Gorgocephalus kyphosi, Manter, 1966

Huston, Daniel C., Cutmore, Scott C., Miller, Terrence L., Sasal, Pierre, Smit, Nico J. & Cribb, Thomas H., 2021, Gorgocephalidae (Digenea: Lepocreadioidea) in the Indo-West Pacific: new species, life-cycle data and perspectives on species delineation over geographic range, Zoological Journal of the Linnean Society 193 (4), pp. 1416-1455 : 1420-1423

Gorgocephalus kyphosi

The type species for the family Gorgocephalidae , Gorgocephalus kyphosi , was described based on five specimens from Kyphosus sydneyanus collected from near Port Noarlunga, South Australia ( Manter, 1966). The species has also been reported from K. vaigiensis from Lizard Island, GBR, Australia and from Moorea, Society Islands, French Polynesia ( Bray, 2005b; Bray & Cribb, 2005). Molecular sequences have been provided previously for a specimen identified as G. kyphosi ( Olson et al., 2003) , although this specimen was collected from K. vaigiensis from off Lizard Island, GBR, rather than from the type host and locality. Port Noarlunga is now a protected marine reserve and the closest locality from which we were able to capture specimens of K. sydneyanus was Point Riley, Yorke Peninsula, South Australia. This locality is approximately 160 km from Port Noarlunga. However, we examined the holotype (borrowed from the Smithsonian National Museum of Natural History, USA; USNM 1356481) and found that the morphology of this specimen was consistent with those from Point Riley; thus, we consider our specimens from South Australia to be conspecific with G. kyphosi .

We obtained adults corresponding to the ‘ Gorgocephalus kyphosi ’ morphotype from all collection localities where gorgocephalids were found, except for Kioloa, NSW, Australia where only gastropods were collected. Based on the measurements and morphological description of G. kyphosi provided by Manter (1966), all of these adult specimens could be diagnosed as that species. However, molecular data indicated that up to six species could be distinguished under the umbrella of this morphological concept. Reassessment of morphology in light of molecular data, on a clade-by-clade basis, allowed separation of G. euryaleae and G. graboides from G. kyphosi , largely on the proportion of the cirrus-sac occupied by the internal seminal vesicle, pars prostatica and ejaculatory duct (see Taxonomy section). Both new species correspond to well-supported clades in all analyses ( Figs 3–6 ). Recognition of these two species allows refinement of our morphological and molecular profile for G. kyphosi .

After exclusion of the two new species, sequences representative of the refined concept of Gorgocephalus kyphosi formed a large clade in all analyses ( Figs 3–6 ), although there was relatively poor bootstrap support (65) for the clade in ML analysis of the COI dataset. This major clade was subdivided into several smaller clades, largely corresponding to collection locality. Sequences of the ITS2 and 28S rDNA gene regions for G. kyphosi were fairly conserved, differing by no more than 3 bp (<1%) within or between localities ( Table 5 ). Phylogenetic analyses of the ITS2 and 28S datasets demonstrated that sequences generated from specimens from two Australian localities (Moreton Bay and South Australia) were more similar to those from French Polynesia than to those from the third Australian locality (Lizard Island, GBR). Although sequences of the COI mtDNA gene region differed by no more than 6 bp (~1.3%) within each locality, large differences up to 62 bp (~13%) occurred between localities ( Table 5 ). As with the ITS2 and 28S data, COI sequences generated from specimens from Moreton Bay and South Australia were more similar to each other and to those from French Polynesia (~1– 6% difference) than to those from Lizard Island, GBR (~12–13% difference; Supporting Information, Table S5 ). These molecular differences, coupled with this geographic pattern, possibly indicate a species-level distinction. However, no significant morphological differences were observed between any specimens from the above named localities, and there are no host differences. Furthermore, in all phylogenetic analyses the Lizard Island clade was sister to the remaining putative sequences of G. kyphosi from other IWP localities. Thus, we conservatively consider all of these specimens as representative of G. kyphosi . Sequences of G. kyphosi differ from the other species of the Gorgocephalidae investigated here by 65–88 bp (14–15%), 4–18 bp (0.9–4.0%) and 5–20 bp (0.5–2.0%) in the COI, ITS2 and 28S gene regions, respectively ( Table 5 ).

