FUNCTIONAL MORPHOLOGY AND DESCRIPTION OF A NEW SPECIES OF AMYGDALUM (MYTILOIDEA) FROM THE OXYGEN MINIMUM ZONE OF THE ARABIAN SEA

A new species of Amygdalum (Amygdalum anoxicolum n. sp.) isdescribedliving in the soft green muds of the oxygen minimumzone off the Omanmargin in the northern Arabian Sea. It isdistinguished by both itsshell and anatomical characters. Theanatomy is described anddiscussed in relation to the environment.The presence of haemoglobinis viewed as a direct adaptationto the low levels of oxygen found inits habitat. The observedwide size range of ingested food particlesis discussed in relationto the low oxygen environment. The nestbuilding habit is assumedto be a key adaptation to living in soft,high porosity mud.The distribution of the genus is examined inrelation to thedistribution of known zones of hypoxia in the world9soceans,but no relationship is evident. Amygdalum species are notindicatorsof low oxygen environments. (Received 17 August 2000; accepted 14 November 2000)