Some digenetic trematodes from synaphobranchid eels.

Four trematodes, all new host records, were found in synaphobranchid eels from the continental slopes in the Gulf of Mexico and the Straits of Florida. Hypertrema ambovatum Manter, 1960 (Fellodistomidae), previously known only from near New Zealand, is reported from Synaphobranchus oregoni, including data in addition to the original description; Pseudopecoelus vulgaris (Manter, 1934) (Opecoelidae) and Hirudinella sp. (Hirudinellidae) are reported from S. affinis and S. oregoni, respectively, and commented upon briefly; and Helicometra robinsorum sp. n. (Opecoelidae) is described from S. oregoni and Ilyophis brunneus. The latter trematode most closely resembles H. antarcticae Holloway and Bier, 1968, from which it differs by having a sucker-width ratio of 1:1.7 to 2.1 rather than 1:1.2, a subterminal rather than terminal oral sucker, a cirrus sac extending to the posterior border rather than middle of the acetabulum, and eggs that are usually smaller. Digenetic trematodes parasitize synaphobranchid eels (Yamaguti, 1938; Guiart, 1938; Manter, 1947; and the present study). These eels, benthic inhabitants of the continental slopes of temperate and tropical waters, are characterized by having scales and possessing either a single slitlike branchial aperture on the midline of the throat or two restricted ventral openings. Many such eels 330 to 776 mm in length were collected by the R/V ALAMINOS along the continental slopes of the Gulf of Mexico and the Caribbean Sea in water 620 to 2,150 m deep, including 134 specimens of Synaphobranchus oregoni Castle, eight of S. brevidorsalis Giinther, one of S. affinis Giinther, and eight of Ilyophis brunneus Gilbert. Digenea occurred in members of the first and last species in the Gulf of Mexico as well as in additional individuals from the Straits of Florida given to us by Catherine H. Robins. All are new host records. Fishes were slit and then fixed in 10% formalin as soon as they were brought aboard the vessel; however, trematodes could have moved to their cited location in the host before or during fixation. Trematodes removed from preserved fishes and later transferred to AFA included many favorable specimens that Received for publication 3 August 1973. * This work is a result of research sponsored in part by NOAA Office of Sea Grant, Department of Commerce Grant No. 04-3-158, Publication MASGP-73-003. The U. S. Government is authorized to produce and distribute reprints for governmental purposes notwithstanding any copyright notation that may appear hereon. t Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564. + Department of Oceanography, Texas A & M University, College Station, Texas 77843. stained well with Van Cleave's hematoxylin. Two individuals were sectioned and stained with Harris' hematoxylin and eosin, and all material was mounted in Permount. Figures, except those designated otherwise, were drawn with the aid of a camera lucida. Measurements are given in microns. Family Fellodistomidae Hypertrema ambovatum Manter, 1960