Taxonomy and ecology of metazoan parasites of otariids from Patagonia, Argentina : adult and infective stages

At present, the metazoan parasite fauna of most species of otariids is generally poorly known, in part because these marine mammals are mostly protected and, therefore, sampling is limited to specimens stranded on the coast or captured as by-catch in fisheries. Similar problems also occur for the larval stages of gastrointestinal helminths of otariids. For most of these parasite species, the specific identity of the intermediate/paratenic of hosts is unknown and, therefore, many stages of their life cycles remain to be described. Similarly, little is known about the routes of transmission of these parasites between intermediate/paratenic hosts to their otariids definitive hosts. The present thesis is committed to improving the knowledge on these aspects, characterizing for the first time, the intestinal helminth fauna of 56 South American sea lions Otaria flavescens (Shaw, 1800), and 5 South American fur seals Arctocephalus australis (Zimmerman, 1783), from the Patagonian coast of Argentina. Additionally, a total of 542 specimens of 20 marine fish species collected in the same locality, were analysed for helminths, identifying and quantifying the larval forms of parasite infecting otariids. The large dataset obtained provided the opportunity to describe the larval forms and to assess pathways of transmission of these parasites between intermediate/paratenic fish hosts and their definitive otariid hosts. Finally, the large number of larval specimens from several fish species collected in the course of this study allowed us to know essential aspects to understand the population dynamics of these parasites, as the effects of the different host species on some life history traits of the larvae, such as growth patterns or sex ratio, or the potential role of the host in the transmission of the parasite. This study targeted the following objectives: 1) To quantify and describe the intestinal metazoan parasite communities of O. flavescens and A. australis off northern Patagonia, Argentina, based on a detailed morphological and taxonomical study. This information is used to ascertain the role of parasite host specificity in shaping helminth community diversity in otariids. 2) To characterize the component populations of cystacanths of Corynosoma australe (Acanthocephala: Polymorphidae) in paratenic fish hosts off the Patagonian coast of Argentina. The main goal is to elucidate the pathways of transmission of this species between paratenic hosts and definitive otariid hosts, and to assess the effect of different fish hosts on growth, body size, fitness and sex ratio of the cystacanths of C. australe. 3) To describe, for the first time, the temporal allocation of investment on holdfast structures (trunk spines) between cystacanths and adults of two congeneric species of acanthocephalans (Corynosoma cetaceum and C. australe), and investigating the factors that may account for the patterns of trunk spine growth. 4) To carry out a taxonomic identification and description of third-stage larvae of species of Pseudoterranova (Nematoda: Ascaridoidea) from various fish species of Patagonia using sequence data for the mitochondrial cytochrome c oxidase subunit 1 (cox 1) gene and a detailed morphological study. This evidence is then used to describe the component populations of third-stage larvae of species of Pseudoterranova in fishes, assessing the role of different fish hosts on the microhabitat selection, transmission strategies and infection parameters of the third-stage larvae. A total of 97,325 helminth specimens were collected from O. flavescens from the Patagonian coast in Argentina. The intestinal helminth fauna of sea lions in this locality comprised 11 taxa (1 trematode, 1 cestode, 5 nematodes and 4 acanthocephalans). Gravid individuals were represented by 6 species: Ascocotyle (Ascocotyle) patagoniensis, Contracaecum ogmorhini (s.s.), Corynosoma australe, Diphyllobothrium spp., Pseudoterranova cattani and Uncinaria hamiltoni. Third-stage larvae of Anisakis sp. type I and Contracaecum sp., and juvenile specimens of Andracantha sp., Corynosoma cetaceum and Profilicollis chasmagnathi were also collected. Four of these parasites species, Andracantha sp., A. (A.) patagoniensis, C. ogmorhini (s.s.) and P. chasmagnathi represent new host records. A total of 1,516 helminth specimens were collected from the intestine of A. australis. The intestinal helminth fauna of fur seals comprises 7 parasite taxa (2 cestodes, 3 nematodes and 2 acanthocephalans). Gravid individuals were represented by 4 species of parasites: C. ogmorhini (s.s.), C. australe, Diphyllobothrium spp., and P. cattani. Third-stage larvae of Contracaecum sp. and juvenile specimens of C. cetaceum were also