Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 144-156). Also available via the World Wide Web.

This study examines the reproductive strategies of the Pill-box crab, Halicarcinus innominatus, at the Oaro Platform (24 km south of the Kaikoura Peninsula, New Zealand). As necessary components of reproductive strategies, the population dynamics, reproductive biology and mating behaviour of H. innominetus were examined from December 1997 through December 1998. There were obvious sexually dimorphic differences in secondary sexual traits in this species. Both males and females display a wide range of sizes over which individuals can moult to maturity. H. innominatus females displayed continuous breeding throughout the year, resulting in continuous recruitment. Females were found to outnumber males in each month. However, when comparisons were made between mature males and females with different brood stages (i.e. 0-5), males outnumbered each female type in each month. Investigations into the reproductive biology of H. innominatus females revealed that brood development and ovary development were in phase. This resulted in the ability of females to produce several broods in quick succession. Ovary development began before the moult to maturity, allowing for immediate production of a brood after the moult to maturity. Egg incubation periods were dependent on water temperature, being longest in the winter and shortest in the summer. Egg numbers were found to increase with female body size, but mortality of eggs through development was apparent. Sperm storage was found to occur in this species with possible layering of different ejaculates. Copulations were only observed between males and females in hard-shell conditions. Males mated more often with females carrying stage 5 broods, but also mated with all other female types, including pre-pubescent females. Postcopulatory mate guarding only occurred with stage 5 females. Males can detect females of different reproductive condition, which seems to be linked to the developmental stages of the females' ovaries. In conclusion, H. innominatus males seem to have two tactics to their reproductive strategies: mating with any receptive female, but only guarding stage 5 females.

This study examines the reproductive strategies of the Pill-box crab, Halicarcinus innominatus, at the Oaro Platform (24 km south of the Kaikoura Peninsula, New Zealand). As necessary components of reproductive strategies, the population dynamics, reproductive biology and mating behaviour of H. innominetus were examined from December 1997 through December 1998. There were obvious sexually dimorphic differences in secondary sexual traits in this species. Both males and females display a wide range of sizes over which individuals can moult to maturity. H. innominatus females displayed continuous breeding throughout the year, resulting in continuous recruitment. Females were found to outnumber males in each month. However, when comparisons were made between mature males and females with different brood stages (i.e. 0-5), males outnumbered each female type in each month. Investigations into the reproductive biology of H. innominatus females revealed that brood development and ovary development were in phase. This resulted in the ability of females to produce several broods in quick succession. Ovary development began before the moult to maturity, allowing for immediate production of a brood after the moult to maturity. Egg incubation periods were dependent on water temperature, being longest in the winter and shortest in the summer. Egg numbers were found to increase with female body size, but mortality of eggs through development was apparent. Sperm storage was found to occur in this species with possible layering of different ejaculates. Copulations were only observed between males and females in hard-shell conditions. Males mated more often with females carrying stage 5 broods, but also mated with all other female types, including pre-pubescent females. Postcopulatory mate guarding only occurred with stage 5 females. Males can detect females of different reproductive condition, which seems to be linked to the developmental stages of the females' ovaries. In conclusion, H. innominatus males seem to have two tactics to their reproductive strategies: mating with any receptive female, but only guarding stage 5 females.

This study investigates the reproductive strategies of the pill-box crab, Halicarcinus cookii on the Kaikoura Peninsula, New Zealand. Various aspects essential to understanding reproductive strategies were examined including growth, population dynamics, reproductive biology and mating behaviour. H. cookii exhibits obvious sexual dimorphism such that females develop wide abdomens forming brood chambers, and males tend to grow larger than females and have larger chelipeds in relation to body size. H. cookii allocates energy into growth and reproduction in separate phases of its life cycle where growth ceases as reproductive maturity begins due to a terminal/pubertal moult. Despite the presence of ovigerous females throughout the 15 month sampling period, the population was highly seasonal, with peaks in recruitment and growth occurring primarily during the winter months and peaks in numbers of mature individuals during the summer months. Reproductive output increased with body size in H. cookii, as larger females produced more eggs and larger males transferred more sperm than their smaller counterparts. Ovaries matured prior to the terminal/pubertal moult (anecdysis) and, in multiparous females, in synchrony with brood development, allowing females to produce broods in quick succession, maximising their reproductive output in their short life span (approximately 12-18 months, 6 months as an adult). Incubation duration of broods decreased as seawater temperature increased, suggesting that temperature is the primary cause of the seasonal population cycling. Sperm storage allowed females to produce at least 4 fertilised broods without re-mating. Some sperm mixing in the spermathecae appeared to occur and the ventral-type structure implies last male sperm precedence. Males therefore preferentially mated with females closest to laying a new brood and guarded them longer than other females to ensure their paternity. Guarding duration varied according to the sex ratio allowing males to maximise their reproductive output.

This study investigates the reproductive strategies of the pill-box crab, Halicarcinus cookii on the Kaikoura Peninsula, New Zealand. Various aspects essential to understanding reproductive strategies were examined including growth, population dynamics, reproductive biology and mating behaviour. H. cookii exhibits obvious sexual dimorphism such that females develop wide abdomens forming brood chambers, and males tend to grow larger than females and have larger chelipeds in relation to body size. H. cookii allocates energy into growth and reproduction in separate phases of its life cycle where growth ceases as reproductive maturity begins due to a terminal/pubertal moult. Despite the presence of ovigerous females throughout the 15 month sampling period, the population was highly seasonal, with peaks in recruitment and growth occurring primarily during the winter months and peaks in numbers of mature individuals during the summer months. Reproductive output increased with body size in H. cookii, as larger females produced more eggs and larger males transferred more sperm than their smaller counterparts. Ovaries matured prior to the terminal/pubertal moult (anecdysis) and, in multiparous females, in synchrony with brood development, allowing females to produce broods in quick succession, maximising their reproductive output in their short life span (approximately 12-18 months, 6 months as an adult). Incubation duration of broods decreased as seawater temperature increased, suggesting that temperature is the primary cause of the seasonal population cycling. Sperm storage allowed females to produce at least 4 fertilised broods without re-mating. Some sperm mixing in the spermathecae appeared to occur and the ventral-type structure implies last male sperm precedence. Males therefore preferentially mated with females closest to laying a new brood and guarded them longer than other females to ensure their paternity. Guarding duration varied according to the sex ratio allowing males to maximise their reproductive output.