of length–frequency distributions indicate that the shrimp may be 6–7 years of age before changing sex. The change in Lmax and L50 observed during the study period is probably caused by increased natural mortality due to sudden temperature changes or due to increased predation, rather than increased growth rates. The life-history strategy of shrimp in the Jan Mayen area can be explained by factors such as depth, temperature and population density variations caused by fluctuation in recruitment and mortality. The shrimp fisheries in the Jan Mayen area began in the late 1970s and reached an annual landing of 2000 tonnes in 1985, and since then landings have oscillated around 500 tonnes depending on a combination of factors. The survey indices of stock biomass varied between 3000 and 6600 tonnes. For most years, the highest shrimp densities are at a depth of 200–299 m, while large shrimp (and therefore also female shrimp) are dominant at depths greater than 300 m. Fish community data were studied as the composition of the demersal fish community is an integrated response to environmental conditions and as predation affects the shrimp stock. Polar cod and capelin are the most abundant fish species in the study area. A high number of blue whiting was registered in 1979, but the number declined in 1980 and 1981 as temperature decreased. During the surveys in 1994 and 1995, no blue whiting was registered. A few individuals were found again in the 1999 samples. The number of Greenland halibut has declined from the beginning of the 1980s to the 1990s.

Observaciones morfométricas y reproductivas en el langostino Pleoticus muelleri Bate, 1888 procedente de embarcaciones comerciales del puerto Rawson, Argentina

The shrimp Pleoticus muelleri is the most important species in the crustacean fishery off Patagonian Argentine Sea. Morphometric and reproductive aspects of 1,564 specimens from Rawson Port zone, South Argentine, were analyzed. The shrimps were taken approximately 12 nm by the trawling coastal fleet, between January and April 2001. From the total sample, only 3.9% were juveniles. Mature and impregnated females were mostly found in January (86.27%) and the lowest peak was in March. Immature female shrimps were caught in only in April. These results show the importance to characterize the shrimps from landing samples, to the fishery management.

Improved maturation of pond-reared, black tiger shrimp ( Penaeus monodon) using fish oil and astaxanthin feed supplements

Penaeus monodon female (49 g) and male (37 g) shrimp were fed formulated diets supplemented with 3 or 8% fish oil and 100 or 500 mg kg − 1 astaxanthin, in addition to fresh squid during a 120 day trail using a 2 × 2 × 2 factorial design. Four formulated diets were provided with different combinations of high and low concentrations of lipid (fish oil) and astaxanthin. We found that fish oil addition, at the concentrations we used did not significantly ( P > 0.05) affect shrimp growth, but there was significantly greater growth of male shrimp and higher astaxanthin concentration. Female shrimp growth was not significantly different at either astaxanthin concentration. Likewise, there were no significant interactions on growth between fish oil and astaxanthin or fish oil and shrimp sex, but there was significant interaction between astaxanthin and sex of shrimp. Reproductive performance, as measured by number of eggs in gravid females and number of spermatozoa in male shrimp was significantly enhanced by both higher concentration of fish oil and astaxanthin. There was no significant interaction between fish oil and astaxanthin on number of eggs or spermatozoa. Likewise, there was no significant interaction between fish oil and astaxanthin, or fish oil and astaxanthin concentrations in shrimp muscle, hepatopancreas, ovaries or shell tissues. Astaxanthin concentrations in these respective tissues were similar for both levels of dietary fish oil. There were, however, significant interactions between astaxanthin and shrimp sex with these tissues. Greater dietary astaxanthin concentration resulted in significantly greater astaxanthin concentration in female shrimp muscle, hepatopancreas and ovarian tissues, but not in their shells. Female shrimp had significantly greater astaxanthin concentration in hepatopancreas tissue compared with males, but not in muscle or shells. Shrimp fed diets containing high levels of fish oil and astaxanthin had significantly greater 22:6n-3, total n-3 PUFA and total n-3 HUFA concentrations in muscle and ovary, whereas 20:4n-6, 20:5n-3, 22:6n-3, total n-6 PUFA, total n-3 PUFA and total n-3 HUFA concentrations were significantly greater in hepatopancreas of shrimp fed diet containing high level of fish oil. We concluded that dietary supplementation of formulated diets with 8% fish oil (12% total lipid) and at least 280 mg kg − 1 astaxanthin will significantly improve Penaeus monodon maturation and spawning success.