collected. Corynosoma australe was the most prevalent and abundant parasite in both hosts, accounting for > 90% of all specimens. In northern Patagonia, sea lions and fur seals harbour the intestinal helminth communities that could be predicted for otariids worldwide, i.e. the combination of species of the genera Corynosoma, Diphyllobothrium, Pseudoterranova, Contracaecum and, in pups, Uncinaria. The estimation of helminth community parameters in sea lions and fur seals, especially species richness at component community level, was affected by the inclusion or exclusion of parasites for which both species of otariids are putative non-hosts (i.e. hosts in which the parasite is unable to reproduce). This study demonstrates that the inclusion of these taxa can exert a significant influence on some community parameters. Information about the reproductive status of helminth species is often lacking in parasitological surveys on otariids and other marine vertebrates, but it is of significance to improve precision in parascript studies or ecological meta-analyses. A new species of a heterophyid trematode was described from the intestine of South American sea lions. A detailed morphological and morphometrical analysis of specimens of Ascocotyle (Ascocotyle) patagoniensis Hernández-Orts, Montero, Crespo, García, Raga and Aznar, 2012 suggests that this trematode can be distinguished from the other species of the subgenus by the number of circumoral spines, which are arranged in 2 rows of 18 to 23, by having a gonotyl without papillae, and by their widest seminal receptacle. Species of the subgenus Ascocotyle usually infect fish-eating birds or mammals in freshwater or brackish habitats. Ascocotyle (A.) patagoniensis is the first species of the subgenus described from a marine mammal. However, no metacercariae of Ascocotyle spp. were found in 542 marine teleosts from 20 species collected along the Patagonian Shelf. The absence of metacercariae in marine fish inhabiting this area could be related to the fact that the life cycle of this trematode is restricted to littoral waters. Nevertheless, more fishes should be analysed to confirm this hypothesis as the small metacercariae could have been overlooked, mainly in host species with small sample sizes. A total of 1,367 cystacanths of C. australe was collected in 18 species of marine fish from the Patagonian coast. The most infected fish species with n ≥ 15 were as follows: Acanthistius patachonicus, Paralichthys isosceles, Prionotus nudigula, Raneya brasiliensis and Xystreurys rasile. Eight fish species, i.e. A. patachonicus, Brama brama, Congiopodus peruvianus, Cottoperca gobio, Genypterus blacodes, Patagonotothen ramsayi, Seriolella porosa and Stromateus brasiliensis represent new host records for C. australe. Results of this study demonstrate that cystacanths of C. australe are able to infect and colonize a wide array of fish species, which would act as paratenic hosts. The ubiquity of this acanthocephalan through the trophic web would guarantee infections to their definitive hosts through alternative pathways. Nevertheless, this study suggest that R. brasiliensis, is one of the prey that most likely contributes to the transmission of cystacanths of C. australe in this area, due to both the high prevalence in this fish species, and its high relative importance in the diet of sea lions and fur seals. There were significant differences in the levels of infection of cystacanths of C. australe between fish inhabiting different zones of the water column, being the ones associated with benthic zone those with highest cystacanth infections. This study suggests that at least 2 main factors could be directly promoting differences in the infection levels of C. australe between fish from different zones: 1) distribution of the invertebrate intermediate hosts; and 2) patterns of transmission of cystacanths between paratenic fish hosts through food webs. The overall sex ratio of cystacanths of C. australe infecting fish hosts was slightly, but significantly, female-biased and no significant differences were found among fish species. This suggests that the sex ratio would begin to be biased before individuals of C. australe infect the definitive host, in which the sex ratio is known to become strongly female-biased because females have a longer life span. In other words, part of the biased sex ratio that we observe in the definitive hosts would be already transferred from paratenic hosts. In theory, 3 factors could be involved in generating the sex ratio biases in our sample, namely, sampling error, differential sampling of female and male larvae, and/or differential mortality between the sexes. This study analyses, for the first time, the potential costs that trophically-transmitted helminths may face in paratenic-to-paratenic transmission. The