The occurrence of protozoan symbionts in the hemolymph of the blue crab, Callinectes sapidus

Between July, 1983 and May, 1984, 788 blue crabs were assayed from the Galveston Bay area of Texas, using one or more methods for hemolymph symbionts. The presence of general macrosymbionts was examined for in 198 of the 788 crabs. A pedunculate barnacle, leech, ribbon worm, and parasitic fluke hyperparasitized by a haplosporidian were found in or on 4.0[percent], 4.0[percent], 0.5[percent], and 20.2[percent] of the 198 crabs respectively. Wet mounts of the hemolymph of 355 crabs and hemolymph of 230 crabs stained with Giemsa's stain showed no presence of three protozoan parasites found on the east coast of the United States- Hematodinium perezi, Paramoeba perniciosa, and a Urosporidium-Iike species. Low concentration, facultative, protozoan symbionts in the hemolymph were assayed for by culturing the hemolymph for six days. Of 273 crabs sampled after topically sterilizing the surface of the crab, seven cultures (2.6[percent]) were positive for protozoan growth. The seven positive cultures contained three types of ciliates of the order Scuticociliatida, one type of ciliate of the order Hypotrichida, and three types of flagellates of the order Kinetoplastida, family Bodonidae. Injections of six of these types of protozoans into the crabs showed that the protozoans could survive in the hemolymph for at least a day, but did not necessarily cause any harm to the crab.