Two new American species of Aberrapex (Eucestoda: Lecanicephalidea: Aberrapecidae) from myliobatid stingrays (Batoidea: Myliobatidae)

Here I describe Aberrapex panamensis sp. nov., a parasite of the rough eagle ray Aetomylaeus asperrimus from the eastern Pacific coast of Panama, and Aberrapex catarinensis sp. nov., found in Myliobatis goodei off southern coast of Santa Catarina, Brazil. Aberrapex panamensis sp. nov. is the second record of Aberrapex Jensen, 2001 for the eastern Pacific Ocean and A. catarinensis sp. nov. is the fifth species of the genus registered in southwestern Atlantic Ocean. The two new species are morphologically distinct from all their congeners. Aberrapex panamensis sp. nov. and A. catarinensis sp. nov. can be distinguished from the majority of their congeners by the microthrix pattern on the scolex surface, number of proglottids and testes, length and width of the scolex, uterus extension, and presence and extension of an external seminal vesicle. The description of these two new species of lecanicephalideans expands the knowledge of this cestode order, with A. panamensis sp. nov. being the third species of the genus reported from Aetomylaeus Garman, and A. catarinensis sp. nov. being the sixth species of Aberrapex reported from Myliobatis Cuvier.

Tapeworms (Platyhelminthes, Cestoda) from marine chondrichthyans of the Southwestern Atlantic Ocean, and the sub-Antarctic and Antarctic islands: a checklist

A parasite-host list of cestodes parasitizing chondrichthyans in the Southwest Atlantic off Argentina and surrounding waters of Antarctica is compiled based on the available literature. The list is based on published descriptions and redescriptions of species, and newly collected worms during the current study. A total of 57 valid species belonging to 28 genera of the orders Cathetocephalidea, Diphyllidea, Gyrocotylidea, Lecanicephalidea, Onchoproteocephalidea, Phyllobothriidea, Rhinebothriidea, "Tetraphyllidea", and Trypanorhyncha is listed. Information on hosts, localities, specimens in collections and comments on tapeworms are also included. A host-parasite list including chimaeras (1 order, 1 genus), batoids (4 orders, 10 genera), and sharks (3 orders, 5 genera) is provided. Tapeworm diversity, distribution range, and host associations are discussed. The cestodes orders Phyllobothriidea and Rhinebothriidea exhibit the highest species richness, with 13 and 12 species, respectively. Onchoproteocephalideans and rhinebothriideans have the broadest geographic distribution in the study area. Regarding hosts, arhynchobatid skates are the group most frequently associated with cestodes. However, further collecting efforts are necessary to understand whether this data reflect the real diversity and host association of these parasites or is a result of a bias in sampling.

Eutetrarhynchus pacificus n. sp. (Cestoda: Trypanorhyncha) from Raja inornata Jordan & Gilbert (Batoidea: Rajiformes) off the coast of California with comments on congeners

Eutetrarhynchus pacificus n. sp. is described from the spiral valve of Raja inornata Jordan & Gilbert off the coast of California, USA. The new species is distinguished from E. ruficollis (Eysenhardt, 1829) and E. leucomelanus (Shipley & Hornell, 1906) in having acraspedote rather than craspedote segments and a saccate rather than a branched uterus. It is distinguished from E. platycephali Palm, 2004 in lacking an enlarged hook in the eighth row of the basal armature and from E. beveridgei Schaeffner, 2013, which has a basal swelling and a distinctive basal armature. A partial redescription of E. ruficollis, the type-species of the genus, is provided based on available museum specimens, highlighting the need for a comprehensive redescription of this species to better define the characteristics of the genus. The presence of an undescribed species in museum collections is also noted. Based on the 28S ribosomal gene, the new species clustered with Dollfusiella in a molecular phylogenetic tree. The delimitation of Eutetrarhynchus and its relationship with Dollfusiella is discussed.

