Macrozooplankton of the inshore waters of Christmas Island (Indian Ocean) with specific reference to larvae of the red land crab, Gecarcoidea natalis
Davies, C. and Beckley, L.E. (2009) Macrozooplankton of the inshore waters of Christmas Island (Indian Ocean) with specific reference to larvae of the red land crab, Gecarcoidea natalis. In: AMSA2009 46th Annual Conference for the Australian Marine Sciences Conference, 5 - 9 July, Adelaide, Australia.
The red land crab, Gecarcoidea natalis, is endemic to Christmas Island in the Indian Ocean. Although the biology of adult crabs, including the seaward migration and spawning, has been well studied the obligate marine larval phase is poorly understood. Surface plankton tows using a 500 μm net were conducted monthly over 14 months, at three sites on the north coast of Christmas Island, to investigate the composition, abundance and seasonal variation of the plankton and to ascertain the presence of red crab zoea in the plankton. Settled volumes of plankton were generally low at all sites, typically <0.1 ml/m3 of water sampled. However, at the end of the south-east monsoon period when the South Equatorial Current was strongest, higher plankton concentrations were attained (up to 1.9 ml settled volume /m3 in September 2006). Brachyuran crab zoea were found in the plankton samples throughout the year with the highest concentrations corresponding roughly to red crab spawning times (up to 18 zoea /m3 water sampled). However, despite rearing some first stage zoea of red crabs in an aquarium positive identification of red crab zoea in the plankton samples could not be confirmed. The larval phase of the red crab remains elusive but some theories on retention of crab larvae will be discussed relative to the known oceanography of the region.
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|Murdoch Affiliation:||School of Environmental Science|
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