Enzymatic Approach to Fungal Association with Arthropod Guts: A Case Study for the Crustacean Host, Nihonotrypaea harmandi, and Its Foregut Fungus, Enteromyces callianassae

Abstract. In the callianassid shrimp Nihonotrypaea harmandi (Bouvier 1901), the trichomycete fungus Enteromyces callianassae Lichtwardt 1961 occurs exclusively on the foregut lining. The enzymes from both the shrimp and the fungus apparently hydrolyze certain nitrogen and carbon compounds in detritus. The activities of various proteases and carbohydrases contained in the foregut juice were compared between fungus-infected shrimps collected from a sandflat in Kyushu, Japan (51 % infection rate) and uninfected shrimps from a nearby sandflat. The concentration of enzymatically hydrolyzable amino acids (EHAA) in sediment liberated by the foregut juice with fungi was slightly lower than that by 0.1 mg·ml^-1 proteinase-K and significantly higher than that by the foregut juice without fungi. In both foregut juices, substantial enzyme activities were recorded for proteinase(s), peptidases, amylase, cellulase and β-1,3-glucanase, and minimal ones for maltase and cellobiase. Of the commercial substrates examined, only in the case of the mixture of 16 kinds of dipeptides was a significantly higher enzyme activity in the foregut juice with fungi observed. In the process of EHAA liberation from sediment, peptidases secreted by the fungus most probably act as a supplement to the endogenous secretion by the shrimp. This may explain the higher shrimp growth rate recorded for the population with fungi. However, the significantly higher sediment EHAA concentration of the sandflat inhabited by this population versus the population without fungi could be another crucial factor explaining the site difference in shrimp growth rate.     

Population Dynamics of Sergio mirim RODRIGUES 1971 Decapoda: Thalassinidea: Callianassidae in Cassino Beach, Southern Brazil

Abstract. Thalassinid shrimps have been extensively exploited for bait in many countries around the world. In order to prepare future management strategies for a little-exploited population of Sergio mirim in southern Brazil, growth, mortality and reproduction of this species were studied between June 1988 and November 1992. Size-frequency distributions were dominated by mature individuals, and recruitment occurred in austral spring, with widely variable abundances between years. Females attained larger mean and maximum sizes than males. The sex ratio was balanced for young individuals and female-biased for the mature segment of the population, as previously reported for other species of burrowing shrimps. Ovigerous females were found mostly between September and January, and egg numbers were a function of carapace length. From parameters of the VON BERTALANFFY growth curves, a maximum life span of approximately 4 years was estimated for both sexes. Among callianassids for which reproductive measures are known. S. mirim represents one of the highest reproductive potentials. The advantages of the thalassinidean female-biased sex ratio pattern is discussed.