Cryptotropa acanthosauri Tkach, Chermak, Patitucci & Binh, 2023

Tkach, Vasyl V., Chermak, Taylor P., Patitucci, Kaylyn K., Greiman, Stephen E., Binh, Tran Thi & Olson, Peter D., 2023, Jumping continents and major host lineages: phylogeny and diversity of the enigmatic Cryptotropidae (Platyhelminthes: Digenea), Zoological Journal of the Linnean Society 199 (2), pp. 533-552 : 539-541

Cryptotropa acanthosauri Tkach, Chermak, Patitucci & Binh sp. nov.

( Figs 4 , 5A )

Type host: Acanthosaura lepidogaster Cuvier, 1829 (Reptilia: Agamidae ).

Site in host: Small intestine.

Type locality: Vinh Phuc Province, Vietnam.

Type material: The type series consists of 20 mature specimens deposited in the HWML. Holotype: HWML 216828, labelled ex. Acanthosaura lepidogaster , small intestine, Vinh Phuc Province, Vietnam, 26 November 2012, coll. T. T. Binh. Paratypes: HWML 216829 (lot of 16 slides), label identical to the holotype.

GenBank sequences: Oº534009 (ribosomal), Oº469314 (cox1).

ZooBank registration: urn:lsid:zoobank.org:act:BBC01881-CE7E-414B-A51A-1BD6C1EF228A .

Etymology: The species is named asser the definitive host from which it was collected.

Description (based on 20 adult specimens; measurements of holotype given in text; measurements of entire series given in Table 4 ): Body 847 long, caudally truncated, oval in shape; body width at ventral sucker 427. Body length-to-body width ratio 2.0. Forebody 374. Tegumental spines minute, densely and almost evenly distributed over entire body. Oral sucker subterminal, 117 × 134; ventral sucker rounded, 79 × 85. Oral sucker width-to-ventral sucker width ratio 1.6. Prepharynx very short, 16; pharynx rounded, 61 × 68. Oesophagus 117. Caecal bifurcation midway between oral and ventral suckers; caeca terminating at level of, or slightly posterior to ventral sucker.

Two testes, rounded or oval, usually with slightly irregular outline, opposite, in posterior third of body. Right testis 176 × 148, less testis 148 × 145. Copulatory pouch large, 305 × 61, its proximal end overlapping with anterior margin of ventral sucker and distal end opening into dorsoventral genital atrium situated close to sinistral side of body approximately at level of posterior margin of pharynx. Distal portion of copulatory pouch curved towards dorsal surface in hook-like manner. Copulatory pouch contains seminal vesicle, prostatic gland and ejaculatory canal; evaginated cirrus not observed.

Ovary subspherical, submedian, immediately posterodextral to ventral sucker, 63 × 58. Seminal receptacle immediately posterior to ovary, 62 × 53. Mehlis’ gland and Laurer’s canal not observed. Vitellarium extensive, in the form of numerous, small, irregularly shaped follicles occupying most of body from midway between pharynx and caecal bifurcation to near posterior end of the body. Vitelline fields coalesce in anterior part of body anterior to ovary, and in posterior part of body posterior to testes; usually, there is break in vitelline fields at the level of the testes. With the exception of few follicles, vitelline fields normally do not overlap testes; space in centre of body between ovary and testes is mostly devoid of vitelline follicles. Uterus ventral to gonads, located in middle third of body, between anterior margin of testes and level of caecal bifurcation, approaching margins of body on both sides. Metraterm well defined, 101. Uterus contains a moderate number of operculate eggs, 46–49 × 19–21. Eggs possess one or two, sometimes more, polar filaments on each pole of the egg. Polar filaments consist of several fibres aưached/glued together. Excretory pore terminal. Excretory vesicle Y-shaped, with broad stem passing between testes and bifurcated at the level of the anterior margin of testes. Anterior ends of excretory vesicle arms reach ends of caeca.

Remarks

Based on the combination of morphological characteristics, such as the dorsal genital pore, the position of suckers, gonads, seminal receptacle and copulatory pouch, shape and distribution of vitelline follicles, vitellarium generally not overlapping testes and uterus not extending into the post-testicular zone of the body, the new species clearly belongs to Cryptotropa .

