Penaeus Schmitti Research Articles

Enhancing Sustainability and Conservation of White Shrimp Penaeus schmitti in Northeast Brazil: Insights Into Life History, Reference Points, and Management Strategies for Beach Seining

ABSTRACTArtisanal fishing significantly not only contributes to socioeconomic development of numerous countries but also exerts pressure on natural populations. The white shrimp (Penaeus schmitti) is a key species in Brazilian artisanal fisheries, yet it is currently classified as data‐deficient. Conducting comprehensive studies on its population dynamics is essential to establish reference points that guarantee sustainable fishing. Therefore, we estimated population parameters to assess status of the white shrimp stock captured by beach seining in Northeast Brazil. Monthly samples of white shrimp were collected using a beach trawl. Based on population parameters, the white shrimp population in the study area, the sex ratio was 1 male to 1.29 females, with females larger and heavier than males. Weight–length relationships revealed positive allometric growth for males, females, and grouped sexes, with no significant difference between sexes. Asymptotic length, t_achor, and growth performance index also did not differ between sexes; however, the growth coefficient was higher for females. Beach trawling in northeastern Brazil predominantly targeted adult white shrimp, with carapace length at first capture (Lc50) averaging 2.12 cm for females and 2.19 cm for males. Mortality and exploitation rates were below maximum sustainable levels, so the stock was classified as underexploited. Overall, beach‐seine fishing was less harmful to this stock (F = 1.42) than motorized fishing and can be considered a sustainable fishing activity for the white shrimp population.

Morphological variations of southern white shrimp Penaeus schmitti (Burkenroad, 1936) (Crustacea: Dendrobranchiata: Penaeidae) in natural populations of Cuba and Brazil

The objective of this study was to identify morphological characteristics of different populations of Penaeus schmitti Burkenroad, 1936 to contribute to its biology and conservation. In order to compare geographically isolated populations, between 2014 and 2016, selected biological variables were analyzed in six populations dispersed along the Brazilian coast and one from the Cuban coast. Specimens with eight upper rostral teeth predominated. The ordination of shrimp measurements by non-metric multidimensional scaling showed the greatest dispersion on data from Cuba, Rio Grande do Norte, and Espirito Santo, which are also the localities that presented the highest coefficient of variation. On the other hand, the values corresponding to Sergipe, Rio de Janeiro, Paraná, and Santa Catarina showed a greater similarity or clustering of the data of each location. Tail weight was estimated using length and depth of the sixth abdominal segment. The populations of Santa Catarina, Brazil (28°S), had the longest and heavier abdomens proportionally among all the compared populations, while the organisms of Manzanillo, Cuba (20°N), had proportionally shorter abdomens and the narrowest cephalothorax. The regression equation indicated a positive allometric growth for P. schmitti, and the largest total length reported for genus Penaeus in the natural environment corresponded to a P. schmitti specimen. This information could be useful in future taxonomic studies to correctly identify the species and its morphological variability. Color differences were also observed, with white ventral spots in the sternite XIV of some females from Brazilian populations, which was not previously reported in the literature. Extending these studies is recommended to contribute to the conservation and culture of P. schmitti.

Assessment of the stock status of two penaeid shrimps in the Northeastern Brazil Marine Ecoregion and implications for their management

Shrimp fisheries is one of the most profitable fishery activities in tropical regions, highlighting the need of assessing the status of those resources more thoroughly. Then, this study aimed to provide a comprehensible stock assessment of two highly exploited marine penaeid shrimps (Xiphopenaeus kroyeri and Penaeus schmitti) in two important fishing grounds within the Northeastern Brazilian Marine Ecoregion (NBME) in the state of Alagoas. In addition, the hypothesis of different stocks between areas is also tested by checking for possible between-area heterogeneity in population parameters. We found remarkably similar patterns of growth and mortality between the two fishing grounds for both species, with homogeneous parameters indicating an absence of regional structuration. Then, the two fishing grounds contain a single stock for both species, which will respond similarly to the same fishing pressures and management scenarios. We also indicate that the seabob shrimp is close to the limit of full exploitation in both regions based on Yield per Recruit analysis. Meanwhile, the white shrimp is overexploited in one of them. Potential management tools to allow sustainable and productive exploitation in these fisheries are effort control and spatial restrictions to conserve nursery habitats and maintain sustainable rates of population growth.

