Javier A. Díaz-Ochoa;
Luis A. Cubillos
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The bigheaded shrimp, Heterocarpus vicarius, is a commercially important species fished by bottom-trawling fleets in the Colombian Pacific. However, the life-history parameters necessary for a proper analysis of the population dynamics of this species remain unknown. This paper studies the growth, maturity, and size-at-age variations, of Heterocarpus vicarious, as well as observations on recruitment patterns. The Von Bertalanffy growth parameters were estimated by sex through modal progression analysis, which consisted of grouping cohorts into age classes. Growth parameters were similar for males and females, without significant differences (F = 3.23, p > 0 . 05 ). The growth of both sexes is described by the following parameters: L ∞ = 15 . 26 ± 1 . 93 cm total length (TL), K = 0 . 594 ± 0 . 24 yr − 1 , and t 0 = − 0 . 66 ± 0 . 31 yr . Size-at-age variability was due mainly to processes occurring before larval settlement, since the mean length of same-age individuals born during different reproductive events (intercohort) varied more than that of individuals born during the same reproductive event (intracohort). Length at 50% maturity was estimated at 11.72 cm TL for females, with 95% confidence intervals between 10.57 and 13.71 cm TL. The growth curve and the relatively advanced age at maturity estimated for H. vicarius in the study area suggest the species is very vulnerable to fishing exploitation.
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The composition, bathymetric distribution, and diel vertical migration of larval euphausiids in the oligotrophic southern Adriatic Sea were studied during the summer of 2003. Larvae of 11 species were identified. Of these, Thysanoessa gregaria is reported for the first time from the Adriatic Sea. Information is presented on the distribution and diel migrations of the five dominant species. Nematoscelis megalops furciliae had the widest bathymetric range, extending from surface to the bottom (1200 m); larvae of Stylocheiron maximum were found from 100 to 1200 m. Euphausia krohnii (calyptopes and furciliae), Stylocheiron abbreviatum calyptopes, and Stylocheiron longicorne furciliae ranged over 800 m. S. abbreviatum (furciliae) and S. longicorne (calyptopes) had more restricted bathymetric distributions. Different populations were associated with layers characterized by specific light intensities. Three migration patterns were observed: (i) nocturnal ascent to upper layers (E. krohnii, N. megalops, S. abbreviatum); (ii) scattered population through the water column (S. maximum); (iii) migration to upper layers at midday and night, and descent during the morning and evening (S. longicorne). Different stages of the same species showed different preferences for light intensity.
Hippolyte obliquimanus is a marine shrimp reported from the Caribbean Sea and Brazil. The literature provides indications for morphological variation between populations from those regions and the species has a troubled taxonomic history. The aims of this study were to analyse morphological and genetic variation in the populations of H. obliquimanus from Brazil and the Caribbean Sea and to verify if those might support separation of H. obliquimanus into two or more species. This hypothesis was tested with the analysis of morphological and genetic data (mitochondrial gene 16S and the barcode region Cytochrome Oxidase I). The material analysed was obtained from samples and from loans of zoological collections. The rostrum as well as pereiopods 3, 4, and 5 were the adult morphological characters that showed variation, but this occurred in samples from both regions, Brazil and the Caribbean Sea. The sequences of the 16S gene were identical among all specimens analysed. There was, however, variation among the sequences of the barcoding gene COI (<2.0%); this divergence separated the specimens into two groups (Brazil versus the Caribbean) and these groups did not share haplotypes. In conclusion, specimens from the regions analysed showed both morphological and genetic variation, but these did not support the separation of H. obliquimanus into two or more species.
Patricio De los Ríos-Escalante;
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The zooplankton assemblages in deep, mostly oligotrophic northern Patagonian lakes are characterized by low species numbers and a marked dominance of calanoid copepods. In the present study, data collected in field work on six water bodies located in Alerce Andino National Park (41°S) were analysed using the Jaccard Index of community similarity and a co-occurrence of null models, and such with the aim of determining potential regulating factors for the observed crustacean assemblages, using a presence-absence matrix. A significant correlation between species number and surface area was found. The null model used species co-occurrence, and the basis of this model is that the species associations observed are random. The results revealed the absence of regulating factors and indicate that the sites are relatively homogeneous, with low species numbers and similar plankton assemblages at all studied sites. This finding is in accordance with similar descriptions for zooplankton assemblages in other Chilean Patagonian lakes.
Unidentified Thalassinidea deposited in the Senckenberg Museum were examined. The collection here presented contains 25 species, including two new genera and five new species, i.e., Axiidae: Anomalaxius floridanus gen. nov., sp. nov.; Meticonaxiidae: Meteoraxius meteor gen. nov., sp. nov.; Callianassidae: Trypaea vilavelebita sp. nov., Callichirus santarosaensis sp. nov.; and Upogebiidae: Upogebia hertwecki sp. nov. The form Calastacus laevis De Saint Laurent, 1972 is recorded only for the second time and is fully described and illustrated from a complete specimen. New distribution data are available herein for all species treated.