Growth rate of the bathypelagic crustacean Gnathophausia ingens (Mysidacea: Lophogastridae). I. Dimensional growth and population structure

Gnathophausia ingens has 13 instars, each with a distinct range of sizes which does not overlap the sizes of adjacent instars. The intermolt interval, measured in the laboratory at 5.5°, 6.5° and 7.5°C, increases with increasing size and decreases with increasing temperature. At 5.5°C it varies from 166 days for the smallest individuals to 253 days for the oldest. The period of larval development in the marsupium of a female is estimated to be 530 days. The life span of females is estimated to be 2,950 days with the onset of reproduction at 2,400 days. It is sugquested that this species is semelparous. The population structure data suggest that there is low mortality through the first 7 instars, progressively higher mortality from Instar 8 through Instar 11, and slightly lower mortality in the remaining 2 instars. These life-history characteristics appear to be directed toward maximizing absolute fecundity (as opposed to time-specific fecundity) in a stable environment. These characteristics may have been selected for by low available food energy and made possible by the stability of the deep sea.