Expression of clottable protein of tiger shrimp ( Penaeus monodon) in gonads and its possible role as nutrient source for the embryo

We have investigated the expression of clottable protein (CP) in gonad of tiger shrimp (Penaeus monodon) and extent of its phosphorylation. Polyclonal antibodies against purified CP were prepared from rabbit serum. Using this anti-CP antiserum, the temporal expression of CP in gonads of tiger shrimp was analyzed. It was found that the CP occurs only in mature ovaries but not in immature ovaries and testes. Results of RT-PCR confirmed that these tissues expressed low levels of CP mRNA transcripts. Upon eyestalk-ablation, the ovaries in female shrimps were induced to develop, and the CP expression levels in ovaries were traced chronically by RT-PCR analyses. The expression level peaked on day 3 with an increase of about 40 folds relative to the basal level and returned to normal level (as the control shrimp) at day 12. The shrimp embryos at different intervals from spawning to 16h post-spawning were also collected, and it was found that CP contents were gradually decreased in the embryos until the nauplii were hatched. In addition, purified CP was shown to react with specific anti-phosphoserine, anti-phosphothreonine, and anti-phosphotyrosine antibodies suggesting that CP is a phosphoprotein with all types of phosphorylations. Taken together the results suggest that expression of CP in shrimp ovaries is coupled to ovarian development and CP possibly supply nutrition for shrimp embryo.

The use of recombinant protein and RNA interference approaches to study the reproductive functions of a gonad‐stimulating hormone from the shrimp Metapenaeus ensis

Although the crustacean crustacean hyperglycemic hormone/molt-inhibiting hormone/gonad-inhibiting hormone neuropeptides have been studied extensively in the last two decades and several neuropeptides from the shrimp Metapenaeus ensis have been cloned, the functions of most of these neuropeptides remained putative. In this article, we describe the use of recombinant protein and an RNA interference approach to study the reproductive function of the previously reported molt-inhibiting hormone (MeMIH-B) in M. ensis. When hepatopancreas and ovary explants were cultured in medium containing recombinant MeMIH-B, the vitellogenin gene (MeVg1) expression level was upregulated in a dose-dependent manner, reaching a maximum in explants treated with 0.3 nm recombinant MeMIH-B. Shrimp injected with recombinant MeMIH-B showed an increase in vitellogenin gene expression in the hepatopancreas. Moreover, a corresponding increase in the vitellogenin-like immunoreactive protein was detected in the hemolymph and ovary of these females. Injection of MeMIH-B dsRNA into the female shrimp caused a decrease in MeMIH-B transcript level in thoracic ganglion and eyestalk. These shrimp also showed reduction of vitellogenin gene expression in the hepatopancreas and ovary. Furthermore, the hemolymph vitellogenin level was also reduced in these animals. In summary, the results from recombinant protein and RNA interference experiments have demonstrated the gonad-stimulatory function of MeMIH-B in shrimp.

