Reevaluation of the taxonomic status of Halipegus occidualis Stafford, 1905 (Digenea: Hemiuridae)

In response to confusion regarding the taxonomy of halipegines inhabiting North American amphibians, the reproductive structures of the hemiurid Halipegus occidualis are described from adult worms reared from cercariae shed by Helisoma anceps from Charlie's Pond, North Carolina. The report of a Laurer's canal is confirmed and the presence of a canalicular seminal receptacle established. The suggestion that H. eccentricus Thomas, 1939 be considered a junior synonym of H. occidualis Stafford, 1905 is rejected.     

Clarification of Cercaria sevillana (Digenea: Microphallidae) life cycle using morphological and molecular data

Cercaria sevillana is the cercaria larval stage that infects the gonads and the digestive gland of its first intermediate host, Nassarius reticulatus. In this study the decapodous crustacean Carcinus maenas was used to determine if it would serve as second intermediate host in the parasite's life cycle. The latter hypothesis was based on the knowledge that C. maenas is the second intermediate host of several other digenean species. After dissection, it was possible to observe encysted metacercariae in the antennal glands of the green crab. After biochemical excystment, the metacercariae were processed for light and scanning electron microscopy. The morphological features observed led us to conclude that this species was a microphallid fluke, and it was identified as Gynaecotyla longiintestinata. To establish a possible relationship between C. sevillana and this metacercariae, the ITS1 region was analyzed. Thus, DNA was extracted from C. sevillana and from the cysts isolated from the antennal glands. The ITS1 region was amplified and sequenced, and the alignment clearly demonstrated that the cercaria and the metacercariae belonged to the same species, G. longiintestinata.     

Redescription and systematic reclassification of the trematode Topsiturvitrema verticalia (Trematoda: Digenea) in a new family

The trematode species Topsiturvitrema verticalia Vélez and Thatcher 1990 is redescribed based on two paratype samples and new material from the small intestine of the bat Myotis levis (Geoffroy), from Bahia Samborombón, Buenos Aires province, Argentina. This species is characterized by the presence of a "rhynchus", that is, an anterior sucker-like attachment organ, by the position of the mouth on the ventral surface (surrounded by the ventral sucker), by two blind digestive structures, by the presence of two false saccular caeca located anteriorly and behind the anterior attachment organ, by the presence of the genital pore in the marginal anterior position of the body, and by the mid-dorsal position of the excretory pore. T. verticalia was originally described as a member of the family Lecithodendriidae (Lühe 1901), however, the presence of "rhynchus" and the position of the mouth opening in the ventral sucker constitute morphological features that preclude its inclusion in this family. On account of this, it is considered necessary to create a new family for the genus Topsiturvitrema Vélez and Thatcher 1990, which is included in a new family, Topsiturvitrematidae fam. nov. Furthermore, the geographic range of the species is expanded from Colombia to Argentina and M. levis is added to the species' host list.     

Identification and description of Bucephalus minimus (Digenea: Bucephalidae) life cycle in Portugal: morphological, histopathological, and molecular data

The cercaria of Bucephalus minimus infects the digestive gland and gonads of its first intermediate host, the edible cockle, Cerastoderma edule. Light microscopy (LM) and scanning electron microscopy (SEM) of the cercaria showed a tail formed by a central stem, with 2 long contractile arms presenting distinct morphological surfaces. The encysted metacercaria naturally infected the flathead grey mullet, Mugil cephalus. The cysts found in the heart, liver, and spleen were shown to be identical by the internal transcribed spacer (ITS 1) sequence and morphological features and were associated with encapsulation, recruitment of cell infiltrates, and presence of melanomacrophages and adipose tissue. To establish the life cycle, we compared the ITS1 sequence in an adult from the known definitive host, Dicentrarchus labrax; encysted metacercariae from the liver, heart, and spleen of M. cephalus; and a cercaria from C. edule. With this comparison, we determined that they had a 100% similarity. Therefore, the ITSI sequence data clearly indicate that these 3 parasitic stages belong to the same species, i.e., B. minimus.     

