New species of Cacatuocotyle (Monogenoidea, Dactylogyridae) parasitizing the anus and the gill lamellae of Astyanax aeneus (Pisces, Ostariophysi: Characidae) from the Rio Lacantún basin in the Biosphere Reserve of Montes Azules, Chiapas, Mexico.

As part of a biological inventory of the Rio Lacantún basin in the Biosphere Reserve of Montes Azules from Chiapas State (southeastern, Mexico), the following monogenoid ectoparasites infecting the external surface of the anal opening and the gill lamellae of the freshwater fish Astyanax aeneus (Characidae) in ten streams were found: Cacatuocotyle chajuli sp. nov. (anus), Cacatuocotyle exiguum sp. nov., and Cacatuocotyle sp. (gill lamellae). C. chajuli is differentiated from its single congener, Cacatuocotyle paranaensis (Boeger et al. Syst Parasitol 36:75-78, 1997), from the gills of Characidium lanei (Characidae) from Paraná Brazil, in having a noticeably V-shaped haptoral bar and larger hooks and anchors. C. exiguum differs from these two latter species in the size of its anchors. Illustrations and data on morphological and biometric variability of individual specimens of C. chajuli and C. exiguum from different streams are provided. The present data support the statement about three species of Astyanax, which harbor the richest monogenoidean diversity in the Neotropics with a total of 18 species reported up to now. Occurrences of species of Cacatuocotyle on different sites of infection on three distant host species [including a Neotropical cichlid (Cichlidae) species] suggest that these monogenoideans switching to new hosts can result in the availability of potential hosts within the same habitat instead of showing signs of preferential switching between closely related hosts or on their respective microhabitats.

Lueheia inscripta (Westrumb, 1821) (Acanthocephala: Plagiorhynchidae) in anurans (Leptodactylidae: Bufonidae) from Mexico.

Juveniles of Lueheia inscripta (Westrumb, 1821 Travassos, 1919 (Acanthocephala: Plagiorhynchidae), an acanthocephalan with six lemnisci, are reported and described from mesenteries of frogs Leptodactylus fragilis Brochi, 1877 and a toad Bufo marinus (Linnaeus, 1758) from Morelos state, Mexico. These are new host records extending the known geographical distribution of this species from Brazil and Puerto Rico to Mexico.

Metacestodes of the family Dilepididae (Cestoda: Cyclophyllidea) parasitising fishes in Mexico.

A survey of metacestodes of dilepidid tapeworms (Cyclophyllidea) occurring in fish from Mexico is presented. They belong to the following species (those first reported from Mexico marked with an asterisk): Cyclustera capito (Rudolphi, 1819); (*)Cyclustera cf. ralli (Underwood & Dronen, 1986); Dendrouterina pilherodiae Mahon, 1956; (*)Glossocercus auritus (Rudolphi, 1819); (*)G. caribaensis (Rysavy & Macko, 1973); (*)Paradilepis caballeroi Rysavy & Macko, 1973; (*)Paradilepis cf. urceus (Wedl, 1855); (*) Paradilepis sp.; Parvitaenia cochlearii Coil, 1955; (*)Parvitaenia macropeos (Wedl, 1855); (*)Valipora campylancristrota (Wedl, 1855); (*)V. mutabilis Linton, 1927; and (*)V. minuta (Coil, 1950). Metacestodes of Dendrouterina papillifera (Fuhrmann, 1908), previously reported from the gall-bladder of the pimelodid catfish Rhamdia guatemalensis from Mexico by Scholz et al. (1996), belong actually to V. minuta. Data on the morphology of metacestodes, their fish hosts and rate of infection, site and distribution in Mexico are provided.

Two new species of rhabdochonids (Nematoda: Rhabdochonidae) from freshwater fishes in Mexico, with a description of a new genus.

Two new nematode species, Beaninema nayaritense n. gen., n. sp. and Rhabdochona xiphophori n. sp., are described on the basis of the specimens recovered from the gall bladder and intestine of 2 fishes, Cichlasoma beani (Jordan) (Cichlidae, Perciformes) and Xiphophorus sp. (Poeciliidae, Cyprinodontiformes), respectively, from Mexico. The monotypic genus Beaninema differs from other rhabdochonid genera mainly in the presence of large conical teeth in the middle of the prostom. Rhabdochona xiphophori is characterized mainly by a unique structure of the prostom (presence of 6 anterior teeth; dorsal and ventral teeth unusually broad, with 2 lateral horns) and the shape of the deirids (bifurcated, with markedly long base).

Monticellia ophisterni n. sp. (Cestoda: Monticelliidae) from the swamp-eel Ophisternon aenigmaticum (Synbranchiformes) from Mexico.

Monticellia ophisterni n. sp. is described from the swamp-eel Ophisternon aenigmaticum Rosen and Greenwood (Synbranchiformes: Synbranchidae) from Lake Catemaco, Veracruz, Mexico. The new species is placed into Monticellia because of the cortical position of the testes, ovary, and uterus. It differs from other Monticellia species (with the exception of Monticellia magna (Rego, Santos and Silva, 1974)) in the position of longitudinal musculature that crosses the vitelline follicles, making them paramuscular. The new species can be distinguished from M. magna--which possesses a similar number of testes (107-139), paramuscular vitelline follicles, and numerous gland cells distributed between the apex of the scolex and suckers--in the position of the genital pore (8-21% vs. 19-27%), in the presence of a weak internal longitudinal musculature, in the arrangement of the testes in the median field, and in the absence of a vaginal sphincter. This is the first proteocephalidean tapeworm reported from a synbranchid fish and the first species of Monticellia found in North America.

Rhabdochona mexicana sp. n. (Nematoda: Rhabdochonidae) from the intestine of characid fishes in Mexico.

A new nematode, Rhabdochona mexicana sp. n., is described based on specimens recovered from the intestine of two species of fishes, Astyanax mexicanus (De Filippi) (type host) and Astyanax fasciatus (Cuvier) (Characidae: Characiformes) in central Mexico. This species is characterised by the following characters: 10 anteriorly directed teeth in the prostom, a larger (left) spicule which is slender in form with a small bifurcation at its distal tip covered by a cuticular membrane, a smaller (right) spicule without a barb at its distal tip, eggs bearing an irregular flock-like coating, and a conical tail without a cuticular spike (in both sexes).

Amapacanthus amazonicus n. g., n. sp. (Acanthocephala: Diplosentidae: Allorhadinorhynchinae) from Arius passany and Anableps microleps (Pisces) at Maraca Island off northern Brazil.

Amapacanthus amazonicus n. g., n. sp. is described from the intestine of Arius passany (Valenciennes) and Anableps microleps Müller. The most important diagnostic features are: a small globular proboscis armed with 6 diagonal rows of 3 stout hooks; middle hooks conspicuously stouter and larger than anterior ones; terminal hooks as long as middle hooks but straighter and more slender; a double-walled proboscis receptacle; a trunk bearing spines anteriorly; and two tubular cement glands in the males. Amapacanthus n. g. is differentiated from Allorhadinorhynchus, Golvanorhynchus and Slendrorhynchus, the other genera of the Allorhadinorhynchinae, by the presence of a globular proboscis armed with a small number (18) of hooks. A key to the species of the Allorhadinorhynchinae is presented.

Pseudocapillaria (Ichthyocapillaria) ophisterni sp. n. (Nematoda : Capillariidae) from the swamp-eel Ophisternon aenigmaticum (Pisces) in Mexico.

A new nematode species, Pseudocapillaria ophisterni sp. n., is described from the intestine and rarely from the stomach of the swamp-eel, Ophisternon aenigmaticum Rosen et Greenwood, from Catemaco Lake, Veracruz, Mexico. In having both caudal lobes in the male interconnected by a distinct dorsal membrane, it belongs to the subgenus Ichthyocapillaria. It differs from the three species in this subgenus mainly in possessing either a distinctly longer spicule or a smaller length of oesophagus relative to body length. It also differs in host type and geographical distribution. P. ophisterni is the first capillariid species reported from synbranchiform fishes.

Spinitectus mexicanus n. sp. (Nematoda : Cystidicolidae) from the intestine of the freshwater fish Heterandria bimaculata in Mexico.

A new nematode, Spinitectus mexicanus n. sp., is described on the basis of the specimens recovered from the intestine of Heterandria bimaculata (Heckel) (Poeciliidae, Cyprinodontiformes) from 3 rivers of the Papaloapan River basin (type locality La Basura River), Los Tuxtlas, Veracruz State, Mexico. It differs from its congeners mainly in having the spination of the cuticle separated into 4 longitudinal sectors, each with posteriorly diminishing numbers of larger spines at the anterior part of body. It is the first species of Spinitectus described from a poeciliid fish and the second reported from freshwater fishes in Mexico.