Temperature induced variation in oxygen consumption of juvenile and adult stages of the northern shrimp, Pandalus borealis

The impact of temperature on oxygen consumption (MO 2) of Pandalus borealis was measured in the laboratory for juvenile, male and female shrimp at 2, 5 and 8 °C, the temperature range where P. borealis is generally found in the Northwest Atlantic. Measurements of MO 2 were taken every 60 min over 7–10 days on 0.22 to 13.80 g shrimp. These long-term measurement periods insured acclimation to the respirometers and allowed calculation of standard metabolic rate of individuals (SMR ind). SMR ind was linearly related to body mass (log transformed data) and the mass-exponent for the species was 0.56. The effects of wet body mass ( W w) and temperature ( T) on SMR ind were described by: SMR ind = 10 (0.57 log ( W w)+0.04 T−1.21) , with SMR ind expressed in mg O 2 h − 1 , W w in g and T in °C. This model explained 92% of the variability in SMR ind. Mass-specific MO 2 adjusted for a 5 g shrimp (SMR 5g) was not influenced by developmental stage indicating that the regression model for SMR ind was valid regardless of variations in size at maturity and sex transition. Routine and active metabolic rates followed the same variation pattern in relation to temperature and developmental stage than SMR. Finally, thermal coefficients ( Q 10) were in the normal range found for crustaceans, Q 10 values varying from 1.73 to 4.97.

Density-dependent effect on reproductive behaviour of Lysmata amboinensis and L. boggessi (Decapoda: Caridea: Hippolytidae)

We compared the reproductive behaviours of two protandric simultaneous hermaphroditic species (Lysmata amboinensis and L. boggessi) that belong to two groups of Lysmata shrimp with different morphology, geographical distribution, and density. Lysmata amboinensis occurs in tropical waters at low population densities, and L. boggessi is found in aggregation in sub-tropical and temperate areas. Reproductive behaviour of L. boggessi under two densities and L. amboinensis in different habitats were compared. Results show that L. amboinensis was much less active during mating than L. boggessi. Male shrimp of L. amboinensis did not display obvious pre-copulation behaviour. They also took significantly longer to transfer spermatophores and lay eggs after mating than L. boggessi shrimp did. For L. boggessi, moulting time of female shrimp, copulation time and the interval between moulting and mating were significantly shorter when three male shrimp were present than when only one male shrimp was present. Our study suggests that the reproductive behavioural differences in the two shrimp species are possibly the results of density-dependent effect.

The Biology of Northern Shrimp (Pandalus borealis) on the Flemish Cap

This study reports on various biological features in the life history of northern shrimp (Pandalus borealis) on Flemish Cap. Northern shrimp on Flemish Cap are males for approximately their first three years. Then usually half change sex at age four years, and the rest at age five years, to become females from then on. Small shrimp are generally found at lesser depth than the larger ones so the size of shrimp increases with depth, especially that of males. Larger females seem to move to shallower waters in March when hatching starts. The size at sex change (L50) and the maximum length (Lmax) are studied within and between seasons. Both L50 and Lmax have decreased in recent years. L50 was 22.5 mm CL on average in the seasons 1996/1997–2003/2004, but has decreased from 23.2 mm CL in 1997/1998 to 22.4 mm CL in 2003/2004 (Icelandic commercial data) and from 24.3 mm CL in 1994 to 20.9 mm CL in 2003 (EU survey data). Also Lmax has decreased from 29.8 mm CL in 1996/1997 to 28.0 mm CL in 2003/2004 (Icelandic commercial data). In spite of this, there is an invariant relationship between L50 and Lmax, where L50 is about 80% of the average Lmax of northern shrimp on Flemish cap. This supports the theory of Charnov and Skuladottir (2000) on the invariant relationship between L50 and Lmax in sex changing organisms. The same is found in Icelandic offshore waters and the Denmark Strait. The decline in L50 could be related to the observed increase in temperature at 150 m in the last decade from 2.6°C in the years 1992–1996 to 3.5°C in 1997–2003. The sudden decline in the female biomass of shrimp on Flemish Cap between 1992 and 1994 appears to coincide with a drop in the age at sex change (A50) by one year in 1995 and 1996. Moreover, the increase in biomass of shrimp follows the disappearance of cod in the mid-1990s. As female shrimp biomass increased there was a delay in changing sex, showing the versatility of shrimp on Flemish Cap in adjusting to changes in sex-ratio. Growth of shrimp was fast in the earlier years and slower in later years indicating that food may be a limiting factor. The growth during the earlier years is faster than that of northern shrimp in the Barents Sea. Compared to other areas in the 1980s, the growth is slightly faster than that of the warm inshore waters of Iceland, but much slower than the growth of shrimp in the inshore waters of Sweden. The ovigerous period is studied for the first time on Flemish Cap and is estimated to be about eight months.

