NERÉIDIDOS (NEREIDIDAE, POLYCHAETA, ANNELIDA) ASOCIADOS A RAÍCES DE MANGLE ROJO, RHIZOPHORA MANGLE, EN ISLAS SAN ANDRÉS Y PROVIDENCIA, CARIBE COLOMBIANO

The family Nereididae Blainville, 1818, is one of the most representative group of errant polychaete worms, with about 535 described species in 43 genera, with great biological and ecological importance. The aim of this research was to make a taxonomic analysis of the nereidids associated to red mangrove roots, Rhizophora mangle, in the San Andrés, Old Providence and Santa Catalina Archipelago. This archipelago is part of the Seaflwer Biosphere Reserve. San Andrés is the largest island, having 27 km2 of landmass area, while Old Providence Island, located 95 km to the north of San Andrés, has 17 km2; both islands have well developed mangrove forests, composed mainly by R. mangle. The nereidids, deposited in the Coleccion Estuarina y Marina de la Universidad de Antioquia (CEMUA), were identifid with updated keys, by performing dissections and extracting parts with taxonomic value. Four species of polychaetes from the family Nereididae were found: Neanthes acuminata, Neanthes succinea, Neanthes sp., and Platynereis mucronata. Only N. succinea and N. acuminata had been reported from the Colombian Caribbean, being N. succinea the only species previously reported from the archipielago. In addition, systematic, ecological and biogeographical considerations were added for each species.

Parasites in the mangrove oyster Crassostrea rhizophorae cultivated in the estuary of the Graciosa River in Taperoá, Bahia

In this work, parasites associated with the mangrove oyster Crassostrea rhizophorae were studied at a cultivation unit in the estuary of the Graciosa River in Taperoá, Bahia. On a monthly basis, between April 2011 and March 2012, 20 oysters were collected, measured and fixed in 10% formaldehyde. In order to identify the parasites, routine histological techniques were used. The specimens were embedded in paraffin and sections, 7 µm thick, were cut. These were then stained with Harris hematoxylin and eosin and were examined using an optical microscope. The parameters analyzed to investigate water quality showed that the temperature ranged from 23.9 °C to 29.3 °C, water salinity from 0.4 to 24.2 Practical Salinity Units PSU and recorded rainfall from 80 mm to 406.4 mm/month. During the parasitological analyses, infestation of the polychaete Neanthes succinea was observed in 41% of the oysters. Through histological techniques, the following parasites were identified: colonies of Rickettsia-like organisms (RLOs); the protozoa Nematopsis sp. and Ancistrocoma sp.; the turbellarian Urastoma sp.; the metacestode Tylocephalum sp. and an unidentified tapeworm. The data collected showed that there was low-intensity infection with and prevalence of parasites, except for Nematopsis sp., thus attesting that these cultivated oysters were in a healthy condition.

Benthic macrofauna associated with decomposition of leaves in a mangrove forest in Ilhéus, State of Bahia, Brazil

We identified and quantified the benthic macrofauna associated with decomposing leaves of Rhizophora mangle and Laguncularia racemosa, to observe the differences in the abundance and composition of macrofauna between these mangrove species, and to examine whether the abundance and composition of organisms changed with different stations and collection times. Benthic macrofauna, mainly polychaetes and amphipods, were recorded from the fifth day after the installation of the experiment. Annelids including Oligochaeta and Polychaeta were the most numerous group. Crustacea were represented by peracarids (Amphipoda and Tanaidacea) and decapods. Of Hexapoda, only juvenile forms and pupae were present. The most abundant polychaete species was Perinereis brevicirrata, followed by Capitella cf. capitata, Heteromastus filiformis and Neanthes succinea. In one-way analysis of variance (ANOVA) there were no statistical differences between the macrofauna of mangrove species, seasons, or collection times, except among collection times for R. mangle litter bags. Two-way ANOVA showed homogeneity for macrofauna abundance between the groups of collection times for both mangrove species. The richness was similar for R. mangle litter bags, and showed a significant difference for L. racemosa. Abundance and richness were also similar between the mangrove species. The colonization of detritus by benthic invertebrates followed a successional sequence during the decomposition process. This suggests that the density of these organisms and their foraging behaviour affected the decomposition rates of leaves of R. mangle and L. racemosa.

The non-indigenous mussel Musculista senhousia in an Adriatic lagoon: effects on benthic community over a ten year period

The Asian date mussel, Musculista senhousia (Mytilidae), is a good example of a species that has dispersed outwards from its native area through human-mediated transport, establishing sustainable populations in distant parts of the world. The date mussel, which is endemic in the Western Pacific region, appeared and became very abundant in the Sacca di Goro, a brackish lagoon in the Po River Delta (northern Adriatic Sea, Italy) in the early 1990s. Effects of M. senhousia on macrobenthic biodiversity were assessed over a ten year time period. At the study site, the increase in abundance and spread of M. senhousia resulted in an alteration of the pre-established macrobenthic community. Changes in benthic dynamics seemed apparent, through the inhibition of epifaunal, suspension-feeding taxa (Ficopomatus enigmaticus, Mytilaster minimus), and the enhancement of detritivores (Neanthes succinea, Streblospio shrubsolii, Microdeutopus gryllotalpa). It is hypothesized that the Asian date mussel was initially successful because it exploited a naturally disturbed, sparsely occupied environment, rather than interjecting itself among and displacing existing species. Musculista senhousia acted, at least initially, as a colonizer rather than an invader.