Macrophyte - mollusc relationship in Lake Kariba

Five species of submerged vegetation Lagarosiphon ilicifolius, Najas pectinata, Vallisneria aethiopica, Ceratophyllum demersum and Potamogeton octandrus; 7 species of gastropods Melanoides tuberculata, Bellamya capillata, Biomphalaria pfeifferi, Bullinus tropicus, Cleopatra sp, and Lymnaea natalensis and 4 species of bivalves Corbicula africana, Caelatura mossambicensis, Mutela dubia and Aspatharia wahlbergii are correlated with environmental variables particularly slope and transparency, in Lake Kariba. A stepwise regression analysis further revealed interdependence between (Cleopatra sp., B. pfeifferi, L. natalensis, B. capillata, and V. aethiopica as well as between as between C. mossambicensis and L. ilicifolius and N. pectinata. The dependence of B. pfeifferi, L. natalensis, B. capillata, Cleopatra sp. on V. aethiopica and C. mossambicensis on L. ilicifolius and N. pectinata implies that a change in the biomass of the vegetation species may affect distribution and biomass of the faunal species.

Sinum haliotoideum (Linnaeus, 1758), a gastropod mollusc new to the marine waters of Pakistan (northern Arabian Sea)

Sinum haliotoideum (Linnaeus, 1758) was collected on only two occasions. However, it was given attention when the recently collected specimen netted on 24 August, 1993 was brought live to the laboratory where its movement towards the source of light was noticed, leading to a careful examination and illustration. The specimen survived for 4 days. Illustrations and shell from the earlier collected specimen (August, 1991) were sent to Dr. Alan R. Kabat, division of Mollusck, National Museum of Natural History, Smithsonian Institution, USA, who confirmed that the specimen was Sinum haliotoideum (Linnaeus, 1758). He further informed that this is a moderately common Indo-Pacific species. The material has been deposited in the collections of the Marine Reference Collection and Resource Centre. (MRC) The species being new to the region is briefly described.

Value addition to mollusc shells for income generation

The poster explains how to make value additions to mollusc shells for income generation among the fishing communities of Lake Victoria, Uganda

Aspects of the biology of the lagoon crab Callinectes amnicola (Derocheburne) in Badagry, Lagos and Lekki lagoons, Nigeria

A preliminary report of the size, composition, growth pattern and food habits of the blue crab, Callinectes amnicola, (De Rocheburne) in the Badagry, Lagos and Lekki Lagoons (Nigeria) is presented. The collection of crabs from the three lagoons covered the period from May 1999 to October 2000. The carapace length for Badagry Lagoon ranged from 2.2 cm to 16.4 cm with weight of 4.4 g to 252.6 g. The crabs showed a unimodal size distribution. For the Lagos Lagoon, crabs sizes ranged from 3.5 cm to 16.8 cm and weighed 3.28 to 277.1 g. The sizes of crabs in the Lekki Lagoon ranged from 3.5 cm to 16.1 cm and weighed 3.5 g to 262.7 g. Crabs from the three lagoons exhibited negative allometric growth. The food items were similar in the three lagoons and comprised mainly mollusc shells, fish parts, shrimps and crab appendages and occasionally higher plant materials

Life cycle of Pisidium obtusale Jenyns. [Translation from: Informatsionnyi Byulleten Biologiya Vnutrennikh Vod No.3 17-21, 1969.]

Pisidium obtusale in the neighbourhood of Borka occurs in deep pools on upland bogs. The majority of water-bodies where this mollusc lives are temporary. Their bottoms are covered with sedges, and sometimes mosses occur. Evidently there is a marked attraction of P. obtusale to places overgrown by willow. In pools remote from scrub or woody vegetation it does not appear. Temporary water-bodies fill up with melt water in the middle or the end of April and finally dry up at the end of July or the beginning of August. Observations on the life cycle of P. obtusale started on 21 April 1966, following on the filling-up of the water-body by melt water. The findings of the study are presented in this paper.

