Rearing Experiments on Marine Teleost Larvæ and Evidence of their Need for Sleep

Abstract

DURING a study of the biology of the shore fishes Blennius pholis L. and Centronotus gunnellus (L.) several series of experiments have been carried out on the rearing of the larvæ. By keeping sufficient eggs in the aquaria it was possible to obtain large numbers of larvæ of similar age. These were evenly distributed between bell-jars which each contained 25 litres of sea water and about fifty larvæ. It was soon found that mechanical stirring by plunger plates as used by previous workers¹ was accompanied by very heavy mortality of the larvæ. The water was therefore kept circulating slowly by gentle streams of small air bubbles. The different batches of larvæ were subjected to various conditions of food and illumination. Larvæ which died were removed daily and percentage survival was used as criterion for comparison between batches. Surviving larvæ grew well, and given suitable conditions a small percentage of these species and of Cottus scorpius L. were reared until metamorphosis, when they adopted the demersal habit of the adults.