Currently, the genus Cryptotropa contains only two species: the type species, Cryptotropa kuretanii Ozaki, 1926 , described from the frog Buergeria buergeri Temminck & Schlegel, 1838 in Japan, and Cryptotropa electrinos Deblock, Capron & Brygoo, 1965 , described from a chameleon, Calumma boettgeri Boulenger, 1888 , in Madagascar. Although Khotenovsky (1965) has transferred Cephalouterina dicamptodoni Senger & Macy, 1953 into Cryptotropa, Lotz and Font (2008a) have resurrected Cephalouterina as an independent genus. Cryptotropa lingnanensis Lingsun & Junyi, 1989 , described from American bull frog, Lithobates catesbeianus Shaw, 1802 , in China ( Lingsun and Junyi 1989), clearly does not belong to Cryptotropa due to numerous differences, including, but not limited to, preacetabular ovary, vitellarium not extending past the anterior margin of testes, and testes occupying the posterior-most position in the body.

The new species differs from Cr. kuretanii in having a significantly smaller body, uterus extending only slightly posterior to the anterior margin of the testes (extends at least to the posterior margin of testes in Cr. kuretanii ), smaller eggs, spherical seminal receptacle (elongated in Cr. kuretanii ), dramatically broader stem of the excretory vesicle (seen in all studied specimens), longer copulatory pouch and relatively longer arms of the excretory vesicle (reach caeca in the new species, but not in Cr. kuretanii ), among other characters. Besides, the two species are geographically isolated and parasitize representatives of different classes of vertebrates. The new species was found in an agamid lizard in Vietnam, whereas Cr. kuretanii was described from a frog in Japan.

Cryptotropa acanthosauri can be differentiated readily from Cr. electrinos by the body shape (broadly oval, almost rounded in Cr. electrinos , with both anterior and posterior ends rounded), dramatically larger copulatory pouch, relative length of the copulatory pouch (entirely extracaecal in Cr. electrinos , but reaching ventral sucker in the new species), more posterior, dorsal position of the genital pore (marginal in Cr. electrinos ) and much larger eggs (42–54 in the new species vs. 28–30 in Cr. electrinos ). The two species can also be distinguished easily by the sucker ratio (oral sucker 1.4–1.7 times larger than the ventral sucker in the new species vs. equal suckers in Cr. electrinos ). Besides, the two species are geographically isolated, because the new species was found in Vietnam, whereas Cr. electrinos was described from Madagascar.

Although Cephalouterina is currently considered a separate genus, we provide differentiation of the new species from Ce. dicamptodoni due to some overall morphological similarity between the two genera and the fact that Khotenovsky (1965) considered Cephalouterina a synonym of Cryptotropa . Cryptotropa acanthosauri differs from Ce. dicamptodoni in several important characteristics. The uterus in the new species does not extend anteriorly past the level of caecal bifurcation, whereas in Ce. dicamptodoni it reaches the oral sucker. The testes in the new species are situated further anteriorly than in Ce. dicamptodoni . Vitelline follicles in the new species extend well posterior to the testes, whereas in Ce. dicamptodoni they reach only the level of the posterior margin of the testes. Lastly, the excretory vesicle in Cr. acanthosauri has relatively longer arms, which reach the caeca, whereas in Ce. dicamptodoni the arms of the excretory vesicle terminate at a significant distance from the ends of the caeca. The two species can also be distinguished easily by their sucker ratios (oral sucker in the new species is 1.4–1.7 times larger than the ventral sucker vs. equal suckers in Ce. dicamptodoni ). In addition, the two species are geographically isolated, because the new species was found in Vietnam, whereas Ce. dicamptodoni was described from the Pacific Northwest of the USA. Thus, several highly distinctive morphological features of Cr. acanthosauri clearly support its status as a new species.

Figures

Figure 4. Cryptotropa acanthosauri. A, ventral view of the holotype. B, ventral view of the paratype.

Figure 5. Position of copulatory pouch in the four new species described in this study. A, Cryptotropa acanthosauri. B, Pseudocryptotropa surniculi. C, Pseudocryptotropa testilobata. D, Paracryptotropa peruviana.