Contracaecum Species Research Articles

Genetic and Morphological Evidences for the Existence of a New Species of Contracaecum (Nematoda: Anisakidae) Parasite of Phalacrocorax brasilianus (Gmelin) From Chile and Its Genetic Relationships with Congeners From Fish-Eating Birds

Contracaecum australe n. sp. is described from the Neotropic cormorant Phalacrocorax brasilianus in Chile based on morphology and the sequence analyses of multiple loci, i.e., mitochondrial cytochrome oxidase 2, mtDNA cox-2, the small subunit of the mitochondrial ribosomal RNA gene, rrnS, and the ITS-1 and ITS-2 regions of nuclear ribosomal DNA. Moreover, sequence analysis of the same genes was carried out on the morphospecies Contracaecum chubutensis Garbin et al. (2008) from Phalacrocorax atriceps. Further, genetic relationships are presented between C. australe n. sp. and C. chubutensis with respect to the related congeners from fish-eating birds previously characterized genetically on the same genetic markers, i.e., Contracaecum rudolphii A, B, C, D, and E, Contracaecum septentrionale, Contracaecum microcephalum, Contracaecum bioccai, Contracaecum pelagicum, Contracaecum micropapillatum, Contracaecum gibsoni, and Contracaecum overstreeti. Several phylogenetic analyses (MP, NJ, and BI) inferred from mitochondrial genes (cox-2 , rrnS) were congruent in depicting C. australe n. sp. and C. chubutensis as forming distinct clades, highly supported, from the remainder of the Contracaecum taxa considered; thus, it validates their specific status. Further, analyses of the ITS-1 and ITS-2 sequence data of C. australe n. sp. and C. chubutensis supported their distinction with respect to the 2 sibling species, C. rudolphii D and C. rudolphii E, previously detected from Phalacrocoracidae of Australia. Morphological analysis and the differential diagnosis of male specimens of C. australe n. sp. enabled the detection of differences in a number of characters, including spicule length, peculiar shape of male tail, paracloacal papillae disposition, and shape and bifurcation depth of interlabia. According to the genetic and morphological results obtained, the erection of a new taxon from fish-eating birds of the Austral region is given and its formal description is presented. Phylogenetic trees support both C. australe n. sp. and C. chubutensis as being included in the same clade with the previously detected species from cormorants, i.e., C. rudolphii A, B, C, and C. septentrionale. The finding of C. australe n. sp. and C. chubutensis parasites of Ph. brasilianus and Ph. atriceps, respectively, appears to support a host-parasite association between the C. rudolphii A, B, and C, C. septentrionale, C. chubutensis, and C. australe n. sp. and different species of cormorants belonging to Phalacrocorax.

Redescription and genetic characterization of selected Contracaecum spp. (Nematoda: Anisakidae) from various hosts in Australia

In the present study, five species of Contracaecum Railliet & Henry 1912 (Nematoda: Ascaridida), including Contracaecum bancrofti, Contracaecum microcephalum, Contracaecum variegatum, Contracaecum eudyptulae, and Contracaecum ogmorhini, were redescribed using light and scanning electron microscopy. In addition, in order to elucidate their taxonomic status, first and second internal transcribed spacers (ITS-1 and ITS-2, respectively) of nuclear ribosomal DNA of each morphospecies were characterized. Analyses of sequence and morphological data sets suggested that C. bancrofti, infecting the Australian pelican Pelecanus conspicillatus, is a valid species and is distinct from C. micropapillatum reported from pelicans in the northern hemisphere. C. microcephalum from cormorants Phalacrocorax melanoleucos and C. variegatum from the darter Anhinga melanogaster and from P. conspicillatus as well as C. eudyptulae from the little penguin Eudyptula minor were also considered as distinct species, which can be differentiated from one another morphologically based on the lengths of spicules and genetically based on the sequences of ITS-1 and ITS-2. Comparison of sequence data of ITS-1 and ITS-2 for the members of C. ogmorhini sensu lato from pinnipeds with those of previous studies suggested that only ITS-2 can be used for differentiation between C. ogmorhini sensu stricto and Contracaecum margolisi, occurring in the southern and northern hemispheres, respectively. Analyses of the ITS-1 and ITS-2 sequence data of Contracaecum spp. in the present study supported the distinction among species of Contracaecum based on morphological data and were useful in confirming the taxonomic status of individual species in Australia.

