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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 97, Num. 1, 2002, pp. 89-92
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Mem Inst Oswaldo Cruz, Rio de
Janeiro, Vol. 97(1) 2002, pp. 89-92
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
†Deceased in January 1999.
+Corresponding author. Fax:+55-31-3499.2970. E-mail: pezzi@icb.ufmg.br
Received 22 February 2001
Acceptd 23 August 2001
Code Number: oc02015
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.
Key words: Cylicocyclus brevicapsulatus
- horses - morphology - scanning electron microscopy
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 1-6, 7-14)
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
4, 13). 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
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© 2002
Instituto Oswaldo Cruz - Fiocruz
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