Aspects of the post-larval life history of Limnadia stanleyana King (Crustacea : Conchostraca)

Abstract

L. stanleyana occurs in some rainwater pools near Sydney, N.S.W.. A study of the life history permits description of some aspects of the growth and morphological variation of the species. No growth rings are formed on the carapace during the initial stage of post-larval development. After this a ring is formed at each moult. Animals moult at regular intervals during the period of rapid growth which continues until after maturity. Moulting then occurs less frequently and eventually ceases in aged animals. The increment in size during each moulting cycle varies. It is greater in immature than is adult animals so although the increase in number of growth rings is linear the increase in size at this time is near exponential. The maximum size attained varies from generation to generation even in the same pool. There are sexual differences in the proportions of the carapace and damage due to injury increases markedly in aged animals. At 7.5°C third- and fourth-stage nauplii did not mature and scarcely grew during incubation for 336 hr. At 16, 20, and 25°C similar larvae grew to maturity in about 349, 161, and 109 hr respectively. The mean number of spines on telsons of animals from one pool is different from that of those from other pools. This situation merits further examination since the biological characteristics of the species facilitate the study of this quantitative, probably genetically determined, character in reproductively isolated populations.