Genus Cylicocyclus Ihle, 1922

Synonyms: Cylicostomum (Cylicocyclus) Ihle, 1922; Cylicobrachytus Cram, 1924; Schulzitrichonema Ershov, 1943.

General. Small or medium size Cyathostominae. MC inflated, high, ring-shape, divided into inner and outer rings. Posterior edge of MC anterior to edge or anterior edge of BC. Amphids project above MC surface. Tip and longer stalk of submedian papillae extend through MC. Tip of submedian papillae spindle or bullet-shaped or very long, uniform thickness 2 - 3 times or more as long as thick. Stalk of submedian papillae longer than broad or broader than long. ELC near equal in number and equal in length to ILC. Elements of ELC longer than broad, tips rounded or pointed; insertion point ontips of ILC. Elements of ILC longer than broad, tips rounded; insertion point on anterior edge of BC. Line formed by insertion of elements of ILC straight. Form of posterior edge of elements of ILC straight, unadorned. Support for ELC continuous with BC, elongate, curving, thin at one end. Septum intracoronare origin on support. Medial insertion of septum intracoronare situated anteriorly to junction of ELC and ILC. Walls of BC concave or straight, with prominent ring-like thickening at base. Buccal cavity cylindrical, wider than deep. Dorsal gutter button-like or less than 1/2 of BC depth. Buccal teeth absent. Esophageal funnel shallow or well enlarged. Esophageal teeth prominent or not. Anterior muscular portion of esophagus about ¼ to 1/3 of esophagus length. Excretory pore posterior to NR or esophageal-intestinal junction EI. Anterior deirids at level of NR, near middle of glandular esophagus or posterior to EI.

Male: Dorsal ray with 6 branches. Ventral shorter or equal laterals. Dorsal lobe longer then lateral lobes. Gubernaculum large, with dorsal handle and ventral notch. Genital cone short, conical. Spicule tips pick-shaped.

Female: Vulva about one, or less than one, tail length from anus. Vagina longer than sphincter. Ovejector vestibule oval or Y-shaped, infundibulum equal or longer than sphincter. Tail digitiform, short, length less than 2x diameter at anus.

Type species: C. radiatus (Looss, 1900) Chaves, 1930

Discussion

The name Cylicocyclus, calling attention to the hooplike thickening at the base of the buccal capsule, was proposed by Ihle (1922) as a subgenus. Cram (1925) elevated the group to generic level. There has been general agreement (Lichtenfels, 1975; Hartwich, 1986; Dvojnos and Kharchenko, 1994; and Lichtenfels et al., 1998) concerning the relationship of most of the species presently included in this genus. According to the molecular analysis ofHung et al. (2000) C. ultrajectinus differs from other members of this genus. However, in a morphological phylogeny of 35 species of cyathostomins (Lichtenfels et al., unpublished) C. ultrajectinus was grouped with the species of Cylicocyclus, closest to C. auriculatus. Hartwich (1986) correctly pointed out that C. leptostomum should retain the nominative singular noun ending “um”.

The question of whether C. elongatus elongatus and C. elongatus kotlani differ sufficiently to be recognized as separate species was raised by Lichtenfels (1975) and Lichtenfels et al. (1998). The available specimens of C. elongatus sensu lato, except the paratypes, are all C. elongatus kotlani (Ihle, 1920). This subspecies were described as a variety with a greatly elongated bursa (1.5 mm compared with 700 um for C. elongatus elongatus). Georgi and Whitlock (1971) also reported C. elongatus kotlani from New York. Barus (1962) and Braide and Georgi (1974) reported C. elongatus kotlani to have 52—57 elements in the ELC rather than 36 as found in C. elongatus elongatus by Looss (1902). This difference in number of ELC elements was also reported by Popova (1958). Lichtenfels (1975) was able to confirm these differences between C. e. elongatus and C. e. kotlani by studying paratypes of the former which Looss deposited in the USNM Helminthological Collection. In addition he observed the vagina of C. e. elongatus females to be significantly shorter than that of C. e. kotlani. These differences between the two subspecies are as great as those between many species and further study may provide convincing evidence that they are separate species. For the present, because males of C. elongatus elongatus are not available, we prefer to retain the subspecies designations.

Cylicocyclus ashworthi was redescribed by Lichtenfels et al. (1997). Hartwich (1986) and others had considered this species to be a synonym of C. triramosus, but Kharchenko et al. (1997) redescribed C. triramosus which is restricted to zebras and differentiated the two species. The species C. triramosus was described from one male and one female from zebra from Namibia (Yorke and Macfie, 1920). The description was completed by Theiler (1923), who added 3 specimens from 2 zebras. These descriptions were repeated exactly in a number of monographs (Ihle, 1922; Skrjabin and Ershov, 1933 in Popova 1958). Noboby disputed the validity of C. triramosus. The confusion arose after C. ashworthi Le Roux (1924) was described and and Ihle (1925) synonimized it with C. nassatus. Some authors around the world and, particulary in Russian language helminthological literature (Ivashkin, Dvojnos, 1984; Ershov, 1933; Mendelevich, 1940 and others), distinguished, in their own material, two species and considered C. ashworthi to be identical to C. nassatus, identified incorectly C. ashworthi as C. triramosus. As a result Hartwich (1986) synonimizied C. ashworthiwith C. triramosus. The study of helminths of zebra conducted by R. Krecek in the South Africa (Krecek, 1984) confirmed, that in spite of cosmopolity of the overwelming majority of species of cyathostomins, some are restricted to zebras. Kharchenko et al. (1997) determined that C. triramosus is parasitic only in zebra and has been found only in Southern Africa. This species is similar to C. ashworthi, C. nassatus, C. leptostomus and C. radiatus. It is most similar with the latter (redescribed by Lichtenfels et al., 1998), particulary with the thin buccal walls, with a slightly hoop-shaped thickening. . Recently a new species, C. asini parasitic in E. asinus in Africa, was added to this genus (Matthee et al., 2002). This species is similar to C. triramosus, but differs in shape of both male and female tails as well as other characteristics.

Cylicocyclus adersi (Boulenger, 1920) Chaves, 1930 was redescribed by Kharchenko et al. (2004). It was considered by Lichtenfels et al. (1998) to be a species inquirenda.

Until recently C. gyalocephaloides Ortlepp, 1938 was considered (Lichtenfels et al., 1998) to be a species inquirenda. It has been redescribed (Lichtenfels et al., 2005) and differentiated from C. insigne. Lichtenfels et al. (2005) speculated that the large species of Cylicocyclus commonly found in zebras and donkeys in Africa, including C. gyalocephaloides, C. adersi, C elongatus elongatus and C. auriculatus may have originated in Africa in these hosts and given rise to the similar species C. insigne and C. elongatus kotlani parasitic in E. caballus. A morphological phylogeny (Lichtenfels et al., unpublished) placed C. adersi basal to all other species of Cylicocyclus with C. brevicapsulatus basal to all but C. adersi. The molecular phylogeny of Hung et al. (2000) agreed with the placement of C. brevicapsulatus but did not include C. adersi in the analysis.