FURTHER STUDY OF CONTRACAECUM PELAGICUM (NEMATODA: ANISAKIDAE) IN SPHENISCUS MAGELLANICUS (AVES: SPHENISCIDAE) FROM ARGENTINEAN COASTS

The anisakid species Contracaecum pelagicum Johnston and Mawson, 1942, is reported for first time at 2 different sites on the Argentine coast (Peninsula Valdés, 42 degrees 04'S, 63 degrees 38'W and Mar del Plata, 38 degrees 05'S, 57 degrees 38'W), parasitizing the Magellanic penguin, Spheniscus magellanicus Foster. Morphometric analysis and further studies of adult specimens of C. pelagicum were done using light and scanning electron microscopy. The presence of bifurcated interlabia differentiates the present species from most others in the genus, except (1) from Contracaecum travassosi, which possesses higher interlabia and longer spicules, and a blunt, more constrained tail; (2) from Contracaecum rudolphii, which has longer spicules, blunter spicule tips, postparacloacal papillae with oblique disposition, and a blunter constrained tail; (3) from Contracaecum eudyptulae, which has a blunter tail and longer spicules; and (4) from Contracaecum variegatum, which possesses smaller-diameter, hooklike extensions on auricle lips, and a less robust interlabium with a more marked furrow. In this paper we present the first detailed description of C. pelagicum adults from S. magellanicus. Morphometric data between adult specimens of C. pelagicum from S. magellanicus and those from the black-browed albatross, Diomedea melanophris Temminck, from Argentinean coasts were compared. In addition, fourth-stage larvae that parasitized both hosts were assigned to a nondeterminated Contracaecum species. Ecological parameters for adults and larvae nematodes were calculated.

Parasitic Helminths of the American White Pelican, Pelecanus erythrorhynchos, from Florida, U.S.A

Thirty-three species of helminths (22 trematodes, 3 cestodes, 7 nematodes, and 1 acanthocephalan) were recovered from 29 American white pelicans, Pelecanus erythrorhynchos, collected in Florida, U.S.A., between 1982 and 2001. The number of helminth species per infected bird ranged from 3 to 17 (x̄ = 11). Three species of Contracaecum (Contracaecum rudolphii, Contracaecum multipapillatum, and Contracaecum micropapillatum) were the most prevalent and abundant helminths. One cestode species (Paradilepis longivaginosus) was considered a specialist in white pelicans, 9 species were considered generalists in pelicaniform birds, and the remainder of the species were considered true bird generalists. White pelicans shared 14 species of helminths with brown pelicans, Pelecanus occidentalis, and the most prevalent helminths appear to have been acquired in marine habitats.

Identification of anisakid nematodes from the Southern Baltic Sea using PCR-based methods

Four common species of Baltic anisakids Anisakis simplex, Hysterothylacium auctum,Contracaecum osculatum from fish (the last one also from the grey seal) and C. rudolphii from cormorants were examined using PCR-RFLP technique for working out the method allowing their identification and differentiation. A fragment of nuclear DNA containing intergenic regions (ITS-1 and ITS-2) of ribosomal DNA together with adjacent sequences of genes coding 18S and 28S rRNA (in total 1500 bp) was amplified and the products were digested using three endonucleases Hin fI,Hae III and Pvu II. Digestion with Hin fI endonuclease enabled species identification and differentiation between all nematode species studied. Digestion with Hae III endonuclease enabled identification of A. simplex and H. auctum while electrophoretic patterns obtained for both Contracaecum species were similar (differentiation between A. simplex, H. auctum and the genus Contracaecum). Pvu II endonuclease was not suitable to this purpose. On the basis of nucleotide sequences obtained, the pairs of species-specific primers were designed for each species studied. By the use of these pairs of primers the species-specific PCR reactions were carried out. The sizes of specific products were: 486 bp for A. simplex, 491 bp for C. osculatum, 505 bp for C. rudolphii and 663 bp for H. auctum. The methods presented herein can be useful in diagnostics of human anisakidosis, especially when parasites are disrupted.

Phylogenetic relationships among species of contracaecum Railliet & Henry, 1912 and Phocascaris Høst, 1932 (Nematoda:Ascaridoidea) based on nuclear rDNA sequence data.

