Monosex male culture of C. quadricarinatus is proposed for increasing yields because males reach a larger size at harvest than females. An experiment was done to evaluate the effects of androgenic gland extract and temperature on sex reversal and somatic growth in early juvenile females. Females were exposed to the following experimental conditions: C: control food and temperature maintained at 26 ± 1°C; HT (high temperature): control food and temperature maintained at 28.5 ± 1°C; VHT (very high temperature): control food and temperature maintained at 31 ± 1°C; AG: food with enriched with androgenic gland (1/10 dose for each juvenile per day) and temperature maintained at (26 ± 1)°C. The juveniles were weighed, sexed, and growth increment (GI) and growth rate (GR) were calculated twice a month. The HT and AG groups differed from the C group in GI and GR indicating a greater somatic growth. At the end of the experiment, the HT and AG groups had similar weight but only the HT group had enhanced oocyte diameter, with some vitellogenic oocytes compared to the C group. In the HT group, there was significant sex reversal, as indicated by development of male and intersex male characteristics in different individuals. Both temperature and AG diet have a high potential for culture of this species because of their enhancement of somatic growth; higher temperature increases the proportion of males, a desirable characteristic of cultured populations.

Abstract:The population dynamics and structure of the cirolanid isopod Excirolana armata were studied from January 2004 through March 2005 in three sandy beaches of Buenos Aires Province (Argentina). Beaches with different types of anthropogenic influences were selected. The von Bertalanffy's growth function parameters were determined for each population. There was a marked fluctuation in growth, with lowest rates in late autumn and winter. The isopod population of the beach exposed to the highest degree of anthropogenic erosion had the lowest and most stable values of abundance and biomass, the highest mortality rate and the shortest life span. Temporal fluctuations of the allometric coefficient of the length-dry weight relationship indicated a cycling pattern, with lowest values during the autumn-winter period and peak values in the summer. Females predominated in the populations due to the short duration of the reproductive season. Argentine and Uruguayan populations showed similar growth performance indices, but differed in their abundance and biomass values, probably as a response to variations in beach morphodynamics and biological interactions. Rev. Biol. Trop. 55 (Suppl.