This study evaluated the starvation resistance of the shrimp Neocaridina davidi during the first and the third juvenile stages (named here as JI and JIII) by means of the estimation of point-of-no-return (PNR 50 ). Two experiments were conducted with increasing numbers of days without food and two controls (one with continuous feeding, CF; the other, with continuous starvation, CS). Time to the first molt and number of molts did not differ among the treatments beginning at JI or JIII. Nevertheless, longer periods of starvation influenced growth and survival of juveniles beginning the starvation as JI, but these effects were not observed in JIII. The estimated values of PNR 50 for JI and JIII were 16.15 ± 0.31 and 9.44 ± 0.26 days, respectively. The early stages of the life cycle are more tolerant to starvation than other decapods previously studied. Such ability indicates a great potential of this species for aquaculture.

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Several decapod crustaceans are invaders, but little is known about the biological characteristics that potentiate the success of these decapods in invaded ecosystems. Here, we evaluate and describe some aspects of the reproductive biology and development of Lysmata vittata, an invasive shrimp species in the Atlantic Ocean. In addition, we intend to provide important insights into the biology of invasion by comparing the reproductive traits of this shrimp with some of the predictions about aquatic invasive species. We used experimental and laboratory observations to evaluate the functionality of protandric simultaneous hermaphroditism (PSH), the macro and microscopic development of the ovarian portion of the ovotestes, the reproductive cycle, and the embryonic development of L. vittata. We confirm the functionality of PSH in L. vittata. This shrimp has a rapid reproductive cycle; the ovarian portion of the ovotestes develops (mean ± SD) 6.28 ± 1.61 days after spawning. Embryonic development also occurs over a short time, with a mean (± SD) of 8.37 ± 0.85 days. The larvae hatch without macroscopically visible yolk reserves. Our study provides evidence that the invasive shrimp L. vittata has reproductive and embryonic developmental characteristics (i.e., short generation time and high reproductive capacity) that may be favorable to the establishment of populations during invasive processes.

AIM: The population biology of the freshwater shrimp Macrobrachium jelskii was investigated here emphasizing the length-frequency distribution, sex ratio, reproductive period and juvenile recruitment. In addition, the abundance of individuals was correlated with the abiotic factors. METHODS: Samples were collected on a monthly basis from July 2005 to June 2007 along the river margin in shallow water of Grande River, at Planura region, State of Minas Gerais, Brazil (20º 09' S and 48º 40' W), using a trawl net (1.0 mm mesh size, and 2.0 m × 0.5 m wide). The fishing gear was handled by two people along the marginal vegetation of the Grande River in a course of 100 m, covered for one hour. In the laboratory, the specimens were identified, measured and sexed. RESULTS: A total of 2,789 specimens was analyzed, which corresponded to 1,126 males (549 juveniles and 577 adults) and 1,663 females (1,093 juveniles, 423 adults non-ovigerous and 147 ovigerous). The sex ratio differed significantly in favor of the females of M. jelskii (1:1.48; χ² = 103.95; p < 0.0001). The mean size of carapace length (CL) of females (6.32 ± 1.84 mm CL) was statistically higher than of males (5.50 ± 1.07 mm CL) (p < 0.001). The length-frequency distribution of the specimens revealed an unimodal pattern and non-normal distribution for males and females (W = 0.945; p < 0.01). No significant relationship between the abundance of M. jelskii and the environmental variables was observed (p = 0.799). CONCLUSION: The presence of ovigerous females and juveniles in the population suggests a continuous reproduction pattern and recruitment for M. jelskii at Planura region.

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An integrative approach was used, combining morphological and molecular analyses, to provide the first report of Lysmata lipkei and L. vittata in Sergipe State, Brazil, and confirm that both species are invasive of the Atlantic Ocean. Lysmata shrimps were sampled in the estuary region of the Vaza-Barris river, Sergipe State, northeastern Brazil, and identified as L. lipkei (n = 8) and L. vittata (n = 20). To molecular phylogenetic analysis was used 16S DNA fragments, comparing 26 species of the Lysmata-Exhippolysmata clade and two species of the genus Merguia (outgroup). Phylogenetic analysis indicated the absence of consistent genetic divergence (p distance < 0.018) between specimens from Atlantic and Indo-Pacific oceans. We conclude that L. lipkei and L. vittata have successfully invaded the western Atlantic and are also present in Sergipe State, northeastern Brazil.

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