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.) is described livin g in the soft green muds of the oxygen minimum zone off the Oman margin in the northern Arabian Sea. It is distinguished by both its shell and anatomi cal characters. The anatomy is described and discussed in relation to the e nvironment. The presence of haemoglobin is viewed as a direct adaptation to the low levels of oxygen found in its habitat. The observed wide size rang e of ingested food particles is discussed in relation to the low oxygen env ironment. The nest building habit is assumed to be a key adaptation to livi ng in soft, high porosity mud. The distribution of the genus is examined in relation to the distribution of known zones of hypoxia in the world's ocea ns, but no relationship is evident. Amygdalum species are not indicators of low oxygen environments.