Suggested citation: Silveira, E.F. & Amato, S.B. 2010. Microsomacanthus hopkinsi (Eucestoda, Hymenolepididae) in Netta
peposaca (Aves, Anatidae). Neotropical Helminthology, vol. 4, nº 2, pp. 105-111.
Resumen
Palabras claves: Argentina - Brasil - marrecão - pólo de invernia - pólo de nidificação - rota de migração.
Netta peposaca (Vieillot, 1816), marrecão, é um anatídeo silvestre, distribuí-se nos ambientes aquáticos
como banhados, lavouras e várzeas. Com o objetivo de conhecer a helmintofauna do marrecão na
América do Sul, 169 aves foram amostradas. Os locais de captura foram os municípios de Santa Vitória
do Palmar e Jaguarão, no Estado do Rio Grande do Sul, sul do Brasil (pólo de invernia), e em Alvear,
Província de Corrientes, região norte da Argentina (pólo de nidificação), entre 2002 e 2004. As aves
foram congeladas em gelo seco logo após o abate. Durante o procedimento de necropsia tiveram o sexo
identificado, e foram classificadas de acordo com estado de maturação sexual, em juvenil e adulto. A
espécie Microsomacanthus hopkinsi (Schiller, 1951) Spasskaia, 1966 foi encontrada na porção anterior
dos cecos. Prevalência de 60.9% e infecção média de 42.9, enquanto a intensidade de infecção foi de 1
to 418 helmintos/ hospedeiro. A alta prevalência e intensidade de infecção estão relacionadas com a
estratégia reprodutiva da espécie que libera vários ovos na forma de uma corrente única.
MICROSOMACANTHUS HOPKINSI (EUCESTODA, HYMENOLEPIDIDAE)
IN NETTA PEPOSACA (AVES, ANATIDAE) IN SOUTH AMERICA
MICROSOMACANTHUS HOPKINSI (EUCESTODA, HYMENOLEPIDIDAE) DE
NETTA PEPOSACA (AVES, ANATIDAE) DE SUDAMERICA
1 2
Eliane F. Silveira & Suzana B. Amato
Abstract
The rosy-billed pochard, Netta peposaca (Vieillot, 1816), is a migratory bird that inhabits wetlands
which have the surface covered by abundant vegetation, but also being found in lagoons or rice
plantations. One hundred sixty-nine rosy-billed pochards, N. peposaca, were examined for helminths in
the Municipalities of Santa Vitória do Palmar and Jaguarão, State of Rio Grande do Sul, Brazil
(wintering site) and Alvear, Corrientes Province, northern Argentina (nesting site). Samples were
obtained in 2002 and 2004. Birds were frozen in dry ice after collection. During necropsy they were
categorized according to sex and maturity, either adult or juvenile. The cestode Microsomacanthus
hopkinsi (Schiller, 1951) Spasskaia, 1966 was found in the anterior portion of caeca. Prevalence was
60.9% and mean infection 42.9, while the intensity of infection was 1 to 418 helminths/ host. The high
prevalence and intensity of infection may be related to the reproductive strategy of the species that
releases the eggs in the form of a single chain.
Key words: Argentina - Brazil - migratory-flyway - nesting site - rosy billed pochard - wintering site.
ORIGINAL ARTICLES / ARTÍCULOS ORIGINALES
Neotrop. Helminthol., 4(2), 2010
2010 Asociación Peruana de Helmintología e Invertebrados Afines (APHIA)
ISSN: 2218-6425 impreso / ISSN: 1995-1043 on line
E-mail: elianefraga3@hotmail.com
2 Departamento de Zoologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970 Porto Alegre, Rio Grande do Sul,
Brasil. E-mail: sbmato@ufrgs.br
1 Departamento de Biologia, Museu de Ciências Naturais, Universidade Luterana do Brasil - ULBRA, 92425-900 Canoas, Rio Grande do Sul, Brasil.
