Restoration of the genus Parasaccocoelium Zhukov, 1971 (Digenea: Haploporidae) and a description of two new species from mugilid fish in the Far East of Russia

First rDNA sequence data for Haplosplanchnus pachysomus (Digenea: Haplosplanchnidae) ex Mugil cephalus from the Black Sea, and molecular evidence for cryptic species within Haplosplanchnus pachysomus (Digenea: Haplosplanchnidae) in Palaearctic and Indo-West Pacific regions

Adult trematodes, morphologically similar to Haplosplanchnus pachysomus (Eysenhardt, 1829), were extracted from the intestine of Mugil cephalus Linnaeus, 1758, collected in the Black Sea basin. Morphological, morphometric and 28S ribosomal DNA (rDNA) partial sequence data were obtained for these trematodes following comparative analysis with previous data on this species. Worms from this study were morphologically identical to all previously reported H. pachysomus specimens from different locations. The results of the morphometric analysis indicated general similarity between H. pachysomus from the Black Sea and trematodes from Vietnam and Australia. Trematodes from the Black Sea and specimens from Spain were identical based on 28S rDNA partial sequences; however, these sequences differed from that of H. pachysomus from Vietnam and Australia by eight fixed substitutions. Overall, our results indicate that H. pachysomus from Spain and the Black Sea and from Vietnam and Australia can presently be considered as two cryptic species, one in Palaearctic and one in Indo-West Pacific regions. Our results provide a molecular base for including Haplosplanchnus purii in the genus Provitellotrema or to consider H. purii, P. crenimugilis and H. pachysomus within the same genus.

New species of Parasaccocoelium (Haploporidae) and new genus Pseudohaplosplanchnus (Haplosplanchnidae) from mullet fish in the Far East of Russia and Vietnam: morphological and molecular data

A description and the molecular characterization of two new species in the Haploporidae and Haplosplanchnidae families are provided herein. Parasaccocoelium armatum n. sp. was collected from the intestine of a Mugil cephalus Linnaeus, 1758 from the Primorsky region, Russia, and Pseudohaplosplanchnus catbaensis n. g. n. sp. was collected from Moolgarda seheli (Forsskål, 1775) in the coastal waters of Cat Ba Island, Vietnam. The morphological features of P. armatum n. sp. closely resemble those of Parasaccocoelium polyovum, but these species differ from one another by hermaphroditic sac and vitellaria area length and by maximal egg size. The main difference between P. armatum n. sp. and P. polyovum is the presence of an armed hermaphroditic duct in the new species. Molecular data support the case for inclusion of the studied trematodes in P. armatum n. sp. Worms P. catbaensis n. g. n. sp. from the mullet from Vietnam are morphologically close to Haplosplanchnus (Haplosplosplanchninae). The only difference between P. catbaensis n. g. n. sp. and species of Haplosplanchnus is the presence of few (1-7) large eggs, measuring 135-142 × 92-104 μm, versus numerous small eggs with a maximal size of 75 × 50 μm. Phylogenetic analysis showed that there is a contradiction between the morphological similarity of the worms and their position in the Haplosplanchnidae system, based on the genetic data. Results of this study indicate that P. catbaensis n. g. n. sp. is genetically distant from other representatives of Haplosplanchnus, despite their morphological similarity. According to the molecular data, P. catbaensis n. g. n. sp. is close to Hymenocotta mulli Manter, 1961 (Hymenocottinae). However, these species are considerably different to each other morphologically. Molecular data argue for the possibility of establishing a new subfamily for P. catbaensis n. g. n. sp. However, considering earlier studies of Haplosplanchnidae, we support the view that creating new subfamilies within this family is unreasonable because of the lack of molecular data for most haplosplanchnid species, which are necessary to resolve the problematic systematics and phylogeny of this family.

New species and new genus of Pseudohaploporinae (Digenea): Pseudohaploporus pusitestis sp. n. and Parahaploporus elegantus n. g., sp. n. (Digenea: Pseudohaploporinae) from Vietnamese mullet fish

