G. Padmavati

Abundance, species composition of microzooplankton from the coastal waters of Port Blair, South Andaman Island

BackgroundMicrozooplankton consisting of protists and metazoa <200 μm. It displays unique feeding mechanisms and behaviours that allow them to graze cells up to five times their own volume. They can grow at rates which equal or exceed prey growth and can serve as a viable food source for metazoans. Moreover, they are individually inconspicuous, their recognition as significant consumers of oceanic primary production. The microzooplankton can be the dominant consumers of phytoplankton production in both oligo- and eutrophic regions of the ocean and are capable of consuming >100% of primary production.ResultsThe microzooplankton of the South Andaman Sea were investigated during September 2011 to January 2012. A total of 44 species belong to 19 genera were recorded in this study. Tintinnids made larger contribution to the total abundance (34%) followed in order by dinoflagellates (24%), ciliates (20%) and copepod nauplii (18%). Foraminifera were numerically less (4%). Tintinnids were represented by 20 species belong to 13 genera, Heterotrophic dinoflagellates were represented by 17 species belong to 3 genera and Ciliates comprised 5 species belong to 3 genera. Eutintinus tineus, Tintinnopsis cylindrical, T. incertum, Protoperidinium divergens, Lomaniella oviformes, Strombidium minimum were the most prevalent microzooplankton. Standing stock of tintinnids ranged from 30–80 cells.L-1 and showed a reverse distribution with the distribution of chlorophyll a relatively higher species diversity and equitability was found in polluted harbour areas.ConclusionsThe change of environmental variability affects the species composition and abundance of microzooplankton varied spatially and temporarily. The observations clearly demonstrated that the harbor area differed considerably from other area in terms of species present and phytoplankton biomass. Further, the phytoplankton abundance is showed to be strongly influenced by tintinnid with respect to the relationship of prey–predator. Consequently, further investigation on microzooplankton grazing would shed light on food web dynamics.

Habitat Ecology and Ichthyofaunal Diversity of Two Creeks and Their Associated Streams from Port Blair, South Andaman Islands

Habitat ecology and ichthyofaunal diversity were analyzed from two creeks and their associated streams in Port Blair: one was perennial and the other one was seasonal. Various habitat types like riffles, pools, and major and minor bends in both streams were studied. The perennial stream has 12 riffles and 14 pools from head point to the entering point of the creek. The seasonal stream has 15 riffles and 13 pools from the starting point to the sink. The perennial stream was found to have higher ichthyofaunal diversity than the seasonal stream: 1701 individuals constituting 8 orders, 30 families, 42 genera, and 54 species were recorded. Among these, 395 specimens represented by 21 species were found in perennial stream, 291 specimens with 11 species were found in seasonal stream, 863 specimens by 48 species were noted in creek, and 152 specimens constituting 14 species in sink were recorded. The physicochemical parameters of the habitats showed more or less a similar trend. The average dissolved oxygen value of the perennial stream was higher than that of the seasonal stream. Higher temperature values were noted during the postmonsoon season. This study has indicated a wide lacuna in the knowledge of the fresh water habitats and their inhabitants on these islands.

Two new species of Tortanus (Atortus) (Copepoda, Calanoida, Tortanidae) from the Andaman Islands

Two new species of the planktonic copepod genus Tortanus, subgenus Atortus, are described from inter- to sub-tidal water of South Andaman Island, India. The new species are assigned to the tropicus group sensu Othman (1987) and distinguished from the other members of the group by the characteristic morphology of the pair of posterior dorsolateral processes on the fifth pedigerous somite in the female and the antennule and leg 5 in the male. An analysis of previous records of the tropicus species group indicates their sporadic occurrence combined with high species richness in Southeast Asia, suggesting future discovery of even more species by sampling with finer geographic and habitat coverage.

First Record of the Pink Lipped Moray Eel, Echidna rhodochilus (Bleeker 1863) (Family: Muraenidae), from Andaman and Nicobar Islands, India

The paper is the first record of the occurrence of the Pink Lipped Moray Eel, Echidna rhodochilus (Bleeker 1863), from India. The current specimen was caught from the mangrove creeks of Carbyn’s Cove, South Andaman. This species is known so far from Western Pacific and southeastern Indian Ocean up to Australia and Indonesia. The present study indicates that there are more studies to be conducted on the ichthyofauna of these islands for a better understanding of the biodiversity of this area.

Food and Feeding Dynamics of Stolephorus commersonnii (Lacepede, 1803) (Family: Engraulidae) from South Andaman

The feeding dynamics of Stolephorus commersonnii along the coastal waters of South Andaman during October, 2011, to September, 2012, were examined by employing “point’s method.” The results of the present study has shown that S. commersonnii mainly is a planktonivorous carnivore chiefly feeding in the pelagic realm on planktonic crustaceans, bivalves, gastropods, and miscellaneous food items. The copepods formed the main prey item, contributing their maximum during November 2011 (47.55%) and lowest in December (24.21%) which was confirmed by various food preference indices. There was no significant seasonal variation in the feeding preference. Lower length classes fed mainly on planktonic copepods and amphipods whereas the higher length classes fed mainly on postlarval shrimps and planktonic crustaceans like Lucifer sp. and Acetes sp. Feeding intensity was seasonal, but independent of the length of fish. Gastrosomatic index was highest during monsoon, indicating active feeding. During the period when a maximum percentage of fully mature individuals were present, the feeding intensity was found to be low. The trophic level of this species was found to be .