Intersex individuals, possessing both male and female genital openings, were assessed in two groups-7 and 19 months old-of Australian red claw crayfish (Cherax quadricarinatus). All intersex individuals investigated were functional males, as suggested by their malelike morphology and the presence of testes, sperm ducts, androgenic glands, and viable spermatozoa. When an ovary was present in an intersex individual from either group, the gonadosomatic index, the diameter of the oocytes, and the ovarian cytosolic polypeptide profile were similar to those of immature, pre-vitellogenic females. We conclude that intersexuality in C. quadricarinatus does not indicate a case of protandric sequential hermaphroditism, as previously suggested. The case of intersexuality described here presents a unique model for the study of the role of the androgenic gland in the regulation of sex differentiation in crustaceans.

The wide range of sizes of sexually mature prawn populations and particularly of the males is very typical of Macrobrachium rosenbergii (De Man) and a major obstacle to increased pro¢tability of prawn culture. Prawn size variation re£ects a complex population structure composed of three major male morpho-types^the small males, the orange-claw males and the blue-claw males^which di¡er in their morphology, physiology and behaviour. Social interactions among juveniles and among sexually mature males a¡ect their growth. Four di¡erent social mechanisms have been suggested to control growth in crustaceans: direct competition for food, appetite suppression, altered food-conversion e⁄ciency and increased energy expenditure on motor activity. Since all growth-controlling mechanisms involve an aggressive behavioural component, our knowledge of prawn agonistic behaviour and prawn social organization has been reviewed. Present knowledge of the social mechanisms regulating growth among juveniles and among sexually mature male morphotypes as well as the sensory modalities involved was evaluated. The possible evolution of social growth-controlling mechanisms is discussed. Various ways for implementing our knowledge on social control of growth into prawn culture to increase pro¢tability are suggested. Aquaculture Research, 2005, 36, 238^254 Review of social control of growth in M. rosenbergii I Karplus Review of social control of growth in M. rosenbergii I Karplus Aquaculture Research, 2005, 36, 238^254 Aquaculture Research, 2005, 36, 238^254 Review of social control of growth in M. rosenbergii I Karplus Review of social control of growth in M. rosenbergii I Karplus Aquaculture Research, 2005, 36, 238^254 Aquaculture Research, 2005, 36, 238^254 Review of social control of growth in M. rosenbergii I Karplus

For four months we marked and followed through female maturation and adult male mophotypic differentiation, the growth of all 150 individuals in an experimental population of Malaysian giant freshwater prawns (Macrobrachium rosenbergii). Small immature female prawns had high growth rates. Growth of female prawns nearly ceased after maturation. This compensatory growth process produces adult females having a unimodal, symmetrical size distribution with a mean above the size threshold for maturation (about 18-26 g). The small male morphotype has a low growth rate, while the orange claw male morphotype has a high growth rate. As the orange claw males transform to the blue claw morphotype, growth ceases. Examination of changes in size rank during the maturation process supported the leapfrog phenomenon. The fastest growing, largest orange claw male is the first to metamorphose to the blue claw morphotype (at a size of 35 g). As other orange claw males exceed this size, they transform in a sequential process so that the most recent blue claw male is generally the largest blue claw male in the population. Thus, growth of males is depensatory throughout the process of morphotypic differentiation, leading to a wide size range of orange and blue claw males. The leapfrog phenomenon is discussed in terms of the reproductive success of the blue claw males and compared with related growth processes in male poeciliid fishes. Implications of this growth process for aquacultural productivity includes the stimulatory effect on the remaining prawns of selectively harvesting the largest blue claw and orange claw prawns and suggests that the inclusion of a small proportion of large "target" blue claw males might stimulate the rapid growth of orange claw males in a population of smaller prawns.

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Mother-offspring relationships were studied in the red-claw crayfish Cherax quadricarinatus during 3 phases: "egg-carrying," "hatching," and "release." The maternal behavior of 16 females and the dispersal of their young were monitored with a video camera in small-and large-sized aquaria. Time allocated to locomotion, aeration, and cleaning was computed for each phase. During the release phase there was an increase in mobility and a reduction in time devoted to fanning as compared to the egg-carrying and hatching phases. A significant negative linear regression was found between the number of juveniles on the mother and days since release. Mother-offspring association was considerably prolonged under conditions of limited space, resulting in a delay in the next breeding cycle of the female. The implications of this study for the commercial production of redclaw crayfish arc discussed.