Fatty acid profiles of three commercial shrimp from southeastern Brazil

This study describes the fatty acid (FA) composition of three commercially important species of shrimp, from a region with the largest mangrove forests in Brazil. Fatty acids composition shows the nutritional quality of the shrimps and their importance as a node of energy transfer in the trophic web. The FA profiles of three shrimp species with different life cycles were collected from Cananéia, São Paulo, Brazil: Xiphopenaeus spp. (offshore), Penaeus schmitti and Penaeus paulensis (both mangrove dependent). A total of 29 different FAs were detected in their FA profile. However, each species presented a different profile of FAs. The fatty acids 16:0, 18:0, 18:1ω9, 20:5ω3 (EPA) and 22:6ω3 (DHA) contributed for the significant differences between the shrimp species. The restricted occurrence of Xiphopenaeus spp. in the marine region explained the difference in the FA concentration compared with the P. schmitti and P. paulensis shrimps, that spend part of their life cycle in the mangrove. The study highlights that these shrimps are essential sources of FAs in the trophic web and are valuable for human health, especially the polyunsaturated FAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Gonadal Development of Females of the White Shrimp Penaeus schmitti (Burkenroad, 1936) Caught in Southeastern Brazil

This study describes the reproductive cell development and ovarian developmental stages, and identifies the nongerminal components of white shrimp (Penaeus schmitti) caught off the southern coast of Espírito Santo, Brazil. P. schmitti specimens were collected monthly from March 2019 to February 2020, by artisanal fishing. All shrimps were analyzed macroscopically (n = 181) and females were randomly selected monthly (n = 154) for ovarian histological analysis. The ovaries were extracted for visual analysis and then submitted to histological analysis. Macroscopic analysis determined five stages of gonadal development from the color and turgidity of the fresh ovary. Histological observations allowed us to observe five stages of gonadal development: immature, initial development, advanced development, mature and spawning. This information are fundamental for understanding the reproductive aspects of P. schmitti, as well as other penaeid shrimps, in order to promote preservation of natural stocks and provide information to assist in the development of the reproductive potential of native species in captivity.

Growth and mortality analyses of the white shrimp Penaeus schmitti (Decapoda: Penaeidae) in Sepetiba Bay, Brazil: An exploited data-deficient species

Penaeus schmitti is fisheries resource explored throughout the area where it occurs and is one of the most important penaeid in terms of fishery biomass in Brazil. The current conservation state of P. schmitti in Brazil is worrisome because inserted in the category of Insufficient Data in the Red book of Crustaceans of Brazil. The goals of this study were to estimate growth and mortality rates of P. schmitti in Sepetiba Bay, Rio de Janeiro State, southeastern Brazil, and to assess the effect of fishing on the population. Monthly samples were collected during one year through regional artisanal fishery. Growth was assessed through modal analysis according to von Bertalanffy growth function (VBGF). Instantaneous mortality rates Z (total), M (natural), F (fishing) and the exploitation rates (E) were estimated. Total mortality (Z) was estimated by length-converted catch curves and M was based on parameters of the VBGF. Growth parameters differed significantly between sexes and a single curve could not be applied to both sexes. Females of P. schmitti, were larger and grow faster (high k value) but were less abundant than males. Instantaneous mortality rates were similar for males and females. Females were vulnerable to fishing activities at three months of age, males at four months of age. The exploitation rate of the species was greater than 50%, highlighting a possible overfishing of the species. Limiting access to nursery areas of juveniles would be a good strategy for stock recovery.

