MEPS 316:127-137 (2006)  -  doi:10.3354/meps316127

Larval development of Euphausia pacifica in the laboratory: variability in developmental pathways

Leah R. Feinberg1,*, C. Tracy Shaw1, William T. Peterson2

1Cooperative Institute for Marine Resources Studies, Hatfield Marine Science Center, 2030 South Marine Science Drive, Newport, Oregon 97356, USA
2NMFS, Hatfield Marine Science Center, 2030 South Marine Science Drive, Newport, Oregon 97356, USA

ABSTRACT: Gravid adult female Euphausia pacifica were collected off Newport, Oregon, USA and transferred to the laboratory, where females spawned eggs, eggs hatched, and larvae were reared at 10.5°C. We fed 4 cohorts of larvae to excess with a combination of phytoplankton species and monitored them daily until they reached the juvenile stage. The euphausiids were maintained separately (1 individual per jar) from the third furcilia (FIII) to the juvenile stage to observe developmental pathways. Individual cohorts developed at nearly the same rate until the first furcilia stage, after which 2 cohorts began to develop significantly faster than the others. Median time to the juvenile stage ranged from 51.9 to 60.6 d, with significant differences among cohorts. The first calyptopis stage and the third furcilia stage lasted longer than any other stages and appear to be bottlenecks in the development of this species. Individual development from FIII to juvenile varied widely both within and among cohorts. We observed 4 main developmental pathways. Over half of the euphausiids skipped 1 development stage between FIII and juvenile (58%), and none skipped multiple stages. There was no tendency for individuals from the same cohort to follow the same developmental pathway. This variability in development may be even higher in the field and could impact mortality calculations and cohort analysis from field samples.

KEY WORDS: Euphausia pacifica · Larval development time · Developmental pathways

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