A new species of Dollfusiella Campbell & Beveridge, 1994 (Cestoda: Eutetrarhynchidae), with remarks on Halysiorhynchus macrocephalus (Shipley & Hornell, 1906) (Cestoda: Mixodigmatidae) from the bowmouth guitarfish Rhina ancylostoma Bloch & Schneider (Rhinidae) in the Persian Gulf

Dollfusiella nimai n. sp. (Cestoda: Eutetrarhynchidae) is described from the intestine of Rhina ancylostoma Bloch & Schneider in the Persian Gulf. The number of the hooks per half spiral row in the metabasal tentacular armature distinguishes the new species from its congeners, except for D. vooremi (São Clemente & Gomes, 1989) possessing approximately the same number of hooks per half spiral row. While the principle hooks 1(1')-21(21') were homeomorphous in the metabasal armature of D. nimai n. sp., the billhooks on the antibothrial surface and the uncinate hooks on the bothrial surface were the principle hooks 1(1')-16(16') in the metabasal armature of D. vooremi. Dollfusiella nimai n. sp. most closely resembles D. michiae (Southwell, 1929) in the tentacular armature as well as the morphology of the scolex and strobila but differs clearly in the number of the hooks per half spiral row in the metabasal tentacular armature (25-26 vs 16 respectively). A detailed examination of the specimens of Halysiorhynchus macrocephalus (Shipley & Hornell, 1906) (Cestoda: Mixodigmatidae) ex R. ancylostoma from the Persian Gulf revealed intraspecific variability including the number of the principle hooks per half spiral row in the metabasal armature, the number of the hook rows in the basal armature, and the size of the basal hooks.

Integrative taxonomy unravels the species diversity of Parachristianella (Cestoda : Trypanorhyncha) from both sides of the Panamanian isthmus

The uplift of the Panamanian isthmus in the Pliocene caused the termination of gene flow among members of many ancestral populations of marine lineages leading the diversification of geminate species confined to opposite sides of Central America. This palaeogeographical event has been evoked to explain the diversification of few lineages of batoids with trans-isthmian distribution. As such, there is the expectation that this vicariance event also affected lineages of parasites associated with them. Our study suggests that this event can explain the diversification of Parachristianella Dollfus, 1946 (Trypanorhyncha:Eutetrarhynchidae) in the Caribbean Sea and tropical eastern Pacific Ocean. We provide molecular, morphological and biogeographical evidence to recognise five lineages within this genus inhabiting the coastal waters of Panama, including P. parva Campbell & Beveridge, 2007 and four new species: P. mendozai, sp. nov., P. kuchtai, sp. nov., P. campbelli, sp. nov. and P. soldanovae, sp. nov. These species can be diagnosed by unambiguous sets of molecular characters. The morphological cohesiveness of sister species, which most likely diverged from around 3million years ago through the uplift of the Panamanian isthmus, suggests that the traditional emphasis on the tentacular armature to circumscribe species within trypanorhynchs might underestimate the diversity of recently diverged lineages.

New species of Aberrapex Jensen, 2001 (Cestoda: Lecanicephalidea) from eagle rays of the genus Myliobatis Cuvier (Myliobatiformes: Myliobatidae) from off Argentina

Three new species of Aberrapex Jensen, 2001 (Cestoda: Lecanicephalidea) have been collected from species of Myliobatis Cuvier along the coast of Argentina. Aberrapex ludmilae sp. n. parasitises M. goodei Garman in the San Matías Gulf. This species is unique in a combination of features including the shape and extent of the uterus, scolex size, testis distribution, and by lacking an external seminal vesicle and postovarian vitelline follicles. Aberrapex sanmartini sp. n. from M. goodei in San Blas Bay and A. vitalemuttiorum sp. n. from M. ridens Ruocco, Lucifora, Díaz de Astarloa, Mabragaña et Delpiani in coastal waters off Buenos Aires Province, are distinguished from all other congeners by the microthrix pattern on the scolex surface, uterus shape and extension, position of the connection of the uterine duct to the uterus, presence and extension of an external seminal vesicle, and its overall size and number of proglottids. The specimens of M. goodei and M. ridens show locally distinct cestode faunas, which are correlated with well-defined biogeographic regions. Some of these areas correspond with mating and nursery zones for species of Myliobatis.

