Three new species of bivalved gastropods, Julia burni from Port Blair, Andaman Islands and Berthelinia (Tamanovalva) ganapatii and B. (Tamanovalva) waltairensis from Visakhapatnam on the south east coast of India are described and their affinities with other species of bivalved gastropods are discussed. Spawning habits and early develomental biology of B. (Tamanovalva) ganapatii are dealt with. The distribution of these unorthodox snails in widely scattered geographical regions is brought to light. The present record of three new species, belonging to two genera brings up the total number of bivalved gastropods in the Indian seas to five species including the two already reported (GANAPATI & SARMA, 1972). In addition the shells of two other species of Julia have been reported from Reunion and Mauritius Islands in the Indian Ocean. However, living animals of the above have not been encountered so far.

View full abstract

The chromosome numbers of 3 species in 3 families of Pteriomorphia are reported, using aceto-orcein squashes of eggs and fire-dryings of gonadal tissues. From Barbatia virescens, chromosome numbers of 14(n) and 28(2n) were counted. From Pecten albicans, 19(n) and 38(2n) chromosomes were counted. Crassostrea ariakensis has 10(n) and 20(2n) chromosomes like 6 species of oysters in last paper. The chromosome complement of B. virescens consists of 5 pairs of meta-or submetacentrics (M-SM) and 9 pairs of subtelo-or telocentrics (ST-T). The chromosome complement of P. albicans consists of 3 pairs of M-SM chromosomes and 16 pairs of ST-T chromosomes, and one of C. ariakensis consists of all M-SM chromosomes, though these karyotype analysis are qualitative.

View full abstract

Anatomical examination was made on Bulinus (Bulinus) truncatus, the vector snail of the human urinary blood fluke in Libya, collected at the oases in the Fezzan area and the habitats of the snail were ecologically surveyed. The anatomical features are as follows : The radula has the arrow-headed mesocone in the lateral teeth and the right midgut gland could not be detected. Among the specimens examined was found a fair number of aphallic specimens, in which the prostate gland degenerates to take the shape of ramifying follicles and the vas deferens ends in a blind tube near the base of the spermathecal duct. The central nervous system is, in general, akin to those of other pulmonate snails in member and arrangement of the ganglia and nervous threads. A nervous thread of the left cerebral ganglion innervates the male copulatory organ and it degenerates in aphallic specimens. The vascular system is similar to those of other Basommatophorus pulmonate species. The Fezzan area is an arid desert and has scanty rainfall, hence water is supplied entirely by pumping up from wells. Water for irrigation is usually reserved in concreate cisterns and supplied through irrigation ditches to small fields. Bulinid snails are restricted in distribution in the cisterns and irrigation ditches.

View full abstract

[in Japanese]

View full abstract

The ovulation of a freshwater clam, Corbicula leana, which has hitherto been believed to be a viviparous species was observed both in indoor laboratory and outdoor culture pond. The results are summarized below : (1) Clams ovulate all the year round in an aquarium with water temperature higher than 19℃. Eggs develop into D-shaped larvae. Spawning and development to D-shape larva are also observed in the same way in an outdoor culture pond. Thus, reproduction of C. leana is of both ovoviviparity and oviparity. (2) D-shaped larvae are reached within 60 hours after being spawned in water temperature higher than 20℃. (3) Ovulation takes place simultaneously for all clams kept in either aquarium or culture pond.

View full abstract