First report of Spirometra (Eucestoda; Diphyllobothriidae) naturally occurring in a fish host.

Spirometra Faust, Campbell et Kellogg, 1929 is a genus of cestodes belonging to the family Diphyllobothriidae. To date, amphibians, reptiles, and mammals are known second intermediate hosts of these parasites; humans can also be infected (the zoonotic disease is known as sparganosis or spirometrosis). Although the number of phylogenetic studies on Spirometra spp. has increased worldwide in recent years, there are few in South America. Specifically in Uruguay, molecular studies have shown that tapeworms of S. decipiens (Diesing, 1850) complexes 1 and 2 are present in this country. In this study, we characterised the larvae of Spirometra present in the annual fish Austrolebias charrua Costa et Cheffe. Phylogenetic analysis of the cytochrome c oxidase subunit I (COI) sequences of these larvae showed that they belong to S. decipiens complex 1. This is the first report of teleost fishes serving as a second intermediate host for tapeworms of the genus Spirometra in nature.

How many species of genus Lernaeopoda Blainville, 1822 (Siphonostomatoida: Lernaeopodidae) are there in the southwestern Atlantic?

The family Lernaeopodidae includes 14 genera parasitizing elasmobranchs. Fourteen species of this family have been cited from Argentina, four of which were found on chondrichthyans. Schroederichthys bivius Mller and Henle and Galeorhinus galeus (Linnaeus) from Argentina harbored parasitic copepods of the genus Lernaeopoda. The objective of this study was to identify the species using an integrative approach. The morphology was examined by Optical Microscopy and Scanning Electron Microscopy and the molecular analysis was based on partial sequences of the COI mtDNA gene. Despite differences in the antenna, antennule, mandible, maxilliped and maxillae among the specimens, the morphological and molecular analyses revealed that they belonged to Lernaeopoda bivia Leigh-Sharpe, 1930. The species so far reported for Argentina are L. bivia and L. galei Kryer, 1837, which are distinguished by the size (less and greater than 7 mm, respectively). Here, we report partial sequences of the COI mtDNA gene of L. bivia for the first time, obtained from eleven specimens attached to the mouth, fins, anal slit and claspers of the two shark hosts. The COI mtDNA gene tree shows that the Lernaeopoda group forms a sister clade with Pseudocharopinus bicaudatus (Kryer, 1837), while the genus Pseudocharopinus does not appear to be a natural group. We propose that the material described from Argentinean waters as L. galei was misidentified and actually belongs to L. bivia. The wide variability within the specimens of L. bivia emphasizes the importance of using an integrative approach to revise the taxonomy of the Lernaeopoda species from all over the world.

OPECHONA CHLOROSCOMBRI AND OPECHONA CORKUMI N. SP. (DIGENEA: LEPOCREADIIDAE) FROM THE NORTHERN GULF OF MEXICO WITH PHYLOGENETIC ANALYSIS BASED ON 28S RDNA.

This study investigated the identity of 2 lepocreadiid digenean species belonging in the genus Opechona Looss, 1907 that infect littoral fishes of the northern Gulf of Mexico. Opechona chloroscombriNahhas and Cable, 1964, a species previously known only from the Caribbean Sea and the Atlantic Ocean off Brazil, is reported herein from the Atlantic bumper, Chloroscombrus chrysurus (L.), in the northern Gulf of Mexico. A second species infects the gulf butterfish, Peprilus burti Fowler, and the American harvestfish, Peprilus paru (L.), and it is described as a new species that occurs in coastal waters of the north-central and northeastern Gulf of Mexico. Metacercariae infecting the mesoglea of pelagic jellyfishes (Bougainvillia carolinensis [McCady], Chrysaora quinquecirrha [Desor], and Stomolophus meleagris Agassiz) and pelagic comb jellies (Mnemiopsis leidyi Agassiz and Beroe ovata Bruguière) were collected that resemble the new species but require further study to identify. Newly generated sequence fragments (28S rDNA) from both species of Opechona plus 2 other lepocreadiids collected during the study were aligned with publicly available sequences from 18 other lepocreadiids, 6 species of Aephnidiogenidae Yamaguti, 1934, and 2 species of Gorgocephalidae Manter, 1966. The alignment was subjected to Bayesian inference analysis rooted using a gorgocephalid. The resulting tree estimated the positions of both Opechona spp. as being unresolved within a group of taxa that included all available species of Opechona plus available species from the morphologically similar genera ProdistomumLinton, 1910, Preptetos Pritchard, 1960, and Clavogalea Bray, 1985. Although relatively similar in morphology, the 2 studied species of Opechona were surprisingly not closely related. Opechona cablei (Stunkard, 1980) Bray and Gibson, 1990 is herein considered to be a junior synonym of Opechona pyriformis (Linton, 1900) Bray and Gibson, 1990.

