A morphological and genetic description of pentastomid infective nymphs belonging to the family Sebekidae Sambon, 1922 in fish in Australian waters

Abstract

Abstract:Infective nymphal stages of the family Sebekidae Sambon, 1922 are reported from four species of fish in Australian waters for the first time. Infected fish were collected from locations in Western Australia, the Northern Territory and north Queensland. The infective nymphs of Alofia merki Giglioli in Sambon, 1922 and Sebekia purdieae Riley, Spratt et Winch, 1990 are reported and described for the first time. The remaining specimens were identified as belonging to the genus Sebekia Sambon, 1922 based on the combination of buccal cadre shape, shape and size of hooks, and overall body size, but could not be attributed to any of the other species of Sebekia already reported due to missing required morphological features. DNA sequences of members of the family Sebekidae are presented for the first time. The lack of knowledge on the pentastome fauna of wild crocodiles, and any potential intermediate hosts, in northern Australia, is also outlined.

Morphological, Molecular, and Histopathological Data for Sebekia mississippiensis Overstreet, Self, and Vliet, 1985 (Pentastomida: Sebekidae) in the American Alligator, Alligator mississippiensis Daudin, and the Spotted Gar, Lepisosteus oculatus Winchell

“…Results of phylogenetic analyses of Sebekia mississippiensis COI sequencing data (Fig. 3) were in agreement with previous phylogenetic placement of Sebekia (Barton and Morgan, 2016). Sebekia mississippiensis sequences formed a sister clade with other congeners, though very little molecular data are presently available for pentastomes.…”

“…Regarding the variety of clearing and mounting techniques used in the present study, some discussion is warranted. It has become common practice to mount pentastomes directly in Hoyer's medium under cover glass for morphological characterization (Overstreet et al, 1985;Barton and Morgan, 2016). While this technique provides rapid visibility of taxonomically informative characters and internal structures, these structures quickly clear to the point where all but the hooks are difficult to discern, making comparisons between specimens quite difficult.…”

“…Without being able to confidently detect the presence or absence of a dorsal accessory piece, it is not possible to determine if many of these specimens are adults or nymphs, making direct, independent morphometric comparisons impossible using such specimens. While mounting would have risked mechanical destruction of the specimens, clearing agents have also been suspected of stymying efforts at subsequent DNA extraction from pentastomes (Barton and Morgan, 2016).…”

“…Standard pentastome hook measurements as adapted from Fain (1961) by Barton and Morgan (2016) were taken from all specimens where possible. Additionally, oral cadre lengths and widths were measured where possible as previously reported for adults and nymphs of Sebekia (Overstreet et al, 1985;Winch and Riley, 1986;Riley et al, 1990).…”

Molecular and Histopathological Data on Levisunguis subaequalis Curran, Overstreet, Collins & Benz, 2014 (Pentastomida: Eupentastomida: Porocephalida: Porocephaloidea: Sebekidae: Sebekinae) from Gambusia affinis in Alabama, USA

“…More sequence data from 18S, 28S, and COI are needed to more thoroughly assess the utility of these markers for phylogenetic inference of the evolutionary relationships between pentastomids. To date, only Barton and Morgan (2016) and Woodyard et al (2019a) provide 18S, 28S, and COI sequence data from the same specimens for 4 of the 141 currently described pentastomid species for the analyses carried out in the present study. While phylogenetic analyses using concatenated ribosomal and mitochondrial sequence data are increasingly being used for phylogenetic inference in other parasitic groups as evidenced by recent works on species ranging from Clinostomidae (Caffara et al, 2016;Woodyard et al, 2017;Briosio-Aguilar et al, 2019) to Emeriidae (Ogedengbe et al, 2018;Woodyard et al, 2019b), the present molecular data from pentastomids are not suitable for such analyses.…”