Egg incubation and yolk utilization in the isopod Ligia oceanica

Abstract

The egg number, which average to 53(9.5 eggs) per female Ligia oceanica of Helgoland, shows no definite correlation to body size of the mother animals. In between the incubated eggs, the occurrence of nematodes Gammarinema ligiae, Rhabditis sp. and Diplogaster sp. is observed. The course of embryyonic development of L. oceanica exhibits progressive increases in content of ash (4.4 to 31.6 per cent) and non protein nitrigen (from 1.5 to 2.7 per cent) and steady decreases in content of protein (from 41.8 to 36.8 per cent), fat (from 48.8 to 27.4 per cent), carbohydrate (from 3.5 to 1.5 per cent) and energy (from 5956 to 4175 cal/g dry weight). Water content of fresh egg is 76.1 per cent anf after an initial increase to 77.2 per cent in the eggs prior to hatching, it decreases to 72.1 per cent in the freshly hatched juveniles. A single egg contains 301 (34.4)g dry substance equivalent to 1.79 calories. Cumulative yolk utilization efficiensy during the total development is 72.1 per cent for energy 90.5 for protein 57.8 per cent for fat and 43.8 per cent for carbohydrate. Of the total energy expended on embryonic metabolic processes, oxidation of protein contributes only 10.1 per cent, while the rest is supplied by non-proteinous substances (fat 86.9 per cent and carbohydrate 3.0 per cent).