Natividad García

Influence of environmental variables and reproduction on the gonadal fatty acid profile of tropical scallop Nodipecten nodosus.

We examined the influence of the reproductive cycle and environmental variables on the gonadal fatty acid profile in the tropical scallop Nodipecten nodosus. Individuals from a natural population in north-eastern Venezuela (Caribbean Sea) were sampled monthly during one year. The gonadosomatic index (GSI) and a visual assessment of gonadic status are also reported. The environmental conditions characterized by chlorophyll a, temperature and seston concentration were measured in parallel. The highest reproductive activity, with a GSI of 13-18%, was observed from November 2003 to April 2004, and a decrease in GSI, taken as an indication of three spawning periods, was recorded in October, January and May-June. The GSI was 5-8% outside these intervals. A similar trend was observed in maturity stage frequency. Statistical analysis (MDS-ANOSIM) established two different periods; one dominated by upwelling (January to July) and the other characteristic of non-upwelling conditions (August to December). The fatty acids 16:0, 22:6n-3, 20:5n-3 and 16:1n-7 were responsible for the differences between two periods and explained 50% of the observed variance. Accordingly, during the upwelling period, fatty acids such as 22:6n-3 were positively correlated with temperature, organic seston and bivalves in the spent sexual stage and inversely related to the GSI. Furthermore, individuals in the ripe sexual stage were positively related to 20:5n-3 and 18:3n-3, whereas chlorophyll a was directly related to 18:1n-7 and 16:1n-7. In the non-upwelling period, a significant and positive correlation was obtained between fatty acids such as 20:5n-3 and 22:6n-3 and the GSI and the bivalves in the ripe sexual stage, whereas these acids were inversely correlated with the spent sexual stage. In addition, chlorophyll a was positively related to 18:1n-9 and 18:2n-6. Changes in the gonadal fatty acid profile of N. nodosus were influenced by the environmental variables (exogenous factors) during the upwelling and non-upwelling periods and by reproductions (endogenous factors).

Influence of Environmental Factors on the Reproductive Cycle of the Eared Ark Anadara notabilis (Röding, 1798) In Northeastern Venezuela

ABSTRACT The reproductive cycle of the eared ark Anadara notabilis and its relationship with environmental factors was evaluated every 15 days between March 2004 and February 2005 at the northern part of the Peninsula de Araya, Venezuela. Environmental factors measured included temperature, salinity, chlorophyll a, and total seston, including the particulate organic matter and particulate inorganic matter fractions. Adult specimens were collected using a net drag and then randomly selected to estimate wet live biomass and dry biomass of soft body tissues. Gonad samples were processed with histological analysis to determine sex ratio, developmental stages, and variations of follicle size. Reproduction in A. nolabilis was continuous throughout the year, with spawning peaks occurring in June and October, coinciding with the lowest water temperatures. In March, September, and November 2004, specimens attained the highest dry biomass values, whereas lowest dry biomass occurred in June and October 2004. Stepwise regression analyses demonstrated that temperature and particulate organic matter values are the main modulators of reproductive events. When temperature decreased, dribble spawning was detected in this species, possibly inducing a survival strategy whereby the spawning period is extended to increase reproductive success.

Biometric and reproductive aspects of the pen shell Atrina seminuda (Bivalvia: Pinnidae) in northeastern Venezuela

ABSTRACT The pen shell Atrina seminuda is a target for a small artisanal Caribbean fishery; however, little is known about its biology. The length frequency distribution, biometric relations and reproduction of this species were studied in northeastern Venezuela. Using transects selected from among 360 stations a population was sampled monthly by SCUBA diving. An analysis of 1748 individuals showed a shell height (SH) between 4 cm and 23.6 cm, with an average of 16.7 ± 2.5 cm. For both sexes, statistical differences in mean SH were observed (analysis of variance F (1, 1113) = 69.538; P < 0.001); organisms larger than 22 cm were females, whereas those between 8 and 10 cm were males. Log-linear regressions were estimated for shell length (SL), total weight (TW) and adductor muscle weight (MW) as a function of SH. In all cases there were statistical differences between males and females, with males presenting positive allometry and females showing isometry. Mean SH at maturity for males (8.24 cm) was lower than for females (11.88 cm), and for sexes combined was estimated at 8.71 cm. Gametogenic activity was observed throughout the year, with two main peaks of spawning (April and August/September 2008). All this information is crucial for demographic modelling and stock assessment for managing this species.

Seasonal change in macromolecular support of reproduction of the tropical scallop Nodipecten nodosus : evidence from lipid content and fatty acid profiles of four tissues

Departement deBiologie, Universite ´Laval, Quebec, P.Q. Canada G1K 7P4Changes in total lipids and fatty acid profiles (FAPs) of gonad, digestive gland, mantle and muscle of the tropical scallopNodipectennodosuswereexaminedduringcoastalupwellingandupwellingrelaxationperiods.Totallipidsweremostabun-dantindigestivegland,andintermediateinfemalegonad.Multidimensionalscalinganalysisofsimilarities(MDS-ANOSIM)andsimilaritypercentageanalyses(SIMPER)revealedsignificantchangesofFAPsofthefourtissuesduringtheupwellingandupwelling relaxation periods. During both periods, SIMPER analysis revealed an internal similarity index greater than 90%for FAP of each tissue. However, during upwelling the gonad-FAP showed a lower dissimilarity index with the digestivegland-FAP (10), than with muscle-FAP (11) or mantle-FAP (13). In general, during upwelling, the fatty acids 16:0, 18:0,16:1 n-7, 20:5n-3, 22:6n-3 and total PUFAn-3 explained 42 to 63% of variance between tissues; during upwelling relaxation,these fatty acids together with 14:0 and 18:1 n-7, explained 46 to 64% of variance. During upwelling period, MDS-ANOSIMshowed a close association between FAP of digestive gland and gonad, suggesting a rapid transfer of fatty acids between thesetissues, and consequently, that N. nodosus follows an opportunistic strategy during this period. In contrast, during upwellingrelaxation,theslowandcontinuousfallintotallipidcontentsofdigestivegland(SeptembertoNovember)andtheprogressivereduction of MDS distances between FAPs of digestive gland and gonad (August until November), suggest a gradual transferof lipids from digestive gland to gonad to support the gonad development observed during this period. This suggests thatN. nodosus switches to a conservative strategy during the upwelling relaxation period.Keywords: bivalve, Caribbean Sea, energy reserves, gonad, upwelling season

Diversity and community structure of soft-bottom benthic molluscs in the Araya Peninsula, Venezuela: a baseline for the assessment of environmental impacts

The north-eastern region of Venezuela includes some of the most productive marine ecosystems of the country, sustaining high abundances of fisheries resources. This feature, coupled with the high diversity of coastal ecosystems, increases the interest for the development of conservation policies to prevent and/or mitigate negative environmental impacts associated with human interventions at the area. However, previous malacological assessments made in the Araya Peninsula are mainly restricted to epibiotic molluscs associated with bivalve banks. In this vein, we performed three different surveys for soft-bottom molluscs in the intertidal (using a stainless steel corer), shallow subtidal (Eckman dredge) and subtidal ( Arca zebra dredge) areas of Araya Peninsula. We found 41 species including Bivalvia, Gastropoda, one Cephalopoda and one Scaphopoda, although according to sample-based rarefaction techniques there may be several more undetected species. Since there is an ongoing project aiming to construct a shipping terminal on Araya Peninsula that could adversely affect coastal marine biodiversity in the region, the knowledge about the molluscan assemblage in the area is a key requirement for designing conservation measures.