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Zoology Publications from Victoria University of Wellington—Nos. 63 and 64

Materials and Methods

Materials and Methods

On 21.7.70 an egg mass of D. puniceus (identification from description by Graham, 1939) was collected from the western shore of Lyall Bay on the north coast of Cook Strait. This was kept in a rectangular plastic container (30 × 28 × 13cm) at the Island Bay Marine Laboratory. The water was changed daily and kept constantly aerated.

On hatching, prolarvae of D. puniceus were transferred to plastic containers (12 × 15cm) which had been sterilized by exposure to ultraviolet light. The water in each container was replaced daily with filtered and sterilized seawater. No artificial aeration was provided. Artemia ("brine shrimp") nauplii were fed to the larvae as soon as most of the yolk sac had been absorbed. The last larva died on the 15th day after hatching. During the 15 days several larvae were anaesthetised with Sandoz MS 222 and sketches were made.

Larvae of D. puniceus larger than 5.5mm were also obtained from the plankton approximately 100m off-shore at Island Bay and Lyall Bay, using a plankton net of standard conical design with a 57cm diameter opening and a mesh size of 500 microns.

Early in July, 1970, 10 adult T. pinnulatus were collected from the western shore of Lyall Bay, and kept in a glass aquarium (60 × 40 × 25 cm). Stones, broken clay piping and empty Haliotis (paua) shells were placed in the aquarium to provide shelter and areas on which to spawn. The tank was supplied with fresh running seawater and fish were fed chopped fish and beef liver. On 28.7.70 freshly deposited eggs were found on the undersurface of a portion of the clay pipe. These eggs were attended by a male T. pinnulatus (61mm s.l.) which, along with the egg mass, was transferred to a plastic container (30 × 28 × 13cm). The water was changed daily and supplied continuously with air.

The egg masses of both species adhered closely to the substrate and hence eggs required for observation were very difficult to remove without damage to the egg membrane. Limited success was obtained by sliding a sharp scalpel between the egg and the substrate and then pipetting the dislodged egg into a petri dish. Development of the eggs of D. puniceus and T. pinnulatus were studied and sketches of the eggs and larvae were made with a camera lucida. An ocular micrometer was used for measuring eggs and larvae. Measurements of the larvae are those recommended by Hubbs and Lagler (1958:24-26), with the exception of head length, taken here as the distance from the snout to the posterior margin of the otic capsule. In the prolarva the otic capsule provides a more positive point of reference than the operculum. Descriptive terminology of eggs and prolarvae follows that used by Rugh (1948), Balinsky (1965) and New (1966).