Now showing items 1-2 of 2

    • Article

      Early development of Crassostrea iredalei (Faustino, 1932) (Bivalvia: Ostreidae), with notes on the structure of the larval hinge 

      LMM Ver - Veliger, 1986 - California Malacozoological Society, Inc.
      Larvae of the oyster Crassostrea iredalei were reared in the laboratory from eggs through settlement. The oysters were induced to spawn by increasing the temperature by 5-10°C and sometimes by adding stripped oyster sperm to the spawning dishes. Eggs avareaged 48 µm in diameter.

      The straight-hinge veligers appeared 22 to 26 h after fertilization. The larval shell length increased from 64 to 84 µm in the straight-hinge stage, from 85 to 275 µm in the umbo stage, and from 210 to 275 µm in the pediveliger stage. Eye-spotted pediveligers were observed mostly at lengths greater than 225 µm. The hinge line did not increase much with larval growth. Although length was initially greater than height, the increase in height was much faster due to the development of the umbo. Height was greater than length in more advanced larvae. Valve growth was asymmetrical and unequal, with the left valve generally larger. Settlement and metamorphosis occurred 20 days from fertilization at lengths of 270 µm and greater, when the oyster larvae were reared at 26.5 to 30°C and salinities of 30 to 32 ppt.

      The larval hinge structure consisted of minute dentition on the central portion of the provinculum and large rectangular teeth on both ends. These teeth became obscured in advanced larvae due to the skewed development of the umbo.

      Data derived from the laboratory culture of larvae of Crassostrea iredalei may be used in spatfall forecasts for the collection of larvae from the wild and as baseline information for the hatchery culture of oyster larvae.
    • Conference paper

      Occurrence of milkfish eggs in the adjacent waters of Panay Island, Philippines 

      T Senta, S Kumagai & L Ver - In Proceedings of the International Milkfish Workshop Conference, May 19-22, 1976, Tigbauan, Iloilo, Philippines, 1976 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Location of spawning grounds of milkfish is one of the most important steps towards gaining knowledge on the spawning habits of the fish as well as the early life history and nature of its eggs and larvae. The present study is an attempt towards this objective. Surveys were made in selected areas in the sea around the Panay Island and milkfish eggs were collected on several occasions from surface to 20 m depth water by towing with larval nets. The eggs floated in the water in a glass jar. The eggs and newly hatched larvae had the same characteristics as described by Delsman (1929). A comparative study has been made to distinguish milkfish eggs from other more or less similar size pelagic eggs of fishes occurring in the same waters at the same time.