Two New Cestode Species from the Dwarf Whipray, Himantura walga (Batoidea: Dasyatidae), from Borneo, with Comments on Site and Mode of Attachment

Abstract

Spiral intestines of 12 specimens of the dwarf whipray, Himantura walga, collected from Malaysian Borneo in 2002 and 2003, were examined for cestodes. These yielded a new species of Acanthobothrium (Tetraphyllidea) and a new species of Echinobothrium (Diphyllidea), both of which are described. Acanthobothrium marymichaelorum n. sp. is a category 1 species. It differs from all but 4 of its category 1 congeners in its possession of postovarian testes. It also differs from these 4 species in its possession of fewer testes, shorter length, fewer proglottids, and/or shorter posterior loculus. Echinobothrium minutamicum n. sp. differs from its congeners in its possession of outer hooks in the dorsal and ventral rostellar groups that are trifid; it is also the smallest member of its genus. The spiral intestine of H. walga consisted of 12 mucosal chambers. Most (89%) of the 35 specimens of E. minutamicum n. sp. for which chamber data were generated were found in chambers 2-4. In contrast, the 57 specimens of A. marymichaelorum n. sp. occurred throughout chambers 5-12, with 86% in chambers 6-10. The modes of attachment of both cestode species were similar, i.e., both embedded their scolex within the lumen of a mucosal crypt with the hooks and/or spines penetrating the lamina propria. Both also eroded the epithelial lining of the crypts and caused modest expansion of crypt diameter. Although the configuration of the mucosal surface may explain sites in which both species were able to attach, it does not explain their absence from other regions; histological sections and scanning electron microscopy showed the mucosal surface to be similar in configuration throughout the length of the spiral intestine. The cestode fauna of H. walga also included at least 1 species of rhinebothriine, 2 lecanicephalidean species, a trypanorhynch species, and 1-2 additional new species of Acanthobothrium. However, formal description of these species must await the collection of additional material, mature material, and/or the erection of the new genera. It is of note that the fauna of the dwarf whipray consists of a suite of unusually small taxa. Although the cestode genera reported here are generally consistent with those reported from other Himantura species, they are completely inconsistent with previous records from H. walga (as Trygon walga) in Sri Lanka. This suggests that either the original host identifications are suspect or that differences exist in the faunas of H. walga between these 2 localities.

A new genus of rhinebothriidean cestodes from batoid elasmobranchs, with the description of five new species and two new combinations

“…The present study contributes to a growing body of knowledge of elasmobranch cestodes by reporting on species of Rhinebothriinae New genus 3 from 17 species of elasmobranchs, nearly all of which have been reported as hosts for other cestode genera and species (see Euzet 1954, Butler 1987, Reyda and Caira 2006, Twohig et al 2008, Ivanov and Caira 2012, Schaeffner and Beveridge 2012, Mojica et al 2013, Cielocha et al 2014, Jensen and Russell 2014, Ruhnke et al 2015. Most such reports are fairly recent and were the result of the same survey efforts that made the present study possible.…”

Five new species of Acanthobothrium (Cestoda: Tetraphyllidea) from an unusual species of Himantura (Rajiformes: Dasyatidae) from northern Australia

“…All 10 of these are found only in hosts from Indo-Pacific waters. To date, seven (i.e., A. cannoni, A. foulki, A. larsoni, A. marymichaelorum, A. saliki, A. popi, and A. zimmeri) are restricted to hosts of the genus Himantura (see Campbell and Beveridge 2002, Fyler and Caira 2006, Reyda and Caira 2006, Twohig et al 2008 and the present paper). Thus, we predict that the Indo-Pacific species of Himantura that remain to be examined for cestodes are very likely to yield additional species of Acanthobothrium exhibiting post-ovarian testes.…”

“…n. is a category 1 species according to the categories of Acanthobothrium species determined by Ghoshroy and Caira (2001) (i.e., <15 mm in total length, <50 proglottids, <80 testes, with symmetrical ovary). At this point, 30 category 1 species are recognized (i.e., the 4 species described by Reyda and Caira [2006] and the 25 listed in their table 2, and A. marymichaelorum Twohig, Caira et Fyler, 2008). Acanthobothrium oceanharvestae conspicuously differs from A. foulki Reyda et Caira, 2006, A. larsoni Reyda et Caira, 2006, A. marymichaelorum, A. saliki Fyler et Caira, 2006and A. southwelli Subhapradha, 1955 in its lack of post-ovarian testes.…”

“…The tetraphyllidean genus Acanthobothrium van Beneden, 1850 is both a ubiquitous and conspicuous component of the cestode fauna of species of the Indo-Pacific stingray genus Himantura Müller et Henle examined to date (e.g., Srivastav and Capoor 1980, Campbell and Beveridge 2002, Fyler and Caira 2006, Reyda and Caira 2006, Twohig et al 2008). In such systems, Acanthobothrium species appear to exhibit oioxenous specificity for their stingray hosts.…”

Spermiogenesis and spermatozoon ultrastructure of the diphyllidean cestode Echinobothrium euterpes (Neifar, Tyler and Euzet 2001) Tyler 2006, a parasite of the common guitarfish Rhinobatos rhinobatos

“…, Echinobothrium sinensis described as belonging to the genus Macrobothridium (Li and Wang 2007), Echinobothrium minutamicum (Twohig et al 2008), Echinobothrium nataliae, Echinobothrium reginae and Echinobothrium vojtai (Kutcha and Caira 2010) the order currently count 42 valid species.…”