Caridean Shrimps

Grass shrimp collected by the Community Aquatic Monitoring Program (CAMP) in estuaries of the southern Gulf of St. Lawrence, Canada were previously assumed to be the native Palaemon vulgaris Say, 1818. Taxonomic identification of grass shrimps from CAMP estuaries revealed most individuals were P. vulgaris, but several from the Souris River and Trout River estuaries in Prince Edward Island (PEI) belong to the European species P. adspersus Rathke, 1837. We provide the first documented presence of P. adspersus in PEI estuaries, extending its known range in Atlantic Canada from coastal Newfoundland and the Magdalen Islands. Boat traffic was probably responsible for the introduction of P. adspersus. The results highlight the importance of community-based monitoring in coastal ecology.

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 (20° 09’ S and 48° 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 nonovigerous 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.

Eight species of alpheid shrimps are reported for the first time from the coral reef systems off Mexico’s northern Yucatan Peninsula (Alacranes, Madagascar and Serpiente Reefs). These species are: Alpheus immaculatus; Alpheus paraformosus; Alpheus punctatus; Parabetaeus hummelincki; Salmoneus depressus; Synalpheus chacei; Synalpheus dominicensis; and Synalpheus elizabethae. The geographical ranges of these species are extended into the southern Gulf of Mexico; most of them are recorded from Mexican territorial waters for the first time. Brief notes on their ecology and taxonomy are provided. Six species are illustrated by colour photographs.

Background: The genus Lysmata includes about 40 described species of which at least 12 species occur in the western Atlantic. The present study records the extension of the southern limit of distribution of two species of Lysmata to the coast of São Paulo. Results: A total of 17 and two individual of Lysmata ankeri and Lysmata cf. intermedia were sampled, respectively. Lysmata ankeri were observed inhabiting crevices and natural burrows formed by rocks from 5 to about 15 m depth, while Lysmata cf. intermedia were found living under a large rocky plate from 8 meters depth.

The objective of this research is to test the effects of copper on the color of pacific white shrimp (Litopenaeus vannamei)
in vivo. Forty-eight shrimps (L. vannamei) were exposed to a low concentration of copper (1 mg/L; experimental treatment)
and forty-eight shrimps were used as controls (no copper added to the water). As a result of this experiment, it was found
that shrimps with more copper are significantly redder than those designated as controls (hue (500–700 nm): P = 0.0015; red
chroma (625–700 nm): P,0.0001). These results indicate that redder color may result from exposure to copper and challenge
the commonly held view that highly pigmented shrimps are healthier than pale shrimps.

Macrobrachium jelskii (Miers, 1877) occurs in all major Brazilian drainage basins. Considering its wide distribution and the supposed isolation of certain populations, we evaluated phylogenetic relationships among populations from several river basins. Analyses of molecular data using the mitochondrial COI and 16S genes suggest the division of the species into two clades, " Amazonian " and " coastal. " The genetic divergence between these two groups is greater than the genetic divergence within the respective groups. Based on the time of divergence and the probable natural distribution of the species, we suggest two evolutionary scenarios to explain the origin of the coastal clade. The first scenario considers the capacity of M. jelskii to tolerate saline environments. The second is based on Pliocene climate changes that would have caused river confluence from sea level regression. The two clades occur sympatrically but this is a recent condition. The wide geographic distribution and low genetic divergence of the Amazonian clade allows us to propose that the current distribution of M. jelskii is partly due to human activity. Pending future analysis, the absence of a consistent morphological synapomorphy precludes the description of a new cryptic taxonomic entity for M. jelskii.

Parasites that invade the nervous system of their hosts have perhaps the best potential to manipulate their host’s behavior, but how they manipulate the host, if they do at all, could depend on their position within the host’s nervous system. We hypothesize that parasites that live in the nervous system of their host will be randomly distributed if they exert their influence through non-specific effects (i.e., general pathology), but that their position in the nervous system will be non-random if they exert their influence by targeting specific neural circuits. We recorded the position of larval tapeworms, Polypocephalus sp., in the abdominal ganglia of white shrimp, Litopenaeus setiferus. Tapeworms are more common within ganglia than in the section of the nerve cord between ganglia, even though the nerve cord has a greater volume than the ganglia. The tapeworms are also more abundant in the periphery of the ganglia. Because most synaptic connections are within the central region of the ganglion, such positioning may represent a trade-off between controlling the nervous system and damaging it.