No abstract

Filter-feeding behaviours of the mussel Perna viridis and the oysters Crassostrea belchen, Crassostl-ea ~radelei, Saccostrea cucculata and Pinctada mal-garifera were compared during natural tidal vanations in the concentration (6 to 40 dry mg total particulate mass I-') and organic content (6 to 2 2 % ) of seston available in the Merbok mangrove system, Malaysia. In P. viridis, C. belcheriand S. cucculata, declining retention eff~ciencles for the largest available particle slze classes of more than 6 to 12 pm diameter were associated w t h an overall organic enrichment of filtered relative to available matter. As seston avdilab~lity increased, a ~n i n~m u m average of 71°,. of the additional filtered matter was rejected by each species as pseudofaeces prior to ingestion. And in all 5 species, preferential rejection as pseudofaeces of filtered particles with higher average inorganic content resulted in the net organic enrichment of ingested relative to filtered matter. In P. viridis and C. belcheri, the efficiency of that net organic selection declined for seston of lower organlc content. Combining all data from each species, absorption efficiencies from ingested organics increased exponent~ally with the organic content of ingested matter Collective findings suggest that key interrelations between component processes of nutrient acquisition were similar to those that have been established for the modeling of feeding, growth and environmental ~mpact among filter-feeding bivalves froin temperate latitudes However, especially fasl growth in P viridis stemmed from higher average (* 2 SE) clearance rates (13.2 A 7.0 l h-' g-' when particulate organic matter c 1 mg I-'), greater average organic enrichment of filtered relative to available matter (0.99 + 0.67) and greater average organic enrichment of ingested relative to filtered matter (0.63 * 0.03) than have hitherto been recorded in any species of bivalve filterfeeder. In contrast, P. margarifera was least well adapted for the pre-ingestive selection of organic matter, with no differential retention on the gill and little selective rejection as pseudofaeces, representing at least part of the physiological basis for characteristically slow growth in pearl oysters.

The invasive ctenophore Mnemiopsis leidyi (Agassiz), which was transported from the Black Sea into the Caspian Sea at the end of the 1990s, has negatively affected the ecosystem of the Caspian Sea. Zooplankton abundance, biomass and species composition were evaluated on the Iranian coast of the Caspian Sea during 2001–2006. A total of 18 merozooplankton (13 species composed of larvae of benthic animals) and holozooplankton (four Copepoda and one Cladocera) species were identified. The total number of zooplankton species found here was 50% less than in a previous investigation performed in the same region in 1996 before the introduction of Mnemiopsis leidyi into the Caspian Sea. Cladocera species seemed to be highly affected by the invasion of Mnemiopsis leidyi; only one species, Podon polyphemoides, remained in the study area, whereas 24 Cladocera species were found in the study carried out in 1996. Whereas among the Copepoda Eurytemora minor, Eurytemora grimmi, Calanipeda aquae dulcis and Acartia tonsa that were abundant before the Mnemiopsis leidyi invasion, only A. tonsa (copepodites and adults) dominated the inshore and offshore waters after the invasion. The maximum in zooplankton abundance (22,088 ± 24,840 ind·m−3) and biomass (64.1 ± 56.8 mg·m−3) were recorded in December 2001 and August 2004, respectively. The annual mean zooplankton abundance during 2001–2006 was in the range of 3361–8940 ind·m−3; this was two‐ to five‐fold less than the zooplankton abundance in 1996. During 2001–2006, the highest abundance and biomass of Mnemiopsis leidyi were observed during summer‐autumn months coincident with warm temperatures and generally when the abundance of other zooplankton organisms was low.

No abstract

This study demonstrates for the first time the presence of marine‐associated mites in the Andaman Sea and Strait of Malacca and reveals a relatively high diversity of these taxa with six species from two different families: Selenoribatidae and Fortuyniidae. Indopacifica , a new genus of Selenoribatidae, is described from Thailand and Malaysia, with two new species, Indopacifica pantai n. sp. and Indopacifica parva n. sp. The genus is characterized by the unique combination of following characters: lacking lamellar ridges, incomplete dorsosejugal suture, fourteen pairs of notogastral setae, and presence of epimeral foveae. A phylogenetic reconstruction based on 18S ribosomal RNA sequences clearly confirms the distinctness of the new genus Indopacifica and places it close to the genus Rhizophobates . The lack of molecular genetic data of possible relatives impedes a clear assessment, and hence, we emphasize the need for further combined approaches using morphological and molecular genetic sequence data. All species show wide distribution areas within this geographic region suggesting that these taxa are good dispersers despite their minute size and wingless body. Molecular genetic data demonstrate recent gene flow between far distant populations of I. pantai n. sp. from the coasts of Thailand and two islands of Malaysia and hence confirm this assumption. The seasonally changing surface currents within this geographic area may favor hydrochorous dispersal and hence genetic exchange. Nevertheless, morphometric data show a slight trend to morphological divergence among the studied populations, whereas this variation is suggested to be a result of genetic drift but also of habitat differences in one population of Alismobates pseudoreticulatus .