Redescription of Ascocotyle (Ascocotyle) felippei Travassos, 1928 (Digenea: Heterophiydae) with new synonymies

The heterophyid trematode Ascocotyle (Ascocotyle) felippei Travassos, 1928, is redescribed and new data on its life cycle are provided, based on types and metacercariae found in the heart bulb and gills of naturally infected guppies, Poecilia vivipara (new fish intermediate host), from a coastal lagoon in Rio de Janeiro, Brazil. Examination of the type and all voucher specimens of A. (A.) felippei collected by Travassos in the type host and locality in Brazil has shown that they possess only 32 (16 + 16) circumoral spines, rather than 36 (18 + 18) spines as previously reported. Based on the identical number and arrangement of circumoral spines, shape of the body, the presence of a long preoral lobe and posterior muscular prolongation of the oral sucker, short and wide ceca, a simple gonotyl lacking refractile bodies, and the site of infection of metacercariae (predominantly heart bulb), A. (A.) puertoricensis Price, 1932 and A. (A.) tenuicollis Price, 1935, are proposed as new synonyms of A. (A.) felippei.     

The Psilostomidae Looss, 1900 (<Emphasis Type="Italic">sensu stricto</Emphasis>) (Digenea: Echinostomatoidea): description of three new genera and a key to the genera of the family

Three new psilostomid genera, Byrdtrema n. g., Longisaccus n. g. and Macracetabulum n. g., each with a single species, are described from ducks, Aix sponsa (L.) and Bucephala albeola (L.) in North America. Byrdtrema n. g. and Macracetabulum n. g. possess a bipartite seminal vesicle and share this character with four psilostomid genera, Grysoma Byrd, Bogitsh & Maples, 1961, Neopsilotrema Kudlai, Pulis, Kostadinova & Tkach, 2016, Psilostomum Looss, 1899 and Psilotornus Byrd & Prestwood, 1969. Byrdtrema n. g. differs from Macracetabulum n. g. in the shape of the body (elongate vs elongate-oval); the position of the ventral sucker (in first third of body vs just pre-equatorial); the shorter forebody; as well as in the smaller size of the eggs in relation to body length. Both new genera differ from (i) Grysoma by the nature of the vitellarium (large, compact follicles with small vitelline cells vs weakly defined follicles with large vitelline cells, respectively) and the smaller size of the eggs in relation to body length; (ii) Psilostomum in the posterior extend of the cirrus-sac in relation to ventral sucker (slightly posterior vs more posterior), the location of the genital pore (at the level of oesophagus vs just postbifurcal), the shorter length of uterine and longer post-testicular fields in relation to body length, and the anterior limits of vitellarium (at the level of ventral sucker vs posterior to ventral sucker); (iii) Psilotornus by the presence of a muscular pharynx (vs absent or rudimentary) and the location of the cirrus-sac (antero-dorsal to ventral sucker or more posterior vs entirely anterior to ventral sucker) and ovary (in hindbody vs in forebody). Byrdtrema n. g. differs from Neopsilotrema in the shape of the body (elongate vs subspherical to elongate-oval) and ventral sucker (elongate-oval vs subspherical to transversely oval), the shorter forebody and smaller eggs in relation to body length. Macracetabulum n. g. differs from Neopsilotrema by the shape of the ventral sucker (elongate-oval vs subspherical to transversely oval), the anterior limits of vitellarium (level of middle of ventral sucker vs level of intestinal bifurcation or anterior testis); and the slightly smaller size of eggs in relation to body length. Among the psilostomid genera, Longisaccus n. g. shows close affinities to Psilochasmus Lühe, 1909 in the presence of the long cirrus-sac and tubular internal seminal vesicle but can be clearly distinguished from the latter by the absence of the retractile tail-like process. In combination with molecular data, the above differences justify the recognition of three new genera. A key to the genera of the Psilostomidae is provided.     

The Acanthocolpidae (Digenea) of fishes from the north-east Atlantic: the status of Neophasis Stafford, 1904 (Digenea) and a study of North Atlantic forms

The genus Neophasis is defined. The taxonomic status of the genus is discussed in the light of its life-cycle, hosts and cercarial and adult morphology. It is considered to be closest to the family Acanthocolpidae due to the utilisation of a fish second intermediate host, the form of the cercarial excretory system and, in the adult, the presence of a uterine seminal receptacle and the absence of an external seminal vesicle. The taxonomic value of morphological features are discussed and a key to the north Atlantic species given. The following species are described: Neophasis oculatus (Levinsen) from Myoxocephalus scorpius off West Greenland (type-material), Norway and Denmark, Lycodes esmarkii off NW Scotland and the Faroes, and L. vahli off Newfoundland; N. burti n. sp. (distinguished from N. oculatus by sucker-ratio and testicular configuration) from Myoxocephalus octodecemspinosus off Nova Scotia (type-locality) and New Brunswick, also? immature in Gadus morhua from the Gulf of St. Lawrence; N. anarrhichae (Nicoll) from Anarhichas lupus in the North Sea and off the Faroes; and N. pusilla Stafford from A. lupus off ‘eastern Canada’ (type-material) and Nova Scotia. The only other species in the genus is N. symmetrorchis Machida from the NW Pacific Ocean.     

