FOUR NEW SPECIES OFACANTHOBOTHRIUM(CESTODA: TETRAPHYLLIDEA) FROM THE WHIPTAIL STINGRAYDASYATIS BREVISIN THE GULF OF CALIFORNIA, MEXICO

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Abstract

Examination of the spiral intestines of 29 whiptail stingrays, Dasyatis brevis, from 6 sites in the Gulf of California, Mexico in 1993 and 1996 resulted in the discovery of 4 new species of Acanthobothrium: Acanthobothrium bullardi, Acanthobothrium dasi, Acanthobothrium rajivi, and Acanthobothrium soberoni. This brings the total number of species of Acanthobothrium known from the eastern Pacific Ocean to 34. With 22 additional species reported from elasmobranchs from the western Atlantic Ocean, and over 100 species globally, the number of interspecific comparisons required to justify the designation of a new species is rather unwieldy. To facilitate these and future comparisons, and in the absence of a phylogenetic hypothesis for this genus, the 56 species of Acanthobothrium from these 2 geographic regions were categorized for 4 characters: total length (< or = or > 15 mm), number of segments (< or = or > 50 segments), number of testes (< or = or > 80), and symmetry of poral and aporal ovarian lobes. These 56 taxa and their categories are presented in tabular form. Based on these characters, A. bullardi, A. dasi, and A. rajivi are category 2 species (they are relatively small, possess few segments, relatively few testes, and exhibit asymmetrical ovaries); A. soberoni is a category 6 species (it is a relatively longer worm with a larger number of segments, but with fewer testes and an asymmetrical ovary). All 4 species differ from 1 another and from species in other geographic regions in further subtleties of these 4 characters as well as hook size and relative length of hook prongs, cirrus sac size, genital pore position, number of columns of testes anterior to the cirrus sac, and number of postvaginal testes. Five specimens that appear to represent a new species of Acanthobothroides were also collected. This species is figured and some details of the morphology are described, but the material was considered to be insufficient to allow for formal description of this species at this time. This is the first record of either of these genera of onchobothriid tapeworms from the Gulf of California.

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Most cited references 19

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On the phylogenetic relationships among tetraphyllidean, lecanicephalidean and diphyllidean tapeworm genera.

J. Caira, K. Jensen, C. J. Healy (1999)

This study had two main objectives: (1) to construct an extensive, explicit list of characters and character states that might serve as a starting point, and perhaps even a model, for the compilation of a more complete list of characters for all cestode taxa; and (2) to use this character list to generate a hypothesis of the phylogenetic relationships among species representing most of the tetraphyllidean, lecanicephalidean and diphyllidean genera. Specimens of one species in each of 48 genera of tetraphyllideans, eight genera of lecanicephalideans, the three genera of diphyllideans, two genera of proteocephalideans and two genera of trypanorhynchs, were examined as whole-mounts and sections, with light and scanning electron microscopy. A list of 120 morphological characters was compiled. Four phylogenetic analyses were conducted using PAUP* and/or NONA. The first was a comprehensive analysis with the 56 tetraphyllidean and lecanicephalidean species as ingroups and the remaining seven species as outgroups. The second was an analysis of the three diphyllidean species as ingroups and the two proteocephalidean and the two trypanorhynch species as outgroups. The third was an analysis of the eight lecanicephalidean species and the "tetraphyllideans" Echeneibothrium sp. and Pseudanthobothrium n. sp. as ingroups and an outgroup consisting of the seven species used as outgroups in the first analysis. In the fourth analysis, the ingroup consisted of the 14 hooked tetraphyllideans (onchobothriids), and the outgroup consisted of the seven species used as outgroups in the first analysis. The results of these analyses support the following phylogenetic hypotheses: The diphyllideans are monophyletic and Echinobothrium n. sp. and Macrobothridium sp. are more closely related to one another than either is to Ditrachybothridium macrocephalum. The tetraphyllideans, lecanicephalideans and proteocephalideans are more closely related to each other than they are to the diphyllideans or the trypanorhynchs. The ordinal status of the lecanicephalideans is dubious. The lecanicephalidean species are more closely related to some of the tetraphyllidean taxa than these tetraphyllidean taxa are to the remainder of the tetraphyllidean taxa. The proteocephalideans appear to belong within the tetraphyllidean clade. The "tetraphyllidean" species Echeneibothrium sp. and Pseudanthobothrium n. sp. are members of the lecanicephalidean clade. The position of "Discobothrium" n. sp. within the lecanicephalideans is dubious. Within the tetraphyllideans, the non-acetabulate species Litobothrium daileyi, Disculiceps galapagoensis and Cathetocephalus sp. are the most basal members of the group. The family Onchobothriidae is monophyletic, as it is currently defined. Within the onchobothriids, the uniloculate species are basal to the multiloculate species; the species with unipronged hooks are basal to the species with multipronged hooks. Although relationships among the phyllobothriids, as they are currently defined, remain poorly resolved, the family Phyllobothriidae is not monophyletic. These results suggest that some aspects of the classification of the lecanicephalidean and tetraphyllidean taxa require revision. However, such revision should be based on further analyses including a broader representation of the genera and species in these groups.