Three new Procamallanus (Spirocamallanus) species from freshwater fishes in Mexico.

The following 3 new species of Procamallanus (Spirocamallanus) are described from the intestines of freshwater fishes in Mexico, all belonging to the morphological group characterized by the presence of wide caudal alae, 3 pairs of subventral preanal papillae, and unequal spicules in the male: Procamallanus (Spirocamallanus) jaliscensis n. sp. (type host: Agonostomus monticola) and Procamallanus (Spirocamallanus) gobiomori n. sp. (hosts: Gobiomorus maculatus [type host], Gobiomorus polylepis and Eleotris picta) from 2 rivers in Jalisco State, western Mexico, and Procamallanus (Spirocamallanus) mexicanus n. sp. (type host: Cichlasoma geddesi) from Xalapa District, Veracruz State (Gulf of Mexico region), southeastern Mexico. Procamallanus jaliscensis is characterized by the length of the spicules (606-900 microm and 282-354 microm), number (15-16) of spiral ridges in the buccal capsule, and the digit-like protrusion with 1 terminal cuticular spike on the female tail; P. mexicanus by the length of the spicules (456-480 microm and 231-233 microm), number (10-12) of spiral ridges in the capsule, and the shape of the female tail (conical with a suddenly narrowed distal part, without any terminal spikes); and P. gobiomori by the length of spicules (318-348 microm and 156-192 microm), number (8-10) of spiral ridges and by the digit-like protrusion with 2 terminal cuticular spikes on the female tail.

Records of the bird capillariid nematode Ornithocapillaria appendiculata (Freitas, 1933) n. comb. from freshwater fishes in Mexico, with remarks on Capillaria patzcuarensis Osorio-Sarabia et al., 1986.

Re-examination of capillariid specimens collected from the freshwater fish Chirostoma estor Jordan from Lake Pátzcuaro in 1985-1986 and deposited as paratypes of Capillaria patzcuarensis Osorio-Sarabia, Pérez-Ponce de León & Salgado-Maldonado, 1986 showed that their morphology was in contradiction with the description of this species and, in fact, they could be identified as the species originally described as C. appendiculata Freitas, 1933 from cormorants Phalacrocorax brasilianus (Gm.) in Brazil; conspecific capillariid specimens were later recorded from Chirostoma estor and Cyprinus carpio L. from the same locality. This species and two others are transferred to Ornithocapillaria Barus & Sergeeva, 1990 as O. appendiculata (Freitas, 1933) n. comb., O. carbonis (Dubinin & Dubinina, 1940) n. comb., and O. phalacrocoraxi (Borgarenko, 1975) n. comb. This is the first record of O. appendiculata in Mexico. Its occurrence in fishes suggests that these nematodes may be acquired by their fish hosts accidentally while feeding on cormorant excrement containing mature nematodes. A female capillariid collected from one of 110 Chirostoma estor examined from this locality in April, 1998 was identified as Capillaria patzcuarensis. Both capillariid species are briefly described and illustrated.

Discapseudes holthuisi (Crustacea: Tanaidacea) as an intermediate host of Caballerorhynchus lamothei (Acanthocephala: Cavisomidae).

The intermediate host of the acanthocephalan Caballerorhynchus lamothei Salgado-Maldonado, 1977, is reported for the first time. Cystacanths of C. lamothei were found in the hemocoel of the tanaid shrimp Discapseudes holthuisi Bacescu and Gutu, 1975, in Alvarado and Sontecomapan lagoons, Veracruz, Mexico. This is the first report of a palaeacanthocephalan using a tanaid shrimp as an intermediate host. Prevalence by locality, shrimp length, sex and developmental stage, and an analysis of the distribution of number of cystacanths per host are presented. A higher prevalence, and percentage of multiple infections and larger host size were found in Alvarado Lagoon.

Observations on cucullanid nematodes from freshwater fishes in Mexico, including Dichelyne mexicanus sp. n.

