Comparative Parasitology 68(2) 2001 - Peru State College

250 COMPARATIVE PARASITOLOGY, 68(2), JULY 2001
without oral lobules; and a preadult characterized by
the presence of oral lobules and a distinct differentiation
between alveoli, with the external morphology
similar to that of the adult.
Results
Postacetabular juvenile
In the recently formed postacetabular juvenile
(Fig. 1), the oral disc characteristic of the adult
phase is not observed. The mouth is a simple
opening, without lobules (Fig. 2).
The preadult shows a rough dorsal cone. Central
and marginal alveoli, completely differentiated
and varying in number, are observed on the
ventral adhesive disc (Fig. 3). The posterior alveoli
are less developed. Monociliate sensory
papillae are found in the internal wall of the
marginal alveoli (Fig. 4). The pores of the marginal
bodies can be observed on the external
border between the marginal alveoli. They are
more developed in the anterior region of the
ventral disc (Figs. 4, 5). The oral disc has 3 ventral
and 2 dorsal lobules as in the adult, though
they are not completely developed (Fig. 6).
Monociliate sensory papillae and dome-shaped
papillae are observed on the posterior surface of
the oral disc. In this region, there is no regular
distribution pattern of sensory structures (Fig.
7).
In the dorsal region of the neck, immediately
behind the oral disc, there are pores and domeshaped
papillae (Fig. 8). The monociliate papillae
each have a cilium emerging from a bulbous
surface.
Adult
The ventral adhesive disc has 16 marginal
pairs and 32 central alveoli. The limit between
both groups of central alveoli cannot be clearly
observed (Fig. 9). The anterior region of the
ventral adhesive disc shows a neat differentiation
among the alveoli, with many sensory structures
(Fig. 10). Completely differentiated pores
of the marginal bodies are found between the
marginal alveoli (Fig. 11). Monociliate papillae
are located on the internal wall of each alveolus,
arranged in 2 concentric circles. Two rows of
dome-shaped papillae occur on the external edge
of the marginal alveoli (Figs. 11-13). Monociliate
and dome-shaped papillae (Fig. 14) are
present on both sides of the transverse dividing
line between the central alveoli. The excretory
pore can be seen in the dorsal cone (Fig. 15).
Copyright © 2011, The Helminthological Society of Washington
Two kinds of monociliate receptors (Fig. 16) and
a single multiciliate structure (Fig. 17) were observed
in the posterior dorsal region.
Discussion
The external morphology of the preadult of L.
jungwirthi is very similar to that of the adult
from C. facetum. Both juveniles and adults show
a single excretory pore that ends at the channel
formed by the union of the lateral ducts, as described
by Lunaschi (1984). In agreement with
the observations of Kritscher (1974) and Lunaschi
(1984), the adult stage does not show a pore
of Laurer's canal.
Four types of sensory receptors were observed
by SEM:
MONOCILIATE PAPILLAE WITH A SHORT CILIUM:
This type of receptor was irregularly distributed
on the dorsal tegument, in the posterior surface
of the oral lobules, and in the neck of juvenile
L. jungwirthi. A denned pattern of distribution
was observed only on the edges of the alveoli
of the ventral adhesive disc. Rohde and Watson
(1992) described this structure as a receptor
formed by a cilium of intermediate length, being
the most common type on the surface of L. manteri.
Halton and Lyness (1971) described this
type of papilla as the most frequent receptor on
the body surface of A. conchicola. This receptor
is more abundant in the oral lobules and in the
central, marginal, and peripheral regions of the
ventral adhesive disc of L. jungwirthi. This distribution
agrees with that observed by Halton
and Lyness (1971) in A. conchicola. The type of
monociliate papilla found in L. jungwirthi may
also correspond to that described by Fredericksen
in the juvenile acetabulum of C. occidentalis
and the simple uniciliate sensory structures observed
in the cotylocidium larva of the same
species (Fredericksen, 1978). Likewise, they are
similar to type I sensilla found in adult C. occidentalis
(Ip and Desser, 1984). Monociliate receptors
were observed in Lobatostoma sp. (Rohde,
1972), and the type I receptor has been observed
in the tegument of posterior suckerlets of
larval Multicotyle purvisi (Rohde and Watson,
1990c). Monociliate tegumental receptors were
also found in the buccal complex of Polylabroides
australis (Murray, 1931) (Monogenea, Microcotylidae)
(Rohde and Watson, 1995b) and in
Udonella sp. (Platyhelminthes) (Rohde et al.,
1989).
MONOCILIATE PAPILLAE WITH A LONG CILIUM: