Two new species of Acanthobothrium Blanchard, 1848 (Cestoda: Onchoproteocephalidea) from rajiform batoids off Argentina

Two new species of Acanthobothrium Blanchard, 1848 (Cestoda, Onchoproteocephalidea) from Urobatisjamaicensis (Cuvier, 1816) (Elasmobranchii, Batoidea, Myliobatiformes) of the Mexican Caribbean

Eight specimens of Urobatisjamaicensis were collected from four localities of the Yucatan Peninsula, Mexico, of which four specimens were infected with cestodes of two new species of Acanthobothrium. Acanthobothriumgarciaprietoisp. nov. differs from congeners by a combination of characters including the size of the scolex and bothridia, length of the cephalic peduncle, length of the axial and abaxial prongs and total length of the abaxial prongs of the hooks, size of the cirrus sac and testes in mature proglottids, and the total number of proglottids. The most prominent characteristic distinguishing A.pulidofloresaesp. nov. from other species of the Atlantic Ocean/Caribbean Sea/Gulf of Mexico is the form of the scolex, which has the "clover leaf" configuration. In addition, it can be distinguished by the total length of the worm, total number of proglottids, small accessory suckers, the form of the bothridia, length of the axial and abaxial prongs and total abaxial prong length of hooks, and the number of testes. According to the current category scheme, A.garciaprietoisp. nov. and A.pulidofloresaesp. nov., belong to categories 1 and 5, respectively.

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.

Threatened, host-specific affiliates of a red-listed host: Three new species of Acanthobothrium van Beneden, 1849 (Cestoda: Onchoproteocephalidea) from the endangered white skate, Rostroraja alba (Lacépède)

The white skate, Rostroraja alba (Lacépède), is listed as an endangered species, the second-highest category before being declared extinct in the wild, in the International Union for Conservation of Nature's (IUCN) Red List of Threatened Species. This species is heavily affected by anthropogenic impacts such as capture induced stress by overfishing and by-catch, habitat degradation and pollution that caused a drastic decline in populations in recent years. As part of a larger study on elasmobranch affiliates in southern Africa, two specimens of R. alba were screened. Three species of the tapeworm genus Acanthobothrium van Beneden, 1849 (Cestoda: Onchoproteocephalidea) were discovered. Application of Ghoshroy and Caira's classification system facilitated the differentiation of congeners through a combination of specific morphological characteristics. As a consequence, three species new to science are described herein, namely Acanthobothrium umbungus n. sp., Acanthobothrium usengozinius n. sp., and Acanthobothrium ulondolozus n. sp. In light of these new discoveries from an endangered host, it is apparent to address the conservation status of its affiliate species, that co-evolved with their elasmobranch hosts for millions of years, thereby creating unique and intimate host-parasite interrelationships. Currently, altering environmental conditions caused by anthropogenic pressures have direct impacts on this host-parasite system with increasing risks of extinction. As merely 9% of elasmobranchs in South African waters have been examined for endohelminths and other affiliate taxa, extensive studies on these organisms and their hosts implementing multisource approaches are needed. This will provide a better understanding on the intimate nature of host-parasite systems that may lead to new prospects in conservation science and the preservation of threatened host species, such as R. alba, together with their unique fauna of affiliate species.

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Three new species of Acanthobothrium were discovered in the endangered white skate, Rostroraja alba, off the coast of South Africa.

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The three species described (A. umbungus n. sp., A. usengozinius n. sp., and A. ulondolozus n. sp.) display merely a single cestode genus among the hidden diversity of species from elasmobranchs.

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The current increase in threatened free-living host species results in an even greater loss in affiliate species that remain unknown and scientifically underexplored.

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Assessing the status and incorporating affiliate species (i.e. cestodes) into novel conservation schemes may contribute to the conservation of threatened host species and marine populations worldwide, which, in turn, will protect affiliate species as vital “key players” for host species and entire ecosystems.

