Life History of Microtetrameres centuri Barus, 1966 (Nematoda: Tetrameridae). II. Adults

Abstract

Dimensions of experimentally reared male Microtetrameres centuri are presented for the first time. Egg and buccal capsule measurements are important diagnostic aids in species determination within the genus Microtetrameres. A key to the species of adult females from the Western Hemisphere is presented. Nematodes of the genus Microtetrameres Cram, 1927 differ markedly from almost all other spiruroids in their striking sexual dimorphism. These unusual nematodes parasitize the proventriculus of birds of at least 10 orders. Although numerous investigators (Schell, 1953; Boyd, 1956; Mawson, 1956; Rasheed, 1960; Ortlepp, 1964; Barus, 1966) have published descriptive accounts of species of Microtetrameres, no life cycle studies have appeared except one by Cram (1934) who reported briefly on M. helix Cram, 1927 and another by Schell (1953) concerning M. corax Schell, 1953. Little information is available concerning details of laboratory-reared adults and juveniles of this genus (Ellis, 1969). The anatomy of adult female Microtetrameres spp. has been described in detail (Seurat, 1913, 1914; Cram, 1927; Schell, 1953; Boyd, 1956; Mawson, 1956; Rasheed, 1960; Barus, 1966). Adult female M. centuri differ only in dimensions from other species except M. accipiter Schell, 1953 with its flanges; M. cruzi (Travassos, 1914) Travassos, 1915 and M. pusilla Travassos, 1915 with their furrows; and M. spiralis (Seurat, 1915) Cram, 1927 as described by Seurat (1913) with their cervical papillae. Finding Microtetrameres sp. in a bronzed grackle (Quiscalus versicolor) and in a meadowlark (Sturnella magna) in north central Iowa (Ellis, 1961, 1967) gave impetus to this study of Microtetrameres centuri. MATERIALS AND METHODS Female Microtetrameres centuri were collected (1963-67) from the proventriculi of infected meadowlarks (Sturnella magna and S. neglecta) taken near Ames, Iowa, and the Iowa Lakeside Laboratory, Milford, Iowa. The birds were necropsied in the laboratory usually within 3 to 4 Received for publication 16 August 1968. hr post-mortem. The females were either expressed from the gland or released by teasing surrounding tissue. Some females gravid with embryonated eggs were fed in toto to laboratory-reared nymph grasshoppers. The grasshoppers were then examined at intervals for the presence of juveniles. Thirdstage infective juveniles were fed to various laboratory-reared avian hosts (Ellis, 1967). Entire specimens were fixed in hot 70% glycerine-alcohol. Males were mounted in CMC-10 or glycerine jelly. Intact females in 70% alcohol were stored in small vials. Both ends of some females were removed after the entire female had been cleared in 70% glycerine-alcohol. These ends were mounted either in CMC-10 (General Biological Supply House Inc.) or in glycerine jelly. Phase-contrast and bright-field microscopy were used to study intact nematodes and the ends of some females. All measurements were made with a calibrated ocular micrometer. All drawings were made, except those noted, with the aid of a microprojector. Dimensions are given in microns unless otherwise stated.