Variation in penaeid shrimp growth rates along an estuarine salinity gradient: Implications for managing river diversions

Freshwater inflows from river diversions may affect nekton populations by altering the salinity and temperature of estuarine waters. To investigate the influence of these environmental variables on the growth and survival rates of brown shrimp Farfantepenaeus aztecus and white shrimp Litopenaeus setiferus, we conducted field experiments in May and September 2007 to expose experimental animals to the range of different combinations of salinity and water temperature that commonly occur in an estuarine environment. Growth rates for shrimp held in mesocosms for approximately 7 days were compared among four locations and three treatments; locations were identified by the dominant marsh vegetation and distance from the Gulf of Mexico (low to high salinity: Intermediate, Brackish, Saline UE = Saline Up Estuary, Saline DE = Saline Down Estuary). At each location, the treatments were replicated four times and included shallow water with additional food, shallow water without food added, and deeper water (an attempt to expose animals to lower temperatures). Our experiments were designed to test the null hypothesis that shrimp growth and survival rates did not differ by location or treatment. Both brown shrimp and white shrimp grew more slowly at the Intermediate than higher salinity locations. Potential prey (benthic infauna) biomass was relatively low at both the Intermediate and Brackish locations in May, and both shrimp species consistently grew faster in mesocosms where food was added. We conclude that reduced growth in low salinity environments is likely due to the combined effects of increased metabolic costs and less food in these areas. River diversions that reduce estuarine salinities over a large portion of available habitat during peak recruitment periods may reduce overall growth rates and shrimp productivity in the affected areas.     

Susceptibility of nontarget organisms to Nosema algerae (Microsporida: Nosematidae), a parasite of mosquitoes.

Host response of two penaeid species, Penaeus aztecus and P. setiferus, from the Gulf of Mexico to the pathogenic fungus Fusarium sp. isolated from the California brown shrimp, P. californiensis, was studied in vivo. The hemocytic response to this fungus was traced histologically in the gills. Both species showed complete resistance to infection by the fungal spores when normal or wounded shrimp were held in seawater containing the spores or when spores were injected directly into the shrimp in low concentrations. Complete melanization and encapsulation of the micro- and macroconidia were observed. Spore dosages of 3.2 × 10⁶ or more were lethal, apparently due to mechanical blockage of the blood sinuses of the gills.     

Population Genetic Structure of Pacific White Shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>) from Mexico to Panama: Microsatellite DNA Variation

Genetic variation and population structure of wild white shrimp (Litopenaeus vannamei) from 4 geographic locations from Mexico to Panama were investigated using 5 microsatellite DNA loci. The genetic diversity between populations was indicated by the mean number of alleles per locus and mean observed heterozygosity, which ranged from 7.4 to 8.6 and from 0.241 to 0.388, respectively. Significant departures from Hardy-Weinberg equilibrium were found at most locations at each locus, with the exception Guatemala at Pvan0013, and were caused by high heterozygote deficiencies. Genetic differences between localities were detected by pairwise comparison based on allelic and genotypic frequencies, with the exception of locus Pvan1003. Significant pairwise F _ST values between locations and total F _ST showed that the white shrimp population is structured into subpopulations. However, population differentiation does not follow an isolation-by-distance model. Knowledge of the genetic diversity and structure of L.vannamei populations will be of interest for aquaculture and fisheries management to utilize and preserve aquatic biodiversity.     