Morphological updates, host-specificity, molecular data and phylogenetic analysis of Acanthobothrium coronatum (Cestoda: Onchoproteocephalidea), a neglected parasite of the nursehound Scyliorhinus stellaris

Acanthobothrium is the most speciose genus of onchoproteocephalidean cestodes, whose adults parasitize the intestine of elasmobranch fishes. Acanthobothrium coronatum, the type species of the genus described from Mediterranean elasmobranchs, remains a little known parasite, with the most recent reports dating back to the fifties. We hereby investigate host-specificity and redescribe A. coronatum from the same locality of its original description by using light and scanning electron microscopy approaches. Moreover, molecular and phylogenetic data inferred from the analysis of the 28S rDNA gene are reported for the first time. Out of the nine elasmobranch species examined from Gulf of Naples, we only detected A. coronatum in the intestine of Scyliorhinus stellaris, with infection patterns that supports evident host-specificity for this shark species. The genetic characterization of 28S rDNA showed 99.8-100% similarity with larvae previously found in Octopus vulgaris from the same area investigated here. Conspecificity between the present material and the larvae found in the octopus was also confirmed by the tree topology. The host-parasite phylogeny is discussed, even if additional molecular data are needed to clarify potential host-parasite patterns. Notwithstanding this limitation, this is the first molecular study revealing conspecificity between an adult Acanthobothrium species from a shark and the larvae found in an intermediate/paratenic host, shedding light on the transmission pathway of A. coronatum in S. stellaris. Finally, the taxonomic, molecular, and phylogenetic data presented here allow a better characterization of a neglected parasite.

Four new species of Acanthobothrium van Beneden, 1849 (Cestoda: Onchoproteocephalidea) from the spotted skate, Raja straeleni Poll, off the Western Cape, South Africa

The examination of eight spotted skates, Raja straeleni Poll, resulted in the discovery of four new species of Acanthobothrium van Beneden, 1849, namely A. microhabentes sp. n., A. microtenuis sp. n., A. crassus sp. n., and A. dolichocollum sp. n., located off the Western Cape of South Africa. With a total of over 200 valid species of Acanthobothrium recognised worldwide, the use of an integrative approach becomes imperative in the interest of simplifying interspecific comparisons between congeners. In accordance with this, the four new species were incorporated into the category classification system established by Ghoshroy and Caira in 2001, where they were identified as category 2 species, which, at present, includes 47 recognised species of Acanthobothrium. Nevertheless, each of the four new species exhibits postovarian testes, a most intriguing and highly unusual feature among Acanthobothrium, instantly differentiating them from most congeners. This feature has been reported in 12 congeners, which have previously been considered to be restricted to waters of the Indo-Pacific Ocean. Not only do the four new congeners represent the first species of Acanthobothrium reported from southern Africa, but they also represent the first reported species with postovarian testes from the southern Atlantic Ocean. Regarding the legitimacy of the four new species, only two other category 2 species are reported to exhibit this feature, namely A. popi Fyler, Caira et Jensen, 2009, and A. bobconniorum Fyler et Caira, 2010, to which the four congeners were compared to. Acanthobothrium microhabentes sp. n. is the smallest of the congeners and differs from A. popi and A. bobconniorum by having fewer testes and postovarian testes, a shorter body, fewer proglottids, a shorter scolex, and longer cephalic peduncle. Acanthobothrium microtenuis sp. n. differs from A. popi and A. bobconniorum by having fewer testes and postovarian testes, a shorter scolex, longer cephalic peduncle, and the possession of columnar spinitriches on the anterior region of the terminal proglottid. Acanthobothrium crassus sp.n. differs from A. popi and A. bobconniorum by having fewer postovarian testes, a narrower cirrus-sac, larger vitelline follicles, and a longer cephalic peduncle. Acanthobothrium dolichocollum sp. n. is the longest of the four new species and differs from A. popi and A. bobconniorum by having fewer postovarian testes, more postporal testes, a larger body, more proglottids, larger testes and vitelline follicles, and an exceptionally long cephalic peduncle. Apart from differences in overall size, the four new species differ in a combination of measurements for the scolex, vitelline follicles, muscular pad and cephalic peduncle, and the number of proglottids and testes. The four species were recovered from a previously unexplored host and locality, expanding the host associations and geographical distribution of the genus.