Annotated checklist of fish cestodes from South America

An exhaustive literature search supplemented by a critical examination of records made it possible to present an annotated checklist of tapeworms (Cestoda) that, as adults or larvae (metacestodes), parasitize freshwater, brackish water and marine fishes, i.e. cartilaginous and bony fishes, in South America. The current knowledge of their species diversity, host associations and geographical distribution is reviewed. Taxonomic problems are discussed based on a critical evaluation of the literature and information on DNA sequences of individual taxa is provided to facilitate future taxonomic and phylogenetic studies. As expected, the current knowledge is quite uneven regarding the number of taxa and host-associations reported from the principal river basins and marine ecoregions. These differences may not only reflect the actual cestode richness but may also be due to the research effort that has been devoted to unravelling the diversity of these endoparasitic helminths in individual countries. A total of 297 valid species, 61 taxa identified to the generic level, in addition to unidentified cestodes, were recorded from 401 species of fish hosts. Among the recognized cestode orders, 13 have been recorded in South America, with the Onchoproteocephalidea displaying the highest species richness, representing c. 50% of all species diversity. The majority of records include teleost fish hosts (79%) that harbour larval and adult stages of cestodes, whereas stingrays (Myliobatiformes) exhibit the highest proportion of records (39%) among the elasmobranch hosts. Fish cestodes are ubiquitous in South America, being mostly recorded from the Warm Temperate Southeastern Pacific (WTSP; 31%) for marine hosts and the Amazon River basin (45%) for freshwater ones. The following problems were detected during the compilation of literary data: (i) unreliability of many records; (ii) poor taxonomic resolution, i.e. identification made only to the genus or even family level; (iii) doubtful host identification; and (iv) the absence of voucher specimens that would enable us to verify identification. It is thus strongly recommended to always deposit representative specimens in any type of studies, including faunal surveys and ecological studies. An analysis of the proportion of three basic types of studies, i.e. surveys, taxonomic and ecological papers, has shown a considerable increase of ecological studies over the last decade.

Surface ultrastructure and the mitochondrial gene rrnl of Parachristianella indonesiensis Palm, 2004 (Trypanorhyncha: Eutetrarhynchidae) with the amended generic diagnosis

The microthrix pattern of adult Parachristianella indonesiensis Palm, 2004 is described for the first time based on the standardized terminology for microtriches, and the generic diagnosis of Parachristianella Dollfus, 1946, regarding microtriches, is also amended. The surface ultrastructure of P. indonesiensis consists of three kinds of microtriches so that the proximal and distal bothrial surfaces are covered respectively with acicular to short capilliform filitriches and aristate gladiate spinitriches interspersed with capilliform filitriches. The remainder of the scolex bears capilliform filitriches. The surface of the proglottid is adorned with acicular filitriches. There was no significant difference in the length of the capilliform filitriches covering the different parts of the scolex peduncle. For the first time, the uniciliated papillae adorned with filitriches as sensory receptors are reported from this parasitic species. The partial rrnl of P. indonesiensis is also presented as the only known sequence of this gene in the superfamily Eutetrarhynchoidea Dollfus, 1969. The pairwise comparisons of rrnl between P. indonesiensis and the trypanorhynch species for which rrnl sequence is available were in accordance with the last phylogeny presented for the order Trypanorhyncha. The infection parameters (prevalence, mean abundance, and mean intensity) of P. indonesiensis parasitizing Pastinachus sephen (Forsskål) from the eastern Persian Gulf were also compared during approximately 5 years, and no significant differences were observed. This may be interpreted as the stability of the factors playing important roles in the life cycle of P. indonesiensis in the eastern Persian Gulf during this period.