A strong colonizer rules the trematode guild in an intertidal snail host.

We examined the extent to which supply-side, niche, and competition theories and concepts help explain a trematode community in which one species comprises 87% of the trematode individuals, and the remaining 15 species each have <3%. We collected and dissected the common and wide-ranging snail host Heleobia australis over four seasons from three distinct habitats from the intertidal area of the Bahía Blanca estuary, Argentina. Inside a snail, trematodes interact with each other with outcomes that depend on facilitation, competition, and preemption, suggesting that dominant species should be common. The abundant trematode species, Microphallus simillimus, is a weak competitor, but has life-history traits and strategies associated with higher colonization ability that could increase its probability of invading the host first, allowing it to preempt the rare species. Rather than segregate by habitat, trematode species aggregated in pans during the summer where dominant trematode species often excluded subordinate ones. Despite losses to competition, and a lack of niche partitioning, M. simillimus ruled this species-rich trematode guild through strong recruitment and (potentially) preemption. Therefore, extremely skewed species abundance distributions, like this one, can derive from extremely skewed colonization abilities.

Morphological characterization and molecular phylogeny of zoonotic trematodes in the freshwater snail Asolene platae.

In the context of a broader program dealing with the symbiotic associations of apple snails, we sampled three species that coexist in Lake Regatas (Palermo, Buenos Aires, Argentina). The population of Asolene platae, (but not those of Pomacea canaliculata and Pomacea scalaris) showed trematode larvae (echinocercariae and xiphidiocercariae) in haemocoelic spaces and connective tissue of the digestive gland. The echinocercariae resembled those of the genus Echinochasmus, but lacked sensory hairs on their body and tail; whereas xiphidiocercariae were similar to the xiphidiocercariae armatae belonging to the Opisthoglyphe type. The phylogenetical positions of these trematodes were inferred by the 28S rRNA, ITS1 and mtCOXI gene sequences. The 28S rRNA gene linked the echinocercarial sequences with the polyphyletic genus Echinochasmus (Echinochasmidae), while the xiphidiocercarial sequences were linked with the genus Phaneropsolus (Phaneropsolidae). The molecular markers used were able to distinguish two cryptic molecular entities of the single echinocercarial morphotype. Although ITS1 and mtCOXI did not allow resolving phylogeny beyond the family level because of the scarce number of sequences in the molecular databases, both cercariae (echinocercariae and xiphidiocercariae) could be distinguished by the Internal Transcribed Spacer 1 amplicon size. This is the first correlative morphological and molecular study of zoonotic trematodes in Neotropical ampullariids.

Two new species of Syndesmis (Platyhelminthes, Rhabdocoela, Umagillidae) from the sea urchin Pseudechinus magellanicus (Echinodermata, Echinoidea) in the Southwestern Atlantic Ocean.

In this paper, we describe two new species of Syndesmis living in Pseudechinus magellanicus in the Southwest Atlantic Ocean. The new species have a long stylet in the male reproductive system, which is different from that of the known species of the genus. Specimens of Syndesmis selknami n. sp. have a ∼220-µm-long stylet (∼1/3 of the body length, 0.69 mm). This ratio is unique because only four species (Syndesmis echinorum, Syndesmis rubida, Syndesmis inconspicua and Syndesmis echiniacuti) have similar stylet lengths but are larger in body sizes (3-5 mm). Specimens of Syndesmis aonikenki n. sp. have a ∼148-µm-long stylet (∼1/10 of the body length, 1.11 mm). Syndesmis pallida has a similar ratio but the uterus is located posteriorly, and the filament glands are very small and located in the posterior region of the body. These are the first flatworms reported parasitizing Pseudechinus magellanicus.