How the fishing effort control and environmental changes affect the sustainability of a tropical shrimp small scale fishery

Global shrimp catches are reported primarily in association with large industrial trawling, but they also occur through small-scale fishing, which plays a substantial role in traditional communities. We developed an Ecopath model in north-eastern Brazil, and applied a temporally dynamic model (Ecosim) to evaluate the potential effects of different fishing effort control policies and environmental changes on marine resources and ecosystem between 2015 to 2030 with a case study for small-scale shrimp fishing, novelty for tropical region. These scenarios included different management options related to fishing controls (changing effort and closed season) and environmental changes (primary production changes). Our findings indicate that it is possible to maintain the same level of landings with a controlled reduction of bottom trawlers activities, for example, close to 10 %, without compromising the ecosystem structure. This scenario provided better results than 3–4 months of closing the fishing season, which led to significant losses in catches of high market-value target species (white shrimp, Penaeus schmitti and pink shrimp, Penaeus subtilis). However, intense negative effects on biomass, catch and biodiversity indicators were reported in scenarios with decreasing primary production, from 2 %, reinforcing the need to simulate and project the possible impacts caused by environmental change. However, the control of bottom trawling activity may help to reduce, even at low levels, the highly adverse effects due to primary production reduction. The impacts of climate change in a near future on organisms and ecosystems is an imminent reality, and therefore the search for measures for mitigating and even minimizing these impacts is crucial.

Zootechnical performance and interaction between Penaeus schmitti Burkenroad, 1936 and Penaeus vannamei Boone, 1931 reared under laboratory conditions

To compare the zootechnical performance of the Brazilian native shrimp Penaeus schmitti and the exotic shrimp Penaeus vannamei, juveniles were grown under controlled conditions. Both species were simultaneously cultivated (monoculture) in separate 70 L plastic tanks at two different densities: 30 and 50 ind m-2. Also, in the other two treatments, both species were cultivated together (mixed), with and without feeding, at 30 ind m-2. During the experiment, P. vannamei generally showed a greater interest in food and voracity than P. schmitti. At harvest, for both stocking densities of monoculture treatments, the mean growth rate observed for P. vannamei was 1.0 g week-1, while P. schmitti achieved only 0.1 g week-1. The mean final weight was 10.4 ± 2.0 g; 10.7 ± 2.1 g for P. vannamei and 2.8 ± 0.3 g; 3.2 ± 0.3 g for P. schmitti, for respective densities of 50 and 30 ind m-2. In the mixed treatment with feeding, while P. vannamei reached 11.9 ± 1.4 g, P. schmitti reached only 2.6 ± 0.4 g in the same tank. The observed differences were 3.7 and 3.4 higher in favor of P. vannamei in the monoculture treatment, and up 4.5 times higher in the mixed treatment. Under strict fasting conditions, both species practiced predation/cannibalism among themselves. The results reflected the zootechnical advantages of P. vannamei, but also corroborated the negative effect that high densities and lack of natural food can exert over native species. The potential for P. schmitti cultivation and the possible impact of the escape of P. vannamei into the natural environment is discussed.