105
INTRODUCTION
The genus Microsomacanthus (Eucestoda,
Hymenolepididae) was proposed by López-Neyra
(1942a) to accommodate species with distinct
characters when compared to Hymenolepis
Weiland, 1858. Microsomacanthus includes
species with a long, thin rostellum armed with 10
hooks, and Hymenolepis microsoma Creplin, 1829
was designated as the type species. In this work,
López-Neyra (1942a) also included a key for the
genera of Hymenolepidae, in which the presence or
absence of a rostellum separated the species of
Microsomacanthus from Hymenolepis. The
presence of a rostellum with hooks characterizes
Microsomacanthus, while Hymenolepis lack or
have only a rudimentary rostellum. Reviewing
Hymenolepis, López-Neyra (1942b), considered
the following species as new combinations:
Microsomacanthus abortiva (Linstow, 1904),
Microsomacanthus collaris (Batsh, 1786),
Microsomacanthus compressa (Linton, 1892)
Microsomacanthus diorchis (Fuhrmann, 1913),
Microsomacanthus fausti (Tseng-Shen, 1932),
Microsomacanthus floreata (Meggitt, 1930),
Microsomacanthus jaegerskioldi (Fuhrmann,
1913), Microsomacanthus microsoma (Creplin,
1829), Microsomacanthus pachycephala (Linstow,
1872), Microsomacanthus pauciannulata
(Meggitt, 1927), Microsomacanthus pigmentata
(Linstow, 1872), Microsomacanthus filirostris
(Wedl, 1855), Microsomacanthus innominata
(Meggitt, 1927), Microsomacanthus longirostris
(Rudolphi, 1819), Microsomacanthus clerci
(Fuhrmann, 1923) and Microsomacanthus falcata
(Meggitt, 1927).
Hymenolepis hopkinsi was described in 1951 by
Schiller as a small, fragile cestode with a long and
thin rostellum, labile rostellar hooks with distinct
size and shape; with a 'U' shaped uterus and eggs
released in a single chain like those found in the
caeca of birds (Schiller, 1951). The shape of the
uterus of H. hopkinsi was mentioned by Schiller
(1951) as a rare characteristic among species of
Hymenolepis.
Spassky & Spasskaia (1954) revised the species of
Microsomacanthus and accepted the new
combinations proposed by López-Neyra (1942b).
These authors described four new species
(M i c r o s o m a c a n t h u s f o r m o s o i d e s ,
Microsomacanthus hystrix, Microsomacanthus
recurvata, and Microsomacanthus tuvensis), and
one unidentified species (Microsomacanthus sp.),
but did not mention the species H. hopkinsi.
Yamaguti (1959) made new combinations and
transferred M. clerci and H. hopkinsi to the genus
Mayhewia Yamaguti, 1956.
The species H. hopkinsi was transferred to
Microsomacanthus only in 1966 by Spasskaia in a
work about hymenolepidideans carried out in
Russia (McDonald, 1969).
McDonald (1969) cited 27 species for
Microsomacanthus in their catalogue on helminth
species parasitizing anatideans. According to these
authors, M. hopkinsi is a common species in North
America and is found as a parasite of wild ducks
such as Anas platyrhynchus Linnaeus, 1758; Anas
acuta Linnaeus, 1758; Anas penelope Linnaeus,
1758; Anas rubripes Brewster, 1902; Anas strepera
Linnaeus, 1758 and Aythya marila (Linnaeus,
1758).
McLaughlin & Burt (1979) studied cestodes
collected from the caeca of Canadian anatideans: A.
rubripes, A. platyrhynchos, and Aix sponsa
(Linnaeus, 1758). After comparing morphometric
and morphological data, the cestodes found were
identified as H. hopkinsi. According to the authors
the specimens found were morphologically
identical to the species H. hopkinsi described by
Schiller in 1951 and, similar to the specimens found
by Maksimova in 1967 which included the species
of Microsomacanthus. However, McLaughlin &
Burt (1979) did not discuss the synonymy of the
species.
Czaplinski (1994) proposed a key for
hymenolepididean cestodes found in birds. In
relation to the genus diagnosis, the author
considered only the presence or absence of a
rostellum as had been proposed by López-Neyra
(1942a).
New species were described for the genus
M i c ro s o m a c a n t h u s : M i c ro s om a c a n t h u s
polystictae was found parasitizing the species
Polysticta stelleri (Pallas, 1769) collected in
C h u k o t k a , R u s s i a ( R e g e l , 1 9 8 8 ) .
Microsomacanthus macrotesticulata in three
anatidean species: Netta erythrophthalma (Wied-
Neuwied, 1833), Anas undulata Dubois, 1839, and
Silveira & AmatoMicrosomacanthus in South America
106
Anas erythrorhyncha Gmelin, 1789 collected in
South Africa (Alexander & Mclaughlin, 1993).
Microsomacanthus paraparvula was reported as a
parasite of surface ducks in lakes of Chukotka,
Russia (Regel, 1994). Microsomacanthus
parasobolevi was recorded parasitizing several
anatidean species in Chukotka, Russia (Regel,
2005). For South America, Microsomacanthus
kaulobatroni was described by Deblock & Vaucher
(1997) parasitizing birds of the species
Himantopus melanurus Vieillot, 1811, collected in
Paraguay.
In the present paper, we review the taxonomy and
also analyze the biology and anatomy of the M.
hopkinsi occurring in wild ducks.
