. The biology of marine animals. Marine animals; Physiology, Comparative. ASSOCIATIONS 603 itself by its antennae. Fixation accomplished, the internal contents of the cypris contract into a cellular mass and the animal sheds its integument together with its appendages. A thin chitinous dart is then formed, which pierces the body wall of the crab, and through this opening the cellular mass of the cypris invades the visceral cavity of the host. Development is slow, occupying twelve months, and during that period the Sacculina migrates from the point of penetration along the intestine. It takes o
. The biology of marine animals. Marine animals; Physiology, Comparative. ASSOCIATIONS 603 itself by its antennae. Fixation accomplished, the internal contents of the cypris contract into a cellular mass and the animal sheds its integument together with its appendages. A thin chitinous dart is then formed, which pierces the body wall of the crab, and through this opening the cellular mass of the cypris invades the visceral cavity of the host. Development is slow, occupying twelve months, and during that period the Sacculina migrates from the point of penetration along the intestine. It takes on the appearance of a mass of branching rootlets and, on arriving at the unpaired. Fig. Sacculina, a Rhizocephalan Parasite of Crabs (a) Nauplius larva; (b) cypris larva; (c) section through external mass of Sacculina; (d), (e) and (/) growth of parasite internally along the intestine of the crab, ((a), {b), (d), (e) and (/), after Smith (94); (c) after Delage, 1884.) intestinal caecum, it gives rise to a tumour-like nucleus, which develops into the saccular structure visible externally. On reaching the outer wall, the nucleus causes necrosis of the host's tissues and softening of the chitin, thus permitting access to the exterior (94). Well-known rhizocephalan forms are Sacculina parasitic on Carcinus, Portunus and Inachus; Peltogaster on pagurids; Parthenopea on Gebia and Callianassa; and Thompsonia on Melia, Thalamita and Alpheus. In an infection with Thompsonia up to 200 reproductive sacs may appear on the outside of the prawn, and these arise from a common system of rootlets due to infection by a single cypris larva (80, 104).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Nicol, J. A. Colin (Joseph Arthur Colin), 1915-. New York, Interscience Publishers
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