Laboratory feeding and egg production in the chaetognath Sagitta crassa Tokioka

Egg production, daily ration, and growth efficiency in Sagitta crassa Tokioka are described along with the morphological characteristics of the ovary and body during laboratory observations. Feeding by S. crassa in small containers containing 50 or 100 ml sea water and feeding rates bore a linear relationship to food concentration from 5 to 20 copepods per 100 ml. Among 100 animals individually isolated in containers, 3 animals were the longest lived and the best egg producers. One of these produced eggs on more than 30 consecutive days, producing almost 1000 eggs. Egg production showed periodic change at intervals from 7 to 10 days. Seminal vesicles also became periodically filled or empty. Fluctuations in ovary length and morphological changes of ovary and body were observed through life. Daily ration of S. crassa ranged from 8.7 to 10.4 prey per day or ≈ 60 μg in dry wt. The specific daily ration ranged from 0.347 to 0.568. S. crassa had a growth efficiency (dry-wt basis) which increased during the early life of the animal (≈28%), then decreased with age (22 → nearly 0%). Reproductive efficiency ranged from 7.0 to 16.4%, with a mean of 12.5%.