results suggest that some fish species, in particular Acanthistius patachonicus, might actually be unsuitable paratenic hosts for C. australe since most cystacanths found in this species were not viable. Also, a slight, but statistically significant, tendency to decrease body size of cystacanths was observed as the trophic level of fish species increased. This tendency, which was not related to crowding effects, appears to suggest that C. australe may incur in non-negligible energetic costs when experiencing putative paratenic-to-paratenic transmission. The implications of this finding cannot be underestimated, since this negative consequence may have an important role on the population dynamics of trophically-transmitted helminths. Acanthocephalans have evolved a hooked proboscis and some taxa have trunk spines to attach to their definitive hosts. These structures are generated before being used, thus a key question is how investment in attachment could optimally be allocated through the ontogeny. The number and arrangement of hooks and spines are never modified in the definitive host, but it is unclear whether these structures grow during adult development. The present study compared, for the first time using inferential statistics, the size of holdfast structures between cystacanths and adults of acanthocephalans. The results suggest that the size of trunk spines grows between cystacanths and adults of C. australe and an allied species infecting cetaceans, C. cetaceum, but only in females, which also had significantly larger spines than males. However, this sexual dimorphism did not result from pure allometry since the body of females was smaller, and did not grow more than that of males. Nevertheless, females have longer lifespan, and therefore this factor would induce different investment and development schedules for spines, in order to withstand the extreme flow conditions prevailing in marine mammals for longer time. Unexpectedly, the patterns of spine growth appear also to differ between both species of Corynosoma. In C. cetaceum fore-trunk spines and hind-trunk spines grew, whereas in C. australe only fore-trunk spines differed between cystacanths and adults. An explanation of these differences is that females of C. cetaceum fine-tune the size of spines during the development in the definitive hosts because they achieve a larger adult size, a trait that correlates with stronger dislodging forces and, possibly, with a longer lifespan. This study sheds light on the question of whether or not the holdfast of acanthocephalans is fully developed prior to entering the definitive host. It suggests that temporal allocation of investment in attachment structures may differ, not only between congeneric species, but also between sexes of the same species, possibly due to the different selective pressures that each population subset faces. A total of 635 encapsulated third-stage larvae of Pseudoterranova (sealworm larvae) were collected from 12 species of marine fish from the Patagonian coast. The most infected fish species with sealworm larvae was P. nudigula, followed by A. patachonicus, P. isosceles, Percophis brasiliensis and Pseudopercis semifasciata. Five species of fish, i.e. C. gobio, Nemadactylus bergi, M. argentinae, P. brasiliensis and P. nudigula represent new host records for larval sealworms. Sequences obtained for the mitochondrial cytochrome c oxidase subunit 1 gene (cox 1) of sealworms from the red searobin, P. nudigula, formed a reciprocally monophyletic lineage with published sequences of P. cattani from definitive hosts. A detailed morphological and morphometrical description of larvae of P. cattani from the red searobin is provided. On the other hand, sealworm larvae from other fish species did not differ morphologically from L3 of P. cattani from the red searobin. However, the results of the comparative morphometric analyses carried out on larvae from different fish hosts indicated significant differences in some distances. However, we provisionally identified all larvae as P. cf. cattani, awaiting further identification based on molecular genetic markers. The results of this study suggest that the main microhabitat for sealworm larvae infecting fish hosts from Patagonia is the muscle (principally the epaxial musculature, followed by the hypaxial muscles), and to a lesser degree, in the mesenteries and liver. The lines of evidence obtained in this study suggest that most important fish prey of otariids inhabiting the Patagonian coast presented low infection levels of sealworm larvae. Given that P. cattani is specific to otariids, transmission of this nematode appears to rely on the catholic diet of both sea lions and fur seals, which include a number of specimens of many fish species from the benthic realm, where transmission most likely occurs