Reevaluation of the systematic position of Scenella

Specimens originally illustrated from Lower Cambrian rocks of the Sierra Morena in Badajoz and Sevilla Provinces, southwestern Spain are supplemented by new material from another locality and are described as Scenella morenensis n. sp. Although Scenella was originally considered to be a patelliform gastropod, for three decades now the genus has been classified as a monoplacophoran. The type species of Scenella, S. reticulata Billings, does not show any paired muscles scars, nor does this new species; such scars are indicative of the Monoplacophora. This new species of Scenella does exhibit features which suggest assignment to the chondrophorine coelenterates. If so, Scenella cannot represent the ancestral form of mollusk.     

Monophyly and systematic position of Glypthelmins (Digenea), based on partial lsrDNA sequences and morphological evidence

Species composition and systematic placement within the order Plagiorchiida has been controversial. Species number in Glypthelmins Stafford, 1905, a genus of cosmopolitan parasites of anurans, has varied between 19 and 28 species, depending on the taxonomic treatment. The present study performs a phylogenetic analysis using partial lsrDNA sequences to test the monophyly of the genus, and compares new sequences obtained with those published for different plagiorchiids to clarify the systematic position of Glypthelmins within the order Plagiorchiida. Maximum parsimony (MP) and maximum likelihood (ML) analyses result in identical tree topology. The single MP tree (L=1587, CI=0.40, RI=0.76) includes several clades with high bootstrap and Bremer support values. Glypthelmins sensu lato as traditionally classified is paraphyletic. Based on molecular and/or morphological evidence, the taxonomic diagnosis for Glypthelmins is emended, only eight species are retained in the genus, and re-establishment of the genera Choledocystus Pereira & Cuocolo, 1941 and Rauschiella Babero, 1951 is proposed, resulting in the following new combinations: Choledocystus simulans (Teixeira de Freitas, 1941) comb. nov., C. vitellinophilum (Dobbin, 1958) comb. nov.; Rauschiella chaquensis (Mañé-Garzón & Holcman-Spector, 1967) comb. nov., R. lenti (Teixeira de Freitas, 1941) comb. nov., R. linguatula (Rudolphi, 1819) comb. nov., R. poncedeleoni (Razo-Mendivil & León-Règagnon, 2001) comb. nov., R. robusta (Brooks, 1976) comb. nov., R. rugocaudata (Yoshida, 1916) comb. nov., R. staffordi (Tubangui, 1928) comb. nov. In the phylogenetic reconstruction, Glypthelmins sensu stricto forms the sister group of Haematoloechus Looss, 1899.     

Two new blood flukes (Digenea: Sanguinicolidae) from Epinephelinae (Perciformes: Serranidae) of the Pacific Ocean

Pearsonellum pygmaeus n. sp. is described from Cromileptes altivelis (Serranidae), the Barramundi Cod, from Heron Island (southern Great Barrier Reef) and Lizard Island (northern Great Barrier Reef). This new species differs from Pearsonellum corventum (type and only species) in the combination of smaller overall body size, the relative distance of the brain from the anterior end, the relative lengths of both the oesophagus and the testis, the degree to which the testis extends outside the intercaecal field, the shape of the testis, the shape and size of the ovary and the extent to which the uterus loops around the ovary. There are in addition, 20 base pair differences between the ITS2 rDNA sequence of P. pygmaeus n. sp. and that of P. corventum. Three new host records for P. corventum are reported. Adelomyllos teenae n. g., n. sp. is described from Epinephelus coioides (Serranidae), the Estuary Cod, from Moreton Bay, southeast Queensland. The new genus differs from the 22 other sanguinicolid genera in the combined possession of two testes, a cirrus-sac, separate genital pores, a post-ovarian uterus and an H-shaped intestine. A. teenae n. sp. is the third sanguinicolid described from the Epinephelinae. Sanguinicolids have now been reported from 11 species of Serranidae.     

