Polymorphus petrochenkoi sp. n. (Acanthocephala) from the Red Phalarope, Phalaropus fulicarius L., in Alaska

Abstract

Polymorphus petrochenkoi sp. n. is described from a red phalarope, Phalaropus fulicarius L., from St. Lawrence Island, Alaska, USA. It is different from all other species of Polymorphus in having an elongated trunk, reminiscent of Arhythmorhynchus. Seven acanthocephalans, collected by Dr. Robert L. Rausch from a red phalarope, Phalaropus fulicarius L., (Charadriiformes) at St. Lawrence Island, Alaska, in 1953, were examined by the writer and found to represent a new species. The worms were stained with Semichon's carmine and mounted in Canada balsam for study. Drawings were made with the aid of a camera lucida and a microprojector. All measurements are in microns unless otherwise indicated. Polymorphus petrochenkoi sp. n. (Figs. 1-6) Description Trunk cylindrical, elongate, with no marked swelling near anterior end. Anterior end of trunk with field of small, evenly distributed spines, each 16 to 23 long. Sexual dimorphism of size apparent (Fig. 1). Neck fairly long. Proboscis (Fig. 2) fusiform. Armature equal in both sexes: 14 to 17 longitudinal rows of 10 to 12 hooks (Fig. 3). Each hook with pronounced cuticular theca around base. Last one or two hooks lacking roots but each possessing anteriorly-directed manubrium. Remaining hooks with strong roots. Hooks 40 to 59 long, except last two, which are 30 to 42 long. Anteriormost hooks delicate, becoming stouter posteriorly. Lemnisci wrinkled, extending well past end of proboscis receptacle. Male (Fig. 4): (One adult specimen) 14.4 mm long, 1.3 mm greatest width at level of testes. Proboscis 490 long, 190 greatest width. Neck 190 long, 190 wide at base. Trunk spines covering anterior 1.9 mm of trunk. Proboscis receptacle 900 long, 260 greatest width. Lemnisci equal, 1.2 mm long. Testes slightly pre-equatorial, tandem, elongate-oval; 1.4 to 1.5 mm long, 450 to 510 wide. Four tubular cement glands, two beginning near the posterior testis, two beginning somewhat farther back. Everted bursa not seen. Genital pore terminal. Female: (Five gravid specimens) 23.0 to 27.5 Received for publication 11 October 1968. mm long, 1.2 to 1.7 mm maximum width near equator of trunk. Posterior end of trunk (Fig. 5) simple, without papilla. Trunk spines covering anterior 1.9 mm of trunk. Proboscis 450 to 565 long, 226 to 258 greatest width. Neck 250 to 300 long, 250 to 260 wide at base. Proboscis receptacle 0.95 to 1.1 mm long, 240 to 280 greatest width. Lemnisci 1.5 mm long. Uterine bell (Fig. 5) 1.85 mm from terminal genital pore. Eggs (Fig. 6), measured through body wall, 65 to 73 long, 16 wide, with polar swellings of middle shell. Host: Red phalarope, Phalaropus fulicarius L. Location: Intestine. Locality: St. Lawrence Island, Alaska, U. S. A. Type specimens: USNM Helm. Coll., holotype male no. 71408, allotype female no. 71409, paratype females no. 71410.