A new species of Hysterothylacium (Nematoda: Anisakidae) parasite of Ariopsis guatemalensis (Osteichthyes: Ariidae) from Tres Palos lagoon, Mexico

Review of the parasitic nematodes of marine fishes from off the American continent

The ichthyofauna of the Atlantic and Pacific coasts off the American continent is very rich. Consequently, a high biodiversity of nematodes parasitizing these vertebrates is also expected. Currently, data on nematode parasites of marine fish off the Americas are fragmented. A review of all adult nematode species reported parasitizing marine fish from off the American continent is herein presented, as well as comments on their patterns of diversity, life cycles and advances in the taxonomic and phylogenetic knowledge. A total of 209 valid species, 19 species inquirendae and 6 dubious records have been recorded, the majority from the fish taxa Eupercaria and Perciformes. The families Sciaenidae, Serranidae and Lutjanidae, as well as the tropical and temperate Atlantic waters, exhibited the highest records of parasitic nematodes. The Cucullanidae, Philometridae and Cystidicolidae were the most speciose families of nematodes, which may be related to technological advances and relatively recent efforts of taxonomists, resulting in description of new taxa and the resolution of taxonomic problems. Numerous taxonomic questions still need resolution and, even though genetic data have been important for this process, the database is very scarce. This is the first review on all currently known nematode species parasitizing marine fish off the Americas and may serve as an important basis of reference for future approaches on these organisms.

Molecular Identification of Hysterothylacium spp. In Fishes From the Southern Mediterranean Sea (Southern Italy)

Samples obtained from 11 teleost fish species collected in waters off of the Mediterranean coasts of Sicily, Italy, were examined for the presence of Hysterothylacium spp. larvae. In total, 3,017 fish samples were examined, and the larvae recovered were used in subsequent phylogenetic studies. Fifty-eight raphidascaridid parasitic nematodes were found in the examined fish, with prevalence values ranging from 0.2% in anchovies to 60% in forkbeard samples. Twenty-seven parasites were identified as Hysterothylacium fabri and Hysterothylacium aduncum by sequencing the following regions: the nuclear ribosomal internal transcribed spacer ( ITS) and the mitochondrial cytochrome c oxidase subunit II ( COXII). Two other larvae collected from Lophius piscatorius had very low identity scores, with ITS and COXII sequences reported in GenBank and high genetic distances (AY603539). Pairwise comparisons between the ITS region of the H. fabri isolated from fishes from Sicilian coastal waters and those isolated from the Mediterranean Sea, Turkey (KC852206), revealed genetic differences ranging from 0.015 to 0.018. Our H. aduncum samples had very low genetic differences to H. aduncum from the Adriatic Sea (KP979763, 0.00-0.003). The concatenated phylogenetic examination of the ITS- COXII sequences by using maximum likelihood analyses indicated 3 distinct clades supported by high bootstrap values. Further molecular identification and detailed morphological analyses are needed to clarify these results and confirm the diversity and relationships within Hysterothylacium.

Molecular characterization of Hysterothylacium fabri (Nematoda: Anisakidae) from Zeus faber (Pisces: Zeidae) caught off the Mediterranean coasts of Turkey based on nuclear ribosomal and mitochondrial DNA sequences

In the present study, Hysterothylacium fabri was found in the coasts of the Mediterranean Sea, Turkey and characterized by sequencing of nuclear (internal transcribed spacer, ITS) and mitochondrial (cytochrome c oxidase subunit 2, cox2) markers. Pairwise comparison between the entire ITS fragment including ITS-1, 5.8S, ITS-2 sequences of the H. fabri isolates from the Mediterranean Sea (Turkey, KC852206) and other H. fabri isolates from the South China Sea (JQ520158), the South Korea waters (JX974558) showed differences ranged from 0.1 and 1.1%. With the present study, H. fabri from the Mediterranean Sea was characterized for the first time by sequencing of the cox2 gene.