Understanding what is what in marine shrimp fisheries

Abstract Shrimps are the main fishery resource in marine waters off Sergipe (northeastern Brazil), where they are landed in three categories: ‘espigao’, ‘escolha’ and ‘pistola’. The objective of this study was to identify which species are landed in each category, relating to the perception of stakeholders, and to analyze their effect on the interpretation of historical catch statistics. Samples of 3kg were collected monthly for each category before landing in Aracaju (May/2015-May/2016) to identify the shrimp species caught. All specimens were identified, measured (carapace length - mm) and weighed (total weight - g), and had their sex determined. We interviewed attendees of two meetings promoted by the Programa de Monitoramento Participativo do Desembarque Pesqueiro in Aracaju and Pirambu, the two main ports where shrimp catches are landed in Sergipe, and asked for their perception of shrimp species included in each category. Finally, we used all shrimp catch data available for Sergipe in a national reconstructed database to improve the reconstruction based on the species composition estimated here for the main shrimp species. The analysis of each category indicated the presence of commercially important species (Xiphopenaeus kroyeri, Penaeus subtilis, Penaeus brasiliensis, and Penaeus schmitti), and also species of no local commercial interest: Exhippolysmata oplophoroides, Nematopalaemon schmitti, Rimapenaeus constrictus, and Sicyonia dorsalis. The category ‘espigao’ was dominated by X. kroyeri (94.2%) and ‘escolha’ by P. subtilis (95.3%). ‘pistola’ was mostly P. subtilis (78.3%), almost all of them females, followed by P. schmitti (12.3%). The perception of stakeholders was correct for ‘espigao’ and ‘escolha’, but not for ‘pistola’, as 38% of the respondents classified it as ‘camarao-branco’ (P. schmitti). The mean carapace length for all species together was: 18.90mm (‘espigao’), 22.34mm (‘escolha’), and 30.96mm (‘pistola’). Decreasing catches of X. kroyeri, P. subtilis and P. schmitti in the last years raise concern.

Lambari fish Deuterodon iguape as an alternative to live bait for estuarine recreational fishing

AbstractFishing tourism is growing steadily in Brazil. Artisanal fishers meeting the demand for recreational fishing are capturing live juvenile shrimp in the estuaries and selling them for live bait, preventing the recruitment of a larger contingent into the ocean. This study compares the efficiency of using lambari, Deuterodon iguape Eigenmann, as live bait with the shrimp, Penaeus schmitti Burkenroad, while fishing for common snook (Centropomus spp.), as well as to evaluate the swimming behaviour of D. iguape in different salinities. The results showed that there was no significant difference between the live baits used (P. schmitti vs D. iguape). The month, the period of the day and salinity presented differences. The size of the species did not depend on the type of bait used. There was no statistical difference in swimming behaviour, but there was a trend of increased speed and displacement in the group exposed to a salinity of 10 g/L. In conclusion, D. iguape appears as effective as P. schmitti and can be successfully used as live bait; and from an ecological point of view, it reduces the impact of fishing on juvenile shrimp.

Artisanal fishing characterization and spatio-temporal occurrence of marine shrimp (Crustacea, Decapoda, Penaeidae) in the littoral of Lucena, Paraíba, Brazil

The present study distinguishes types of fishing activities. It records the most economically exploited shrimps in the municipality of Lucena, Paraíba, Xiphopenaeus kroyeri (“espigudo”), and Penaeus schmitti (white shrimp). From October 2014 to October 2015, samples containing 700 gr of shrimp were collected at three sites of artisanal fishing. Data on temperature, ammonium, nitrate, nitrite, chlorophyll-a, salinity, pH, and dissolved oxygen were recorded. Two different shrimp species are commercially used in the region, of 2,628 sampled individuals, X. kroyeri predominated, with 1,957 individuals, followed by P. schmitti, with 671 individuals. At localities 1 (in Lucena beach) and 2 (Fagundes beach) both species were present, the X. kroyeri being predominant, but at locality 3 (Costinha beach) only the P. schmitti was recorded. The regional wet season influenced salinity during the months of the year, producing positive or negative correlations among species found at each locality depending on what was analysed. It is relevant to understand the relationship between fishing resources and environmental variables which provide information about fishing dynamics and permits the development of strategies for the maintenance of stocks and fishing areas, as well as permitting the establishment of public regulations for the better preservation and conservation of marine areas and estuaries on which many species depend for the completion of their life cycles.