First molecular identification of Ascocotyle (Phagicola) longa in its first intermediate host the mud snail Heleobia australis.

This is the first study that used species-specific DNA primers to confirm the presence of the heterophyid Ascocotyle (Phagicola) longa Ransom, 1920 in its first intermediate host. The larval stages (rediae and cercariae) of this parasite were morphologically and genetically identified in the gonad of the intertidal mud snail Heleobia australis (d'Orbigny, 1835) (Cochliopidae) in the Bahía Blanca estuary, Argentina. In addition, we asked whether the prevalence in H. australis varied between seasons. Mullets - the second intermediate host of this heterophyid - migrate in estuaries during the warmer seasons and it is expected that piscivorous birds and mammals - the definitive hosts - prey more intensively on this species at those times. Thus, the number of parasite eggs released into the tidal flat within their feces should be higher, thereby increasing the ingestion of the parasite by H. australis.We therefore expected a higher prevalence of A. (P.) longa in H. australis in the Bahía Blanca estuary during spring and summer than autumn and winter. We found that 16 out of 2,744 specimens of H. australis had been infected with A. (P.) longa (total prevalence of 0.58%). Nonetheless, the prevalence showed no significant variation between seasons. Hence, we discuss an alternative scenario where the lack of seasonal changes might be mostly related to the permanent residence of definitive hosts in the estuary and not to the seasonal recruitment of mullets. Finally, we highlight the need for more experimental and comparative approaches in order to understand the diagnosis and geographical distribution of this worldwide heterophyid.

Larval trematodes infecting the South-American intertidal mud snail Heleobia australis (Rissooidea: Cochliopidae).

Larval trematodes infecting the snail Heleobia australis (Cochliopidae) from the Bahía Blanca estuary, Argentina were surveyed for two years. A total of 7,504 snail specimens was dissected and the larval stages of 15 different trematodes were recovered and examined morphologically. These larvae included four species that had previously been reported from H. australis in Brazil, Uruguay, and Argentina: the heterophyid Ascocotyle (Phagicola) longa and the microphallids, Maritrema bonaerense, Maritrema orensense, and Microphallus simillimus. Three other species, the echinostomatid Stephanoprora uruguayensis, the microphallid Levinseniella cruzi, and the psilostomid Psilochasmus oxyurus are reported here for the first time as parasites of H. australis. Eight other trematodes found in H. australis are described and placed in the appropriate superfamilies, families or genera (Cryptogonimidae, Apocreadiidae, Aporocotylidae, Notocotylidae, Haploporidae, Renicolidae, Himasthla, and Renicola). The prevalence of the trematode taxa infecting H. australis in the Bahía Blanca estuary was low (<3%) with a single exception (M. simillimus; >20%). Microphallidae were the richest and the most prevalent family, probably because of the high abundance of crabs - the second-intermediate hosts of certain microphallid species - and the considerable diversity of gulls. Here we compare the parasite assemblage found in the H. australis from Bahía Blanca estuary with other parasite assemblages infecting Heleobia spp. and other rissooids from the rest of the world.

Maritrema orensense and Maritrema bonaerense (Digenea: Microphallidae): descriptions, life cycles, and comparative morphometric analyses.

We elucidate the life cycle of Maritrema orensense for the first time and experimentally confirm that of the sympatric Maritrema bonaerense. In Argentinean estuaries, both species parasitize the cochliopid snail Heleobia australis as first intermediate host, the grapsid crabs Neohelice granulata and Cyrtograpsus angulatus as second intermediate hosts, and gulls as definitive hosts. Here, we describe the daughter sporocysts and cercariae of M. orensense and redescribe these stages for M. bonaerense. Sporocysts of M. orensense are shorter, with fewer developed cercariae than M. bonaerense. The cercariae of M. orensense have longer, larger, and more undulating cephalic glands than M. bonaerense. We redescribe metacercariae and adults of both species and compare them with the previous descriptions. Intestinal ceca length, vitellaria shape and extension, and egg size are the most relevant characteristics in metacercariae and adults for differentiating the species. Hence, the detailed morphological description and comparative analyses of morphometrics obtained from natural and experimental infections permit clear differentiation of M. orensense and M. bonaerense at each life stage.

