LARVAL DEVELOPMENT OF BALANUS EBURNEUS IN THE LABORATORY

¹ Duke University Marine Laboratory, Beaufort, N. C.
² Department of Zoology, Duke University, Durham, N. C.

A technique has been devised for rearing segregated barnacle nauplii, under controlled laboratory conditions, which permits daily observations on the frequency of molting, the number of stages, and the specific characteristics of each stage. From a study of 121 segregated Balanus eburneus, plus hundreds in mass culture, reared on Chlamydomonas sp. and Arbacia larvae at 26° C. the following conclusions may be drawn:

1. Ecdyses provide a definitive method for staging nauplii. The larval phase of B. eburneus consists of six naupliar stages and one cyprid stage. Secondary criteria, such as body size, spine structure, and appendage setation, are given for the larval stages.

2. The duration of the six naupliar stages is as follows: first stage, 15 minutes to 4 hours; second stage, one to two days with an average of one day; third stage, one to four days with an average of 1.5 days; fourth stage, one to four days with an average of two days; fifth stage, one to five days with an average of 2.6 days; and the sixth stage, two to four days with an average of 2.5 days.

3. The cyprid stage ranges from one to fourteen days but successful attachment was observed only in those which settled one to three days following the final naupliar molt.

4. The over-all larval development in the laboratory ranges from 7 to 13 days.

5. The first ecdysis occurs from 15 minutes to 4 hours after hatching and is usually followed by the second molt during the first day. The third molt occurs from the second to the fifth days and the fourth molt takes place from the third to the eighth day. The fifth ecdysis occurs from the fifth to the ninth day with the sixth molt ranging from the seventh to the twelfth day.

6. Tables are given for the size of the nauplii and the setation of the appendages.

7. Successful metamorphosis and attachment was observed in 16.3 per cent of the 121 barnacle nauplii studied under segregated laboratory conditions.