Composition and abundance of decapod crustaceans in mixed seagrass meadows in the Paraguaná Peninsula, Venezuela

ABSTRACT Thalassia testudinum and Halodule wrigthii are the dominant seagrasses in the Caribbean, being common across shallow shorelines, either as monospecific or as intermixed meadows. Among the macrofauna associated with these beds, crustaceans are considered essential for the whole ecosystem functioning. However, knowledge about the associated community of decapod crustaceans in assemblages of T. testudinum and H. wrigthii is still scarce, particularly outside of protected areas. Here we report eight new decapod species for the Paraguaná Peninsula (Falcón State, Venezuela) in association with intermixed seagrass beds: Achelous tumidulus Stimpson, 1871, Alpheus aff. floridanus Kingsley, 1878, Chorinus heros (Herbst, 1790), Clibanarius antillensis (Stimpson, 1859), Clibanarius sclopetarius (Herbst, 1796), Latreutes parvulus (Stimpson, 1866), Panopeus occidentalis Saussure, 1857, and Processa fimbriata Manning & Chace, 1971. These records represent habitat extensions and fill gaps in the geographical distribution of the species along the northern coast of South America. Furthermore, we found that statistical differences in decapod species abundance and composition are likely to be caused by the joint action of coverage and heterogeneity of the beds. Our results indicate that typical Caribbean species were the most influential in the community; nevertheless, the abundance of juvenile Penaeus schmitti Burkenroad, 1936 was notable, since they have rarely been found in these habitats. This finding highlights the role of non-protected areas as nursery habitats for economically important species. Our results show that seagrass meadows in the Paraguaná Peninsula reflect overall good health when compared to other Caribbean zones, representing an important habitat for the maintenance of crustacean populations.

Reproductive cycle and size at first sexual maturity of the white shrimp Penaeus schmitti (Burkenroad, 1936) in northeastern Brazil

The present study aimed to investigate the reproductive cycle and size at first maturity of Penaeus schmitti through a macro and microscopic approach. Between August 2011 and July 2012, 1169 specimens were collected by an artisanal fishing vessel operating a double trawl off the coast of Pernambuco, northeast Brazil. The total proportion of males (42%) was significantly lower than females (58%), corresponding to the sex ratio of 1:1.38. The total body length at first ovarian maturation (TL 50 ) in females was estimated at 14.2 cm. The ovarian development was divided into four distinct stages based on histological characteristics and visual observations. This is the first reported occurrence of vitellogenic oocytes in the spent stage of P. schmitti , indicating a rapid ovarian maturation after spawning. Furthermore, the frequency of maturation stages, diameter of oocytes and gonadosomatic index were distributed homogeneously throughout the study period, reinforce a continuous reproductive cycle for P. schmitti population in northeastern Brazil.

Ecological distribution of Penaeus schmitti (Dendrobranchiata: Penaeidae) juveniles and adults on the southern coast of São Paulo state, Brazil

ABSTRACTThis study aimed to describe the ecological distribution and the effects of environmental factor oscillation on the life cycle of Penaeus schmitti along the coastal area of Cananéia, southern São Paulo state, Brazil. Shrimp and environmental factors were sampled monthly from July 2012 to May 2014 at seven sampling stations covering both estuarine and marine environments, using a shrimp fishing boat. A total of 273 juveniles and 829 adults were sampled, and there were significant differences in body size (carapace length – CL) throughout the seasons (ANOVA). Smaller animals were observed in the summers of 2013 and 2014 and at sites closer to the coast, which are under estuarine influence. Adults were observed mostly in autumn and in deeper regions. We detected a positive relationship between the abundance of juveniles and the bottom water temperature and between the abundance of adults and the water salinity (canonical correspondence analysis). The presence of smaller individuals in the estuarine environment demonstrates the importance of the estuaries in this species’ ontogeny, mainly concerning their protection, since this environment has physical (depth) and physiological (salinity) barriers to their predators. Furthermore, we could clearly observe the plasticity of juveniles in relation to environmental factors. In contrast, adults were less tolerant to the variation in environmental factors, mainly water salinity, which was a limiting factor of their distribution. Seasonal differences in body size could be directly associated to this species’ life cycle and characterized by trophic and reproductive migratory activities between the estuarine and oceanic regions.