Water mites: predators and parasites

The majority of water mites found in freshwater belong to the Hydrachnellae, a group which exhibit striking morphological diversity. This paper reviews work on the structure, morphology and taxonomy. The role of water mites as predators, their life history and their parasitic associations with aquatic insect or freshwater mollusc hosts is discussed along with the distribution of water mites in the British Isles.

Farming experiments and transfer of technology of bivalve culture along the southwest coast of India

The Central Marine Fisheries Research Institute (CMFRI) in India developed bivalve farming technologies in the 1970s, but these were not widely adopted at the time. In 1993, CMFRI undertook an action research program to encourage farming of edible oysters (Crassostrea madrasensis), mussels (Perna viridis and Perna indica), clams (Paphia malabarica) and pearls (Pinctada fucata) along the southwest coast of India. Successful demonstration of the viability of bivalve farming led to the initiation of commercial farming of mussels and generated interest among farmers and entrepreneurs in developing production of pearls and farming of edible oysters. Given the high potential for the mollusc aquaculture, both for the local and export market, issues such as demarcation and issuance of lease right on aquaculture zones in public waterbodies by the government, organization of marketing systems and provisions for technical and financial support to farmers need to be addressed.

Clam farming in the Mekong Delta, Vietnam

The Mekong Delta region in southern Vietnam has high potential for coastal aquaculture, including mollusc culture. Many mollusc species are cultured for domestic and export markets including white clam (Meretrix lyrata Showerby) and blood cockle (Arca granosa). Techniques for clam farming include the nursery and grow-out phases. At present, there are approximately 600 coastal families engaged in clam farming over a total area of 1,870 ha, of which 82.63% is used for the grow-out phased and 17.7% for the nursery phase. Nursery areas are near the coast and receive less than 5 hours of sunlight per day. The average area for a nursery is 3-4 ha and it is fenced with a net or bamboo stakes to prevent clams from escaping and to prevent water currents from carrying them away. Grow-out farm areas are further from the coast and are exposed to sunlight for only 2-3 hours/day. Average farm area for grow-out is 5-6 ha, and may or may not be fenced. Average operating cost is US$1100 per ha for nursery and US$757 per ha for grow-out (the cost of capital assets are not included) with loans being the main source of financial. Problems for clam farmers in the area include natural phenomena, inadequate culture techniques, lack of financing or credit systems, and marketing. Environment-related problems that cause clam mortality include flooding, and freshwater effluent and siltation or sedimentation from Mekong River. Other problems that constrain the development of clam culture in the area are: marketing problems such as lack of buyers and price fluctuations; exploitation of the natural clam populations.

A few observations on the biology of Tachysurus thalassinus Ruppell from Veraval (Gujarat)

The length-weight relationship of T. thalassinus differed in the sexes and, therefore separate equations were obtained; for males log W = -5.1728 4- 3.0495 log L; and for females log W = -5.7456 + 3.2798 log L. The spawning period of this species appears to be restricted to a short period from October to November. Fecundity has been found to range from 33 to 55 mature eggs in specimens of the size range 421-564mm. The sex ratio of males to females was 1.8:1. T. thalassinus is a bottom carnivore, crustaceans ranking first in food followed by fishes, mollusc and polychaetes.

Characterisation of neurons in the pedal ganglia of the green-lipped mussel, Perna canaliculus, using antibodies raised against neuropeptides and neurotransmitters involved in gastropod egg-laying behaviour and bivalve reproduction and spawning

To characterise central neurons in the pedal ganglia of both male and female green lipped mussel, Perna canaliculus immunohistochemical techniques were used. Mollusc antibodies were used against neuropeptides and neurotansmitters known to control reproduction and spawning. Anti-ELH and anti-APGWamide showed very strong immunoreactivity in small type of neurons. Anti-5-HT and anti-DA immunoreactivity was mostly in large type of neurons. The labelled neurons are consistent with descriptions of neurosecretory cells implicated in the control of reproduction and spawning on the basis of earlier histological staining techniques used in this species. The use of selective immunological markers for peptides and amines appears to be a, promising tool for further characterisation of neurosecretory cells, and to isolate an'tl characterise neuropeptides and other biologically active materials involved in the control of reproduction in Perna canaliculus.

