THE LIFE HISTORY AND BIOLOGY OF A MARINE HARPACTICOID COPEPOD, TISBE FURCATA (BAIRD)

¹ Scripps Institution of Oceanography of the University of California, La Jolla, California

1. Tisbe furcata is a littoral copepod that commonly invades salt-water systems connected with the sea. It is readily reared through all of its developmental stages. Being a scavenger, it thrives on various types of food, but thin slices of fresh sea-weed and dehydrated kelp were especially acceptable.

2. Following the egg, there are six naupliar and six copepodid stages, the last of which is the adult. Each stage is separated by one molt.

3. The incubation period is from two to four days, usually about 2.5 days.

4. The total duration of the naupliar stage is three to eight days, usually about five days.

5. The first indication of sexual maturity as shown by clasping by the male occurred between the 10th and 25th days, usually about the 16th day.

6. The minimum time between generations (i.e., from egg to egg production) was 15 days, but usually between 19 to 24 days.

7. The span of life of individuals varied greatly. It was studied mainly in the females, some individuals of which lived for 40 to 50 days. The oldest specimer had a life span of 70 or 71 days, but no eggs were produced after the 53rd day.

8. The number of broods indicated by egg-sacs produced by isolated females varied from 7 to 12, with an average of about 9. Following the first egg sac, the subsequent ones appeared at intervals of two to five days, usually about three days.

9. The number of eggs in a brood varied from 29 to 93 with an average of 43 in one sampling and 72 in another.

10. Each female mated but once, and this mating sufficed for fertilization of all of the eggs to be produced. Males were capable of several matings.

11. About 80 per cent of the larvae hatched survived to adult state.

12. There is no evidence of parthenogenesis.