Nuclear-encoded large-subunit ribosomal DNA sequences were used to infer a phylogenetic hypothesis for 17 taxa (16 nominal species) of the genera Contracaecum and Phocascaris. Phylogenetic trees based on these data have been used to assess the validity of the taxonomic distinction between these genera, which was based on the presence or absence of certain structural features, rather than on explicit hypotheses of evolutionary history. Phylogenetic hypotheses based on parsimony, likelihood, and neighbor-joining analyses of these sequence data strongly support the hypothesis that species of Phocascaris are nested within the clade of Contracaecum species hosted by phocid seals, and are more closely related to species of the Contracaecum osculatum complex than to other Contracaecum species. Alternative tree topologies representing Phocascaris as not nested within the C. osculatum complex were significantly worse interpretations of these sequence data. Phylogenetic analysis also provides strong support for the monophyly of all taxa (Contracaecum and Phocascaris) from phocid seals, which is consistent with Berland's (1964) proposal that such species form a natural group; however, his proposal to recognize all species in phocid seals as Phocascaris, with all species from birds as Contracaecum would result in a paraphyletic Contracaecum, according to the molecular phylogenetic hypothesis.

Contracaecum multipapillatum (Nematoda: Anisakidae) from Egretta alba (Aves: Ardeidae) and comments on other species of this genus in Argentina.

During a parasitological survey of aquatic birds in Mar Chiquita coastal lagoon (Buenos Aires province, Argentina), specimens of Contracaecum Raillet & Henry, 1912 sp. were found in the esophagus and stomach of the great egret Egretta alba (Gmelin, 1789) (Aves: Ardeidae). The nematodes were identified as Contracaecum multipapillatum (Drasche, 1882) on the basis of the following features: ratio of ventricular appendage length to esophagus length, ratio of intestinal caecum length to esophagus length, spicule lengths, number and arrangement of postcloacal papillae (3-4 pairs of adanal papillae, 1 double pair, and a subterminal group of 2 subventral and 3 sublateral pairs). A complete description of the adult specimens of C. multipapillatum is given in the present paper, together with a discussion regarding the validity of other species of Contracaecum reported from Argentina. Contracaecum philomultipapillatum Labriola and Suriano, 1996 is reduced to a junior synonym of C. multipapillatum, and Contracaecum longicaecum Schuurmans Sterkhoven, 1952 is considered a species inquirenda. A revision of Contracaecum spheniscus Boero and Led, 1970 based on appropriate material is necessary.

Preliminary survey of parasites and bacterial pathogens of fish at Lake Ziway

Parasites and bacterial pathogens of fish at Lake Ziway, during 1996B97 were studied. A total of 613 fish were sampled. These included 495 Nile tilapia (Oreochromis niloticus), 75 Catfish (Clarias gariepinus), 24 Barbus species, 11 Tilapia zillii and 8 carp species. The fish were thoroughly examined both externally and internally for the presence of parasites and lesions and samples were taken for bacteriological investigations. Among the bacteria, Edwardsiella tarda, (new geographic record) isolated from the liver of one O. niloticus and kidney of another carp species is known to be pathogenic to fish. On the other hand Shigella species, Escherichia coli, Citrobacter, Klebsiella oxytoca, and Yersinia enterocolitica were the major bacteria identified from the apparently healthy fish. The major parasites identified included Contracaecum species from 77 (15.56 %) of O. niloticus, 3 (27.27%) T. zillii, 4 (5.33%) C. gariepinus and 2 (8.33%) Barbus species. Clinostomum species were recovered from the branchial cavity of 45 (9.09%) Oreochromis niloticus, 2 (18.18%) Tilapia zillii and 3 (4.00%) C. gariepinus. Only 1 Euclinostomum species (new geographic record) was recovered from the branchial cavity of O. niloticus. Moreover 13 (17.33%) C. gariepinus were carrying Amplicaecum species in their mesentery and one C. gariepinus was positive to Bothriocephalus species. The significance of these parasites and bacterial pathogens as causes of diseases to fish is discussed. SINET: Ethiopian Journal of Science Vol. 23, No. 1 (June 2000), pp. 25-33 Key words/phrases: Bacteria, Edwardsiella tarda, fish diseases, Lake Ziway, parasites

Isozyme variation and taxonomic rank of Contracaecum radiatum (v. Linstow, 1907) from the Antarctic Ocean (Nematoda, Ascaridoidea)

