Fig. 209 represents the two allied creatures that may sometimes be dug out of the sandy beach, or from the mud in the estuary of a river. The one on the left is the mud-borer (Gebia stellata), which is of a dull yellowish colour, marked more or less distinctly by pinkish starlike spots—a feature that has suggested the specific name. The beak in front of the carapace is very prominent and spiny, and the long abdomen is narrower in front than in the middle. This creature hides in the holes that have been excavated by boring molluscs, and seems also to extend the cavities it inhabits by its own labours.
The other is very similar in general form, but has no spiny beak and the abdomen is much broader in the middle than at the base. It is also to be distinguished by the very unequal size of its front legs, one of which is much more developed than the other.
It is known as the mud-burrower (Callianassa subterranea), and is said to burrow very deeply into mud-banks, scooping out its retreat principally by means of the second and third pairs of legs. Although found at times between the tide-marks, its principal habitat is probably in the mud that is covered by deep water, for it is not uncommonly to be found in the stomachs of fishes that habitually feed in such localities.
Fig. 209.—The Mud-borer (Gebia stellata) (1) and the Mud-burrower (Callianassa subterranea) (2)
Lobsters of all kinds, and, indeed, the marine crustaceans generally, are essentially the scavengers of the sea, for they are carrion-feeders, greedily devouring flesh in all stages of decomposition. Hence the value of their work on the sea shore is very considerable.
An examination of shrimps and prawns will at once show their close relationship with lobsters. The general build of their bodies is practically the same, and their appendages, though often different in form from the corresponding limbs of the lobster, will be seen to resemble them closely in arrangement and structure. The exo-skeletons of these creatures are, however, generally hardened by a horny substance (chitin) instead of a stony deposit of carbonate of lime.
The shrimps and prawns sold for food in our markets are very similar in appearance when alive, the leading distinguishing feature being, perhaps, the presence of a sharp, serrated beak projecting forward from the front portion of the carapace of the latter.
The reader is probably acquainted with the fact that the shrimps and prawns used as food have quite a different appearance when alive and in their native element to that displayed by the corresponding wares in the fishmonger’s shop—a fact that applies equally well to the edible crabs and lobsters. Most crustaceans change to a bright red colour when boiled, and, as stated in a previous chapter, the same result is produced by the action of strong spirit.