A total of 169 rosy-billed pochards [Netta peposaca
(Vieillot, 1816)] were captured by shot gun, with
permission from the “Instituto Brasileiro do Meio
Ambiente e Recursos Naturais Renováveis”
(IBAMA n° 042/ 2004/RS) in: the municipality of
Santa Vitória do Palmar (33°16'13”S,
53°26'28”W); in the locality of Fazenda Sossego
(33°04'03”S, 53°19'20”W); in the municipality of
Jaguarão (32°37'53”S, 53°09'3,6”W), all in the
state of Rio Grande do Sul, southern Brazil; and in
Alvear, province of Corrientes, northern Argentina
(29°09'13”S, 56°54'34”W). The birds were
collected between 2002 and 2004. After being
killed, they were frozen in dry ice, taken to the
laboratory, and separated by sex and maturation
stage (juveniles or adults) based on presence/
absence of the cloacal pouch. Adult cestodes and
hooks from the rostellum were fixed, stained and
mounted according to Silveira & Amato (2008). All
measurements are given in micrometers (ìm), or
otherwise indicated. Mean, standard deviation, and
number of specimens measured for a determined
character appear in parentheses when different
from the established number. Ecological terms
were used according to Bush et al. (1997).
Drawings were made with a drawing tube using a
Nikon E-200 microscope. The photographic
images and scanned line drawings were prepared
®
using Adobe's Photoshop CS2 . Representative
specimens of the cestode were deposited in the
“Coleção Helmintológica do Instituto Oswaldo
Cruz” (CHIOC), Rio de Janeiro, RJ, Brazil. The
remaining specimens are in the “Coleção
Helmintológica do Laboratório de Helmintologia”,
Porto Alegre, RS, Brazil. Bird carcasses were
deposited in the “Coleção Ornitológica do Museu
de Ciências Naturais” (MCN), Fundação
Zoobotânica do Rio Grande do Sul, Porto Alegre,
RS, Brazil.
Microsomacanthus hopkinsi (Schiller, 1951)
Spasskaia, 1966 (Figs 1-8)
Description. Based on 40 specimens mounted 'in
toto', 13 measured and 5 scolex mounted in Faure.
Hymenolepididae, Hymenolepidinae. Scolex
triangular, 140-198 (167, 50, n=12) in length, 128-
160 wide at base (Fig. 1). Four unarmed suckers,
52-106 long, and 52-90 wide (Figs 1, 6, and 7).
Rostellum long, thin (Figs 1, 6, and 7), 280-360
long (300, 68, n=12), 10 diorchoid hooks in one
line, 24-32 long (Figs 2, 5, and 5a). Strobilum 12
mm long, 0.4 mm wide. Proglottids craspedot,
rectangular when immature, square when mature,
slightly longer than wide when gravid.
Male reproductive system with three testicles,
circular to oval, forming an interverted triangle in
anterior half portion of proglottid (Fig. 3). Cirrus
pouch rounded 105-162 (160, 68, n = 10) long, 14-
38 (28, 17, n = 10) in diameter, extending beyond
excretory vessels to middle of proglottid or slightly,
not reaching aporal excretory vessels (Fig. 3).
Internal and external seminal vesicle present;
external to antiporal middle of proglottid, slightly
anterior to posterior end of cirrus pouch, 45-61 (52,
12, n = 10) long and 41-48 wide. Unilateral, non-
alternating genital pores (Fig. 3). Cirrus spineless,
12-20 (18, 7, n = 10) long. Genital atrium at anterior
end (Fig. 3). Ovary median, lobed, ventral to
testicles; 60-81 (76, 20, n = 10) wide (Fig. 3).
Vitelarium 15-28 long, and 10-22 wide. Vagina
inconspicuous, uterus 'U' shaped with few eggs, 25-
29 (27, 8, n = 10) in diameter (Fig. 4); eggs in packs
forming single delicate chains (Figs 8, and 8a).
Synonyms: Hymenolepis hopkinsi Schiller,
1951; Mayhewia hopkinsi (Schiller, 1951)
Yamaguti, 1959
MATERIAL AND METHODS
RESULTS
Taxonomic summary
Neotrop. Helminthol., 4(2), 2010
107
Figures 1-4. Incomplete diagrams of Microsomacanthus hopkinsi (Schiller, 1951). (1) Scolex showing the suckers
(asterisk), rostellum (r), and rostellar diorchoid hooks (h). Bar = 50 µm. (2) Diarcuatoid rostellar hooks. Bar = 25
µm. (3) Mature proglottid. Ventral excretory vessels (vev), dorsal excretory vessels (dev), atrium (a), cirrus pouch
(cp), internal seminal vesicle (isv), external seminal vesicle (esv), testicles (t), ovary (ov), and vitellarium (v). Bar =
50 µm. (4) Gravid proglottids showing the uterus (u) filled with eggs. Bar = 100 µm.