Informative microsatellites for freshwater and marine shrimp species

Marine and freshwater shrimp are overexploited worldwide due to their high commercial value being usually fished in a predatory manner. The concern about conserving the stocks for economical or ecological reasons has been threatened by the absence of molecular markers for the majority of these species. In this work, we described ten anonymous microsatellites isolated from an enriched-library with magnetic beads technology of Penaeus (Litopenaeus) vannamei genome, considered the most economically important marine shrimp in the world. In addition, we tested these loci and a panel of 21 Simple Sequence Repeat from Expressed Sequence Tag (EST-SSR) loci, also isolated from P. vannamei, in ten other marine and two freshwater shrimp species. The cross species amplification success rate ranged from 32 to 77% in Macrobrachium jelskii and Penaeus (Litopenaeus) schmitti, respectively. These microsatellites appear conservative in a wide spectrum of shrimp groups, facilitating genetic studies in those species in which no microsatellites have been yet described. Key words: Conservative, Simple Sequence Repeat (SSR), shrimp genetic, penaeid, Macrobrachium.

Effects of juvenile hormone antagonist KK-42 on temporal and spatial expressions of FAMeT in shrimp Penaeus schmitti

It has been demonstrated that the treatment of juvenile hormone antagonist KK-42 can significantly accelerate growth of Penaeus schmitti,which has been applied in P.schmitti aquaculture,but the mechanism of KK-42 is unclear.To provide the theory support involved in KK-42 application,the temporal and spatial expressions of farnesoic acid O-methyltransferase (FAMeT),a key synthesis enzyme of methyl farnesoate (MF) which is the important hormone regulating directly crustacean growth,was assayed and the effect of KK-42 on the enzyme was researched.The shrimps (Penaeus schmitti),3.5 5.0 cm long,were randomly divided into two groups,soaked in KK-42 solution at a concentration of 1.95×10-4 mol/L or in the solution without KK-42 for 1 min,respectively,and then cultured in normal way.The levels of FAMeT mRNA were determined using real-time PCR and hemolymph MF titer was analyzed by normal phase high-performance liquid chromatography.Results showed that the expression pattern of FAMeT derived from the muscle,eyestalk and mandibular organ (MO) tissues varied in control,of which,the mRNA levels in muscle and eyestalk tissues were not only relatively low but also little various during the experiment.However,an obvious fluctuation of mRNA level occurred in MO during the stage of experiment,more than 1-fold of increase in mRNA level was observed on days 2,6,7,and 8 comparing to that on day 0.The hemolymph MF content in control shrimps rose during the experiment.Administration of KK-42 resulted in the universal depression on FAMeT expression in three tissues mentioned above;the most significant inhibitory effect occurred in MO where the level of FAMeT mRNA was considerably lower than that in control group from day 1 to day 7;the level even decreased to 50.9% (P0.01),63.4% (P0.01) and 55.7% (P0.01) on day1,day 4 and day 6 after KK-42 treatment,respectively.Meanwhile,the amount of hemolymph MF fell in KK-42-treated shrimps compared to that in control ones during the duration of the experiment,which might be involved in famet transcription depression in the animal tissues,especially in the MO.Our present study demonstrates that KK-42 can significantly inhibit FAMeT expression in the MO and muscle as well as eyestalk tissues of the shrimp Penaeus schmitti and decrease the hemolymph MF titer,which may be one of the growth-promoting mechanisms of KK-42 on Penaeus schmitti.

A novel CYP450 gene (CYP4V18) of the shrimp Penaeus schmitti Burkenroad, 1936 (Decapoda, Dendrobranchiata): cloning and down-regulation of CYP4V18 expression by the imidazole derivative KK-42

