Life-history biology of Peniagone azorica and P. diaphana (Echinodermata: Holothurioidea) from the north east Atlantic ocean

Aspects of the reproduction and population biology of two elasipodid holothurians collected during the period 1973-1984 were examined. The reproductive biology of both the benthic species P. azorica and the benthopelagic P. diaphana are similar. A primary oocyte forms from an oogonium and grows to about 100 mu m diameter, whereupon it undergoes vitellogenesis and increases to 300 mu m before being spawned. A high proportion of primary oocytes are not spawned and undergo a complicated breakdown process resulting in the formation of an amorphous sac in the ovary wall. The maximum egg size for both species suggests abbreviated larval development. Recruitment to the population is probably infrequent and may occur irregularly. Comparison of the population structure of closely spaced samples suggests a patchy distribution on the bottom. The benthopelagic lifestyle of adult P. diaphana suggests that the larva is also planktonic.