Two intermediate hosts were identified for this species using COI, ITS2 and 28S sequences ( Figs 3–6 ). Six Bembicium auratum , collected from near Dunwich, North Stradbroke Island, Moreton Bay, Australia, were found infected with gorgocephalids. Three infections were matched to adult worms obtained from Kyphosus cinerascens collected nearby, from off Amity Point, North Stradbroke Island. In addition, a single infected Echinolittorina vidua , collected from Lizard Island, GBR, was matched to adults obtained from K. vaigiensis collected from off the same locality using ITS2 gene sequences.

Gorgocephalus euryaleae and Gorgocephalus graboides

These two new species are morphologically differentiated from Gorgocephalus kyphosi , and each other, largely on features within the cirrus-sac (see Taxonomy section). Sequences for these species form well-supported clades in all analyses ( Figs 3–6 ), with presumed conspecifics collected from the same locality differing by no more than 3 bp in any of the three sequenced gene regions ( Table 5 ). Sequences of G. euryaleae differ by 10–11 bp (~2%), 1 bp (~0.2%) and 1–2 bp (0.1–0.2%) in the COI, ITS2 and 28S gene regions, respectively, between Western Australia and South Africa. Sequences of G. euryaleae differ from the others species of the Gorgocephalidae recognized here by 66–87 bp (14–18%), 4–19 bp (0.9–4.2%) and 5–23 bp (0.5–2.3%) in the COI, ITS2 and 28S gene regions, respectively. Sequences of G. graboides , found at only one locality, differ from other gorgocephalid species by 65–81 bp (14–17%), 14–19 bp (3.1–4.2%) and 18–23 bp (1.8–2.3%) in the COI, ITS2 and 28S gene regions, respectively ( Table 5 ).

Gorgocephalus graboides was recovered only from Kyphosus cinerascens collected from off Lizard Island, GBR, whereas G. euryaleae was recovered from K. cinerascens in South Africa and from K. gladius and K. sydneyanus from Western Australia. Although the two new species are apparently geographically isolated from one another, they share at least one definitive host. Both species also have an overlapping definitive host range with G. kyphosi ( K. sydneyanus and K. cinerascens for G. euryaleae and K. cinerascens for G. graboides ). Furthermore, intramolluscan gorgocephalids from a single infected Echinolittorina vidua from Lizard Island were successfully matched to G. graboides . Thus, G. graboides also shares an intermediate host with G. kyphosi .

Figures

Figure 3. Bayesian majority-rule consensus tree of the COI mtDNA single-gene alignment. Bayesian inference (BI) posterior probabilities and maximum likelihood (ML) bootstrap support shown at nodes. A ‘-‘ symbol indicates the node was not recovered in ML analysis. The scale-bar indicates the number of substitutions per site.

Figure 4. Bayesian majority-rule consensus tree of the ITS2 single-gene alignment. Bayesian inference (BI) posterior probabilities and maximum likelihood (ML) bootstrap support shown at nodes. An asterisk indicates different topology recovered in ML analysis. The scale-bar indicates the number of substitutions per site.

Figure 5. Bayesian majority-rule consensus tree of the 28S rDNA single-gene alignment. Bayesian inference (BI) posterior probabilities and maximum likelihood (ML) bootstrap support shown at nodes. A ‘-‘ symbol indicates the node was not recovered in ML analysis. The scale-bar indicates the number of substitutions per site.

Figure 6. Bayesian majority-rule consensus tree of the concatenated COI + ITS2 + 28S alignment. Bayesian inference (BI) posterior probabilities and maximum likelihood (ML) bootstrap support shown at nodes. A ‘-‘ symbol indicates the node was not recovered in ML analysis. The scale-bar indicates the number of substitutions per site.