Differentiation of Mexican species of Haematoloechus looss, 1899 (Digenea: Plagiorchiformes): molecular and morphological evidence

Molecular evidence is interpreted in the light of morphology to examine the validity of several species of Haematoloechus described as Mexican endemics. Internal transcribed spacers 1 and 2 and 28S ribosomal genes were sequenced for 11 isolates. Phylogenetic analysis of separate partitions and combined databases was conducted. Results were analyzed, in the light of morphological evidence. Haematoloechus macrorchis is proposed as a junior synonym of Haematoloechus longiplexus. Haematoloechus pulcher is a sibling species with Haematoloechus complexus in Lerma wetlands. In Mexico, Haematoloechus medioplexus is distributed along the east coast coinciding with the distribution of Rana berlandieri. The sister species of H. medioplexus is Haematoloechus coloradensis, sharing the distribution of the uterus as a synapomorphic character. Haematoloechus illimis is more closely related to H. medioplexus and H. coloradensis than to H. complexus. It can be distinguished by the distribution of the uterus, lobed ovary, and testes.     

Renicola metacercariae (Digenea: Renicolidae) in clupeoid fish: new host records

Two distinct types of Renicola metacercariae were found in herring, Clupea harengus L., from Scottish waters, and one in anchovies, Engraulis encrasicholus (L.), from the central North Sea. Both constitute new host records. These parasites may prove to be of value as biological tags for herring and other clupeoid fish.     

鹅观草与大鹅观草杂种的细胞遗传学及形态学研究

大鹅观草（ Ｒｏｅｇｎｅｒｉａ ｇｒａｎｄｉｓ Ｋｅｎｇ） 是分布于我国陕西的一种多年生四倍体植物。为了探索大鹅观草与鹅观草（ Ｒｏｅｇｎｅｒｉａ ｋａｍｏｊｉ Ｏｈｗｉ） 间的物种生物学关系, 通过对其进行远缘杂交,幼胚离体培养, 合成了远缘杂种; 并对亲本及杂种Ｆ１ 代花粉母细胞减数分裂中期Ⅰ染色体配对行为及形态学进行了研究。结果表明杂种Ｆ１ 减数分裂染色体配对平均构型为： Ｒ－ ｋａｍｏｊｉ ×Ｒ－ｇｒａｎｄｉｓ１０－２６ Ⅰ＋ １２－３７ Ⅱ（ｃ－ 值＝ ０－７４） , 大鹅观草与鹅观草所含的ＳＹ 染色体组间存在较大的同源性分化; 杂种穗部特征大多数介于双亲之间。     

Molecular and morphological evidence for the Holarctic distribution of Urogonimus macrostomus (Rudolphi, 1803) Monticelli, 1888 (Digenea: Leucochloridiidae)

Species of Urogonimus Monticelli, 1888 (Leucochloridiidae Poche, 1907) are difficult to distinguish using adult morphology, and their taxonomy has been repeatedly subjected to revision. Some Nearctic species have been regarded as synonymous with the Palearctic type species Urogonimus macrostomus (Rudolphi, 1803) Monticelli, 1888. This implies that U. macrostomus is present in the Nearctic, but there is no additional evidence for this putative distribution. We collected trematodes morphologically indistinguishable from U. macrostomus from a house sparrow (Passer domesticus) in Edmonton, Alberta, Canada. Sequences 2958 bp in total length from the small and large subunits of ribosomal DNA from 2 specimens were 99.8-100% identical to those of U. macrostomus in the Ukraine and Japan. In light of the lack of morphological differences and small degree of genetic variation, we consider the specimens we collected to be conspecific with U. macrostomus in the Palearctic, and the Holarctic range of the species is thus supported. Sequences from a more rapidly evolving gene, cytochrome c oxidase 1, were obtained to aid future study of this and related species.     

Phylogenetic systematic evaluation of a classification of the Zoogonidae Odhner, 1902 (Cercomeria: Trematoda: Digenea: Plagiorchiiformes)

A recent systematic study of the digenean family Zoogonidae presented a series of cladograms, which are the product of phylogenetic systematic, or cladistic, analysis. However, one of the two subfamilies and nine of the 21 genera recognised in that study lacked putative synapomorphies, a requirement for phylogenetic systematic studies. This study presents a re-analysis of the database for the zoogonids, based on rigorous application of phylogenetic systematic methods. A new phylogenetic tree is presented, which better fits the original data than the published tree (with a consistency index of 52.3% vs. 46.3%). Four subfamilies, three monophyletic and one of uncertain status, and 10 genera could be recognised phylogenetically. This would affect the nomenclatorial status of one-third (26) of the species in the family. However, it is recommended that another analysis, based on more characters, be carried out before nomenclatorial changes are proposed.