Dynamics of reproduction in a captive shrimp broodstock: unequal contribution of the female shrimp and a hidden shortage in competent males

Summary The major bottleneck in the breeding in captivity of penaeid shrimp is the fact that females do not spontaneously undergo vitellogenesis, which thus has to be induced endocrinologically by eyestalk ablation. Partial compensation for the low responsiveness of the females to this treatment is obtained by the use of very large broodstock populations. This old problem was newly approached in the current study by monitoring individual female life-spans and vitellogenic cycles in a small population of the Pacific white shrimp, Litopenaeus vannamei. Vitellogenic activity and spawning peaked during the second month of the four-month trial and decreased thereafter due to the sharp fall in the number of reproductively active females. Only about 75% of all the females in the broodstock were reproductively active, and most of them spawned for the first time, or exhibited fully vitellogenic ovaries, during the first two weeks post-ablation. Nevertheless, the best performing females, which comprised less than 20% of the female broodstock, matured more rapidly, exhibiting fully vitellogenic ovaries 4.1±3.4 days after eye-stalk ablation. These animals contributed more than 50% of the total eggs and nauplii produced. The total number of vitellogenic cycles recorded from all reproductively active females was 305, but in less than a third of these cycles were the females observed to be carrying spermatophores or sperm masses. Since females-but not males-in captivity undergo accelerated reproductive cycles due to the endocrine induction, it is suggested that the lack of mating consistently reported from maturation systems may be due to the lack of sufficient ready-to-mate males.

Population structure and egg production of the seagrass shrimp Hippolyte kraussiana Stimpson, 1860 (Decapoda: Hippolytidae) at Inhaca island, Mozambique

Summary Hippolyte kraussiana, a poorly known tropical species, was collected from seagrass beds of Inhaca island, Mozambique, in August 2005 during neap/spring and low/high tides by means of a small aluminium trawl fitted with a 1 mm mesh body and cod-end-net. Specimens were identified, sexed, counted and morphometric measurements were made. Ovigerous females were classified as small [carapace length (CL): 1.10–1.35 mm] and large (CL: 1.40–1.80 mm); the embryo mass was staged and counted. Females showed, on average, a much higher density when compared with males (0.064 ± 0.003 and 0.153±0.11 ind.m−2 for males and females, respectively) and were significantly larger (0.9 ± 0.1 and 1.3 ± 0.1 mm of CL for males and females, respectively). At 1.28 mm of CL at least 50% of the females were found carrying eggs on the pleopods. Average (±SD) brood size of small and large ovigerous females were 33 (±7) and 43 (±13). The number of embryos decreased significantly over the incubation period for each size-class. Average (±SD) brood loss from embryonic stage I to stage IV for small and large female shrimp was 47% (±12.4) and 58% (±15.8), respectively. Senescence seems to occur since larger females always had a higher brood loss and negative allometry was recorded. The mean embryo volume in the same development stage was not significantly different among the small and large shrimps, increasing significantly from 0.013 mm3 to 0.022 mm3 (69%) from first to last embryonic stage, respectively. This study intends to give baseline information about egg production and population structure, to contribute to a better knowledge of this little known species.

