Biology and life cycle of Natatolana borealis Lilj.1851, a scavenging isopod from the continental slope of the Mediterranean

The biology of Natatolana borealis, a deep-sea (−500 m) scavenging isopod that lives on the continental slope of Mediterranean canyons, was studied in the field and in the laboratory. Animals were collected at two stations using a baited trap. Whatever the site at which the animals were collected, a strong correlation was always found to exist between their length and weight, which shows variably marked seasonal variations. The growth pattern was modelled by fitting the Von Bertalanffy growth equation to the length of animals of various ages. The lifespan was estimated to be 6 years in the case of the largest animals collected. Sexual maturity is presumably reached at the age of 2.5 years. Not all the females were found to be sexually active at the same period of the year. A scheme of reproductive cycle is proposed for the mature females. It seems likely that each female may produce at least four broods during her lifetime. The emergence of offspring occurs at various times throughout the year, resulting in successive cohorts. At some periods in the year, some developmental stages were lacking in the samples, possibly owing to alimentary behaviour that helps to protect the animals from predators.