Enteric infections by trematodes and nematodes in Olrog's gull, Larus atlanticus.

Trematodes and nematodes can be pathogenic helminths of birds. Every year during the breeding season, there is variable mortality among chicks from the largest Olrog's gull (Larus atlanticus) colony in Argentina. During two consecutive breeding seasons of Olrog's gull, we studied epidemiological and pathological aspects of infections by digeneans (Microphallidae) and nematodes (Acuariidae) in Olrog's gull chicks. Prevalence of nematode infection was 80.3% in 2005 and 89.2% in 2006, and mean intensity was 23.7 in 2005 and 50.8 in 2006. The risk for infection rose 34.3% and the intensity of infection 6.7% for every increase of 1 mm in head-beak length. The nematodes occupied the proventricular glands and caused disruption of their structure and mild inflammatory proventriculitis. Prevalence of digenean infection was 97.0% in 2005 and 97.3% in 2006. In 10-day-old live chicks, prevalence was 98.0% in 2006 and 95.3% in 2007. Infection was associated with severe catarrhal enteritis, lymphocyte/eosinophil-rich inflammatory responses, extensive fibroblast proliferation around the parasites, and disruption of the architecture of the adjacent crypts.

Trichodinids (Ciliophora: Peritrichida) of Mugil platanus (Mugiliformes: Mugilidae) and Micropogonias furnieri (Perciformes: Sciaenidae) from Samborombón Bay, Argentina, with the description of a new species.

During surveys of parasites of the whitemouth croaker Micropogonias furnieri (Desmarest) and the mullet Mugil platanus Günther from Samborombón Bay, Argentina, Trichodina puytoraci, T. lepsii, T. jadranica, T. murmanica, Diparitella simplex and Trichodina scalensis sp. n. were morphologically studied. Taxonomic and morphometric data for these trichodinids based on dry silver nitrate-impregnated specimens are presented. This study is the first formal report of these trichodinids from the southwest Atlantic Ocean, and the description of a new species from M. platanus.

Ligophorus saladensis n. sp. (Monogenea: Ancyrocephalidae) from Mugil platanus Günther in Samborombón Bay, Argentina.

Ligophorus saladensis n. sp. (Monogenea: Dactylogyridae) is described from the gills of the grey mullet Mugil platanus Günther collected in Samborombón Bay, Argentina. The new species differs from L. mugilinus Euzet & Suriano, 1977, L. mediterraneus Sarabeev, Balbuena & Euzet, 2005 and L. huitermpe Fernandez, 1987 by the morphology of the accessory piece of the male copulatory organ and mean values derived from measurements of the sclerotised hard-parts. This is the second report of monogeneans on M. platanus in the Southwestern Atlantic Ocean region and the first description of a species of Ligophorus Euzet & Suriano, 1977 from M. platanus. Some aspects of the speciation and host-specificity of Ligophorus spp. are discussed.

Intestinal Acanthocephaladiosis in Olrog's gulls (Larus atlanticus): Profilicollis chasmagnathi as possible cause of death.

In 2003 and 2005, mortality events were observed among hatch-year Olrog's gulls (Larus atlanticus) in a breeding colony in the Bahía Blanca estuary, Argentina. Freshly dead chicks were collected for parasitologic and parasite-associated pathologic studies. Profilicollis chasmagnathi was found at various intensities in all of the birds examined (n=28). On gross and histopathologic examinations, severe lesions ranging from intestinal obstruction to complete perforation were present in small and large intestines of the birds. Larval forms of P. chasmagnathi were being found in prey items of L. atlanticus in the study area, which suggests that diet may play a central role in the epidemiology of disease and mortality events in this species.

A new cercaria and metacercaria of Acanthoparyphium (Echinostomatidae) found in an intertidal snail Zeacumantus subcarinatus (Batillaridae) from New Zealand.

