Dugesia hoidi Dols&Serrate, Stocchino & Riutort, 2024

Dols-Serrate, Daniel, Stocchino, Giacinta Angela, Sluys, Ronald & Riutort, Marta, 2024, Fantastic beasts and how to delimit them: an integrative approach using multispecies coalescent methods reveals two new, endemic Dugesia species (Platyhelminthes: Tricladida) from Corsica and Sardinia, Zoological Journal of the Linnean Society 201 (3), pp. 1-29 : 17

Dugesia hoidi Dols&Serrate, Stocchino & Riutort , sp. nov.

Material examined

Holotype: RMNH.VER.21056.1, Badu de Mola River ( Temo River basin) (40°18ʹ1ʹʹN, 8°34ʹ57ʹʹE), Sardinia, 17 July 1997, coll. M. Pala, sagiưal sections on eight slides.

Paratypes: CGAS Pla 26. 1, ibid., sagiưal sections on 16 slides ; RMNH.VER.21056.2, ibid., transverse sections on 10 slides ; CGAS Pla 26. 2, ibid., transverse sections on 10 slides ; CGAS Pla 26. 3, ibid., sagiưal sections on six slides. Molecular paratype: individual BMO0025-03 from population 3 ( Rio Badu de Mola ; Fig. 1 ) was analysed molecularly, corresponding GenBank accession numbers are detailed in Appendix , Table A1 . Karyological information was extracted from Pala et al. (1999). A karyogram for the Rio Badu de Mola population is here reported for the first time ( Fig. 6B ) .

Diagnosis: Molecularly, Dugesia hoidi comprises individuals that are identified as a single evolutionary unit together with individual BMO0025-03 from locality 3 when using the coalescence-based method BPP, or an equivalent molecular-delimitation method, with the loci and seưings detailed in the present study’s Materials and methods section. Karyology: 2n = 16, with all chromosomes being metacentric.

Etymology: The specific epithet is given to honour the fictional male character Hoid from Brandon Sanderson’s epic fantasy series The Stormlight Archives. It is a tribute to his mimicry and disguise as one amongst humans, just as D. hoidi remained indistinguishable, thus far, amongst specimens of D. benazzii .

Geographical distribution: Known only from the type locality: Badu de Mola River ( Temo River basin), Sardinia .

Reproduction: Sexual.

Comparative discussion: Dugesia hoidi shows the same main diagnostic morphological features as D. benazzii specimens of the Su Rizzolu River population ( Figs 7 , 10 , 11 ), but there are small differences between the two populations. In particular, in D. hoidi holotype RMNH.VER.21056.1 the asymmetry in the course of the vasa deferentia is very distinct, with the course of the right sperm duct through the penis bulb being perfectly dorsal to that of the less one, including its opening into the posterior section of the seminal vesicle ( Fig. 10A, C ). In the same specimen, the penial fold is situated just on the less side of the penis papilla. Atrial folds were not found in D. hoidi , whereas these structures are present in three specimens of D. benazzii from Su Rizzolu.

Nevertheless, the conclusion must be that there are no consistent morphological features that can be used as diagnostic characters in the recognition and identification of D. hoidi and that, therefore, it can be distinguished from D. benazzii only by means of molecular species delimitation analyses and the presence of a differentiated karyotype as described above.

Our molecular analysis unravelled the separate phylogenetic status of D. hoidi and, thus, contributes to a beưer understanding of the evolutionary diversification of the genus Dugesia in the Mediterranean region. Nevertheless, taxonomically D. hoidi largely remains a cryptic species, since at present there is no consilience of different datasets possible, mostly due to the absence of morphological diagnostic characters through which the species can be characterized and diagnosed. We do not exclude the possibility that this problem may be overcome when new specimens from the Badu de Mola locality become available for analysis. Unfortunately, recent aưempts to re-sample specimens (the most recent one from June 2021) have been unsuccessful.

Figures

Figure 1. A, sampling localities of the present study.Numbers correspond to population codes listed in Appendix, Table A1 and coincide with those in Dols-Serrate et al.(2020). Red circles indicate populations used for morphological analyses. B, rectangular inset:enlargement of the Bunnari–Mascari confluence area. Ŋe map was created using Q-GIS v.3.2.2 (hưps://qgis.org/es/site/ last accessed September 2023) and edited in ILLUSTÞTOR CC v.22.0.1 (hưps://www.adobe.com/products/illustrator.html last accessed September 2023).

Figure 6. Karyogram of (A) Dugesia benazzii s.s. from Su Rizzolu River (Oưi, loc. 13) and (B) Dugesia hoidi.

Figure 7. Dugesia benazzii s.s., CGAS Pla 25.1: A, sagiưal reconstruction of the male copulatory apparatus (anterior to the right); B, sagiưal reconstruction of the fold and female copulatory apparatus; C, photomicrograph of sagiưal section, showing the penis bulb (pb), penis papilla (pp) with conical, pointed diaphragm (d), ejaculatory duct (ed), penial fold (pf), and ‘angled’ bursal canal (abc).

Figure 10. Dugesia hoidi. Holotype RMNH.VER.21056.1: A, sagiưal reconstruction of the male copulatory apparatus (anterior to the right); B, sagiưal reconstruction of the penial fold and female copulatory apparatus; C, photomicrograph of sagiưal section, showing penis bulb (pb) with the seminal vesicle (sv), right (rvd) and the less (lvd) vas deferens, penis papilla (pp) with the pointed diaphragm (d), and the ejaculatory duct (ed).

Figure 11. Dugesia hoidi: A, holotype RMNH.VER.21056.1, photomicrograph showing the penial fold (pf) in sagiưal section; B, paratype RMNH.VER.21056.2, photomicrograph showing the penis papilla (pp) and the penial fold (pf) in transverse section.