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)

Abstract

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.

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

“…Many of them have been assigned to the genus Acanthobothrium , which currently is represented world-wide by 213 nominal species. Of these, 25 have been recently described: 13 from the Atlantic ( Franzese and Ivanov 2018 , 2020 ; Rodríguez-Ibarra et al 2018 ; Van Der Spuy et al 2020 ; Van Der Spuy et al 2022 ; this study), six from the Persian Gulf, Gulf of Oman, and Indic Ocean ( Maleki et al 2018 , 2019 ), and six from the Pacific Ocean ( Zaragoza-Tapia et al 2019 , 2020b ; Gallagher and Caira 2020 ). Table 2 includes the most recently-described species as a complement to the information presented by Zaragoza-Tapia et al (2020a) .…”

“…Its members principally parasitize batoids and sharks ( Caira and Jensen 2017 ). Recent descriptions include 23 species, eleven from the greater Atlantic Ocean ( Franzese and Ivanov 2018 ; Rodríguez-Ibarra et al 2018 ; Franzese and Ivanov 2020 ; Van Der Spuy et al 2020 , 2022 ), six from the Persian Gulf and Gulf of Oman in the northwest Indian Ocean ( Maleki et al 2018 , 2019 ) and six from the Pacific Ocean ( Zaragoza-Tapia et al 2019 , 2020b ; Gallagher and Caira 2020 ). Of the 211 species, 17 species have been described from Mexican waters and three species known from other localities have been reported off México.…”

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

“…Cestodes as parasites of chondrichthyans have been mostly recorded in the Northern Hemisphere ( Caira et al 2022 ). However, reports in southern latitudes have remarkably increased in the last decades due to focused sampling efforts in the area ( Menoret and Ivanov 2012a , b , 2014 , 2015 , 2021 ; Pickering and Caira 2012 ; Caira et al 2013a ; Abbott and Caira 2014 ; Mutti and Ivanov 2016 ; Menoret et al 2017 ; Franzese and Ivanov 2018 , 2020a , b , 2021 ; Palm et al 2019 ; Oosthuizen et al 2021 ; Franzese et al 2022 ; Van Der Spuy et al 2022 ). The present annotated checklist comprises 57 valid cestode species of 28 genera in nine orders, registered in the Río de la Plata estuary, Southwestern Atlantic off Argentina and the surrounding waters off Antarctica.…”

Fish tapeworms (Cestoda) in the molecular era: achievements, gaps and prospects

“…Onchoproteocephalidea II of Caira and Jensen (2017) consists of hooked cestodes parasitizing rays and sharks. They encompass the most species-rich genus of elasmobranch tapeworms Acanthobothrium with 211 valid species (Caira et al ., 2022; Van der Spuy et al ., 2022), including 11 species described from giant freshwater whipray in Borneo and potamotrygonid stingrays in South America (Fyler and Caira, 2006; Caira et al ., 2022). Moreover, all 7 species of Potamotrygonocestus with unique acetabula and unipronged hooks are specific parasites of potamotrygonid stingrays in South America (Marques et al ., 2003) and may represent elasmobranch tapeworms most closely related to proteocephalideans (Caira et al ., 2017 e ).…”