Effect of Lactobacillus plantarum isolated from digestive tract of wild shrimp on growth and survival of white shrimp (Litopenaeus vannamei) challenged with Vibrio harveyi

Two hundred and two strains of lactic acid bacteria (LAB) isolated from digestive tracts of cultivated and wild adult shrimp, including Litopenaeus vannamei, Metapenaeus brevicornis and Penaeus merguiensis were selected based on their antibacterial activity against Vibrio harveyi. LAB strain of MRO3.12 exhibiting highest reduction of V. harveyi was identified as Lactobacillus plantarum MRO3.12 based on the nucleotide sequence of its 16S rDNA, which showed 99% (780/786 bp) homology to L. plantarum strain L5 (GenBank accession number DQ 239698.1). Co-cultivation of V. harveyi and L. plantarum MRO3.12 showed complete reduction of V. harveyi at 24 h under aerobic and anaerobic conditions, whereas L. plantarum increased from 5.29 to 9.47 log CFU ml⁻¹. After 6-week feeding trial with L. plantarum supplemented diet, white shrimp (L. vannamei) exhibited significant differences (p < 0.05) in relative growth rate (% RGR), feed conversion ratio (FCR) and survival compared to the control group fed with non-supplemented diet. LAB-fed group showed 98.89% survival, whereas only 68.89% survival was observed in the control group. LAB from the digestive tract of probiotic-fed shrimp showed higher level of 5.0 ± 0.14 log CFU/g than the non-supplemented ones (3.34 ± 0.21 log CFU/g). However, total bacterial and non-fermenting vibrios counts decreased in shrimps fed on L. plantarum. Ten days after infection with V. harveyi (5.3-5.5 log CFU ml⁻¹), significant survival (p < 0.05) of 77% was observed in LAB supplemented shrimp, while only 67% survival was observed in the control.     

Isolation and characterization of new microsatellite loci in the Pacific white shrimp Litopenaeus vannamei and cross‐species amplification in other penaeid species

The goal of the present study was to obtain valuable microsatellite markers useful in genetic approaches of the shrimp Litopenaeus vannamei, an important aquaculture species of the world. Eight loci produced suitable polymorphic patterns with allele number ranging from two to 12 and expected heterozygosity from 0.18 to 0.89. Cross‐species amplification was successfully performed in five other penaeid species (Litopenaeus schmitti, Farfantepenaeus brasiliensis, Farfantepenaeus paulensis, Xiphopenaeus kroyeri and Rimapenaeus constrictus), indicating that some these loci can be useful in studies of other related species.     

Structural and functional differences of Litopenaeus vannamei crustins

Penaeid crustins were described in Litopenaeus vannamei and L. setiferus as proteins belonging to an antibacterial peptide family with similar sequences but different sizes. Six crustin-coding clones were isolated from a cDNA library from L. vannamei hemocytes, sequenced and compared. Two different isoforms (named I and P) were found, based on two nucleotide differences that produce one change in amino acid sequence (Ile/Pro). Other single differences in nucleotide sequences were also noted, but they did not change the translated product. The mRNA steady state levels of crustin I, but not of crustin P, were down regulated by Vibrio alginolyticus inoculation. Thus, the differences among penaeid crustins seem to be associated with one amino acid substitution, which affects their expression after bacterial inoculation. By structural similarity, shrimp crustins seem to belong to an antibacterial WAP-domain containing protein family.     

Feeding rhythms and diet of Farfantepenaeus paulensis under pen culture in Patos Lagoon estuary, Brazil

The feeding habits of Farfantepenaeus paulensis under pen culture in the Patos Lagoon estuary (Brazil) were studied. A total of 1074 shrimp had their stomach contents analyzed. Samples were taken bi-hourly over a 24 h period at about 10 day intervals during 2 months. F. paulensis did not exhibit strict feeding periodicity (except at D_21-22 and D_32-33). Thus, the offering of feed pellets during daylight is recommended but the rates of feeding must be further investigated. F. paulensis showed an omnivorous feeding behavior. Despite daily supply of feed pellets, natural food comprised the major part of the shrimp stomach contents. Among prey organisms, polychaetes and tanaids were the main groups recorded. Consumption of detritus and plant material decreased as shrimp grew. Intake of feed pellets increased significantly in the second month of culture (i.e. 5 g mean shrimp weight), thus it might be possible to reduce the initial input of commercial feed.     

