MEPS 223:225-233 (2001)  -  doi:10.3354/meps223225

ABSTRACT: Individual in vivo broods of the swarming mysid species Anisomysis mixta australis, Tenagomysis tasmaniae and Paramesopodopsis rufa developed synchronously and at rates identical to those cultured in vitro. Hence it appears that the parent does not influence the synchrony of development. Synchronous development was also evident among P. rufa females within swarms and a strong peak of release of their brood was evident over 1 or 2 nights. In contrast, swarms of the sympatric species A. mixta australis and T. tasmaniae released their young in a staggered fashion over a longer time period. At the time of emergence from the marsupium, young are vulnerable to cannibalism from adults and older juveniles. Newborn young moulted within 30 min of emergence from the marsupium. Both pre-moult and post-moult juveniles were cannibalised by older life stages, though the former were eaten in larger numbers probably because post-moult newborns were more agile swimmers. Pre-moult newborns were not cannibalised by the parent females though they became vulnerable after the first moult. Whether the strategy of synchronous development and release is manifested in mysid swarms may depend on the size of the swarm. For species that form relatively small swarms (up to 1000 individuals), such as P. rufa, synchronous release from a large number of females may be important to promote early swarming among newly liberated juveniles. Synchronous release may be less important for the reproductive success of species that form larger swarms that continuously release large numbers of young, such as A. mixta australis and T. tasmaniae.

KEY WORDS: Mysid · Crustacea · Anisomysis mixta australis · Paramesopodopsis rufa · Tenagomysis tasmaniae · Larval development · Swarms · Synchronous development · Synchronous release · Cannibalism