ABSTRACT
Little is known of the biology or functional anatomy of the euryalinid snake star Astrohrachion constrictum which lives mutualistically on black corals of the genus Antipathes in the fiords of southern New Zealand. As a first step in a longer term investigation of the biology and ecology of A. constrictum the general anatomy of the animal was studied. Samples were collected from Doubtful Sound and subjected to gross and histological examination. It was found that A. constrictum conformed to the general asteroschematid pattern of having unbranched arms and gonads extending down roughly half the length of the arms and, like many euryalinids, the bursae are fused to form a peri-oral ring. The structure of the gonads and their relation with the bursae were examined and the madreporites were described. The discovery of an aboral pore in the disc of some specimens that opens into the bursal lumen was also made. The possible functional significance of this unusual structure is discussed.
