Synergy advances parasite taxonomy and systematics: an example from elasmobranch tapeworms

Abstract

The synergism facilitated by a series of recent developments has conspired to catalyze rapid advancements in the taxonomy and systematics of elasmobranch tapeworms. These developments are: (1) increased interest in global biodiversity; (2) globalization-facilitated communication; (3) enhanced microscopic and digital technologies; (4) availability of web-based taxonomic resources; (5) ease of use and low cost of molecular techniques and (6) the impressive repertoire of available phylogenetic methods. As a consequence, an estimation of global elasmobranch tapeworm diversity is now within our grasp, as is a basic understanding of the effort and resources required to complete the discovery and description of this fauna globally. The generation of robust hypotheses of the phylogenetic relationships for most elasmobranch-parasitizing cestode orders is also well underway. An international community of cestodologists has emerged and through their sharing of knowledge and specimens is making great strides towards expanding knowledge of the cestode fauna of vertebrates worldwide. It is important that these efforts continue to move forward in a collaborative fashion, integrating morphological and molecular data, but also fully engaging elasmobranch taxonomists and systematists. It is equally important that efforts to characterize and describe global biodiversity are not derailed by such seductive, but ultimately unrewarding impracticable initiatives as molecular taxonomy. Integrated taxonomy is certainly not for the feint of heart, but those with the courage to pursue this strategy will be responsible for maintaining and enhancing the biologically relevant context required for effective species recognition well into the future.

Systematics and diversification of Anindobothrium Marques, Brooks & Lasso, 2001 (Eucestoda: Rhinebothriidea)

“…Independent of the status of A. inexpectatum as a truly cryptic species or a pseudocryptic one—those not initially recognized as phenotypically distinct due inadequate analysis of morphological data [ 84 , 85 ]—, this species would not have been recognized by traditional approaches applied by taxonomists in the group. The taxonomy of cestodes, in particular those lineages parasitic in elasmobranchs, has historically been based on morphological discontinuities and on the assumption that cestode fauna of a species of elasmobranch does not vary substantially across its distribution [ 86 ]. Since cryptic lineages have been shown to be common throughout the metazoan taxa (see [ 87 – 91 ], and references therein), we should expected to find them also among cestode species.…”

“…The inclusion of scanning electron microscopy is a common practice in the taxonomy of elasmobranch cestodes to document tegumental structures ( i.e. , microtriches patterns) and it has been useful in taxonomic decisions (see Caira [ 86 ] and references therein). Also, the concern for selecting characters not subject to fixation artifacts and the search for those thought to display interspecific variation are credited to have improved the taxonomy of cestodes over the years [ 86 ].…”

“…, microtriches patterns) and it has been useful in taxonomic decisions (see Caira [ 86 ] and references therein). Also, the concern for selecting characters not subject to fixation artifacts and the search for those thought to display interspecific variation are credited to have improved the taxonomy of cestodes over the years [ 86 ]. Molecular data have contributed to the taxonomy of many groups of cestodes, however timidly so.…”

Host relationships and geographic distribution of species of Acanthobothrium Blanchard, 1848 (Onchoproteocephalidea, Onchobothriidae) in elasmobranchs: a metadata analysis

“…At the present time, 201 species of Acanthobothrium are considered to be valid (Maleki et al 2013;Caira and Jensen 2017;Rodríguez-Ibarra et al 2018;Franzese and Ivanov 2018;Maleki et al 2019;Zaragoza-Tapia et al 2019, 2020. The genus consists of species that exclusively parasitize elasmobranchs as adults and, in many cases, individual species are thought to parasitize only a single species of elasmobranch (Caira 2011;Caira and Jensen 2017). Therefore, the genus Acanthobothrium is an excellent model for future studies of hostparasite co-speciation.…”

Molecular phylogeny of the Bothriocephalidea (Cestoda): molecular data challenge morphological classification

“…The genus is mor-51 phologically characterised by a wide, heart-shaped scolex with narrow, deep bothria. Over the past decade, a global collaborative effort has been 58 undertaken to relate cestode classifications to their phylogeny on 59 the basis of available molecular sequence data (Caira, 2011). 60 Among the 19 currently recognised cestode orders (Caira et al,61 2014), a few of the early diverging 'true' tapeworm (Eucestoda) 62 groups differ from the others by possessing one or two pairs of 63 bothria on the scolex ('bothriate', or formerly 'bifossate', cestodes), 64 which act as sucking grooves and facilitate attachment to the host's senting families sensu Yurakhno (1992), complemented by the 126 Philobythiidae.…”