Effect of rearing density on growth, survival and reproductive performance of domesticated Penaeus monodon

The growth, survival and reproductive performance of tank-reared, 2nd generation domesticated Penaeus monodon, originating from founder stocks collected from a population off the coast of Weipa (12°48′, 141°32′), Gulf of Carpentaria, Queensland, Australia, were compared when reared at a standard density for maturation (SD) (approx. 3 individuals m − 2 ) and a low density for maturation (LD) (approx. 1 individual m − 2 ). Growth and survival of the shrimp reared at the two densities in 10·000 L tanks (3.6 m dia.; 10 m 2 tank-bottom area) were assessed from 5.5 months of age through to 10.5 months of age. Reproductive performance of shrimp in the two density treatments was assessed from 10.5 months of age for two moult period's post-ablation under standardized conditions. The weight of the female shrimp at 10.5 months of age (mean ± S.E.) was significantly greater at LD (131.2 ± 4.9 g) than at SD (120.3 ± 2.5 g). No difference in 10.5 month weight was found between males at LD (90.9 ± 2.2 g) and SD (87.4 ± 1.5 g). Significantly more spawnings were produced at LD (2.2 ± 0.2 ablated female − 1 ; 3.4 ± 0.6 spawning female − 1 ) than at SD (1.3 ± 0.2 ablated female − 1 ; 2.4 ± 0.6 spawning female − 1 ). The percentage of spawnings that hatched (LD 87.2 ± 5.1%; SD 61.8 ± 6.6%), eggs per spawning (× 10 3) (LD 231 ± 21; SD 148 ± 16) and nauplii per spawning (× 10 3) (LD 39 ± 8; SD 16 ± 3) were also significantly higher at LD. Hatch rates per spawning were low and did not differ between LD (19.0 ± 2.7%) and SD (16.8 ± 2.4%). No significant differences in spermatophore weight (LD 0.19 ± 0.02 g; SD 0.20 ± 0.01 g) or sperm count (× 10 6) (LD 6.25 ± 0.77; SD 8.44 ± 1.15) were found between males at the two densities. While egg and nauplii production (× 10 3) were significantly higher at LD than SD when expressed per female (LD 434 ± 115 eggs, 73 ± 26 nauplii; SD: 160 ± 44 eggs, 17 ± 7 nauplii), no significant difference was found when expressed per m 2 tank-bottom area of the maturation tanks (LD 272 ± 67 eggs, 46 ± 21 nauplii; SD 271 ±109 eggs, 29 ± 15 nauplii). Our results found that lowering the maturation density of tank reared P. monodon stocks from approx. 3 individuals m − 2 to 1 individual m − 2, over a 5 months maturation period, improved growth of females and reproductive performance when expressed per spawning or per female. However, no significant increases in egg and nauplii production were obtained by reducing the maturation density when expressed per tank-bottom area.

EFFECT OF DIFFERENT LEVELS OF DIETARY α-TOCOPHEROL ON OVARIAN MATURATION AND REPRODUCTIVE PERFORMANCE OF BROODSTOCK LITOPENAEUS VANNAMEI (BOONE)

Effects of 4 grade levels of dietary α-tocopherol (37.82, 115.64, 349.42 and 522.56 mg kg−1 diet) on ovarian maturation and reproductive performance of broodstock shrimp, Litopenaeus vannamei were investigated. The α-tocopherol concentrations in hepatopancreas, ovaries, eggs and muscle of female shrimp increased significantly as dietary α-tocopherol levels increased. Survival, spermatophore weight, sperm count, gonadosomatic index (GSI), hepatosomatic index (HSI), fecundity and egg diameter were not significantly affected by dietary α-tocopherol levels. Average daily spawns, hatching rate and fertilization rate significantly increased as dietary α-tocopherol levels increased. Results of this study confirmed the importance of supplementation of α-tocopherol to broodstock diets fed to L. vannamei, and suggested that at least 350 mg α-tocopherol kg−1 of diet was needed to achieve significantly better ovarian maturation and reproductive performance.