Two new species of Pseudohaploporinae, Pseudohaploporus pusitestis sp. n. and Parahaploporus elegantus n. g., sp. n., are described from intestines of the Vietnamese mullet fish Moolgarda seheli and Osteomugil cunnesius, respectively. Pseudohaploporus pusitestis sp. n. differs from two known Pseudohaploporus species, P. vietnamensis and P. planiliza, by the absence of a diverticulate hermaphroditic duct and muscular sphincters at the proximal end of the hermaphroditic sac. Metrically, P. pusitestis sp. n. is close to P. vietnamensis and differs from this species and from P. planilizum by lower maximum sizes of most parameters. Parahaploporus elegantus n. g., sp. differs from representatives of Pseudohaploporus by the presence of a single testis and the armament of hermaphroditic duct and is morphologically close to trematodes of the genus Haploporus. However, P. elegantus n. g differs from all known Haploporus species from mugilids of the Indo-West Pacific by the structure of the armament of the hermaphroditic duct and also by size of body, organs and eggs. The validity of designating two new species and a new genus of trematodes is supported by ITS and 28S rDNA sequence data. Phylogenetic reconstructions showed that the new trematodes belong to the Pseudohaploporinae, which formed a well-supported cluster within the monophyletic Haploporidae.

Population genetic analysis of trematode Parasaccocoelium mugili Zhukov, 1971 (Haploporidae Nicoll, 1914) from the Russian Far East and Vietnam based on ribosomal ITS and mitochondrial COI gene partial sequence data

Intraspecific variation of Parasaccocoelium mugili collected from mullet fish of the south of Russian Far East and Vietnam has previously been estimated on the basis of two molecular markers: ribosomal internal transcribed spacer 1 (ITS1) rDNA and mitochondrial cytochrome oxidase I (COI) gene sequences. In the present study, molecular identification of this species from the Kievka River, Primorye and from Vietnam was performed by analysis of 28S rDNA sequences. Analysis of ITS1 rDNA sequences variation revealed two highly differentiated main groups, representing trematode specimens from the two regions. Genetic variation within each region was relatively low. Mitochondrial COI gene sequence data analysis revealed fixed nucleotide and amino acid substitutions, and supported the existence of two genetically different groups associated with geographical origin. Analysis of the COI gene fragments showed extremely high variation within Russian and Vietnamese P. mugili samples. Our results for P. mugili most probably represent a case of initial step of allopotric speciation for this trematode, caused by living strategy of its definitive host at evolutionary scale. Mitochondrial DNA sequence data show that existence of gene flow between local populations of P. mugili in the Primorye Region caused by definitive hosts can be proposed.

A new subfamily, Pseudohaploporinae subfam. n. (Digenea: Haploporidae), with morphometric and molecular analyses of two new species: Pseudohaploporus vietnamensis n. g., sp. n. and Pseudohaploporus planilizum n. g., sp. n. from Vietnamese mullet

Adult specimens representing Pseudohaploporus vietnamensis n. g., sp. n., Pseudohaploporus planilizum n. g., sp. n., and Pseudohaploporus sp. were collected from the intestines of Osteomugil engeli (Bleeker, 1858), Moolgarda seheli (Forsskål, 1775), and Planiliza subviridis (Valenciennes, 1836) from Vietnam. The new genus Pseudohaploporus n. g. is similar to the genus Haploporus Looss, 1902 in morphology and host-specificity. Species of Pseudohaploporus and Haploporus both possess an elongated body, a long oesophagus, an intestinal bifurcation behind the ventral sucker, a large hermaphroditic bursa, vitellarium consisting of two compact accumulations, concretions in the excretory vesicle, and numerous small eggs that contain miracidia with a pigment eye, and both infect mullet. In contrast to Haploporus, both species of the genus Pseudohaploporus possess two testes. These species differ from each other morphometrically. Pseudohaploporus planilizum sp. n., in comparison with P. vietnamensis sp. n., possess a larger maximum and mean size for the body length, oral and ventral suckers, pharynx, oesophagus length, hermaphrodite bursa, and egg width. Molecular data (ITS and 28S rDNA sequences) support the validity of the new genus and the two new species and indicate the presence of another representative of this genus, Pseudohaploporus sp. Phylogenetic reconstructions show that Pseudohaploporus formed a well-supported clade within a large clade that represents the Haploporidae Nicoll, 1914. Based on morphological and molecular data for P. vietnamensis sp. n. and P. planilizum sp. n., we erected a new subfamily, Pseudohaploporinae subfam. n., which appears to be a sister taxon to Haploporinae Nicoll, 1914. Molecular data show that Pseudohaploporus differ from other haploporids at a level similar to that between other subfamilies.