The CYP4 family is the most ancient and diversified group of P450 and some members are associated with ecdysteroid metabolism in arthropods. In an attempt to research the possible molecular mechanism of KK-42 action on Penaeus schmitti Burkenroad, 1936, one CYP4 cDNA sequence from the hepatopancreas was first cloned and its spatiotemporal expressions were analysed using real-time PCR, and the haemolymph 20-hydroxyecdysone (20E) level was measured by reverse-phase high-performance liquid chromatography. Results showed that the full-length cDNA contains a 1545 bp open reading frame encoding a predicted protein of 515 amino acids named CYP4V18 by the P450 nomenclature committee. The highest cyp4v18 mRNA level was detected in hepatopancreas. Compared with that of the KK-42 treatment group, the hepatopancreas cyp4v18 expression in the control group increased to >72.3%, even 187.7% () on day 6. The haemolymph 20E levels increased slightly in KK-42-treated shrimps compared to that in controls during the experimental stage. The results show that the hepatopancreas CYP4V18 is not involved in 20E biosynthesis, and likely plays other roles in the shrimp, P. schmitti.

Effects of KK‐42 on Expression of 3‐Hydroxy‐3‐Methylglutaryl‐Coenzyme A Reductase in Penaeus schmitti

Methyl farnesoate (MF) is an important hormone controlling crustacean growth. Our previous study has demonstrated that the treatment of juvenile hormone antagonist KK‐42 can accelerate growth of Penaeus schmitti. The expression of 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase (HMGR), a key enzyme of MF precursor production, was assayed using real‐time PCR, and hemolymph MF titer was determined by high‐performance liquid chromatography. Shrimp, 3.5–5.0 cm long, were soaked for 1 min in KK‐42 solution at a concentration of 1.95 × 10−4 mol/L or in the solution without KK‐42 and then cultured in normal way. Results showed that the highest level of hmgr transcript occurred in mandibular organ (MO). Administration of KK‐42 resulted in HMGR expression to be notably depressed in the MO, even reduced by 80.2% (P < 0.01) and 90.7% (P < 0.01) on Day 1 and Day 7, respectively. The MF level showed a decline trend in KK‐42 treatment compared to that of corresponding control group. Our present study demonstrates that treatment of KK‐42 significantly inhibits HMGR expression in different tissues especially in the MO, which is likely one of KK‐42 growth‐promoting mechanisms on P. schmitti.

A new and practical application of JH antagonist KK-42 to promoting growth of shrimp Penaeus schmitti

The shrimps ( Penaeus schmitti), 0.6–0.8 cm long, were soaked for 1 min in juvenile hormone antagonist KK-42 solution at a concentration of 1.95 × 10 − 4 mol/L, and then cultured in normal way. The body weight of animals rose with increasing culture time in all groups, but was higher in KK-42 treatment. The increase rate of body weight of treatment group was 167% and 68% higher than control group at 30th day and 60th day, respectively; the body weight rose by 42.5% at 90th day and 22.1% at 120th day. Histological observations showed that the number of acini of mandibular organ increased gradually as animals grew, and the diameter of acinus-forming cells was statistically bigger at 120th day than at other times. After KK-42 treatment, both the number of acini and the diameter of gland cells decreased in the entire experiment observed. The results indicated the inhibition of anti-juvenile hormone KK-42 on the development of mandibular organ in P. schmitti.

Spatial and temporal genetic analysis of the Cuban white shrimp Penaeus (Litopenaeus) schmitti

The white shrimp Penaeus (Litopenaeus) schmitti [Burkenroad, M.D., 1936. A new species of Penaeus from the American.Atlantic. Anais Acad. Brasil. Cienc. Rio de Janeiro 8, 315–318.] has been part of commercial fisheries in Cuba since 1953. Over exploitation led to a serious decline of the captures in the early 1980s until the fishery was finally closed due to a population crash and captures were reduced to the extraction of only some breeders for the Cuban hatcheries. Previous population genetic studies in this species had shown that wild populations are genetically diverse over geographic distances as small as a few hundred kilometres providing useful information for managers. The present study provides new evidences on the spatial (and also temporal) variation of the genetic diversity and population structure in P. schmitti Cuban wild populations using both allozymes and microsatellites. It is highly probable that low effective population size of P. schmitti in Cuba results in genetic changes through time as a result of genetic drift. Two likelihood-based methods used in this work to estimated effective population size Ne revealed concordant low effective numbers taking into account the species characteristics.