The Life Cycle of Telolecithus pugetensis Lloyd and Guberlet, 1932 (Trematoda:Monorchidae)

Abstract

The fishes Cymatogaster aggregata, Embiotoca lateralis, and Phanerodon furcatus serve as definitive hosts for the trematode Telolecithus pugetensis Lloyd and Guberlet. Eggs from the terminal part of the uterus have undergone several cleavages, but complete development occurs only in eggs eaten by the clam Transennella tantilla, the first intermediate host. The miracidium is oval, covered with long cilia, and internally has germ balls and possibly flame cells. Sporocysts are found around the intestine of the clam in the vicinity of the gonad. No mother sporocyst generation was identified. In the fall and winter the sporocysts were mostly immature. Mature sporocyst infections were often of two sizes, one short and the other long, which suggests that the sporocysts may reproduce by transverse fission. Clams that harbored sporocysts were always sterile. Brevifurcate cercariae without a tail stem and with the furcae oriented dorsally and ventrally developed in sporocysts and left the clam via the excurrent siphon. The cercaria could only crawl, not swim. If a cercaria touched the soft part of a potential host, it would attach, penetrate within 1.5 to 2 hr, and become an encysted metacercaria within 24 hr. The following pelecypods from the same environment as T. tantilla served experimentally as second intermediate hosts: Clinocardium nuttalli, Schizothaerus nuttalli, Transennella tantilla (harbored both stages), Macoma nasuta, and Tellina salmonea. In the laboratory the gastropods Acmaea digitalis and Littorina planaxis, though not found in the same environment as the other hosts, served as second intermediate hosts, indicating that among molluscs host specificity of the cercaria was primarily ecological. In the field and in the laboratory, the clams Tellina salmonea and Macoma nasuta were the most highly infected with metacercariae, indicating that there was a certain degree of physiological specificity at this stage. Lloyd and Guberlet (1932) described the monorchid trematode Telolecithus pugetensis from worms obtained from the intestine of the embiotocid shiner perch Cymatogaster aggregata Gibbons, collected in the Puget Sound region. Stunkard (1959) reviewed the life history studies on members of the subfamily Asymphylodorinae Szidat, 1943, and reported his work on Asymphylodora amnicolae Stunkard, 1959. Rediae were reported in all the partial life histories he reviewed; A. amnicolae had both sporocyst and redia. All cercariae were of the cercariaeum type. Hoshina (1951) found that the metacercaria of Proctotrematoides pisodontophides Yamaguti, 1938 (Lasiotocinae Yamaguti, 1958) was Received for publication 3 September 1963. * Published with the approval of the Oregon State University Monographs Committee. Research Paper No. 458, Department of Zoology, School of Science. harbored by a pelecypod. He recovered the adults from the experimentally infected eel Anguilla japonica Temminck and Schlegel. The natural definitive host was the fish Pisodontophis cancrivora (Richardson). Of this subfamily, the life cycle of Postmonorchis donacis Young, 1953 is best known. Young (1953) found that the clam Donax gouldii Dall served as both the first and second intermediate hosts. The cercaria developed in a sporocyst, left the clam, reentered the same species, and became a metacercaria. Adults were recovered from experimentally infected embiotocids Embiotica jacksoni Agassiz, Micrometris sp., and Cymatogaster aggregata. In nature, mature worms were obtained from the sciaenid Menticirrhus undulatus (Girard) as well as Embiotoca jacksoni. The only known life history of the subfamily Monorchinae Odhner, 1911 is that of Monorcheides cumingiae Martin, 1938. Martin (1938) described Cercaria cumingiae, which developed