It's time to learn more about tanaids


20 November 2010
Tanaids, very small crustaceans of the order Tanaidacea – are found all over the world, from the tropics to the polar regions.
But the close to 1200 species already described are just the tip of the iceberg, according to tanaid expert Professor Magdalena Blazewicz, of the University of Lodz, Poland.
"Before the Census of Marine Life started, we knew something like 800 species," Magda explains.
"Now, more than 1100 species have been classified, and we have another 700 species that are recognised but not yet described.
"In the last 10 years, during the Census of Marine Life, we have almost doubled the number of species that are known in the world," Magda says.
Magda's work on the CReefs trip to Heron Island is part of the first extensive study of tanaids in coral reef habitats.
"Very little research has been dedicated to Tanaidacea so far," she says.
"The high level of taxonomical novelty makes identification of tanaids to species difficult; a problem aggravated by their small size, sibling species, sexual dimorphism or polymorphism, and few and often reduced species-specific morphological taxonomic characters. Thus, Tanaidacea are one of the most reluctantly studied groups and have often been neglected in ecological studies," she explains.
Of the described species, only 40 or so are from coral reefs, because tanaids have been poorly studied on reefs until now. Magda estimates, however, that a further 50 new species will be described from recent samples collected on the Great Barrier Reef.
Based on these samples, Magda aims to establish a baseline for the diversity of the group, describe new genera and species, and investigate the distribution and habitat specificity of tanaids.
"Tanaids appear almost everywhere: in shallow water and in the deep sea; in marine water and estuarine; near hydrothermal vents and cold seeps; in the Antarctic, in tropical waters and also in corals," Magda explains.
"One genus has been described from cold seeps in the Gulf of Mexico and off the coast of Portugal – and recently the same genus has been found in Angola Bay. This suggests that Angola Bay may serve as the same type of habitat; and from the presence of this genus of tanaid, we can predict that cold seeps are there," she says.
That the same genus was found on different sides of the Atlantic Ocean also tells science about the evolution of tanaids.
"These animals cannot swim and they don't have planktonic larvae, so they cannot be distributed by currents; so it means that they had to have already evolved when the Atlantic started to spread out, more than 100 million years ago," she says.
Magda's study of tanaids collected from Heron Island will contribute to better understanding of coral reef habitats and biogeography.
"Australia has high diversity and has had a long isolation since the break-up of the Gondwana landmass, although elements of Indo-West Pacific fauna do occur. For these reasons, global surveys of biodiversity cannot be completed without examination of the Australian fauna," she says.