DISEASES O F MARINE FISHES
27
strated to be pathogenic to fish in iiatural habitats. Heavy infestation
of sticklebacks in the White Sea was felt to be partially responsible
for mass mortalities (Dogie1 et uZ., 1958). Fish had beell isolated in
tide pools, and the trematodes multiplied to numbers up to 1000 per
fish. Two parasite species, G'yrodactylus arcuatus Bychowsky and
G . bychozoskyi Sproston, were involved ; most of the fish died. Dogie1
and Lutta (193'7) studied an epizootic in the Aral Sea sturgeon.
Acipenser nudiventris LOV., caused by the gill trematode Sitzschia
sturionis (Abilgaard). As a result of mortalities during 1936 the
fishery, which previously had reached a peak of 400 tons per year,
ceased to be of commercial significance for the next 20 years (Osmaiiov,
1959). Recent level of infestation in all conditions of salinity was
reported at 50 to 75%.
2. Cestodes
Adult cestodes are commoii and occasionally harmful digestivetract parasites of fishes, but, as with the trematodes, larval stages are
of greatest concern to man. Larval tapeworms occur frequently in
the viscera and flesh of marine and estuarine fishes (Fig. 8). The
definitive hosts of many of these parasites are elasmobranchs or fisheating birds and mammals. Tapeworms which localize in the body
muscles may occur in large numbers in individual hosts. Linton (1907)
described such an infestation in butterfish, Poronotus triacasithus
(Peck), of the North American east coast, in which several thousand
larvae could be found in individual fish. Encysted plerocercoids, less
than a millimeter in diameter, were concentrated in the flesh adjacent
to the vertebral column, and up t o 75% of individuals in a sample
were heavily infected. The parasite was identified as Otobothriuwi
crenacolle Linton, which matures in the spiral valve of certain shark
species, particularly the hammerhead, Sphyrna zygaenn (L.). Ripe,
highly motile proglottids of the tapeworm are shed in the feces and
presumably ingested by butterfish and other teleosts, in which the
embryos invade the musculature and encyst.
Other members of the cestode order Trypanorhyncha occur as
adults in the digestive tract of elasmobranchs, and as larvae in the
flesh and viscera of many teleost species. Elongate larvae of Poecilancistrium robustum (Chandler), called " spaghetti worms ", are very
abundant in the flesh of drum, Pogonius croniis (L.), in the Gulf of
Mexico. According to Chandler (1954) some municipal health departments have considered banning drum from markets because of frequent
worm parasitization. Oppenheimer (1 962) reported that spaghett,i
worms were common in the flesh of many other fishes from the Gulf of
27
strated to be pathogenic to fish in iiatural habitats. Heavy infestation
of sticklebacks in the White Sea was felt to be partially responsible
for mass mortalities (Dogie1 et uZ., 1958). Fish had beell isolated in
tide pools, and the trematodes multiplied to numbers up to 1000 per
fish. Two parasite species, G'yrodactylus arcuatus Bychowsky and
G . bychozoskyi Sproston, were involved ; most of the fish died. Dogie1
and Lutta (193'7) studied an epizootic in the Aral Sea sturgeon.
Acipenser nudiventris LOV., caused by the gill trematode Sitzschia
sturionis (Abilgaard). As a result of mortalities during 1936 the
fishery, which previously had reached a peak of 400 tons per year,
ceased to be of commercial significance for the next 20 years (Osmaiiov,
1959). Recent level of infestation in all conditions of salinity was
reported at 50 to 75%.
2. Cestodes
Adult cestodes are commoii and occasionally harmful digestivetract parasites of fishes, but, as with the trematodes, larval stages are
of greatest concern to man. Larval tapeworms occur frequently in
the viscera and flesh of marine and estuarine fishes (Fig. 8). The
definitive hosts of many of these parasites are elasmobranchs or fisheating birds and mammals. Tapeworms which localize in the body
muscles may occur in large numbers in individual hosts. Linton (1907)
described such an infestation in butterfish, Poronotus triacasithus
(Peck), of the North American east coast, in which several thousand
larvae could be found in individual fish. Encysted plerocercoids, less
than a millimeter in diameter, were concentrated in the flesh adjacent
to the vertebral column, and up t o 75% of individuals in a sample
were heavily infected. The parasite was identified as Otobothriuwi
crenacolle Linton, which matures in the spiral valve of certain shark
species, particularly the hammerhead, Sphyrna zygaenn (L.). Ripe,
highly motile proglottids of the tapeworm are shed in the feces and
presumably ingested by butterfish and other teleosts, in which the
embryos invade the musculature and encyst.
Other members of the cestode order Trypanorhyncha occur as
adults in the digestive tract of elasmobranchs, and as larvae in the
flesh and viscera of many teleost species. Elongate larvae of Poecilancistrium robustum (Chandler), called " spaghetti worms ", are very
abundant in the flesh of drum, Pogonius croniis (L.), in the Gulf of
Mexico. According to Chandler (1954) some municipal health departments have considered banning drum from markets because of frequent
worm parasitization. Oppenheimer (1 962) reported that spaghett,i
worms were common in the flesh of many other fishes from the Gulf of