MEM INST OSWALDO CRUZ, RIO DE JANEIRO, 97(1) January 2002
PAGES: 89-92 DOI: Short communication
Some Morphological Aspects of Cylicocyclus brevicapsulatus (Nematoda: Cyathostominae) Parasite of Horse

Helio MA Costa, Amalia VM Silva, Marcos P Guimarães* +

União Educacional do Vale do Aço, Ipatinga, MG Brasil
*Departamento de Parasitologia, ICB, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, 31270-901 Belo Horizonte, MG Brasil

Abstract

This paper describes some morphological aspects of Cylicocyclus brevicapsulatus (Ihle, 1920) (Nematoda: Cyathostominae) from Equus caballus in Brazil. The worms were studied using an optical microscope (measurements and illustrations) and a scanning electron microscope for a more detailed examination of the external morphology. The buccal capsule is very short, with a very thin wall, and the dorsal gutter is absent. Other morphological aspects are described including measurement of the spicules and gubernaculum.

Approximately 14 species have been described for the genus Cylicocyclus, some of which are difficult to identify because their original descriptions were incomplete. Lichtenfels et al. (1997) suggested a key with characters for the microscopical identification of C. nassatus and C. ashworthi. Kharchenko et al. (1997) and Lichtenfels et al. (1998) have redescribed some of the other species, but the only study carried out on C. brevicapsulatus since it was first described by Ihle in 1920 (as Cylicostomum brevicapsulatus) was by Skrjabin and Ershov (1933), Foster and Ortiz (1937), Lanfredi and Honer (1984) and Souto-Maior et al. (1999). Here we describe some morphological aspects of the species in order to facilitate its identification

Sixteen males and eight females were studied under an optical microscope. The specimens were cleared in phenol-alcohol (80 parts of phenol, 20 parts of absolute alcohol). Six male and six female specimens were identified and processed for the examination under scanning electron microscope (SEM) (Guimaraes & Caldeira 1997).

Morphometric study

Cylicocyclus brevicapsulatus (Ihle, 1920)
Ershov, 1943 (Figs 1-14)

The general characteristics are the same as those for the genus, but the hoop-like thickening of the posterior margin of the buccal capsule is more difficult to observe. The mouth collar is poorly developed. Lateral papillae are prominent above the mouth-collar. Submedian papillae have spindle-shaped tips extending above the mouth collar to the level of external leaf-crown (Figs 1, 2). The external leaf-crown has 42-44 elements (Figs 7, 8) measuring approximately 2.5 µm at the base, recurved outwards at the middle, and becoming pointed at the tip. The internal leaf-crown has approximately 64 small elements measuring approximately 3.65 x 2.67 µm. The buccal cavity is very short, and nearly 9-10 times wider than it is deep. The walls of the buccal capsule are poorly developed. The dorsal gutter is absent. The esophagus is club-shaped. The cervical papillae (Fig. 9) lie posterior to the nerve ring, near the terminal end of the esophagus.

Males: measurements are shown in the Table. The dorsal lobe of the copulatory bursa is short and not separated, although the dorsal system is distinct. The middle dorsal ray is split from the base of externodorsal rays. Each of the middle branches has two auxiliary branches. The posterior auxiliary and middle branches have small offshoots (Fig. 5). The base of the lateral rays is a common stem (Fig. 3). The ventral system, with ventro-ventral and ventro-lateral rays, is not separated. The margin of the bursa is serrated, and has cilium-like formations (Fig. 10). Genital cone (Fig. 11), presenting on each side of the ventral surface, one appendage from which three or more papilla-like projections originate. Spicules thin, long, few sclerotised, fused in the final third and with an anchor-like tip with two bi-divided flukes (Fig. 12). Gubernaculum compact, with manubrium (Fig. 6).

Females: measurements are in the Table. The posterior end of the female is relatively broad, without lateral prominences. The tail is a little shorter than the vulva-to-anus distance (Fig. 4), cone like, and recurved dorsally (Figs 413). Vulva simple (Fig. 14). Vagina is relatively short, vestibule large and bulky, sphincters and infundibula shorter than vestibule.

Taxonomic summary 
Synonyms: Cylicostomum brevicapsulatum Ihle, 1920 
C. (Cylicodontophorus) brevicapsulatum Ihle, 1922 
Cylicobrachytus brevicapsulatus (Ihle, 1920) Cram, 1924 
Trichonema brevicapsulatus (Ihle, 1920) Mönnig, 1926 
Host: Equus caballus 
Location in host: colon and caecum 
Origin: State of Goiás, Brazil

The specimens (males and females) studied are shorter than those described by Ihle (1920) and Skrjabin and Ershov (1933). Measurements of height and width of the buccal cavity are very important in identifying the species, and our data are similar to those of Ihle (1920) and Skrjabin and Ershov (1933). Although the most distinctive characteristic of C. brevicapsulatus is the buccal cavity (morphology and measurements), additional characters are presented in the microscopical identification of the species, as was used by Lichtenfels et al. (1997) for C. nassatus and C. ashworthi. Measurements of vagina in Ihle (1920) and Skrjabin and Ershov (1933) are equivalent to the measurements of vagina and vestibule of females we studied.

 

REFERENCES

Foster AO, Ortiz PO 1937. A further report on the parasites of a selected group of equines in Panama. J Parasitol 23: 360-364.

Guimarães MP, Caldeira MCM 1997. Scanning electron microscopy of Haemonchus similis (Nematoda: Trichostrongylidae) parasite of cattle. Rev Bras Parasitol Vet 6: 139-141.

Ihle JEW 1920. Cylicostomum brevicapsulatus n. sp. eine neue Strongylide due dem Darm des Pferdes. Zentbl Bakteriol I Abt Orig Bd 84: 562-565.

Kharchenko VA, Dvojnos GM, Krecek RC, Lichtenfels JR 1997. A redescription of Cylicocyclus triramosus (Nematoda: Strongyloidea): a parasite of the zebra, Equus burchelli antiquorumJ Parasitol 8: 922-926.

Lanfredi RM, Honer MR 1984. Uma nova chave para identificação simplificada das espécies da sub-família Cyathostominae (Strongylidae-Nematoda) parasito de Equus caballus no Brasil. Pesq Vet Bras 4: 67-72.

Lichtenfels JR, Kharchenko VA, Sommer C, Ito M 1997. Key characters for the microscocopical identification ofCylicocyclus nassatus and Cylicocyclus ashworthi (Nematoda: Cyathostominae) of the horse, Equus caballusProc Helminthol Soc Wash 64: 120-127.

Lichtenfels JR, Plit PA, Dvojnos GM, Kharchenko VA, Krecek RC 1998. A redescription of Cylicocyclus radiatus(Nematoda: Cyathostominae), a parasite of the ass, Equus asinus, and horse, Equus caballus. J Helminthol 65: 56-61.

Skrjabin KI, Ershov VS 1933. Gel'mintozy loshadei (horse helminthiases). Moskva-Leningrad, Sel'khozgiz, 408 pp. "apud"Popova (1965). Strongyloids of Animals and ManTrichonematidae, Israel Program for Scientific Translations, Jerusalem, p. 41-63.

Souto-Maior MP, Rodrigues MLA, Anjos DHS, Andrade AA 1999. Estrutura das infracomunidades de nematóides estrongilídeos (Nematoda: Strongylidae) do ceco de Equus caballus naturalmente infectados proveniente da Região Metropolitana do Rio de Janeiro. Parasitol al Dia 23: 24-32.

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