A new fungus disease of the white shrimp Penaeus setiferus

A primary mycosis of larvae of the white shrimp, Penaeus setiferus, is described. The disease first became apparent in larvae in the second protozoeal stage and disappeared as the shrimp reached the first mysis stage. Affected shrimp became immobilized by near complete tissue destruction and replacement by the expanding mycelium. The fungus was found to be Lagenidium sp. and was infective to larval brown shrimp, Penaeus aztecus.     

Preferential behavior of white shrimp Litopenaeus vannamei (Boone 1931) by progressive temperature–salinity simultaneous interaction

For different combinations acclimation temperature–salinity of shrimp (Litopenaeus vannamei) the preferred temperature range was from 26.1 to 31.4 °C without salinity effect.     

Combined effects of temperature and salinity on critical thermal minima of pacific white shrimp Litopenaeus vannamei (Crustacea: Penaeidae)

Critical thermal minima (CTMin) were determined for the Pacific white shrimp Litopenaeus vannamei juveniles from four different acclimation temperatures (15, 20, 25, and 30 °C) and salinities (10‰, 20‰, 30‰, and 40‰). The lowest and highest CTMin of shrimp ranged between 7.2 °C at 15 °C/30‰ and 11.44 °C at 30 °C/20‰ at the cooling rate of 1 °C h⁻¹. Acclimation temperature and salinity, as well as the interaction of both parameters, had significant effects on the CTMin values of L. vannamei (P<0.01). Yet, the results showed a much more profound effect of temperature on low thermal tolerance of juveniles. Only 40‰ salinity had an influence on the CTMin values (P<0.01). As the acclimation temperature was lowered from 30 to 15 °C thermal tolerance of the shrimp significantly increased by 3.25–4.14 °C. The acclimation response ratio (ARR) of the Pacific white shrimp exposed to different combinations of salinity and temperature ranged between 0.25 and 0.27. When this species is farmed in sub-tropical regions, its pond water temperature in the over-wintering facilities (regardless of the water salinity level) must never fall below 12 °C throughout the cold season to prevent mortalities.     

Immunological dietary analysis of two penaeid shrimp species from a South Carolina tidal creek

The natural, visually unrecognizable components of the diets of two species of penaeid shrimp were studied utilizing immunological methods. Seine samples of Penaeus aztecus Ives and P. setiferus (L.) were collected biweekly from May to November, 1983 in a tidal creek of North Inlet, South Carolina. Three size classes were established to examine possible ontogenetic shifts in diet as the shrimp grew. Immunoassays for P. aztecus indicated both macrofaunal and meiofaunal taxa present in all three size classes, with no single dominant prey. P. setiferus proventricular contents, however, revealed consistent presence of three prey items (Palaemonetes pugio (Holthuis), Uca pugnax (Smith), and Sesarma reticulatum (Say), as well as gammarid amphipods, polychaetes, periwinkles, and foraminiferans.     

Whiteleg shrimp (Litopenaeus vannamei, Boone, 1931) isotrypsins: Their genotype and modulation

Based on information about isotrypsins found by substrate-SDS-PAGE in the whiteleg shrimp Litopenaeus vannamei and their segregation, an explanation for the presence of three-trypsin phenotype was sought. Isotrypsins A, B, and C depend on two loci: locus β, which is homozygous, yielding isoenzyme C, and locus α, which is heterozygous, yielding isoenzymes A and B. Segregation in locus α in offsprings from 20 families was analyzed. Results demonstrated that isotrypsins were segregated according to Mendelian rules, and hence, external stimuli did not affect the phenotype. To corroborate this, the phenotype was evaluated in relation to changes in trypsin activity during a digestion process. Trypsin phenotypes found in shrimp feces were also analyzed. Results showed that phenotypes were conserved by individuals. Therefore, changes in trypsin activity found in previous investigations must be related to changes in the concentration of the established isotrypsins.     

