The Larvæ of the Decapoda Macrura and Anomura of Plymouth

Abstract

The larvæ of the Decapod Macrura occur throughout the year in the tow-nettings taken in Plymouth Sound; while during the summer months they form an important and conspicuous feature of the coastal plankton. In only a few cases have their life-histories been fully worked out, owing probably to the difficulty of rearing the larvæ under artificial conditions; and the literature on the subject is consequently both scanty and scattered. It has therefore been suggested that a brief review of the larvæ already described, together with a few additional ones which have been identified during two years' examination of the Plymouth plankton, from 1917–1919, might be of some use to future investigators. The object of the present paper is to enable future workers to see at a glance how far these forms have been investigated, and especially to facilitate the identification of the living larvæ from the tow-nets. No attempt has been made to describe the appendages in detail, as such particulars can generally be found in the literature cited. A general outline drawing is given of the more important forms in their first larval stage, and a figure of the telson and uropods in the fourth or last larval stage is also shown. As the coloration of the larva is often of great assistance in identifying the living animal, it is here described rather fully, and, whenever possible, the drawings and the colour notes have been made from the living larva. In cases where no direct observations were available the colour descriptions are quoted from other authorities.