Laboratory culture and development of Euphausia pacifica

Abstract

Euphausia pacifica was reared from eggs released by gravid females taken from the field to 1‐year‐old adults. The duration of each larval stage, the number of instars in each stage, and the molting sequence in the laboratory were determined. For all broods the median developmental time to juvenile 1 was 45 days at 12°C, 68 days at 8°C. The range between broods was 41–53 days at 12°C; many of these times were statistically different. Mean developmental time was not correlated with female size, brood size, or survivorship. Survivorship was greater at 12° than 8°C, but varied considerably. The developmental pathway is not fixed. An individual may spend from zero to four instars in any one stage. One stage found off southern California, furcilia V, was rarely found in these laboratory‐reared animals. Only about 20% had two instars between furcilia IV and VI. The data indicate that some furcilia III did not grow enough in their molt to furcilia IV and thus required more than one instar to make the transition into furcilia VI.