Comparative Parasitology 68(2) 2001 - Peru State College

Comp. Parasitol.
68(2), 2001, pp. 249-255
Tegumentary Ultrastructure (SEM) of Preadult and Adult
Lobatostoma jungwirthi Kritscher, 1974 (Trematoda: Aspidogastrea)
ANALIA PAOLA' AND MARIA CRISTINA DAMBORENEA2
Departamento Cientffico Zoologia Invertebrados, Facultad de Ciencias Naturales y Museo,
Paseo del Bosque s/n° -1900- La Plata, CONICET.PIP 4728/96 Argentina
(e-mail: 'apaola@museo.fcnym.unlp.edu.ar; 2cdambor@museo.fcnym.unlp.edu.ar)
ABSTRACT: Larval Lobatostoma jungwirthi Kritscher, 1974 (Trematoda: Aspidogastrea) parasitize the digestive
gland of Heleobia parchappii (d'Orbigny, 1835) (Mollusca: Hydrobiidae) and, as adults, the posterior intestine
of the chameleon cichlid Cichlasotna facetum (Jenyns, 1842) (Pisces, Cichlidae). Currently, L. jungwirthi is the
only aspidogastrid reported from freshwater fishes in Argentina. Tegumentary structures of preadults and adults
of L. jungwirthi were observed under scanning electron microscopy. In the preadult, 2 types of sensory receptors
were observed: monociliate papillae of intermediate length on the walls and crests of the ventral adhesive disc
as well as on the disc periphery and oral lobules, and nonciliate dome-shaped papillae on the crests of the
ventral adhesive disc, neck, and oral lobules. In adults, other types of sensory receptors could be observed: in
the posterior dorsal region, monociliate papillae with longer cilia than those found in the preadult, and a multiciliate
structure in the dorsal region at the posterior third of the body. This is the first record of a surface
multiciliate receptor in aspidogastreans. The pores of marginal glands were found only between the anterior
alveoli.
KEY WORDS: Aspidogastrea, Lobatostoma jungwirthi, tegument, sensory papillae, SEM, Argentina.
Lobatostoma jungwirthi Kritscher, 1974
(Trematoda: Aspidogastrea), is the only species
of the genus that parasitizes freshwater fishes. It
was first found in 1974, in the stripefin eartheater
Gymnogeophagus rhabdotus (Hensel,
1870), in the Sinus River, Brazil (Kritscher,
1974). Lunaschi (1984) found it in the posterior
intestine of the chameleon cichlid Cichlasoma
facetum (Jenyns, 1842) (Pisces: Cichlidae) at 2
localities in Buenos Aires Province. Later, Zylber
and Ostrowski de Nunez (1999) described
the larval stages of L. jungwirthi from the gonad
of Heleobia castellanosae (Gaillard, 1974) (Gastropoda:
Hydrobiidae) collected in an artificial
pond in Buenos Aires City.
To date, the morphology of the larval (Zylber
and Ostrowski de Nunez, 1999) and adult
(Kritscher, 1974; Lunaschi, 1984) stages of this
species is known only at the light microscopy
level. Several investigators have described the
tegumentary ultrastructure of adult aspidogastrids,
such as Aspidogaster conchicola Baer,
1826 (Halton and Lyness, 1971), and Cotylogaster
occidentalis Nickerson, 1902 (Ip and
Desser, 1984). The variability of tegumentary
sensory structures of the cotylocidia of C. occidentalis
(Fredericksen, 1978), the development
and growth of the ventral adhesive disc of C.
Corresponding author.
249
occidentalis and A. conchicola (Fredericksen,
1980), and the sensory receptors of the larval
stage of Lobatostoma manteri Rohde, 1973
(Rohde and Watson, 1989a, b, 1992), and Multicotyle
purvisi Dawes, 1941 (Rohde and Watson,
1990b, c, d), were also studied. The aim of
the present paper is to describe the tegumentary
ultrastructure of juvenile and adult specimens of
L. jungwirthi under scanning electron microscopy
(SEM).
Materials and Methods
Parasites removed from the posterior intestine of C.
facetum were identified as L. jungwirthi on the basis
of the descriptions of Kritscher (1974) and Lunaschi
(1984). Juvenile stages were found in the digestive
gland of Heleobia parchappii (d'Orbigny, 1835) (Mollusca:
Hydrobiidae), and adult specimens were obtained
from the posterior intestine of C. facetum. Both
host species were naturally parasitized by this aspidogastrid
in Saladita Pond, Avellaneda District, Buenos
Aires.
The specimens were fixed in 10% formalin and
washed in distilled water. They were dehydrated by 2
changes in 35, 50, 70, and 90% acetone for 15 min
each and 3 changes in 100% acetone. The material was
critical point dried, then mounted on stubs and coated
for SEM observation (JEOL 100).
The immature stage was named the postacetabular
juvenile, following the nomenclature used by Fredericksen
(1980). Two stages could be distinguished according
to the development of the ventral adhesive
disc: a recently formed postacetabular juvenile, with
little differentiation of alveoli and the buccal opening
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