Patterns of distribution of the helminth parasites of freshwater fishes of Mexico

In order to draw patterns in helminth parasite composition and species richness in Mexican freshwater fishes we analyse a presence-absence matrix representing every species of adult helminth parasites of freshwater fishes from 23 Mexican hydrological basins. We examine the distributional patterns of the helminth parasites with regard to the main hydrological basins of the country, and in doing so we identify areas of high diversity and point out the biotic similarities and differences among drainage basins. Our dataset allows us to evaluate the relationships among drainage basins in terms of helminth diversity. This paper shows that the helminth fauna of freshwater fishes of Mexico can characterise hydrological basins the same way as fish families do, and that the basins of south-eastern Mexico are home to a rich, predominantly Neotropical, helminth fauna whereas the basins of the Mexican Highland Plateau and the Nearctic area of Mexico harbour a less diverse Nearctic fauna, following the same pattern of distribution of their fish host families. The composition of the helminth fauna of each particular basin depends on the structure of the fish community rather than on the limnological characteristics and geographical position of the basin itself. This work shows distance decay of similarity and a clear linkage between host and parasite distributions.

Hysterothylacium simile n. sp. and H. aduncum (Rudolphi, 1802) (Nematoda: Raphidascarididae) from marine fishes in the Bohai and Yellow Sea, China, with comments on the record of H. paralichthydis (Yamaguti, 1941) from Chinese waters

Hysterothylacium simile n. sp., collected from the Japanese seabass Lateolabrax japonicus (Cuvier) (Perciformes: Lateolabracidae) in the Bohai Sea off China, is described using both light and scanning electron microscopy. The new species differs from its congeners in the presence of narrow lateral alae originating a short distance posterior to the base of the ventrolateral lips, a long intestinal caecum (60.4-79.1% of oesophageal length) and a relatively short ventricular appendix (intestinal caecum to ventricular appendix ratio 1:0.58-0.85), long spicules (2.11-2.99 mm, 4.25-7.83% of body length), the number and arrangement of the caudal papillae (32-36 pairs arranged as follows: 27-31 pairs precloacal, 1 pair paracloacal, and 4-5 pairs postcloacal with the second or third pair double) and the presence of a particular midventral precloacal papilla. Specimens originally identified as Contracaecum paralichthydis Yamaguti, 1941 [now H. paralichthydis (Yamaguti, 1941)] by Xü (1957), collected from the yellow striped flounder Pseudopleuronectes herzensteini (Jordan & Snyder) (Pleuronectiformes: Pleuronectidae) in the Yellow Sea off China, were also re-examined. Their morphology clearly revealed they belong to H. aduncum (Rudolphi, 1802), which is also redescribed based on Xü's material. In addition, the morphological variation of caudal papillae in H. aduncum from P. herzensteini was compared, using scanning electron microscopy, with specimens collected from another three fish hosts, Lophius litulon (Jordan) (Lophiiformes: Lophiidae), Scomberomorus niphonius (Cuvier) (Perciformes: Scombridae) and Cleisthenes herzensteini (Schmidt) (Pleuronectiformes: Pleuronectidae), from the Yellow Sea off China.

Morphological and molecular diagnosis of anisakid nematode larvae from cutlassfish (Trichiurus lepturus) off the coast of Rio de Janeiro, Brazil