Seasonality and zonation in the reproductive biology and population structure of the shrimp Alvinocaris stactophila (Caridea: Alvinocarididae) at a Louisiana Slope cold seep

Ecological patterns in deep-sea chemosynthetic environments are often considered to be independent of variations in photosynthetic primary production. This study examines spatial and temporal variation in the population structure and reproductive development of the caridean shrimp Alvinocaris stactophila at the Brine Pool cold seep on the Louisiana Slope. To assess spatial variation, samples were collected by submersible from different locations at the Brine Pool mussel bed in November 2003. The proportion of males in samples declined from the outer to the inner zone of the mussel bed, while the proportion of female shrimp carrying eggs increased. This zonation may result from congregation of large ovigerous females towards the inner zone, where sulphide flux from underlying sediments may be absent or reduced. To examine temporal variation in reproductive development, oocyte size-frequency distributions were compared between August 1997, March 2002, February 2003, November 2003 and July 2004. All oocytes in early spring samples were small and previtellogenic, while summer samples contained larger vitellogenic oocytes. The largest oocytes were found in large non-ovigerous females from the autumn, while ovigerous females from the same season contained the smallest oocytes in this study. Embryos in the autumn exhibited no differentiation, in contrast to well-developed embryos from early spring that hatched into zoea larvae. These features indicate seasonal and iteroparous reproduction in A. stactophila, with females carrying embryos from autumn to early spring and releasing planktotrophic larvae to exploit a seasonal peak in surface productivity and its export.

Necrotizing hepatopancreatitis (NHP) infected Penaeus vannamei female broodstock: Effect on reproductive parameters, nauplii and larvae quality

Necrotizing hepatopancreatitis (NHP) is a disease of cultured Penaeus vannamei caused by a gram-negative intracellular bacterium rickettsia-like organism. NHP was first reported in Texas in 1985, as being responsible for mortalities in shrimp ponds in Central and South America. The growth and proliferation of NHP within the hepatopancreatic epithelial cells is associated with anorexia, lethargy, abdominal muscle atrophy, softened exoskeleton, growth retardation and mortalities ranging from 20% to 95%. Although NHP can cause high mortalities in commercial ponds, it has been considered a problem only in broodstock ponds and maturation laboratories due to an increase in broodstock mortalities in Colombia. In order to evaluate additional negative effects at this level, we investigated the effect of NHP infection upon the reproductive behavior of females and the effect of maternal infection on nauplii and larval quality. Broodstock from NHP affected ponds were transferred to a maturation laboratory. After copula, females were transferred to individual spawning tanks. After spawning, females were sacrificed for histopathology and PCR analysis, while the eggs were placed in individual tanks for hatching. Females were classified into three groups according to their histopathological findings: NHP negative ( n = 23) had no NHP lesions, positive for NHP with lesions grade 1 ( n = 20) and NHP positive females with lesions grade 2 ( n = 12). For each group, we analyzed the number of eggs, hatching percentage and number of nauplii per female. Our results show that females with NHP lesions grade 2 presented a significant reduction in the number of eggs and nauplii ( P < 0.05) as compared with NHP negative females and females grade 1 NHP disease. No significant differences were found in hatching percentage among the three groups. Triglyceride levels in nauplii II were significantly higher in NHP negative females than in females with grade 2 NHP ( P < 0.05), whereas there was no difference between NHP negative and grade 1 females. No significant differences were found for glucose and cholesterol levels in nauplii among the three groups. No differences were found in survival at zoea I, mysis I, PL-1 and PL-10 for the three groups. However, after a salinity stress test, the PL-10 survival decreased significantly in larvae from NHP positive females. Also a significant decrease in PL-10 length was also observed in the progeny of these females (grades 1 and 2). This study demonstrated that NHP disease in female shrimp spawners affects both maturation and larviculture causing a decrease in the number of eggs and nauplii per female, a reduction in the levels of triglyceride in nauplii II and decreasing larvae growth and resistance to osmotic stress test at PL-10 stage.

Characterization of vitellogenin in the shrimp Metapenaeus ensis: Expression studies and hormonal regulation of MeVg1 transcription in vitro

During gonad maturation, female shrimp accumulate the major egg yolk protein vitellin (Vn) in premolt stage, and the process of molting and reproduction is synchronized. Using a polyclonal anti-Vn antibody, immunopositive signals could be detected in the ovary and among the proteins secreted by the hepatopancreas by Western blot. In the ovary, Vn immunoreactivity was located in the posterior lobe. Hepatopancreas proteins with sizes identical to ovary vitellogenin (Vg) subunits (i.e., 78 and 157 kDa) were immunoreactive to the Vn antibody and these proteins included amino acid sequences identical to parts of the MeVg1 precursor. A major 7.8 kb MeVg1 transcript, was detected in the ovary. In the hepatopancreas, the transcripts were primarily small (<2.3 kb) and while the 7.8 kb transcript which constitutes <50% of the total Vg mRNA. MeVg1 transcript could be detected in the hepatopancreas of juvenile females with a maximum level during late intermolt and early premolt. To study the effect of different hormones on expression of MeVg1, explant cultures of hepatopancreas and ovary were developed. Although several hormones (20-hydroxyecdysone, estradiol (ES), farnesoic acid (FA), juvenile hormone (JH) III, methyl farnesoate, and progesterone (PG)) apparently stimulated MeVg1 gene expression, only FA consistently stimulated MeVg1 expression by the hepatopancreas explants, while both FA and 20-hydroxyecdysone were stimulated ovarian explants. In summary, (i) Vg transcripts can be detected in both reproductive and nonreproductive females; (ii) the presence of large quantities of smaller Vg transcripts and the absence of a large Vg precursor from the hepatopancreas suggests that smaller MeVg1 transcripts provide an important contribution to Vg synthesis in shrimp. Our results suggest that there is differential processing of the MeVg1 precursor in the ovary and hepatopancreas of shrimp.

Detailed monitoring of white spot syndrome virus (WSSV) in shrimp commercial ponds in Sinaloa, Mexico by nested PCR

WSSV has caused great losses to the global shrimp industry in recent years. This virus can infect shrimps asymptomatically. However, once the clinical signs are developed, mortalities can reach 100% in 3–10 days. PCR has been extensively used to detect WSSV in a specific and sensitive manner. Nested PCR is even more sensitive than single-step PCR and had been used for the detection of WSSV in asymptomatic populations. In this work, a detailed monitoring of WSSV by nested PCR in shrimp commercial ponds in Guasave County, State of Sinaloa, Mexico, is presented. Five ponds from two different farms were monitored for growth and presence of WSSV. At the beginning of the culture, ponds from both farms showed no or very slight WSSV presence. A 3-day period of rain occurred at both farms 10 and 14 weeks of culture for farms 1 and 2, respectively. At this time, WSSV was widely distributed in the shrimp populations of farm 1 according to nested-PCR data, although no visual symptoms were observed. In ponds of farm 2, WSSV was present at low level. However, the number of PCR-positive groups was drastically increased in both farms by nested and single-step PCR. Abrupt fluctuations in temperature and salinity were documented in farm 2 after the rain, which may have contributed to the increasing of viral load in the pond's shrimp populations. Twelve days after the rain period, estimated mortalities of 80% occurred in farm 1. Nevertheless, the study ponds at farm 2 culture continued normally for three more weeks and were harvested successfully (52% and 67% of survival for ponds 1 and 2, respectively). The removal of 40% and 50% of shrimp population 2–4 days after the raining period may have contributed to the thriving of the cultures. Analyses of the presence of WSSV in individuals of both sexes indicated that there is no preference for this virus to infect male or female shrimp. Also, no differences in weight were found between WSSV infected and non-infected individual shrimps, as well as nested-PCR positive against single-step PCR positive organisms. Nested PCR is more useful to monitor shrimp cultures than single-step PCR since it allows knowing how widely distributed the virus is in asymptomatically populations.

