New records of rare derogenids (Digenea: Hemiuroidea) from Mediterranean sparids, including the description of a new species of Magnibursatus Naidenova, 1969 and redescription of Derogenes adriaticus Nikolaeva, 1966

Redescription and Molecular Characterisation of Derogenes ruber Lühe, 1900 (Hemiuroidea: Derogenidae) from Chelidonichthys lastoviza (Scorpaeniformes: Triglidae) in the Western Mediterranean

PURPOSE

Derogenes ruber Lühe, 1900, the type-species of the genus Derogenes Lühe, 1900, is a poorly known derogenid digenean. The original description of this species was not illustrated and aspects of the morphology of the parasite from the type-host remain scarce. Available records of this species were brief and/or lacked illustrations and were based on morphology alone. Additionally, molecular data for Derogenes spp. are warranted to untangle species complexes as they provide a better assessment of interspecific genetic divergence.

METHODS

Derogenes ruber is redescribed based on newly collected specimens from the gall bladder of its type-host Chelidonichthys lastoviza (Bonnaterre, 1788) collected in the Western Mediterranean off the Algerian coast during 2017-2019 and molecular data are provided using a partial fragment of the nuclear 28S ribosomal RNA gene (28S rRNA), the internal transcribed spacer 2 (ITS2) and a fragment of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene.

RESULTS

We herein provide a detailed illustrated redescription and morphometric data of D. ruber from its type-host C. lastoviza. We report a new geographical record (off Algeria) for it. Derogenes ruber is also genetically characterised for the first time. Species/lineages of Derogenes were recovered in five strongly supported reciprocally monophyletic clades: (i) D. ruber from C. lastoviza off Algeria; (ii) D. lacustris from Galaxias maculatus (Jenyns) off Argentina; (iii) Lineage "D. varicus DV1" (D. varicus sensu stricto) from fish hosts in the White and Barents seas and the North Sea; (iv) Lineage "D. varicus DV2" from mollusc hosts in the White Sea; and (v) Lineage "D. varicus DV3" from Eumicrotremus fedorovi Mandrytsa. in the Pacific Ocean. Hence, comparison of the newly generated sequences with other available data for Derogenes species supports the distinction of D. ruber confirming its taxonomic status and helping assess interspecific variation. Comparison of D. ruber with the closely related species Derogenes latus revealed overlaps in morphometric data and the validity of the latter species is questioned.

CONCLUSION

The combination of morphological and molecular data provided for D. ruber provides a firm foundation for further investigations of Derogenes spp. Although we do describe herein material of D. ruber from the type-host, given that the occurrence of a single Derogenes species in various hosts has been challenged by molecular data, and both D. lacustris and D. varicus sensu stricto had been genetically proven to occur in various hosts, D. ruber and D. latus may be indeed synonymous. Additional sequencing effort on Derogenes spp. will strengthen systematic comparative studies and evolutionary relationships within the Derogenidae in general.

Infection with a novel derogenid trematode in a Flap-necked chameleon (Chamaeleo dilepis)

A 2-year-old female Flap-necked chameleon (Chamaeleo dilepis) was presented with a history of anorexia. On physical examination, three 11×4×2 mm, light tan-pink, raised, gelatinous, freely movable, poorly demarcated, raised nodules were identified within the oral cavity. An impression smear contained multiple, light blue to green structures exhibiting an 18×35 μm, elliptical-shaped anterior portion and a single 1×150 μm filament with a tapered end. Initial differential etiologies included trematode ova, flagellate protozoa, fungal sporangia, plant material, and sperm. Fungal culture yielded no growth. The structures described above did not stain with Gomori methenamine silver stain. A calcofluor white stain yielded positive fluorescence. The DNA was extracted from the impression smears and pan-trematode PCR was performed; products were directly sequenced and phylogenetic analysis revealed maximum similarity with a digenean trematode in the family Derogenidae that was distinct from other trematodes for which a reference sequence was available. To our knowledge, this is the first description of cytologic features of trematode ova from an oral lesion in a chameleon.