Aquarium Notes

Abstract

Marine Copepoda—The lump-sucker.—In the salt water tanks of the Edinburgh Aquarium at the present date may be seen an immense number of white specks flitting rapidly through the water, after the fashion of the familiar Cyclops and its neighbours in fresh streams. On subjecting these “tenants at will” of the tanks to microscopic scrutiny, they are seen to belong to the Entomostracous division of the Crustacea, and may in all probability be classified in the cyclops-family, as near kith and kin of the well-known “fresh-water flea.” The cephalothorax is well-defined, the body being flattened, whilst the posterior edges of the cephalothorax are prominent and somewhat hooked. The feet number five pairs, and are setose. No external ovisacs oexist, and the antennæ are of simple conformation. Under the microscope the intestinal canal, filled with brownish matter, is seen to pulsate in rhythmical fashion. The abdomen is apparently composed of some four joints, and is terminated by two long caudal bristles. The eye is single, median, and red-coloured. In the absence of more definite characters, I should feel inclined to allocate the form near the genus Alteutha, of Baird, from the hooked character of the cephalo-thoracic edges. It differs from Alteutha, however, in the absence of the characteristic hooked edges of the fourth somite of the abdomen. The sudden appearance of myriads of these creatures in the tanks may probably be attributed to the recent favourable temperature; the eggs of the adults having lain dormant, as do the cyclops themselves, through the winter.