Neurons characterization in the cerebral ganglia of the green-lipped mussel, Perna canaliculus, using antibodies raised against neuropeptides and neurotransmitters involved in gastropod egg-laying behaviour and bivalve reproduction and spawning

Immunohistochemical techniques were used to characterise central neurons in the cerebral ganglia of both male and female Perna canaliculus. We used mollusc antibodies raised against neuropeptides and neurotransmitters known to control reproduction and spawning. Anti-ELH and anti-APGWamide showed very strong immunoreactivity in small type of neurons. Anti-5-HT and anti-DA immunoreactivity was mostly in large type of neurons. The labelled neurons are consistent with descriptions of neurosecretory cells implicated in the control of reproduction and spawning on the basis of earlier histological staining techniques used in this species. The use of selective immunological markers for peptides and amines appears to be a promising tool for further characterisation of neurosecretory cells, and to isolate and characterise neuropeptides and other biologically active materials involved in the control of reproduction in Perna canaliculus.

Status of the biodiversity of St. Martin's Island, Bay of Bengal, Bangladesh

A total of 234 species of fish have been recorded from the St Martin Island. Of which, 98 species are coral associated. The total number of recorded mollusc and crab species stands at 187 and 7 species respectively. A total of 66 coral species were recorded, of which 19 are fossil corals, 36 living corals and the rest are under 6 families of subclass Octocorallia (soft corals). A total of 14 species of algae have been recorded from the St. Martin's Island. There is an estimated amount of 1500 MT red sea weed biomass available around the St. Martin's Island. The island contains some of the most unique, benthic community associations in Bangladesh, not found anywhere else in the South Asian region. The unique marine communities have very high scientific value for research and monitoring and there are only a few examples worldwide, where coral-algal communities dominate rocky reefs. The economy of the island is based on fishing. It is estimated that, about 1650 MT of fish are caught annually. Over-exploitation of renewable marine and coastal resources (e.g., rocky reef fisheries, coral and shell extraction; removal of coastal vegetation from inter-tidal and sub-tidal habitats) is a major threat to this ecosystem. Destructive fishing practices, mainly the use of rock-weighted gill nets over the inshore boulder reefs is of prime aggravates. Proper implementation of the rules and regulation for Ecologically Critical Areas (ECA's), alternative livelihood for the local people and further research should be immediately taken for sustainable utilization and to save the rich biodiversity of the only coral island in Bangladesh.

A mesocosm analytical study on the impact of freshwater mussel (Lamellidens marginalis Lamarck) mediated bioturbation and biodeposition on some ecological factors of a freshwater lake

The biotic potential of the benthic filter feeding freshwater bivalve mollusc Lamellidens marginalis (Lamarck) influencing the nutrient dynamics of the bottom sediments of the lake by means of biodeposition and bioturbation activities were analysed using a lake mesocosm experiment. Five control as well as experimental mesocosms was maintained up to 60 days (d). The factors studied included the percentage of water content of the sediment, percentage of total nitrogen, percentage of organic matter along with the total phosphorus and humic acid content. While total phosphorus and humic acid content of the experimental mesocosoms showed gradual and significant increases from 30d of the experiment to reach the maximum levels after 60d, the percentage of organic matter registered significant increases right from 15d onwards and reached the maximum values after 60d. On the other hand, while the percentage of water content of the sediments of the experimental mesocosoms increased only up to 30d experiment, percentage of nitrogen was increased during the first half and at the fag end of the experiment. All the investigated ecological factors were found to be significantly influenced by the presence of L. marginalis in the experimental mesocosms. The study indicated that the mussel influence the nutrient dynamics of the inhabitant ecosystem through the processes of excretion, biodeposition of pseudofaeces and faeces, along with the bioturbation of the sediments brought about by their ploughing movements. KEYWORDS: freshwater mussel, Lamellidens marginalis, bioturbation, biodeposition, mesocosms.