Myxobolus spp. (Cnidaria: Myxozoa) in introduced yellow perch Perca flavescens (Mitchill, 1814).

We surveyed introduced yellow perch Perca flavescens (Mitchill, 1814) from the Willamette River, OR, USA, to determine if these fish have co-introduced myxosporean parasites. Mature parasite myxospores were observed in brains of 3/19 fish, and were morphologically and molecularly consistent with Myxobolus neurophilus (Guilford 1963), a parasite known from yellow perch in their native range. We identified another Myxobolus species from the gill filaments of 1/22 fish. The spores from the gill filaments were oval-shaped, 11.7 (10.7-12.3) µm long × 8.6 (7.7-9.0) µm wide × 5.2 (4.6-5.6) µm thick, with two oval-shaped polar capsules 5.7 (5.1-6.5) µm × 2.7 (2.4-3.2) µm, each containing a polar tubule with 8-9 turns. Small-subunit ribosomal DNA sequences from each of four plasmodia were identical, and 4.0% different (over 1800 nucleotides) from the closest known myxosporeans. Interestingly, these sequences had overlapping peaks in their chromatograms, which suggested that DNA from multiple species was present. Hence, we isolated and sequenced three individual myxospores and found that they too had mixed chromatograms, which indicated presence of at least two sequence types of small-subunit ribosomal DNA in each spore (GenBank accession MK592012, MK592013), a rare character among described myxosporeans. The spore morphology, morphometry, tissue tropism, and DNA sequence supported a diagnosis of a novel species, Myxobolus doubleae n. sp. This parasite is unknown from yellow perch in its native range, despite extensive historical surveys, which suggests that introduced yellow perch might have acquired an endemic Myxobolus species via spillback from another fish host.

Molecular and Morphological Characterization of Anisakid Nematode Larvae from the Sandperches Pseudopercis numida and Pinguipes brasilianus (Perciformes: Pinguipedidae) off Brazil.

Morphological and genetic data on the larvae of Anisakidae parasitizing the sandperches Pseudopercis numida and Pinguipes brasilianus were recorded from Cabo Frio, State of Rio de Janeiro, Brazil (23°S, 42°W). Twenty-five specimens of P. numida and 25 specimens of P. brasilianus were necropsied. The 352 larvae collected included 1 Anisakis sp., 344 Hysterothylacium sp., and 7 Raphidascaris sp. We present mtDNA sequence data for Anisakis sp. and Hysterothylacium sp., and we sequenced the ITS ribosomal DNA (rDNA) of Hysterothylacium sp. and Raphidascaris sp. The morphological and genetic profiles confirmed the identification of Anisakis typica (Diesing, 1860). Hysterothylacium sp. and Raphidascaris sp. were not identified to the species level due to the absence of similar sequences for adult parasites. The mtDNA sequence of Hysterothylacium sp. from P. numida showed a high similarity to the sequence of Hysterothylacium deardorffoverstreetorum. However, a phylogenetic analysis demonstrated the presence of different clades under the same name as the larval H. deardorffoverstreetorum. Pseudopercis numida is a new host record for A. typica.

Monogeneans in introduced and native cichlids in México: evidence for transfer.

We examined 2 cichlid fish species native to México, Cichlasoma callolepis and C. fenestratum, and 2 introduced African cichlids, Oreochromis aureus and O. niloticus, from 3 localities in southeastern México for monogeneans. Six monogenean species infected the African cichlids: Cichlidogyrus haplochromii, C. dossoui, C. longicornis longicornis, C. sclerosus, C. tilapiae, and Enterogyrus malmbergi. We found all these parasite species, except C. haplochromii and C. dossoui, on the native C. fenestratum and C. callolepis. Prevalences of Cichlidogyrus spp. were 3-10% and abundances ranged from 0.03 +/- 0.2 to 0.1 +/- 0.3 for native cichlids. We only recovered a single E. malmbergi from 1 C. callolepis. We found Sciadicleithrum bravohollisae, a monogenean of native Cichlasoma spp., on the gills of the introduced O. aureus from Lake Catemaco (prevalence 3%, abundance 0.03 +/- 0.2). Although prevalence and abundance in atypical hosts were fairly low, the present findings provide evidence of monogenean transfer from African to American cichlids and vice versa. This is the first record of exotic monogeneans in the genus Cichlidogyrus and Enterogyrus infecting native American cichlid fish. It is also the first record from southeastern México of a native American monogenean infecting introduced African cichlids.

Potential interactions between the intestinal helminths of the cichlid fish Cichlasoma synspilum from southeastern Mexico.

This study presents and analyzes positional data on 18 helminth species forming the intestinal infracommunities of 59 Cichlasoma synspilum from southeastern Mexico. Interspecific interactions were found between 4 pairs of host specialists: Crassicutis cichlasomae (Digenea) with Neoechinorhynchus golvani (Acanthocephala), Spirocamallanus rebecae (Nematoda) with N. golvani, and Raillietnema kritscheri (Nematoda) with N. golvani. The interactions were expressed as negative correlations, positional shifts, and reductions in realized distribution. It is suggested that N. golvani produces unsuitable habitats for C. cichlasomae, S. rebecae, and R. kristscheri. All interactions were found among phylogenetically unrelated helminth specialists of cichlids.

