ABSTRACT

Collection of cestodes from the Taiwan saddled carpetshark, Cirrhoscyllium formosanum, for the first time led to the discovery of Pentaloculum hoi n. sp. This species provided important insights into the identity of the heretofore monotypic Pentaloculum—known previously only from the blind electric ray, Typhlonarke aysoni, in New Zealand. The new species differs from Pentaloculum macrocephalum in testis number, vitelline follicle and cirrus sac configuration, and in that it is hyperapolytic rather than euapolytic. Maximum-likelihood analysis of sequence data generated for the D1–D3 region of the 28S rDNA gene not only confirmed this generic placement but also confirmed the close affinities between both species of Pentaloculum and specimens previously referred to in the literature as new genus 7 n. sp. 1. Examination of limited material of the latter, including that of a second specimen from which partial 28S rDNA sequence data were generated here, led to the realization that new genus 7 n. sp. 1 represents an undescribed species of Pentaloculum, referred to here as Pentaloculum n. sp. 2. All 3 species share bothridia divided into 1 anterior and 2 consecutive pairs of loculi. Given that Pentaloculum n. sp. 2 parasitizes a member of the second and only other genus of parascylliid sharks (i.e., Parascyllium), we predict that the 4 other species of Parascyllium and the 2 other species of Cirrhoscyllium are likely to host other species of Pentaloculum. The factors that might account for the eclectic host associations of Pentaloculum, which include a torpediniform ray and 2 species of orectilobiform sharks, are currently unclear. The compilation of diet data for these elasmobranchs and determination of the final intermediate hosts for these cestodes would be interesting avenues of further investigation given that cestodes are trophically transmitted between their intermediate and definitive hosts. The phylogenetic affinities of Pentaloculum among elasmobranch cestodes remain unresolved.

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