Description of a new species of giant clam (Bivalvia: Tridacnidae) from Ningaloo Reef, Western Australia

Abstract

A new species of giant clam from northern Australian coastal waters is distinguished principally on genetic evidence. Of Recent tridacnids, Tridacna ningaloo n. sp. is morphologically closest to the most widespread species in the Indo-Pacific, Tridacna maxima (Röding, 1798), yet genetically closest to the species pair T. squamosa Lamarck, 1819 plus T. crocea Lamarck, 1819. Genotype data are provided for the type material of T. ningaloo n. sp. The greatest significance of this new, cryptic species is that it casts doubt on the correctness of the ‘historical’ giant clam species defined solely on conchological characters, particularly T. maxima. This paper supports the retention of all giant clams in the family Tridacnidae, as distinct from the Cardiidae, because of their numerous morphological apomorphies, specialised ecological niche, and independent acquisition of symbiotic zooxanthellae.

Keywords:

• genetics
• taxonomy
• cryptic species
• international legislation
• Cardioidea
• Tridacnidae
• Cardiidae
• Indo-Pacific

Acknowledgements

Material of the new species was collected under a Section 7 exemption (Permit number 2046) from Western Australian Fisheries, Perth, in addition to a Wildlife Permit (number SF 008861) issued by the Western Australian Department of Environment and Conservation. The authors sincerely thank Frazer McGregor (Coral Bay, Western Australia) for collecting and preserving the whole voucher specimens and the tissue samples of giant clams in addition to generously supplying fuel and boat time. We wish especially to thank Jude Keyse (University of Queensland) for her time spent in the laboratory to provide additional sequences and comments on early drafts of this manuscript. We would also like to thank the Riginos Laboratory (University of Queensland), and in particular Cynthia Riginos, Libby Liggins, Thomas Huelsken and Eric Treml for advice and supplying genetic sequences. Markus Huber kindly assisted with literature and discussed nomenclatural matters. Michio Otani kindly translated the paper by Kubo and Iwai. Finally, we thank both reviewers for their constructive comments.