Some aspects of the development of Lobatostoma jungwirth Kritscher, 1974 (Aspidogastrea) in snails and cichlid fishes from Buenos Aires, Argentina

The mollucs Heleobia castellanosae and Ampullaria canaliculata and cichlid fishes were collected from an artificial pond at Tres de Febrero Park (Buenos Aires city), between June 1994 and May 1995. One hundred and eight of 2,467 H. castellanosae examined were infected with pre-adults of Lobatostoma jungwirthi, 112 of them in concurrent infections with digeneans. L. jungwirthi was significantly more prevalent in larger snails, specially those infected with larval digeneans, but the prevalence of infection did not fluctuate significantly throughout the year. A. canaliculata and cichlids smaller than 10 cm were not infected, but larger Cichlasoma facetum harboured adults of L. jungwirthi in their intestines. Experimental infections of C. facetum and Gymnogeophagus meridionalis with pre-adult aspidogastreans obtained from H. castellanosae were successful. The development of L. jungwirthi in the snail host involves five arbitrary growth phases. Its life-cycle is heteroxenous, similar to that described for L. manteri, with H. castellanosae as the intermediate host and cichlid fishes as the definitive host in this pond.

Campechetrema herrerai n. gen., n. sp. (Trematoda: Cryptogonimidae) from the intestine of Petenia splendida (Pisces: Cichlidae) from Campeche, Mexico.

Campechetrema herrerai n. gen, n. sp. is described from the cichlid fish Petenia splendida from EI Vapor lagoon, an oligohaline lagoon, Campeche, México. It is distinguished from other genera of Cryptogoniminae by the presence of a single gonotyl, a preequatorial acetabulum, few vitelline follicles, and lack of pars prostatica and prepharynx.

Ascocotyle (A.) nunezae n. sp. (Digenea: Heterophyidae) from Yucatan, Mexico.

A new heterophyid species, Ascocotyle (Ascocotyle) nunezae n. sp., is described from adults found in the intestine of naturally infected heron, Casmerodius albus (type host), from the coastal lagoon of Celestún. Yucatan, Mexico, and a domestic chick (Gallus gallus), experimentally infected with metacercariae from Cichlasoma octofasciatum. The new species is characterized mainly by the number (32-37) and arrangement of circumoral spines, which form I complete row of 25-27 circumoral spines and 6-10 accessory spines on the dorsal side, and by the morphology of the ventrogenital sac with a large gonotyl, consisting of 2 indistinctly separated lobes of vesicular tissue. Ascocotyle (A.) nunezae is placed into the nominotypical subgenus Ascocotyle because of the presence of uterine loops at the pharyngeal region and position of vitelline follicles. However, it differs distinctly from other members of this subgenus by the presence of long intestinal ceca reaching posterior to the ventral sucker. Cichlids of the genus Cichlasoma from cenotes, lakes, and the river Río Hondo in the Yucatan Peninsula were natural second intermediate hosts of A. (A.) nunezae, with metacercariae encysted on their gills. Cichlasoma meeki (Brind) was the most heavily infected fish host (total prevalence 75%; mean intensity 11 +/- 9).

Bothriocephalus pearsei n. sp. (Cestoda: Pseudophyllidea) from cenote fishes of the Yucatan Peninsula, Mexico.

The cestode Bothriocephalus pearsei n. sp. is described from the intestine of the cichlid Cichlasoma urophthalmus (Günther) from cenote (= sinkhole) Zaci near Valladolid, Yucatan, Mexico. The pimelodid catfish Rhamdia guatemalensis Günther, which also harbored conspecific cestodes, seems to represent accidental or postcyclic host of B. pearsei. The new species differs from congeners mainly by the morphology of the scolex, which is clavate, with the maximum width in its middle part, has a distinct but weakly muscular apical disc; 2 short and wide bothria distinctly demarcated in their anterior part, becoming indistinct posteriorly in the middle part of the scolex, and 2 elongate, lateral grooves. In addition to the scolex morphology, the new species can be differentiated from Bothriocephalus species parasitizing North American freshwater fishes as follows: B. claviceps (Goeze, 1782), a specific parasite of eels in the Holarctic, B. cuspidatus Cooper, 1917, occurring mostly in perciform fishes in North America, B. musculosus Baer, 1937 found in the cichlid Cichlasoma biocellata (Regan) (= C. octofasciatum (Regan)), and B. texomensis Self, 1954, described from Hiodon alosoides (Rafinesque), are much larger, with strobilae consisting of relatively short and very wide proglottids versus small-sized strobila (length 26-32 mm) composed of about 70 proglottids, which are only slightly wider than they are long (ratio 1:1-3), rectangular, or even longer than wide in the last proglottids in B. pearsei. Bothriocephalus formosus Mueller and Van Cleave, 1932, described from Percopsis omiscomaycus (Walbaum) in the USA, can be distinguished from B. pearsei, besides the different shape of the scolex, by the distribution of vitelline follicles, which are not separated into 2 lateral fields and are present along the midline of proglottids in the former species. Bothriocephalus acheilognathi, a widely distributed parasite of fishes of many families, in particular of cyprinids, distinctly differs from B. pearsei by its arrow- or heart-shaped scolex, larger strobila, and vitelline follicles scattered along the midline of proglottids in the former taxon. Bothriocephalus pearsei is also typified by its fish hosts, which are both of Neotropical origin, and by its geographical distribution limited to isolated deep-lying cenotes of inferior Yucatan.