Susceptibility to an inoculum of infectious hypodermal and haematopoietic necrosis virus (IHHNV) in three batches of whiteleg shrimp Litopenaeus vannamei (Boone, 1931)

The present study evaluated the susceptibility of three different batches of whiteleg shrimp Litopenaeus vannamei from Mexico to an inoculum of infectious hypodermal and haematopoietic necrosis virus (IHHNV). Each of the three shrimp batches came from a different hatchery. Because of their origin, it was possible that the genetic makeup of these batches was different among each other. The three batches tested showed differences in IHHNV susceptibility. Here, susceptibility is defined as the capacity of the host to become infected, and it can be measured by the infectivity titer. Susceptibility to IHHNV was observed in decreasing order in shrimp from batch 1 (hatchery from El Rosario, Sinaloa), batch 3 (hatchery from Nayarit) and batch 2 (hatchery from El Walamo, Sinaloa), respectively. The largest susceptibility difference between batches was 5012 times, and that between early and late juveniles from the same batch was 25 times. These results indicate that within a species, susceptibility to a pathogen such as IHHNV can have large differences. Susceptibility to pathogens is an important trait to consider before performing studies on pathogenesis. It may influence virological parameters such as speed of replication, pathogenicity and virus titer. In order to evaluate the potential use of IHHNV as a natural control agent against white spot syndrome virus (WSSV), it is necessary to know host susceptibility and the kinetics of IHHNV infection. These features can help to determine the conditions in which IHHNV could be used as antagonist in a WSSV infection.     

Isolation and characterization of microsatellite markers from Pacific white shrimp (Litopenaeus vannamei)

We report the development of 11 polymorphic microsatellite loci in pacific white shrimp (Litopenaeus vannamei) using an unenriched genomic library. The number of the alleles ranged from two to 18 and observed hererozygosity ranged from 0.0286 to 0.9429, indicating that these markers will be useful for population studies and mapping in pacific white shrimp. Seven loci were detected deviated from Hardy–Weinberg, caused by deficiency of heterozygote, suggesting population genetic structure across the sampled population. No evidence for linkage disequilibrium was found.     

Effects of salinity on larval stages of the rhizocephalan barnacle Loxothylacus texanus: survival and metamorphosis in response to the host, Callinectes sapidus

It is known that the rhizocephalan barnacle Loxothylacus texanus infects the greater blue crab, Callinectes sapidus, in the Gulf of Mexico and adjacent waters, however, factors that affect the prevalence and distribution of this parasite, particularly the dispersive larval stages of this organism, are not well understood. In the current study, the effects of salinity on larval survival and the metamorphosis of L. texanus in response to postmolt host exoskeleton were examined. Acute and acclimated responses were similar. Larval survival was highest in the 20-35‰ range, with 100% mortality of nauplii at all salinities <20‰ and >50‰. L. texanus cyprids were able to metamorphose over a broad range of salinities (15-60‰). In several cases, metamorphosis was actually greatest at high salinities (40-50‰). These data predict that L. texanus larvae would be concentrated in portions of Gulf of Mexico waters with salinities >20‰ such as the mouths of estuaries and bays. Conversely, upper regions of estuaries may be inhospitable to the dispersive (naupliar) stage of the parasite and may serve as a refuge from infection for host crabs.     

Histochemical demonstration of melanin in cellular inflammatory processes of penaeid shrimp

Brown-to-black pigment deposits present in association with sites of hemocytic activity in penaeid shrimp (Crustacea, Decapoda) were demonstrated to be melanin by use of histochemical techniques. The brown-black pigment was associated with cellular inflammatory disease processes of infectious and noninfectious etiologies in Penaeus californiensis, P. stylirostris, P. vannamei, and P. duorarum.     

Implication of an environmentally induced hamartoma in commercial shrimps

An overgrowth of muscle protruded through the ventral portion of the sixth abdominal segment of Penaeus aztecus and P. setiferus. This hamartoma was observed in 33 postlarval shrimp and is the first reported from a crustacean. Even though afflicted individuals represented a small proportion of the shrimp examined, nearly all such individuals were collected from the presumed most heavily polluted site. We suggest an unidentified pollutant as the cause of the abnormality.