거문도 해역 대롱수염새우(Solencer melantho)의 성자과 성 성숙

This paper describes reproduction, population structure, growth and size at sexual maturity of a deep-water mud shrimp (Solenocera melantho) in the adjacent waters of Geomun Island, Korea. The shrimp was caught by a beam trawl from November 1998 to December 1999. Spawning period was estimated by gonadosomatic index to be from August to early November with a peak in October to early November. Female shrimps were <TEX>$12\%$</TEX> matured at 16 mm in carapace length, <TEX>$33\%$</TEX> matured at 18 mm and <TEX>$75\%$</TEX> matured at 22 mm. The size at <TEX>$50\%$</TEX> maturity for female was estimated to be 20.65 mm in carapace length. Breeding season was estimated to be from August to early November with a peak in October to early November. The size at <TEX>$50\%$</TEX> inseminated was 19.81 mm CL. The fecundity was 87,500-405,200 and related exponentially to carapace length and total weight. This species survived between 25 and 26 months. The maximum carapace length of females and males were 48 mm and 34 mm respectively. Sex ratio was <TEX>$51.3\%$</TEX>, and the females were preponderant. Growth was estimated by modified von Bertalanffy growth function incorporating seasonal variation in growth in both years females (K=1.019/yr and <TEX>$L_{\infty}$</TEX>=51.731 mm CL) grew faster, reaching a larger size at a given age than males (K=1.848/yr, and <TEX>$L_{\infty}$</TEX>=27.499 mm CL). This is indicated by differences in growth performance indices <TEX>$(\varphi')$</TEX> between females (3.291) and males (3.145).

Development of a specific pathogen-free (SPF) population of the Chinese fleshy prawn Fenneropenaeus chinensis: Part 1: Disease Pre-screening and Primary Quarantine

A total of 36 gravid female shrimp Fenneropenaeus chinensis, captured off the coast of Qingdao, Peoples Republic of China, from April 20 through April 24, 2001, were examined by PCR for the presence of WSSV and HPV, the two most prevalent viral diseases affecting this species of shrimp in this region of China. Eight spawns, derived from 8 different females, were selected from shrimp where no WSSV or HPV had been detected. Nauplii obtained from 7 individual spawns and unhatched eggs from one other shrimp were transported to the University of Arizona, in Tucson, Arizona, USA, for larval rearing and production of postlarvae under quarantine protocols. The resultant postlarvae were kept in Primary Quarantine for approximately 2 months, while additional tests were performed to determine their specific pathogen-free (SPF) status according to criteria set by the United States Marine Shrimp Farming Program (USMSFP). By the time the shrimp had reached an average weight of approximately 0.4 g, no USMSFP specific listed pathogens had been detected in any of the 7 hatches and the shrimp were released into Secondary Quarantine at the Oceanic Institute in Kailua-Kona, Hawaii for production of a F1 generation. This F1 generation may be used as a SPF founder population for propagation and selection programs.

Heritability of the categorical trait ‘number of spawns’ in Pacific white female shrimp Penaeus (Litopenaeus) vannamei

We estimated the heritability for the number of spawns during a reproductive period of 30 days in female Pacific white shrimp, Penaeus (Litopenaeus) vannamei. The estimate was based on Bayesian statistical methods, with data collected on full-sibs and mothers and daughters during two generations (years). Heritability was estimated in a threshold model for categorical data, including the fixed effects of year and sets within years. All ablated females provided information regardless of whether they spawned or not. Phenotypes were reordered for each of 5 categories: 0, 1, 2, 3, and 4 or more spawns. Heritability of spawn numbers was 0.20, with a 95% confidence interval of 0.06–0.43, indicating that this trait can be improved by selective breeding.