B Madhusoodana Kurup

Variations in hepatosomatic index and biochemical profiles among the male morphotypes of Macrobrachium rosenbergii

Abstract Hepatosomatic indices and biochemical profile of the male morphotypes of Macrobrachium rosembergii such as small males, weak orange clawed males, strong orange clawed males, pre-transforming strong orange clawed males, weak blue clawed males, strong blue clawed males of grow-outs and old blue clawed males from the Vembanad lake were studied. Size characterization of M. rosenbergii agreed with the earlier reports. A marked variation in hepatosomatic index (HSI) of morphotypes indicated the possibility of differences in food assimilation and growth rates. Mean HSI values were highest in strong orange clawed males (6.351) and lowest in small males (2.814). Among the various biochemical components of male morphotypes studied, protein, RNA and DNA in muscle tissue as well as carbohydrate and RNA in hepatopancreas showed significant differences. Faster somatic growth observed in strong orange clawed males can be correlated with the higher values of protein, DNA and RNA recorded in the muscle tissue as well as high HSI, carbohydrate and RNA contents of hepatopancreas. The results of the present study reveal that there exists perceptible variations in HSI and biochemical profiles among the male morphotypes of M. rosenbergii .

Size at sexual maturity, egg number and reproductive output of the snapping shrimp Alpheus euphrosyne euphrosyne De Man, 1897

Abstract Aspects of the reproductive biology of snapping shrimp Alpheus euphrosyne euphrosyne inhabiting a tropical estuary were studied between August 2007 and July 2008 by examining 1309 females of 8.5–21.5 mm carapace length. Although the occurrence of ovigerous females was noted from October, the main breeding season extended from January to March. Size at 50% sexual maturity was estimated as 10.6±1.40 mm CL. Number of eggs per brood ranged from 141 to 1553 in females of 11.2 to 19.2 mm CL and mean absolute fecundity was estimated as 480±272 eggs. Regressions of log egg number on log total length, log carapace length and log weight revealed isometric relationships (p <0.01). Results of ANOVA revealed significant variation between mean short and long axes of eggs among five embryo developmental stages (P <0.05). The estimated egg batch 33 volume ranged from 4.99 to 32.09 mm3 with a mean of 12.44 mm3. Estimates of reproductive output from 41 females ranged between 8.21 to 31.25% with a mean value of 18.55±5.81.

Reproductive traits of deep-sea armoured shrimp, Glyphocrangon investigatoris from Bay of Bengal, Indian Ocean

Details on size at first maturity, embryo number and size, brood chamber volume and reproductive output of deep-sea armoured shrimp, Glyphocrangon investigatoris caught off the south-east coast of India by using EXPO trawl from 633 m depth in FORV ‘Sagar Sampada’ are reported here. Eighty-four female shrimps ranging from 17.29–36.31 mm carapace length and 2.28–16.54 g weight formed 7.73% of total catch, 30% of which was constituted by embryo-bearing females. Regression of weight on carapace length revealed negatively allometric growth (r 2 = 0.85, P

Food and feeding habits of the exotic fish Oreochromis mossambicus (Peters, 1852) from a tropical reservoir of Chalakudy River, Kerala

The diet composition of the exotic fish, Oreochromis mossambicus (Peters, 1852) was studied in Poringalkuthu Reservoir, Kerala from June 2011 to May 2012. O. mossambicus (2.52 t) forms a regular fishery which indicate that the fish has been established successfully in the reservoir. Gut content analysis revealed detritus to be the dominant food item followed by chlorophyceae, cyanophyceae, bacillariophyceae, zooplankton, plant matter, sand particles, fish parts, insects and miscellaneous items. The present study shows that the species is an omnivore, with a euryphagous feeding habit.