The Life Cycle and Larval Development of Echinorhynchus lageniformis Ekbaum, 1938 (Acanthocephala: Echinorhynchidae)

Abstract

The life cycle of Echinorhynchus lageniformis was completed experimentally in the laboratory, and the adult worm redescribed. Shelled acanthors ingested by the amphipod Corophium spinicorne penetrate the intestine within 2 days, remain attached to the intestinal serosa for about 10 days, and then drop free into the hemocoel. The acanthella becomes infective in 30 days at 23 C. The starry flounder, Platichthys stellatus, serves as the final host in estuarine waters of the Oregon coast. The acanthocephalan Echinorhynchus lageniformis Ekbaum, 1938 was first described from the starry flounder (Platichthys stellatus) and the rock sole (Lepidopsetta bilineata) collected in Departure Bay, British Columbia. It is a common parasite of the starry flounder on the Oregon coast in Yaquina Bay, Alsea Bay, and in the Columbia River estuary. The intermediate hosts for only four species of Echinorhynchus have been determined (Yamaguti, 1963): E. clavula (Dujardin, 1845) nee Hamann, 1892, E. gadi (Zoega) Miller, 1776, E. salmonis Muller, 1784, and E. truttae Schrank, 1788. Only in E. truttae has larval development been studied (Awachie, 1966). Prakash and Adams (1960) studied the histopathology of E. lageniformis in the starry flounder and Barnes (1968) studied its ecology in Yaquina Bay. The purpose of this investigation was to determine the life cycle of E. lageniformis and to study its development in the intermediate host. Because the original description of E. lageniformis lacks detail, the adult is redescribed. MATERIALS AND METHODS Specimens of starry flounder were collected primarily in Yaquina Bay with a 16-ft otter trawl and were transported to the Oregon State University Marine Science Center for study. The total length of each fish was measured, the intestine removed, and the contents examined for E. lageniformis. Worms were collected and placed in distilled water until fully extended. A number of gravid female worms were punctured in order to obtain eggs. The eggs placed in bay water and stored under refrigeration were viable for at least several months. The remaining worms were fixed in AFA, stained with Semichon's acetocarmine, cleared in methyl salicylate, and mounted in Harleco synthetic resin. The intermediate host was determined by allowReceived for publication 29 June 1970. ing various bay amphipods to feed on large numbers of eggs in small dishes. After 3 to 4 hr, the amphipods were transferred to aerated finger bowls and held at 23 C. After varying periods of time, amphipods were examined for infections. When the proper host was determined, large numbers were infected and examined at regular intervals. When recovered, immature acanthocephalans were studied alive in 0.5% saline, then made into permanent mounts in the same manner as adult worms. The time required for the development of an infective juvenile was determined by feeding larvae of various ages to young P. stellatus.