Dirofilaria lutrae sp. n. (Nematoda: Filarioidea) from Otters in the Southeast United States

Abstract

Dirofilaria lutrae sp. n. is described from the subcutaneous tissues of the American otter in Louisiana and Florida. The species is characterized by long and slender form, absence of longitudinal cuticular ridges (except on the tail of the male), extremely large left and relatively short right spicules, and an unusually large, unsheathed microfilaria. Morphologically, the species is most similar to Dirofilaria incrassata which parasitizes certain Central and South American sloths. In the course of a survey of filariae of animals in southern Louisiana in 1959 and 1960, a species of Dirofilaria producing a very large, unsheathed microfilaria was found in the subcutaneous tissues of the otter, Lutra canadensis texensis Goldman. Similar surveys were undertaken in south Florida in 1960-61 and the same species of Dirofilaria was recovered from the otter, Lutra canadensis vaga Bangs, in Dade and Collier counties. Preliminary studies indicated that the species was morphologically distinct from others of the genus. Additional specimens from the same host were obtained from Dr. J. F. Schacher who made collections at the Rockefeller Refuge in Louisiana and from Dr. W. H. Leigh whose material was collected in the Everglades region of Florida. Dirofilaria spp. have not previously been reported from the otter in North America. However, two species have been found in the South American otter, Pteronura brasiliensis. Vogelsang (1940) reported D. immitis in the heart and pulmonary vessels of an otter in Venezuela. Freitas and Lent (1949) described a new species, D. spectans, from the heart and pulmonary arteries of otters in Brazil. The species description presented in this report is based on the examination of specimens recovered from an otter captured in Terrebonne Parish, Louisiana. Measurements are in millimeters unless otherwise indicated. Range is followed by average in parentheses. Received for publication 29 May 1964. * Supported by Grant EF-10,217 from NIH, U. S. Public Health Service. t Present address: Delta Regional Primate Research Center, Covington, Louisiana. Dirofilaria lutrae sp. n. (Figs. 1-9) Description Onchocercidae (Leiper, 1911); Dirofilariinae (Sandground, 1921); Dirofilaria Railliet and Henry, 1911. Body long, slender, uniform in diameter except at the tapered extremities. Cuticle finely striated transversely; longitudinal ridges lacking except on ventral surface of male tail. Oral opening small, circular (Fig. 6), surrounded by four pairs of submedian papillae in addition to a pair of amphids. Esophagus distinctly divided into muscular and glandular portions (Figs. 1, 7, 8). Microfilariae circulate in peripheral blood. Male (15 specimens): Body length 49 to 73 (55); width 0.20 to 0.28 (0.23) at nerve ring, 0.20 to 0.31 (0.26) at mid-body, 0.07 to 0.10 (0.09) at level of cloaca. Esophagus length 0.87 to 1.00 (0.92). Nerve ring 0.26 to 0.29 (0.27) from anterior end. Cloaca 72 to 84 t from posterior end of body. Preanal papillae large, elongate, pedunculated, usually six or seven on left side, five to seven on right; posteriormost pair set inward toward midline (Fig. 2). Single pair of papillae immediately behind cloaca in midventral line. Paired postanal papillae on line with preanals, thre or four in number, usually four; first pair large, second, third, and fourth tall, slender, closely grouped (Fig. 2). Phasmids ventrolaterally placed near tip of tail. Spicules unequal and dissimilar; left 0.55 to 0.70 (0.60) long, right 0.15 to 0.20 (0.17); mean left : right spicular ratio, 3.5: 1. Left spicule with slender tubular shaft and lamina composed of two laterally oriented elements, one short, the other very long and filamentous (Fig. 3). Right spicule short, relatively narrow, boat-shaped (Fig. 3). Tail spirally coiled, usually in two turns. Caudal alae broad. Female (15 specimens): Body length 130 to 180 (151), width at nerve ring 0.33 to 0.36 (0.34), at vulva 0.32 to 0.40 (0.37), at mid-body 0.32 to 0.37 (0.36), at anus 0.09 to 0.11 (0.10). Esophagus 1.15 to 1.33 (1.28) long; nerve ring 0.31 to 0.37 (0.36) from anterior end. Vulva posterior to esophageal-intestinal junction, 1.7 to 2.9 (2.1) from anterior end. Vagina vera muscular, bulbous, ovejector-like; remainder of vagina, usually di-