A new 23-collar-spined cercaria and metacercaria are described from intertidal molluscs of the coast of New Zealand. The new cercaria found emerging from the mud snails Zeacumantus subcarinatus (Sowerby) (Prosobranchia: Batillariidae) is characterized mainly by the number and arrangement of the cephalic glands, the size of the suckers, and the size and number of the collar spines. The cercaria encysts in the cockle Austrovenus stutchburyi (Wood) (Bivalvia: Veneridae) which lives in sympatry with the first intermediate host throughout New Zealand. Laboratory infections of cockles by cercariae from naturally infected snails resulted in metacercariae identical to those found in naturally infected cockles. The main features of the cercaria and metacercaria are the presence of a reniform collar with 23 spines, two pairs of small cephalic glands at the oral sucker level, another two pairs of much longer ones posterior to the pharynx, and the excretory vesicle Y-shaped with the main collecting canals extending to the anterior level of the ventral sucker. Each of the main collecting canals had 10-11 pairs of bilateral diverticula between the anterior edge of the ventral sucker and anterior body end. A brief discussion of its possible life cycle and ecology is also provided.

Description and proposed life cycle of Maritrema novaezealandensis n. sp. (Microphallidae) parasitic in red-billed gulls, Larus novaehollandiae scopulinus, from Otago Harbor, South Island, New Zealand.

Maritrema novaezealandensis n. sp. is described from Otago Harbor, South Island, New Zealand, on the basis of adult specimens collected from the Red-billed gull, Larus novaehollandiae scopulinus, and excysted metacercariae obtained from crabs. It belongs to the "eroliae group" and differs from other related species mainly in the shape, size, and patterns of distributions of the spines on the cirrus, the shape of the metraterm, the presence of an unlobed ovary, and the complete ring of the vitelline follicles. Based on morphometric features of metacercariae and adult specimens, the trophic relationships among invertebrate and vertebrate hosts, experimental infections, and previous reports of species of Maritrema with similar transmission patterns, the life cycle of M. novaezealandensis n. sp. is described. A 3-host life cycle is proposed for this parasite. The first intermediate host is the mud snail, Zeacumantus subcarinatus, in which the cercarial stage is produced in sporocysts located within the gonad of the snail. At least 3 crab species (Hemigrapsus crenulatus, Macrophtalmus hirtipes, and Halicarcinus whitei) and several species of amphipods act as second intermediate hosts, with metacercariae encysted in the body cavity of the crustacean host. Finally, the definitive host, the gull, L. n. scopulinus, harbors the adult worms in its intestine.

El rol de Cyrtograpsus angulatus (Crustacea; Brachyura) en los ciclos de vida de Microphallus szidati (Digenea; Microphallidae) y Falsifilicollis chasmagnathi (Acanthocephala; Filicollidae): algunos aspectos de su ecologia parasitaria / The role of Cytograpsus angulatus (Crustacea; Brachyura) in the life cycles of Microphallus szidati (Digenea; Microphallidae) and Falsifilicollis chasmagnathi (Acanthocephala; Filicollidae): some aspects of their ecological parasitology

El rol de Cyrtograpsus angulatus (Crustacea; Brachyura) en los ciclos de vida de Microphallus szidati (digenea; Microphallidae) y Falsifilicollis chasmagnathi (Acanthocephala; Fillicollidae). Algunos aspectos de su ecologia parasitaria - Basándose en el estudio de los helmintos larvales parásitos del cangrejo Cyrtograpsus angulatus Dana, 1851 (Microphallus szidati Martorelli, 1986 (Digenea; Microphallidae) y Falsifilicollis chasmagnathi Holcman-Spector et al., 1977 (Acathocephala; Fillicollidae) conjuntamente con el análisis de sus ciclos biológicos y el estudio de la prevalencia, intensidad y de los índices de asociación (comparados entre los hospedadores intermediarios y definitivos) se pudo concluir que: a) C. angulatus parece ser un excelente hospedador intermediario en los ciclos de vida de los helmintos estudiados; b) el tamaño de los cangrejos y la ocurrencia de amputaciones naturales en las hembras de mayor tamaño Spivak & Politis (en prensa) aparecen correlacionadas con la prevalencia; c) en los cangrejos estudiados la prevalencia para F. chasmagnathi fue mayor en los machos que en las hembras; d) la intensidad no apareció correlacionada con el tamño y el sexo de los hospedadores intermediarios; e) M. szidati y F. chasmagnathi estan fuertemente asociados en el hospedador intermediario; f) C. angulatus e Himantopus melanurus Vieilot, 1817 (Aves; Recurvirostridae) son citados como nuevos hospedadores, intermediario y denitivo respectivamente, para F. chasmagnathi;...