Reproductive inequalities in the acanthocephalan Corynosoma cetaceum: looking beyond "crowding" effects

Background: At present, much research effort has been devoted to investigate overall (average) responses of parasite populations to specific factors, e.g., density-dependence in fecundity or mortality. However, studies on parasite populations usually pay little attention to individual variation (inequality) in reproductive success. A previous study on the acanthocephalan Corynosoma cetaceum in franciscana dolphins, Pontoporia blainvillei, revealed no overall intensity-dependent, or microhabitat effects, on mass and fecundity of worms. In this study, we investigated whether the same factors could influence mass inequalities for this species of acanthocephalan.Methods: A total of 10,138 specimens of C. cetaceum were collected from 10 franciscana dolphins accidentally caught in Buenos Aires Province between 1988-1990. To investigate mass inequalities, all the specimens were sexed, and females were classified according to their developmental stage and weighted. Additionally, the relationship between biomass and fecundity (estimated as the number of acanthors) was investigated for some females. Inequalities in fecundity and biomass were assessed using standard methods, i.e. the Lorenz curve and the Gini coefficient (G).Results: We found a modest, but highly significant linear relationship between mass and fecundity. The G was very low (0.314) compared with that from other helminth species. G values were significantly lower in gravid females, which presumably exhibit a slow rate of growth. Also, G values significantly increased with total intensity, but only for gravid females, and the effect was more predictable considering only the number of gravid females.Conclusions: Apparently, competition between reproducing females increases inequality without producing crowding effects. Although the mechanism whereby this occurs is unclear, gravid females, at higher intensities, expanded their distribution and occupied gut chambers with contrasting environmental conditions, which might result in greater variability in body size. The observed inequalities are not expected to strongly influence the population genetics of C. cetaceum, but they reveal subtle individual effects beyond an overall population impact.Fil: Aznar Avendaño, Francisco Javier. Universidad de Valencia; EspañaFil: Hernández Orts, Jesús Servando. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; ArgentinaFil: Vélez Rubio, Gabriela Manuela. Universidad de Valencia; España. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de la República; UruguayFil: Fernández, Luis M.. Ceiba Foundation for Tropical Conservation; Estados UnidosFil: Muriel, Nadia T.. No especifíca;Fil: Raga, Juan Antonio. Universidad de Valencia; Españ

From mammals back to birds: host-switch of the acanthocephalan Corynosoma australe from pinnipeds to the Magellanic penguin Spheniscus magellanicus.

Trophically-transmitted parasites are regularly exposed to potential new hosts through food web interactions. Successful colonization, or switching, to novel hosts, occur readily when 'donor' and 'target' hosts are phylogenetically related, whereas switching between distantly related hosts is rare and may result from stochastic factors (i.e. rare favourable mutations). This study investigates a host-switching event between a marine acanthocephalan specific to pinnipeds that is apparently able to reproduce in Magellanic penguins Spheniscus magellanicus from Brazil. Detailed analysis of morphological and morphometrical data from acanthocephalans from penguins indicates that they belong to Corynosoma australe Johnston, 1937. Partial fragments of the 28S rRNA and mitochondrial cox1 genes were amplified from isolates from penguins and two pinniped species (i.e. South American sea lion Otaria flavescens and South American fur seal Arctocephalus australis) to confirm this identification. Infection parameters clearly differ between penguins and the two pinniped species, which were significantly lower in S. magellanicus. The sex ratio of C. australe also differed between penguins and pinnipeds; in S. magellanicus was strongly biased against males, while in pinnipeds it was close to 1:1. Females of C. australe from O. flavescens were smaller than those from S. magellanicus and A. australis. However, fecundity (i.e. the proportion of fully developed eggs) was lower and more variable in females collected from S. magellanicus. At first glance, the occurrence of reproductive individuals of C. australe in Magellanic penguins could be interpreted as an adaptive colonization of a novel avian host through favourable mutations. However, it could also be considered, perhaps more likely, as an example of ecological fitting through the use of a plesimorphic (host) resource, since the ancestors of Corynosoma infected aquatic birds