A new cucullanid nematode, Dichelyne mexicanus sp. n., is described from the intestine of three species of fishes, Agonostomus monticola (Bancroft) (Mugilidae, Perciformes) (type host), Ictalurus balsanus (Jordan et Snyder) (Ictaluridae, Siluriformes) and Cichlasoma beani (Jordan) (Cichlidae, Perciformes), from three rivers (La Maquina River, Veracruz; Chontalcoatlán River, Guerrero and Santiago River, Nayarit) in central Mexico. This species is characterised by the absence of a ventral sucker in the male (subgenus Dichelyne) and it differs from its congeners mainly in possessing very unequal and dissimilar spicules (left 0.465-0.768 mm and right 293-548 mm long), an asymmetrical gubernaculum, and two intestinal caeca. Another cucullanid nematode, Cucullanus caballeroi Petter, 1977, is reported from Dormitator maculatus (Bloch) (Eleotridae, Perciformes) from the La Palma and La Maquina Rivers and Balzapote stream, Veracruz, being briefly described and illustrated; this represents a new host record. Findings of D. mexicanus and C. caballeroi represent a new record of cucullanid nematodes from fishes in Mexican fresh waters.

New observations on Mexiconema cichlasomae (Nematoda: Dracunculoidea) from fishes in Mexico.

The dracunculoid nematode Mexiconema cichlasomae Moravec, Vidal et Salgado Maldonado, 1992, originally described from the abdominal cavity and viscera of Cichlasoma spp. from Mexico, was recorded from the abdominal cavity of the poeciliid Xiphophorus helleri Heckel in Lake Catemaco and its small tributary Arroyo Agrio, Veracruz and from the intestine of the nurse shark Ginglystoma cirratum (Bonnaterre) off the southern coast of the Gulf of Mexico in Campeche; both these findings represent new host records. The nematode specimens from these hosts are briefly described and illustrated. Whereas X. helleri evidently served as the true definitive host of this parasite, G. cirratum probably acquired Mexiconema infection accidentally while feeding on fish definitive hosts in the brackish or salt-water environment. The ability of M. cichlasomae to utilize fishes of different orders (Perciformes and Cyprinodontiformes) as definitive hosts is rather exceptional among dracunculoid nematodes.

Creptotrema agonostomi n. sp. (Trematoda: Allocreadiidae) from the intestine of freshwater fish of México.

Creptotrema agonostomi n. sp. is described from the mugilid fish Agonostomus monticola from Río Cuitzmala, Jalisco, east México, from Río Las Palmas and Río Máquinas, Veracruz, west México, and from the ictalurid, Ictalurus balsanus from Río Chontalcoatlán, Guerrero, east México. It is distinguished from other species of Creptotrema by its small size, large acetabulum with vertical incision, cirrus sac not reaching the posterior border of acetabulum, and very small eggs, measuring 0.041-0.057 x 0.020-0.033 mm.

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.

Two pharyngodonid nematodes, Alaeuris mexicana n. sp. and Ozolaimus ctenosauri, from the iguanid lizard Ctenosaura pectinata from Nayarit, Mexico.

Two species of nematodes, Alaeuris mexicana n. sp. and Ozolaimus ctenosauri Caballero, 1938, were found in the iguanid lizard Ctenosaura pectinata (Wiegmann) from Aguamilpa, Nayarit, central Mexico (Pacific region). The new species, A. mexicana, differs from all congeners mainly in the length of the spicule (0.228-0.233 mm) and in the shape and size of the tail and caudal alae. Ozolaimus ctenosauri (syn. Ozolaimus prolixa Caballero et Cerecero, 1943) is considered a valid species parasitic in Ctenosaura spp. Scanning electron microscopic studies of both species revealed substantial differences in the structure of the mouth, which were used for the separation of the closely related genera Ozolaimus and Alaeuris.

Ascarophis mexicana n. sp. (Nematoda: Cystidicolidae) from two species of Epinephelus (Pisces) from the Gulf of Mexico in southeastern Mexico.

A new cystidicolid nematode, Ascarophis mexicana n. sp., is described from the stomach of 2 species of the genus Epinephelus, E. morio and E. adscensionis (Pisces: Serranidae), from the Gulf of Mexico, southeastern Mexico (states of Yucatan and Veracruz). It is distinguished mainly by small body measurements (body length of male and female 3.39-4.18 mm and 5.94-6.23 mm, respectively), a conspicuously long left spicule (1.58-2.05 mm), length ratio of spicules (1:10-12), and by eggs provided with 2 filaments on 1 pole. Ascarophis mexicana is the second Ascarophis species known to parasitize fishes of the genus Epinephelus (groupers).

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.