Pristiorhynchus palmi n. g., n. sp. (Cestoda: Trypanorhyncha) from sawfishes (Pristidae) off Australia, with redescriptions and new records of six species of the Otobothrioidea Dollfus, 1942

Novelty and phylogenetic affinities of a new family of tapeworms (Cestoda: Rhinebothriidea) from endangered sawfish and guitarfish

The parasites of hosts of conservation concern are often poorly known. This is the case with the iconic group of elasmobranchs known as the sawfish of the genus Pristis, all four species of which are considered as Endangered or Critically Endangered by the International Union for Conservation of Nature (IUCN, Switzerland). Examination of cestodes from three species of sawfish (Pristis pristis, Pristis clavata, and Pristis zijsron) in Australia and one of their close relatives, the also critically endangered widenose guitarfish, Glaucostegus obtusus, in India collected over the past 25 years yielded four new species of tapeworms which are described herein. All four belong to the previously monotypic Mixobothrium; the diagnosis of the genus is revised to accommodate the new species. Among the new taxa is a species that had been included in previous molecular phylogenies but whose identity and affinities within the order Rhinebothriidea and thus also its familial placement were unclear. This species exhibits the morphological features of Mixobothrium and thus its identity is, at long last, revealed. Sequence data generated for the 28S rDNA gene for three of the new species, as well as an additional new but yet undescribed species from Pristis pectinata from Florida (USA), confirms the uniqueness of this group among the rhinebothriideans. The new family Mixobothriidae is established to house these taxa. The members of this family differ from all but one of the five other families of rhinebothriideans in lacking apical suckers on their bothridia. They are also distinctive in that their bothridia are divided into three distinct regions. The anterior and posterior regions have similar locular configurations to one another and differ from the locular configuration of the middle region. As a consequence, the bothridia are symmetrical along both their vertical and horizontal axes. We predict that a focus on species of guitarfish in the genus Glaucostegus will be the most productive approach for discovering additional diversity in this family of cestodes.

A new genus and species of fish blood fluke, Achorovermis testisinuosus gen. et sp. n. (Digenea: Aporocotylidae), infecting critically endangered smalltooth sawfish, Pristis pectinata (Rhinopristiformes: Pristidae) in the Gulf of Mexico

Achorovermis testisinuosus gen. et sp. n. (Digenea: Aporocotylidae) infects the heart of the smalltooth sawfish, Pristis pectinata Latham (Rhinopristiformes: Pristidae), in the eastern Gulf of Mexico. Specimens of the new genus, along with the other blood flukes that infect batoids are similar by having an inverse U-shaped intestine and a curving testis as well as by lacking tegumental spines. The new genus differs from all of the other blood flukes infecting batoids by having an elongate body (>50 × longer than wide), a testis having >100 curves, and an ovary wholly anterior to the uterus. It differs from Ogawaia glaucostegi Cutmore, Cribb et Yong, 2018, the only other blood fluke infecting a rhinopristiform, by having a body that is >50 × (vs <30 ×) longer than wide, a testis that is >75 × (vs <40 ×) longer than wide and has >100 (vs <70) curves, an ovary wholly anterior to (vs lateral and dorsal to) the seminal vesicle, a uterus wholly posterior to (vs overlapping and lateral to both) the testis and ovary, and a sinuous (vs convoluted) uterus. The new species joins a small group of chondrichthyan blood flukes that lack tegumental spines: O. glaucostegi, Orchispirium heterovitellatum Madhavi et Rao, 1970, Myliobaticola richardheardi Bullard et Jensen, 2008, Electrovermis zappum Warren et Bullard, 2019. Blood flukes infecting batoids are further unique by having a curving testis. That is, the blood flukes infecting species within Selachii are morphologically distinct from those infecting species within the Batoidea (excluding Gymnurahemecus bulbosus Warren et Bullard, 2019). Based on the morphological similarity, we suspect that the new species shares a recent common ancestor with O. glaucostegi. The discovery of the new species brings the total number of chondrichthyan blood flukes to 11 species assigned to nine genera.

A new genus and two new species of trypanorhynch cestodes (Tentaculariidae) from the sharksCarcharhinus sorrah(Müller & Henle) andSphyrna lewini(Griffith & Smith) from off the coasts of Malaysia and Mexico

Two new tentaculariid species were found infecting carcharhiniform sharks from off the coasts of Malaysian Borneo and the southwestern coast of the Baja California Sur, Mexico. Both new species exhibit a homeoacanthous heteromorphous basal and a homeoacanthous homeomorphous metabasal armature. Since this hook arrangement is unique within the tentaculariids and the taxonomy in this group deeply depends on the tentacular armature, Reimeriella n. g. is erected to accommodate R. varioacantha n. sp. ex Carcharhinus sorrah (Müller & Henle) and R. mexicoensis n. sp. ex Sphyrna lewini (Griffith & Smith). Unlike R. mexicoensis n. sp., R. varioacantha n. sp. has a pars bothrialis not overlapping the pars bulbosa and the number of testes is higher. Reimeriella mexicoensis n. sp. possesses very large uncinate to falcate hooks in the basal armature, while in R. varioacantha n. sp. these hooks are almost the same in size as the remaining hooks in both the basal and metabasal armature. The latter species is the first tentaculariid species where the metabasal armature very closely resembles an eutetrarhynchid with a heteroacanthous typical homeomorphous metabasal armature and a high number of spiniform hooks per half spiral row (10-11 vs 6-7 in R. mexicoensis n. sp.) in the metabasal and apical armature. This pattern provides further morphological evidence for the close relationship of the Eutetrarhynchoidea and the Tentacularioidea. Reimeriella varioacantha n. sp. enriches the trypanorhynch fauna from off the coast of Malaysian Borneo while R. mexicoensis n. sp. is a novel record of a tentaculariid trypanorhynch from the Mexican Pacific.

A new genus and species of the trypanorhynch family Otobothriidae Dollfus, 1942 from the slender weasel shark Paragaleus randalli Compagno, Krupp & Carpenter (Hemigaleidae) in the Persian Gulf

A survey on the cestode fauna of Paragaleus randalli Compagno, Krupp & Carpenter in the Persian Gulf resulted in the discovery of a new trypanorhynch species of the family Otobothriidae Dollfus, 1942, the second otobothrioid species hosted by the family Hemigaleidae Hasse. The new species exhibits the closest morphological similarity to Pristiorhynchus palmi Schaeffner & Beveridge, 2013, the type- and only species of its genus. However, the new species differs from P. palmi in the position of the bothrial pits, the morphology and oncotaxy of the basal armature, the commencement of the hook files on the internal surface, a wider scolex peduncle in the pars bulbosa than in the pars vaginalis, a long neck and the presence of a lateral bothrial groove connecting the two bothrial pits to each other. The latter character is a unique trait within the Otobothrioidea Dollfus, 1942. Considering such differences, a new genus, Olgaella n. g., was erected to accommodate O. elenae n. g., n. sp. within the Otobothriidae. The evolutionary relatedness of the bothrial pits of the Otobothrioidea and the bothrial grooves of the Lacistorhynchoidea Guiart, 1927 is discussed.