Natural history of the American lobster...

Abstract

The development is abbreviated in the Gegarcinus ruricola, the gaily colored terrestrial crab of the West Indies, the large eggs and young of which were a puzzle to the early observers.(4) Mysis or schizopod stage. The biramous condition of the thoracic legs characteristic of this stage is transitoryLin_th.e-J[aryie of the higher Crustacea, but permanent in the lower order of schizopods. The oar-like exopods of the larval thoracic appendages persist in the lobster until the fourth molt, when they are suddenly reduced to rudiments, and after the fifth stage no vestige of them remains.(5) Larval period reduced in various degrees, and metamorphosis in some cases practically absent.In addition to the crayfishes, lobsters, and other illustrations of abbreviated development already given, we may mention Synalpheus longicarpus of the West Indies as a striking example, in addition to certain fluviatile and many deep-sea forms.Like other animals, the Crustacea tend to recapitulate, in some degree the history of their ancestors in the course of their own development, and to become modified in * On the other hand, the egg of the starfish or sea urchin, which is unencumbered by a great mass of yolk, and very small in consequence, measuring about^^inch in diameter, hatches at ordinary temperatures in 24 hours. It must, however, lead a long life as a larva, make its own living, run the gauntlet of enemies, and keep up the struggle for months. Thus the handicap at the start may count for little in the end. The advantage gained by the fowl in having a few very large eggs is offset by that of a vast number of almost microscopical ova in the echinoderm.

The Biology ofCrangon VulgarisL. in the Bristol Channel and Severn Estuary

“…This strip forms a spiral owing to the convolution of the duct so that a homogeneous layer is laid down around the sperm mass and initial matrix. It was originally shown by Grobben (1878) that the' spermatophore in the Decap9da is composed of two substances apart from the sperms and similar conclusions were reached by Herrick (1894) for Homarus americanus (although he modified this sQmewhat later (19II)), by Mouchet (1931) for Penaeus trisulcatus and by Spalding (1942) for Carcinus maenas. In Crangon the spermatophore is finally extruded as a thin strand-like vermicelli containing masses of sperms at irregular iIltervals.…”

Gross Dissection of the Stomach of the Lobster, <em>Homarus Americanus</em>

“…The anatomy of lobster stomach has been well described previously [5][6][7] , and we recommend becoming familiar with its anatomy. Doing so will reduce the risk of damaging the delicate nerves and muscle.…”

Developmental changes in the structure and function of lobster hemocyanin

“…At Stage III the gills are fully formed (Herrick, 1909) and the exoskeleton is thicker than in previous stages; thus this may be the first stage unable to utilize any cutaneous respiration. This, combined with the increased demands of swimming discussed above, could result in significantly lower oxygen tensions in the tissues of Stage III larvae in comparison to previous stages or subsequent ones (Stage IV larvae swim more efficiently, and can also spend a good deal of time walking on the sae floor).…”