Dollfusiella qeshmiensis n. sp. (Cestoda: Trypanorhyncha) from the cowtail stingray Pastinachus sephen (Forsskål) in the Persian Gulf, with a key to the species of Dollfusiella Campbell & Beveridge, 1994

A new species of the genus Dollfusiella Campbell & Beveridge, 1994 is described from Pastinachus sephen (Forsskål) in the Persian Gulf. Dollfusiella qeshmiensis n. sp. is allocated to the genus Dollfusiella based on the possession of two bothria, prebulbar organs, a heteroacanthous typical armature with tightly spaced rows of hollow hooks, a basal swelling and a characteristic basal armature without prominent macrohooks. The presence of an enlarged external seminal vesicle in Dollfusiella qeshmiensis n. sp. distinguishes this species from D. michiae (Southwell, 1929), D. bareldsi (Beveridge, 1990), D. owensi (Beveridge, 1990), D. geraschmidti (Dollfus, 1974), D. angustiformis Schaeffner & Beveridge, 2013, D. hemispinosa Schaeffner & Beveridge, 2013, D. spinosa Schaeffner & Beveridge, 2013 and D. taminii Menoret & Ivanov, 2014. The new species is distinguished from the remaining species within the genus by a combination of the following morphological features: the number of testes per segment, the number of testis columns and the number of homeomorphous hooks per half spiral row in the metabasal region. In the most recent taxonomic key to the species of Dollfusiella, the presence or absence of enlarged, microscopically visible spinitriches on the scolex was used as the first distinguishing character dividing the congeners into two groups. Since the existence of visible microtriches on the scolex peduncle of D. vooremi (São Clemente & Gomes, 1989), a species so far grouped among the species lacking visible microtriches on the scolex, has been recently demonstrated, and given the fact that the presence of microscopically visible microtriches on the scolex is variable in some eutetrarhynchid species, a new key to the species of Dollfusiella is provided in which the spinitriches have been given less priority.

Trypanorhynch cestodes (Eutetrarhynchidae) from batoids along the coast of Argentina, including the description of new species in Dollfusiella Campbell et Beveridge, 1994 and Mecistobothrium Heinz et Dailey, 1974

During a recent parasitological survey of elasmobranchs along the coast of Argentina, two new species of eutetrarhynchid cestodes of the genera Dollfusiella Campbell et Beveridge, 1994 and Mecistobothrium Heinz et Dailey, 1974 were collected from batoids. Dollfusiella acuta sp. n. was found in four arhynchobatid skates, i.e. Sympterygia acuta Garman (type host), Sympterygia bonapartii Müller et Henle, Atlantoraja castelnaui (Miranda Ribeiro) and Atlantoraja platana (Günther), and Mecistobothrium oblongum sp. n. in the eagle ray Myliobatis goodei Garman. Dollfusiella acuta sp. n. has a tentacular armature consisting of basal rows of uncinate hooks, a distinct basal swelling with uncinate, falcate and bill hooks, and a heteroacanthous metabasal armature with heteromorphous hooks (bothrial uncinate hooks and antibothrial falcate hooks), hooks 1(1') not separated, testes in two columns and an internal seminal vesicle. The tentacular armature of M. oblongum sp. n. is characterised by basal rows of uncinate hooks, a basal swelling with uncinate and falcate hooks, a typical heteroacanthous metabasal armature with heteromorphous hooks (uncinate and falcate to spiniform), and hooks 1(1') separated and of a constant size along the tentacle. It also possesses an elongate scolex, numerous testes arranged in 5-6 irregular columns, and an internal seminal vesicle. The discovery of M. oblongum in M. goodei represents the first record of species of Mecistobothrium in the southwestern Atlantic Ocean. An amended description of Dollfusiella cortezensis (Friggens et Duszynski, 2005) is also provided to clarify details of the scolex and tentacular armature. Members of Dollfusiella in the southwestern Atlantic are specific to a single host species or to a particular host family, while M. oblongum was found in a single host species. Although globally some plerocerci of eutetrarhynchids have been found in teleosts, extensive examination of teleosts off the coast of Argentina suggests that the transmission pathways of these species are exclusively based on invertebrates as intermediate or paratenic hosts.