Plathelminths in tropical intertidal sediments of northeastern Australia

Assemblages of free-living interstitial plathelminths are described from the tropical coast of northeastern Australia. About one hundred species were recorded from sediments of mangroves, tidal flats, and seagrass beds. The majority (88%) of the plathelminths occurred in only one havitat. Richest in species were Kalyptorhynchia (39), followed by Acoela (17) and Typhloplanoida (16). Over 50% of the species found were represented by one to three individuals, but a few species were frequently encountered. The preferred habitat was sand with 86% of all species, while abundances were higher in muddy sediments. The mean species density was 7 in 10 cm^-2 of sediment, and abundances ranged from 8 to 52 individuals 10 cm^-2 with an average plathelminth abundance of 25 individuals 10 cm^-2. Predatory plathelminths were predominant with up to 77% of the individuals. A comparison is made to plathelminth assemblages in temperate tidal flats.