Anisakid nematode larvae from Trichiurus lepturus off coast of Rio de Janeiro were studied using light, laser confocal and scanning electron microscopy, in addition to a molecular approach. Mitochondrial cytochrome c-oxidase subunit 2 (mtDNA cox-2), partial 28S (LSU) and internal transcribed spacers (ITS-1, 5.8S, ITS-2) of ribosomal DNA were amplified using the polymerase chain reaction and sequenced to evaluate the phylogenetic relationships between the nematode taxa. The morphological and genetic profiles confirmed that, of the 1,030 larvae collected from the 64 fish examined, 398 were analysed, of which 361 were Hysterothylacium sp. and 37 were Anisakis typica. Larvae of Hysterothylacium sp. were not identified to the species level due to the absence of similar sequences for adult parasites; however, the ITS sequence clustered in the phylogenetic tree with sequences of H. deardorffoverstreetorum, whereas an mtDNA cox-2 and LSU concatenated phylogenetic analysis demonstrated the presence of two clades, both of them under the same name as the larval H. deardorffoverstreetorum. Data on the occurrence of parasites during the winter and summer months were compared using the t-test. The greatest prevalence and intensity of infection were recorded for larval Hysterothylacium, with a prevalence of 51.56% and an intensity of up to 55 parasites per fish. The larval Anisakis exhibit a higher abundance and intensity of infection in the winter months, and those of Hysterothylacium during the summer. However, the t-test indicated no significant differences between the abundance and intensity of infection recorded during the months of collection for either of these larval nematodes. All sequences generated in this study were deposited in GenBank.

New species of Rhabdosynochus Mizelle and Blatz 1941 (Monogenoidea: Diplectanidae) from the gills of centropomid fishes (Teleostei) off the Pacific Coast of Mexico

In the course of the investigations into the fish parasites in the Tres Palos Lagoon in the State of Guerrero off the Pacific coast of Mexico, the following diplectanid species (Monogenoidea) from the gills of centropomids were found: Rhabdosynochus alterinstitus n. sp. from Centropomus nigrescens; Rhabdosynochus lituparvus n. sp., Rhabdosynochus volucris n. sp., and Rhabdosynochus siliquaus n. sp. from Centropomus robalito (Centropomidae). The apparent synapomorphic character supporting a sister relationship of these diplectanids is a single, sheathlike accessory piece comprising 3 distal branches of the male copulatory organ. The origin of the present diplectanid on centropomids is discussed, and it is suggested that this may be the result of allopatric speciation as a result of the uplift of the Panamanian Isthmus, thereby separating the Pacific and Atlantic Oceans during Pleistocene (3-5 million yr ago).

A checklist of metazoan parasites of fish from Tres Palos Lagoon, Guerrero, Mexico

An extensive survey of helminth parasites in fish species from Tres Palos Lagoon, in Guerrero, Mexico, resulted in identification of 39 metazoan parasite species (37 helminth and 2 crustaceans) in 13 fish species (n = 1,498). Specimen collection in this coastal lagoon was done between April 2000 and November 2003. Digenean species (18, 8 adult and 10 metacercariae) dominated the parasite fauna. The most widespread species of parasite were: Contracaecum sp. (Nematoda), Pseudoacanthostomum panamense, Austrodiplostomum compactum, Ascocotye (Phagicola) longa (Digenea), Neoechinorhynchus golvani (Acanthocephala), Ergasilus sp. (Copepoda), and Argulus sp. (Branchiura). Parasite fauna species composition exhibited a clear freshwater influence as 56.4% (22 of 39) of the identified species have a freshwater distribution in Mexico. For 32 of the parasite species, this report constitutes the first geographical host record for Tres Palos Lagoon, Guerrero, Mexico.

Larval Hysterothylacium sp. (Nematoda, Anisakidae) and trematode metacercariae from the amphipod Paracorophium excavatum (Corphiidae) in New Zealand

Previously undescribed fourth-stage larvae of anisakid nematodes were found in the haemocoel of the amphipod Paracorophium excavatum (Thomson, 1884) (Corophiidae) in New Zealand. Morphological examination by light microscopy showed that the worms belonged to a species of Hysterothylacium Ward et Magath, 1917, based on several characters including the presence of interlabia, the location of the excretory pore posterior to the nerve ring, and the characteristics of the intestinal caecum and ventricular appendix. Interestingly, several male specimens showed precocious sexual development. This is the first record of fourth larval stage and precocious adult male specimens of Hysterothylacium in an invertebrate host, as well as the first record of anisakid larvae in New Zealand crustaceans. In addition, metacercariae of two trematode species, Coitocaecum parvum and Microphallus sp., are recorded for the first time from the amphipod P. excavatum.