Fungal contamination of shrimp feeds a¡ects the shelf life leading to substantial economic losses. Ultrastructural changes in Penaeus monodon sub-adults fed three di¡erent doses (50, 1000 and 2000 ppb) of a£atoxin B 1 (AFB 1 ) were studied. At the end of 4 and 8 weeks of experiment, the hepatopancreas of shrimps were observed for ultrastructural changes. The prominent ultrastructural changes in hepatopancreas of the shrimps fed 1000 and 2000 ppb AFB 1 were rupture of cell membrane and microvillus border, damage and swelling of mitochondria, fragmentation of endoplasmic reticulum, nuclear vacuolation, chromatin condensation and autophagy. This study helps to decipher the ultrastructural changes and relate the e¡ects on biochemical, pathological, immunological and histological architecture of the shrimps fed AFB 1 -incorporated feed. The observed ultrastructural changes could serve as indicators in shrimps exposed to toxicants.

The haemocytes of the Indian edible oyster Crassostrea madrasensis were characterized using light and electron microscopy. The light microscopic study was conducted by staining a monolayer of the haemocytes with Geimsa. Cells without granules and with a large nucleus occupying much of the cytoplasmic area were grouped as hyalinocytes. Those with lesser amounts of basophilic cytoplasmic granules were characterized as semigranulocytes and those with large amounts of a mixture of acidophilic and basophilic granules were termed as granulocytes. Ultrastructural studies also revealed the presence of three types of haemocytes. Scanning electron microscopic studies were used to study the spreading behaviour of the haemocytes. Cytochemical studies revealed the presence of acidphosphatase, peroxidase and prophenol oxidase in the cells.

Recurring mortalities in£icted by the cirolanid isopodCirolana £uviatilis in the juveniles of the Asian seabass, Lates calcarifer, stocked in a cage farm in the Cochin backwaters, from November 2006 to May 2007, were investigated. Hatchery-reared ¢ngerlings (size 8^12 cm) were cultured in £oating cages and mortalities were observed after a rearing period of 1 month. The ¢sh were found dead in the cages, with only the remnants of ¢sh skeleton and all the £esh eaten away. Investigations revealed a very high abundance of isopods, identi¢ed as C. £uviatilis (Crustacea, Malacostraca, Isopoda and Ciroloanidae). During the ¢rst 2 months of stocking, 35% of the ¢ngerlings died, and the cumulative mortality reached 45% in 6 months, considerably reducing the pro¢ts from the venture. Management measures for the control of the isopods are discussed. This is the ¢rst report on the isopod, C. £uviatilis, in£icting serious mortalities in a tropical cage-rearing system in the southwest coast of India.

The present communication deals with a histological study of the pituitary gland of the teleost fish Mugil cephalus, found in the estuarine waters of Cochin area. Six different cell types were identified in the pituitary gland on the basis of their grouping, distribution and staining properties. The prolactin and the TSH cells (thyroid stimulating hormone producing cells or thyrotrops) were identified in the rostral pars distalis and the ACTH cells (adrenocorticotropic hormone producing cells or corticotrops) in the interphase between the neurohypophysis and the rostral pars distalis. The STH cells (somatotropic hormone producing cells or somatotrops) and the gonadotropic cells were distinguished in the proximal pars distalis and the MSH cells (melanin stimulating hormone producing cells or melanotrops) in the pars intermedia.