Genetic variation of the Antarctic anisakid Contracaecum radiatum from the Ross and Weddell Seas is studied at 24 enzyme loci. All polymorphic loci proved to be in Hardy-Weinberg equilibrium, with no significant differences between the samples tested. Several loci were found to be diagnostic between C. radiatum and the five known members of the C. osculatum complex, indicating that no gene exchange occurs between them and confirming their specific status. No F1 hybrids, recombinant or introgressed individuals, sharing radiatum and osculatum alleles, were detected in the Antarctic Contracaecum samples; this directly proves the reproductive isolation of C. radiatum. Biochemical keys are given for the identification of Antarctic C. radiatum, C. osculatum D and E, both for adults (males and females) and larvae. Higher values of genetic variability were observed in these Antarctic Contracaecum species than in the Arctic-Boreal C. osculatum members, possibly related to a lower degree of habitat disturbance (i.e. by pollution, fishing and hunting) in the Antarctic region. On the basis of genetic distances, the evolutionary divergence between C. radiatum and C. osculatum (sensu lato) started about 5 million years ago, possibly with the first colonisation of the Antarctic region by seals. Data on paratenic (fish) and definitive (seal) hosts of C. radiatum and C. osculatum D and E are given.

Adjustment of anisakid nematode life cycles to the high Antarctic food web as shown by Contracaecum radiatum and C. osculatum in the Weddell Sea

The infestation of Weddell seals and several fish species by the anisakid nematodes Contracaecum osculatum and C. radiatum was compared. Nematode numbers in Weddell seal stomachs ranged from 30 560 to 122 640. Third stage larvae from seals and fish were separated into a short and a long type. The short type was related to C. radiatum and the long type to C. osculatum. The short type was more abundant in pelagic fish species, whereas the long type prevailed in benthic fish species. Fish-feeding channichthyids Cryodraco antarcticus and Chionodraco myersi seemed to play an important role as paratenic hosts for the third stage larvae of both Contracaecum species. Different advantageous and detrimental features of a benthic versus a pelagic life cycle under high Antarctic ecological conditions are discussed. Varying abundance of the two nematode species in hosts may be controlled by differences in their life cycles, which follow either a pelagic or a benthic food web. Crucial importance is thus given to the local availability of pelagic versus benthic food resources for Weddell seals.

A nematode parasite of the penguin Spheniscus magellanicus (Forster) (Ascaridoidea, Anisakidae)

The nematodes were collected from the penguin Spheniscus magellanicus (Forster) (Sphenisciformes). A study from the main species of Contracaecum that occur in penguins and piscivorous birds from the south hemisphere is made, more specifically the C. eudyptulae Johnston & Mawson, 1942a, C. eudyptes Johnston & Mawson, 1953, C. heardi Mawson, 1953, C. antarcticum Johnston, 1938, C. prevosti Tchéprakoff, 1966, C. spiculigerum (Rudolphi, 1809), C. osculatum (Rudolphi, 1802), C. scotti (Leiper & Atkinson, 1914) and C. pelagicum Johnston & Mawson, 1942b. C. pelagicum is redescribed and turns to be a new reference for Spheniscus magellanicus (Forster).

The Natural History of Anisakiasis in Animals

Adult anisakid nematodes are known to be parasites in the alimentary tracts of amphibians, reptiles, birds, and mammals. The known life cycle patterns among the anisakids are reviewed and from what is known, it is not possible to predict whether those hosts in which larval forms occur are true intermediate hosts or paratenic hosts. This is especially true of marine fishes in which third- and fourth-stage larvae are common.Among physical parameters known to influence the survival, development, and distribution of anisakids, temperature apparently is an important one. Similarly, a series of experiments has revealed that two unidentified species of Contracaecum from marine fish are not infective to laboratory mammals primarily because of their inability to survive mammalian body temperatures.It has also been demonstrated that Contracaecum larvae normally present in the digestive tracts of marine fishes will migrate out of dead hosts or into their mesenteries and musculature. Thus, in considering the potential public health importance of larval anisakids in marine fish, those in the digestive tract should not be considered as unimportant since they will migrate into muscles.

On the ascarids parasitic in seals, with special reference to the genus Contracaecum

Difficulties encountered in the determination of species of Contracaecum from seals led the writer to undertake a comparative morpholgical study of a considerable amount of material. This included the Ascarids from seals collected by the Scottish National Antarctic Expedition (Scotia) in 1902–4, and deposited in the Royal Scottish Museum, Edinburgh, which were obtained on loan through the courtesy of Dr A. C. Stephen. In the present paper some results of this investigation are presented, and short notes are added on other species of Ascaridae recorded from Pinnipedia.