Thromidia catalai
The marine component of the Santo 2006 Biodiversity Project has already revealed within the first week of operations, a wealth of species diversity, particularly in major target groups such as marine Molluscs, Crustacea and Reef Corals. The species richness in Vanuatu waters is proving to be high and comparable to species inventories in the Indo-Malay Archipelago diversity hotspot to the west.

Santo Echinoderms [sea stars and their relatives], scientifically surveyed in detail for the first time in local waters, are likewise rich in tropical species. There have also been some surprises. In particular, the intensive scientific diving programme has discovered two large and spectacular Echinoderm species. These animals, the giant sea star and the pyjama-striped sea cucumber, are relatively new to science, having been described and formally named only in recent decades. Therefore little is known of their biology. Their discovery at Santo adds important information on their distributional range and certainly creates an additional attraction for diving ecotourism operations in the area.

The giant sea star, otherwise known as Thromidia catalai, is truly enormous! It is the most massive sea star in all the world’s seas and has even been featured in the Guiness Book of World Records. The specimen pictured has a diameter of nearly three quarters of a metre.

Thromidia is not as rare as was once thought. It is more true to say that it is rarely sighted as it lives below the reef on sandy rubble slopes at depths of 35-45 metres or more. Therefore it is not observed by many recreational divers who rarely venture this deep and who usually only interested in slopes with high coral cover.

The other spectacular Echinoderm diving-discovery in the first few days of the Santo 2006 expedition was another deep-water reef-associated species, this time a large sea cucumber known scientifically as Thelenota rubralineata. Its maze-like pattern of crimson lines on a cream background gives this animal a stunningly attractive appearance.

It was first found in New Guinea and Indonesia only about 17 years ago and has subsequently been found in more and more West Pacific locations, including now, Vanuatu. Again, like the giant sea star, little is known of its biology or faunal associates. This sea cucumber is uncommon and is rarely reported in the sea cucumber or bêche-de-mer trade. Although it is now known to be more common than once thought, there are now suggestions that this animal, along with several other species that are fished commercially, should be given some protection under the Convention for Trade in Endangered Species (CITES).

While these new records of rarely known marine species suggest that they are endangered and therefore specimens should not be collected for scientific purposes, this assumption is not necessarily correct. The collection and preservation of specimens for scientific collections, provide scientific proof of their existence and facilitate access for further studies. They can be compared with specimens of other species to study their mutual relationships. Such specimens are available in natural history museums all over the world (including Asia, Australia, Europe and the USA).

The scientists of the French-organised international Santo 2006 expedition represent specialists from many countries (mainly Asia, Europe, and the USA). Their discoveries reveal the richness of marine life in Vanuatu. Such knowledge is relevant for nature conservation and the diving industry. This information is made accessible to the public in the form of nature field guides (usually written by professional biologists and underwater photographers) and on the internet. The collection of specimens is not harmful to the resident populations of snails, crabs, starfish, and other groups of animals because the coastline of Santo is very long and much less than one millionth of the sea floor of Santo is actually being investigated. This implies that after the expedition, many mysteries of the seas will remain hidden, but we do know that the underwater wonders of Santo will finally get the attention they deserve.

The authors of this report are from the Universiti Brunei Darussalam and from the National Museum of Natural History Naturalis, Leiden, The Netherlands.

Locality:
Vanuatu, Santo
Method:
Hand picked during a dive
Scientist:
Dr. Bert W. Hoeksema
National Museum of Natural History 'Naturalis', Leiden
The Netherlands
Specialist in coral reefs

Scientist:
Dr. David J.W. Lane
Department of Biology
University of Brunei Darussalam
Brunei
Specialist in Tropical marine ecology and
Echinoderm biology

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