A checklist of the helminth parasites of marine mammals from Argentina

Based on published records and new data accumulated by the authors, we generated a list of the helminth parasites of marine mammals from off the coast of Argentina. We found 49 reports of helminths parasitizing cetaceans and pinnipeds from Argentina from 1952 to 2015. The list includes 54 taxa of helminths (8 acanthocephalans, 24 nematodes, 11 cestodes and 11 trematodes) associated with 18 species of cetaceans and 5 species of pinnipeds. Most of the records represent adults (5 canthocephalans, 16 nematodes, 6 cestodes and 11 trematodes), followed by larvae (10 nematodes and 3 metacestodes) and juveniles (4 acanthocephalans and 2 cestodes). The checklist contains 24 named species (5 acanthocephalans, 8 nem- atodes, 4 cestodes and 7 trematodes) and 30 undetermined helminth taxa (3 acanthocephalans, 16 nematodes, 7 cestodes and 4 trematodes). The present account contains a parasite/host lists and information on the habitat, developmental stage and distribution of the parasites listed, repositories of their type and voucher specimens and references. A host-parasite list is also presented. The data compiled on the helminth of marine mammals from Argentina in the present study revealed gaps in the knowledge of their taxonomic identification, composition, distribution, host specificity and life cycles. These gaps are also briefly discussed in order to provide an outline for future research.Fil: Hernández Orts, Jesús Servando. Universidad Nacional Autónoma de México; MéxicoFil: Paso Viola, María Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Garcia, Nestor Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: González, Raul Alberto Candido. Universidad Nacional del Comahue. Instituto de Biologia Marina y Pesquera Almirante Storni; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia Varela, Martin. Universidad Nacional Autónoma de México; MéxicoFil: Kuchta, Roman. Biology Centre of the Academy of Sciences of the Czech Republic; República Chec

Hooking the scientific community on thorny-headed worms: interesting and exciting facts, knowledge gaps and perspectives for research directions on Acanthocephala

Although interest in Acanthocephala seems to have reached only a small community of researchers worldwide, we show in this opinion article that this group of parasites is composed of excellent model organisms for studying key questions in parasite molecular biology and cytogenetics, evolutionary ecology, and ecotoxicology. Their shared ancestry with free-living rotifers makes them an ideal group to explore the origins of the parasitic lifestyle and evolutionary drivers of host shifts and environmental transitions. They also provide useful features in the quest to decipher the proximate mechanisms of parasite-induced phenotypic alterations and better understand the evolution of behavioral manipulation. From an applied perspective, acanthocephalans’ ability to accumulate contaminants offers useful opportunities to monitor the impacts – and evaluate the possible mitigation – of anthropogenic pollutants on aquatic fauna and develop the environmental parasitology framework. However, exploring these exciting research avenues will require connecting fragmentary knowledge by enlarging the taxonomic coverage of molecular and phenotypic data. In this opinion paper, we highlight the needs and opportunities of research on Acanthocephala in three main directions: (i) integrative taxonomy (including non-molecular tools) and phylogeny-based comparative analysis; (ii) ecology and evolution of life cycles, transmission strategies and host ranges; and (iii) environmental issues related to global changes, including ecotoxicology. In each section, the most promising ideas and developments are presented based on selected case studies, with the goal that the present and future generations of parasitologists further explore and increase knowledge of Acanthocephala

Ortholinea concentrica n. sp. (Cnidaria: Myxozoa) from the Patagonian seabass Acanthistius patachonicus (Jenyns, 1840) (Perciformes: Serranidae) off Patagonia, Argentina

The Patagonian seabass Acanthistius patachonicus (Jenyns, 1840) (Serranidae) is a marine fish valued for commercial and sport fisheries from Argentina. We report a new myxosporean (Cnidaria: Myxozoa) infecting the urinary system of the Patagonian seabass from San Antonio Bay, San Matías Gulf, on the Atlantic Ocean. The mature myxospores were subspherical, 8.2–11.0 μm × 7.9–11.0 μm and 7.7–9.0 μm in thickness; two subspherical polar capsules, 2.4–3.8 μm × 2.3–3.6 μm, with 3 to 4 turns of the polar tubule; openings on different valves in almost opposite directions. Ornamented shell valves exhibited 17–20 concentrically organized surface ridges. SSU rDNA phylogenetics analyses placed the new species in the freshwater urinary tract clade, clustering in a clade formed by Myxobilatus gasterostei (Parisi, 1912), Acauda hoffmani Whipps, 2011, and other Ortholinea spp. Based on spore morphology, site of infection, and molecular data, we described this myxozoan as Ortholinea concentrica n. sp.Fil: Alama Bermejo, Gema. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentina. Academy of Sciences of the Czech Republic. Biology Centre. Institute of Parasitology; República ChecaFil: Hernández Orts, Jesús Servando. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentin

Review of five species of cyclocoelids (Digenea: Cyclocoelidae) from aquatic birds in Mexico with notes on their interspecific variation

Based on a morphological approach, five species of cyclocoelids (Digenea: Cyclocoelidae) are revised based on material from birds in Mexico. The species studied are: Cyclocoelum cf. leidyi Harrah, 1922 from the black-necked stilt Himantopus mexicanus Müller (Recurvirostridae); Cyclocoelum mutabile (Zeder, 1800) from the northern jacana Jacana spinosa L. (Jacanidae) and the willet Tringa semipalmata Gmelin (Scolopacidae); Cyclocoelum pseudomicrostomum Harrah, 1922 from the American coot Fulica americana Gmelin (Rallidae); Selfcoelum lamothei Blend & Dronen, 2008, from the long-billed curlew Numenius americanus Bechstein (Scolopacidae); and Neohaematotrephus arayae Zamparo, Brooks, Causey & Rodriguez, 2003 from J. spinosa. New morphological data, illustrations and measurements are presented for these trematodes. Three species, insufficiently described, i.e. C. cf. leidyi, C. mutabile and C. pseudomicrostomum, are redescribed in detail. Our results indicate morphological variation in some important features used in the diagnosis of Cyclocoelum Brandes, 1892 (i.e. the presence or absence of oral sucker, the position of the genital pore relative to the pharynx, and the posterior extension of the uterus) and Selfcoelum Dronen, Gardner & Jiménez, 2006 (i.e. anterior extension of vitelline follicles). Finally, this study provides the first molecular data for the large subunit of the ribosomal RNA (28S rRNA) gene for N. arayae.Fil: López Jiménez, Alejandra. Universidad Nacional Autónoma de México; MéxicoFil: García Varela, Martín. Universidad Nacional Autónoma de México; MéxicoFil: Hernández Orts, Jesús Servando. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentin

A new species of Notocotylus (Digenea: Notocotylidae) from the black-necked swan Cygnus melancorhyphus (Molina) of Argentina

Notocotylus cygni n. sp. is described here, taken from the intestine of the black-necked swan Cygnus melancoryphus (Molina) of Patagonia, Argentina. This new species differs from other members of the genus Notocotylus by having the genital pore anterior to the caecal bifurcation (located slightly posterior to oral sucker) and the unequal number and arrangement of ventral papillae (2–3 in the lateral rows and 10–12 in the median row). Phylogenetic analyses of the 28S and ITS1–5.8S ribosomal DNA (rRNA) sequences of the new species and other notocotylid trematodes available in GenBank indicate that N. cygni n. sp. is a sister taxon of Notocotylus fosteri Kinsella et Tkach, 2005, a trematode of the intestine of the rice rat Oryzomys palustris of Florida, United States. The new species differs from N. fosteri in the unequal number and arrangement of ventral papillae, number of uterine loops, size of the egg, definitive hosts (birds vs. mammals), and disparate environment and geographical distribution (freshwater environment in Patagonia vs. salt marsh in North America). This is the eighth species of Notocotylus reported from birds in Argentina, and the ninth species from the family Notocotylidae recorded in black-necked swans in South America.Fil: Flores, Verónica Roxana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Hernández Orts, Jesús Servando. Natural History Museum; Reino Unido. Biology Centre of the Academy of Sciences of the Czech Republic; República ChecaFil: Viozzi, Gustavo Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

Morphology, performance and attachment function in Corynosoma spp. (Acanthocephala)