Biology of Crassicutis cichlasomae, a parasite of cichlid fishes in Mexico and Central America.

Field study on the biology of Crassicutis cichlasomae Manter, 1936 (Digenea: Homalometridae) was carried out in a small swamp in a limestone factory near Mérida, Yucatán, Mexico. Aquatic snails, Littorina (Littoridinopis) angulifera, harbouring C. cichlasomae rediae, cercariae and metacercariae, served both as the first and second intermediate hosts. Feeding experiments confirmed the conspecificity of metacercariae from naturally infected snails with adults from naturally infected fish. Gravid C. cichlasomae worms were obtained from experimentally infected fish 19 days post exposure at 22-24 degrees C. Examination of fish from the swamp in Mitza and other localities in the Yucatan Peninsula showed that the cichlids Cichlasoma urophthalmus and C. meeki were definitive hosts of C. cichlasomae. There was no pronounced preference of C. cichlasomae adults for the site of their location in the intestine of the definitive host; a slightly higher proportion (41%) of worms was only found in the anterior third of the gut. The time of miracidium development varied from 18.5 to 27.5 days; different temperature (20.1-35.7 degrees C) or light/darkness regimes influenced only slightly the rate of embryonic development, with shorter development times at higher temperature (34.8-35.7 degrees C) and constant darkness and/or light. With the exception of the sporocyst, all developmental stages are described and figured.

Capillaria (Hepatocapillaria) cichlasomae (Nematoda: Capillariidae) from the liver of the cichlid fish Cichlasoma urophthalmus from Yucatan, Mexico.

Capillaria (Hepatocapillaria) cichlasomae sp. n., parasitic in the liver of the cichlid Cichlasoma urophthalmus (Günther) from a small freshwater lake ("aguada") Xpoc in Yucatan, Mexico, is described. The parasite is characterized mainly by its small body size (male 1.8 mm, female 4.5 mm), the structure of the stichosome (markedly short stichocytes in one row) and the male (the presence of a pair of small subventral postanal papillae) and female (anus distinctly subterminal) caudal ends, and by the size and structure of the spicule (spicule 0.068-0.085 mm long, with marked transverse grooves on surface) and eggs (size 0.053-0.058 x 0.023 mm, with protruding polar plugs). This is the second known Capillaria species from the liver of fish and the first one from the liver of a freshwater fish.

On Genarchella isabellae (Digenea: Derogenidae) from cichlid and pimelodid fishes in Mexico.

Evaluation of comparative material, including type specimens, of 2 derogenid species (Digenea: Derogenidae) in freshwater fishes of the families Cichlidae and Pimelodidae in Mexico revealed the invalidity of Genarchella luistoddi (Jiménez, Guajardo, and Briseño, 1981), a parasite of cichlid fishes in northern Mexico. This taxon is considered to be conspecific with Genarchella isabellae (Lamothe-Argumedo, 1977), originally described from the pimelodid Rhamdia guatemalensis (Günther) and frequently occurring in cichlids of the genus Cichlasoma in southeastern Mexico.

Diphyllobothrium dendriticum and Diphyllobothrium latum in fishes from southern Argentina: association, abundance, distribution, pathological effects, and risk of human infection.

Diphyllobothrium dendriticum and Diphyllobothrium latum are reported for the first time from Argentina. The following species from Lake Moreno (southern Argentina) were studied to determine whether plerocercoids were present: 11 brook trout (Salvelinus fontinalis), 32 perca (Percichthys sp.), 21 pejerrey (Patagonina hatcheri), and 114 rainbow trout (Oncorhynchus mykiss). Brook trout harbored both species (27.3% prevalence of D. dendriticum and 9.0% of D. latum); perca harbored only D. latum (18.7% prevalence); pejerrey were not infected and rainbow trout also harbored both species, with significant association. Diphyllobothrium latum was less abundant (1.4 plerocercoids/fish, 28.0% prevalence) than D. dendriticum (7.2 plerocercoids/fish, 57.8% prevalence) implying a lower health risk for humans. For both parasites, rainbow trout seem to be more important than the other host species studied. There is no evidence that either of the species is more harmful to the host. The lack of significant weight variation of the liver as related to intensity of infection strongly suggests that competition for energy is not an important aspect of the host pathology.