Silveira & AmatoMicrosomacanthus in South America
108
Host: Netta peposaca (Vieillot, 1816) – new
host.
Host specimens deposited: N. peposaca – new
host record (NHR). MCN Nºs 2775 (male);
2776 (female).
Locality: Fazenda Sossego and Ponta da
Antena, Municipality of Santa Vitória do
Palmar, RS, southern Brazil; Alvear, Province
of Corrientes, northern Argentina.
Site of infection: anterior portion of caeca.
Prevalence: 60.9%.
Mean intensity of infection: 42.9 helminths/
host.
Mean abundance of infection: 26.1 helminths/
host.
Intensity of infection: 1 to 418 helminths/ host.
Deposited specimen: CHIOC 3745a-b –
voucher specimens fixed in AFA and stained in
Delafield's hematoxylin.
In the present study we followed a proposal made
by Czaplinski (1994), who validated the genus
Microsomacanthus, proposed by López-Neyra
DISCUSSION
Neotrop. Helminthol., 4(2), 2010
109
Figures 5-8. Photomicrographs of the Microsomacanthus hopkinsi (Schiller, 1951). (5) Scolex with rostellum (r) and introverted
hooks (h). Bar = 25 µm. (5a) Diorchoid rostellar hooks. Bar = 10 µm. (6) Scolex showing one of the four suckers (asterisk),
rostellum (r), and hooks (h) partially everted. Bar = 50 µm. (7) Scolex showing one of the four suckers (asterisk) and rostellum (r)
completely everted. Bar = 50 µm. (8) Egg chain showing one of the eggs (e). Bar = 100 µm. (8a) Oncosphere (on) and embryonic
hooks (eh). Bar = 25 µm.
Silveira & AmatoMicrosomacanthus in South America
(1942a). Cestodes found in the caeca of rose-billed
pochards were identified as M. hopkinsi, due to the
presence of a thin, long rostellum armed with 10
diorchoid hooks (Figs 1, 6, and 7); three testicles
forming an inverted triangle, bilobed ovary, and a
'U' shaped uterus. The eggs formed a single chain
when released from the proglottid (Figs 8, and 8a).
Measurements in the present study are similar to
those given by Schiller (1951) in the species
description, and those given by McLaughlin & Burt
(1979) in their study on the hymenolepididean
cestodes from anatideans in Canada.
According to Jarecka (1961) the eggs in M.
hopkinsi differ in shape from those of H. abortiva
and H. microsoma, which also infect anseriform
birds. Eggs of M. hopkinsi are characterized by
forming a single chain (Figs 8, and 8a) while in
other related species they could form two or three
lines. M. hopkinsi infected 60.9% out of 169 rose-
billed pochards studied in the present study with a
mean intensity of 42.9 specimens/ bird. The high
prevalence and intensity of infection may be related
to the reproductive strategy of the species that
releases the eggs forming a single chain. The
intermediate host will ingest several cysticercoids
by consuming eggs released in a chain, and,
consequently, the definitive host will receive a
large number of larvae from a single amphipod.
Considering that anatideans ingest a high number
of amphipods throughout the day, the mean
intensity of infection of M. hopkinsi will always be
high in any host, as recorded in the present study.
This relationship was also recorded by Jarecka
(1961) and MacLauchlin & Burt (1970).
This is the first study documenting ecological data
of this species, in addition to the discussion on
taxonomy after the species description published
by Schiller in 1951; the first record of
Microsomacanthus hopkinsi to the South American
continent, extending its known geographical
distribution
The authors are grateful to IBAMA (“Instituto
Brasileiro do Meio Ambiente e Recursos Naturais
Renováveis”) for the license to capture the hosts; to
Prof. João O. Meneghetti, for ornithological
information; to Mr Jair Nunes and Mr Sidnei A.
Bavaresco for the capture of the birds, and to Dr
Philip J. Scholl for reviewing the English version of
the manuscript.
ACKNOWLEDGEMENTS
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*Correspondence to author/ Autor para
correspondencia:
Eliane F. Silveira
Departamento de Biologia, Museu de Ciências
Naturais, Universidade Luterana do Brasil.
ULBRA, 92425-900 Canoas, Rio Grande do Sul,
Brasil.
E-mail/correo electrónico:
elianefraga3@hotmail.com
Received July 20, 2010.
Accepted October 27, 2010.
Neotrop. Helminthol., 4(2), 2010
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111