Abstract Background Functional inference on the attachment of acanthocephalans has generally been drawn directly from morphology. However, performance of structures is often non-intuitive and context-dependent, thus performance analysis should be included whenever possible to improve functional interpretation. In acanthocephalans, performance analysis of attachment is available only for Acanthocephalus ranae, a species that solely relies on the proboscis to attach. Here we compare body morphology and muscle arrangement in 13 species of Corynosoma, which use their spiny body as a fundamental holdfast. A basic performance analysis using live cystacanths of two representative species is also provided. Methods Adults of 13 Corynosoma spp. were obtained from 11 marine mammal species. Specimens were cut and carefully cleaned to examine muscle arrangement through light and scanning electron microscopy. Live cystacanths of C. australe and C. cetaceum were selected for performance analysis. Video records of evagination-invagination cycles of the proboscis were obtained and analysed with a video editor. Results The basic arrangement of proboscis retractors, trunk circular and longitudinal muscles, neck retractors and receptacle retractors, was conserved in all Corynosoma species. Interspecific variability was found in the relative development of disk muscles: minimum in C. enhydri, maximum in C. cetaceum; the distal insertion of the ventral neck retractor: ventro-lateral in C. cetaceum, C. hamannni and C. pseudohamanni and ventral in the other species; and the distal insertion of the receptacle retractors: more proximal in species with a longer hindtrunk. Performance analysis indicated striking similarities to that described for A. ranae except that (i) the foretrunk bends ventrally during the evagination-invagination cycles of the proboscis; (ii) disk muscles can flatten the tip of the foretrunk regardless of these cycles; and (iii) the receptacle bends ventrally and is driven to the hindtrunk by coordinated action of receptacle retractors. Conclusions Species of Corynosoma are able to use up to six holfast mechanisms. Attachment relies on a similar performance to that described for A. ranae. However, structural ventral bending of an inflated, spiny foretrunk, with a parallel re-arrangement of foretrunk muscles, have generated unexpected novel functions that make attachment extremely effective in species of Corynosoma. Interspecific variability in trunk shape and muscle arrangement grossly correlates with the rheological conditions each species experiences in their microhabitats within the gut of marine mammals

A morphological and molecular study of Pseudocorynosoma Aznar, Pérez Ponce de León and Raga 2006 (Acanthocephala: Polymorphidae) from Mexico with the description of a new species and the presence of cox 1 pseudogenes

Pseudocorynosoma tepehuanesi n. sp., is described from the intestine of the ruddy duck Oxyura jamaicensis Gmelin, 1789 from single locality from northern Mexico. The new species is mainly distinguished morphologically from the other five described species of Pseudocorynosoma from the Americas (P. constrictum, type species, P. peposacae, P. anatarium, P. enrietti and P. iheringi) associated with waterfowl species by possessing a proboscis with 15 longitudinal rows with 7–8 hooks each, a trunk expanded anteriorly and by having smaller lemniscus. Partial sequences of the mitochondrial gene cytochrome c oxidase subunit I (cox 1) and the large subunit (LSU) of ribosomal DNA including the domains D2 + D3 were used independently to corroborate the morphological distinction between the new species and other two congeneric species (P. constrictum and P. anatarium) from North America. The genetic divergence estimated among the new species and the other two species ranged from 15 to 18% for cox 1 and from 3.2 to 4% for LSU. The cox 1 alignment shows 24 sequences from P. anatarium with abnormalities, which were defined as pseudogenes due the presence of insertions, deletions and premature stop codons. Maximum likelihood and Bayesian inference analyses with each data set showed that the acanthocephalans from ruddy duck represent an independent clade with strong bootstrap support and posterior probabilities. The phylogenetic tree inferred with cox 1 gene placed all the pseudogenes from P. anatarium in single clade suggesting that those genes arose after speciation process within genus Pseudocorynosoma. The morphological evidence, plus the monophyly in both phylogenetic analyses indicate that the acanthocephalans collected from intestine of the ruddy duck from northern Mexico represent a new species.Fil: García Varela, Martín. Universidad Nacional Autónoma de México; MéxicoFil: Hernández Orts, Jesús Servando. Universidad Nacional del Comahue. Instituto de Biología Marina y Pesquera Almirante Storni; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pinacho Pinacho, Carlos D.. Universidad Nacional Autónoma de México; México. Universidad de la Sierra Sur; Méxic