Two New Species of Saccocoelioides (Digenea: Haploporidae) with Phylogenetic Analysis of the Family, Including Species of Saccocoelioides from North, Middle, and South America

Two cryptic species of haploporid digeneans belonging in Saccocoelioides are described from Costa Rica: one from a poeciliid fish, Poecilia gillii, and the other from a characid fish, Astyanax aeneus. Traditional morphological features are examined and found to be largely inefficient for differentiating among the new species and 20 New World congeners. Comparison of ribosomal DNA sequences among the 2 new species, 2 North American, 4 Middle American, and 3 South American species of Saccocoelioides, including the type-species Saccocoelioides nanii from Argentina and Saccocoelioides sogandaresi from Texas, is effective in differentiating among these species. A Bayesian inference analysis is conducted using a concatenated alignment of the same 2 ribosomal gene regions from 35 species belonging in the Haploporoidea and rooted by the atractotrematid Isorchis anomalus. The analysis provides stronger support for a close relationship between species in Saccocoelioides and Intromugil; thus, Intromugil is transferred from the Waretrematinae to the Chalcinotrematinae. Additionally, interrelationships among 11 species of Saccocoelioides are resolved and reveal a distinct genetic rift suggesting the presence of 2 distinct lineages within the genus, 1 containing the type-species and the other containing a group of species that more closely resemble other genera in the subfamily. Taxonomy of Saccocoelioides is discussed, and observations made during the present study justify taking several taxonomic actions: new combinations are proposed for Saccocoelioides tilapiae n. comb., formerly in the now-defunct Culuwiya, and Saccocoelioides ruedasueltensis n. comb., formerly in Chalcinotrema; Saccocoelioides guaporense nomen novem is proposed for Lecithobotrioides elongatus; Saccocoelioides papernai is considered a junior subjective synonym of Saccocoelioides overstreeti; Saccocoelioides godoyi is considered a junior subjective synonym of Saccocoelioides szidati; Saccocoelioides magnorchis and Saccocoelioides saccodontis are considered species inquirendae; and Saccocoelioides adelae is considered a nomen nudum. Four new hosts are reported for Saccocoelioides cichlidorum: Amphilophus lyonsi, Amatitlania nigrofasciatus, Amatitlania septemfasciatus, and Hypsophrys nicaraguensis. Molecular data call into question some existing species identifications in Saccocoelioides and reveal that molecular tools combined with traditional taxonomy are required for accurately identifying species in the genus. Twenty-two species of Saccocoelioides are formally accepted, but it is noted that as new molecular data become available, some of these species may be transferred to other genera in the subfamily.

Morphometric and molecular analyses of Skrjabinolecithum pyriforme n. sp. (Digenea: Haploporidae) in mullet fish from the Primorsky Region, Russia

A new species of Skrjabinolecithum (Digenea: Waretrematinae), Skrjabinolecithum pyriforme n. sp., has been found in the intestines of Liza haematocheila and Mugil cephalus from the Primorsky Region, Russia. These worms differ from S. vitellosum and S. lobolecithum by the presence of two caeca, as do S. spasskii, S. indicum and S. bengalensis. These species differ morphologically from S. pyriforme n. sp. by a number of features, including body width, oral sucker, pharynx, eggs and ratio of length and width of the body. The most similar species to S. pyriforme n. sp. is Platydidymus flecterotestis (Zhukov, 1971) with some differences in maximal body length, testis and egg sizes. The results of molecular analysis confirmed that this new species belongs to Skrjabinolecithum on the basis of close relationships with S. spasskii-type species.

Erection of the haploporid genus Litosaccus n. g. and its phylogenetic relationship within the Haploporidae Nicoll, 1914

Litosaccus n. g. is erected for Paralecithobotrys brisbanensis Martin, 1974 n. comb. for which an amended description is given. The new genus is morphologically similar to the haploporine Lecithobotrys Looss, 1902 but with a more elongate and cylindrical body; an infundibuliform oral sucker; a thin-walled hermaphroditic sac; a shallow genital atrium; and unequal, cylindrical and elongated caeca. It also resembles Pseudolecithobotrys Blasco-Costa, Gibson, Balbuena, Raga & Kostadinova, 2009, but the only member of that genus has a hermaphroditic sac that is twice the length of the ventral sucker, a hermaphroditic duct with intensely-staining cuboidal cells, an elongate testis, and single or paired caeca. A Bayesian inference analysis of partial 28S rDNA sequences of L. brisbanensis and 24 other haploporoids revealed that L. brisbanensis grouped with other haploporines and placed Intromugil Overstreet & Curran, 2005 in a clade with the chalcinotrematine Saccocoelioides Szidat, 1954 rather than the other seven tested waretrematine species. This analysis represents the first phylogenetic study of the Haploporidae Nicoll, 1914 that incorporates a haploporine from outside of the Mediterranean Sea.