Helobdella gulloae, Torres-Carrera & Duarte-De Lima & Oceguera-Figueroa, 2025

Torres-Carrera, Gerardo, Duarte-De Lima, Lucas & Oceguera-Figueroa, Alejandro, 2025, Description of two new species of freshwater leeches of the genus Helobdella (Hirudinea, Glossiphoniidae) from Mexico, with a redescription of Helobdella socimulcensis (Caballero, 1931), ZooKeys 1261, pp. 141-164 : 141-164

Helobdella gulloae sp. nov.

Figs 8 , 9

Type material.

Holotype. Mexico • adult; Laguna Escondida, Municipio de San Andres, Tuxtla , Veracruz; 18 ° 35 ' 39.5761 " N, 95 ° 04 ' 55.6140 " W; collected by GT-C and AO-F on April 2017; CNHE 11133 . Paratypes. Mexico • 6 adults paratypes; same data as for Holotype; CNHE 12296 .

Other material.

Mexico • Four stained adults; Nanciyaga, Catemaco , Veracruz; 18 ° 26 ' 50.1169 " N, 95 ° 04 ' 09.2788 " W Collected by GT-C and FR-E in November 2021. CNHE 12297 .

Diagnosis.

Small leech, 4.5–8 length and 2–2.5 maximum width at somite XIX ( n = 6). Dorsum with ~ 37 longitudinal brown stripes. A pair of midline brown stripes originates near the eyespots until XVI, then fusing forming a single, broad stripe that reach XXI. Beyond this somite, the stripe is interrupted by square white spots, from XXI a 3 to the posterior end. Three longitudinal rows of black-tipped papillae present; additional, incomplete rows occasionally observed near the body margins. Papillae slightly wider than individual annuli. Eyespots semi-oval. Whole body with total of 69 annuli. Esophagus short, extending one or two annuli in length. Crop with five pairs of caeca, last pair forming post-caeca. Intestine with four caeca. Testisacs in four intersegmental pairs.

Description.

Description based on holotype (stained), 9.6 length and 2.3 maximum width at somite XIX a 2, and six paratypes, five stained and one processed for SEM.

External morphology. Body slightly lanceolate, 4.5–8 length and 2–2.5 maximum width at somite XIX. Ground color pale yellow or cream; dorsal preocular zone unpigmented (I + II to Va 2) except for the anterior end of the dorsal midline stripes that extend to reach the eyespots (Fig. 8 A ). Dorsal surface with the characteristic brown longitudinal striping pattern of species of the “ triserialis ” series, with ~ 37 brown stripes visible in stained specimens. A pair of longitudinal midline stripes from IVa 3 and fuse into a single, broad stripe from XVI to the anus; this band is interrupted by square-shaped white spots located at each a 3 / a 1 from XXII to the posterior end. The remaining pairs of dorsal brown stripes extend from IVa 3 to the anus. Three rows of dorsal papillae heavily pigmented on a 2. Additional lateral may occur though these are typically incomplete. Papillae slightly exceed the width of individual annulus. Midline row of papillae extends from X, with conspicuous papillae evident from XII or XIII to XXVI (Fig. 8 C ). Lateral rows of papillae begin at XIV to XXV. White spots conspicuous, square to circular in shape, and smaller than the width of individual annulus; arranged in two paired rows on each side of the body, located on a 2, flanking each papilla. White spots flanking central papillae begin at V or VI, and extend to XXVI, lateral rows of white spots extend from XII to XXVII. Eyespots semioval, at IVa 1 + a 2, well-separated. Anus on XVII, typically surrounded by black pigment. Ventral surface ground cream-colored, with faint, thin longitudinal brown stripes (Fig. 8 B ). Oral sucker white; mouth located at the anterior margin. Gonopores separated by a single annulus (XII a 2). Whole body with 69 annuli. Annulation: I and II fused; III and IV bi-annulate; V – XXIV tri-annulate; XXV bi-annulate, and XXVI, XXVII uni-annulate (Fig. 8 C ).

Internal morphology. Proboscis straight, not recurved, 1.52 length, extending from X to XIV. Salivary glands diffuse into parenchyma between XII and XV; ductules not forming bundle, insert independently into base of proboscis. Esophagus short, from at XVa 1 to XV a 2. Crop with five pairs of caeca; first four pairs digitiform and laterally directed; last pair with descending sinuous path or post-caeca, from XIX to XXII (Fig. 9 A ). Intestine with four pairs of digitiform caeca, the first three pairs directed anteriorly and last pair directed posteriorly. Testisacs in four intersegmental pairs, the first pair between XV / XVI, last pair XVIII / XIX. Ejaculatory ducts reaching the first pair of testisacs or XV / XVI (Fig. 9 B ). Ovisacs saccular, reaching XIX when it is filled (Fig. 9 C ).

Reproductive information. No specimens were observed with spermatophores attached to the body wall, nor were any specimens found carrying eggs or young leeches on the ventral surface.

Etymology.

The species is named in honor of the Argentinian biologist Dr. Betina Sandra Gullo, in recognition of her significant contributions to the knowledge of South American leeches, in particular those within the genus Helobdella .

Remarks.

The morphological characteristics of Helobdella gulloae sp. nov. are consistent with those diagnostic of the genus ( Sawyer 1986; Siddall and Borda 2003); including their dorsoventrally flattened body, gonopores separated by a single annulus, one pair of cephalic eyespots and the absence of esophageal organs (bacteriomes). The presence of multiple, longitudinal dorsal stripes and metamerically arranged papilla clearly support its inclusion in the “ triserialis ” series sensu Sawyer 1986.

Helobdella gulloae can be differentiated from other species of the “ triserialis ” series by difference of patterns of dorsal pigmentation and papillae distribution. Helobdella papillata has three rows of papillae restricted to the posterior third of dorsum (XIX or XX), while in H. gulloae sp. nov., dorsal rows of papillae begin at X. Additionally, H. papillata lacks dorsal pigmentation. In H. lineata , dorsal papillae are irregularly scattered, while in H. gulloae sp. nov. dorsal papillae are regularly arranged. Helobdella transversa lacks both longitudinal pigmented stripes and papillae ( Sawyer 1972; Light and Siddall 1999), clearly contrasting with H. gulloae sp. nov. Helobdella lineata exhibits 12–14 longitudinal stripes on the dorsal surface, whereas H. gulloae sp. nov. display ~ 37. Helobdella fusca and Helobdella virginiae are characterized by irregularly arranged dorsal spots, clearly contrasting with the metameric pattern characteristic of H. gulloae sp. nov. (Table 2 ).

Helobdella gulloae sp. nov. is morphologically and phylogenetically (see below) closely related to H. papilloprocta sp. nov. The presence of two prominent papillae adjacent to the anus in H. papilloprocta sp. nov. appears to be a consistent and reliable character to separate both species. Furthermore, H. gulloae sp. nov. seems to be the only species of the “ triserialis ” series with only four pairs of testisacs, contrary to five or six pairs, which are more common in this genus.

The cox 1 genetic distance, calculated under the K 2 P substitution model, between H. papilloprocta sp. nov. and H. gulloae sp. nov. is 3.33 %. This value is comparable to the interspecific distance found between other sister species of Helobdella , such as H. austinensis and H. virginiae or H. socimulcensis and H. farmeri . The remaining pairwise genetic distances are presented in Table 3 .

Figures

Figure 8. Helobdella gulloae sp. nov. A. Dorsal view; B. Ventral view; C. SEM microphotograph showing somite numbering. Abbreviations: an = anus. Scale bar: 2 mm.

Figure 9. Internal morphology of a stained paratype specimen of Helobdella gulloae sp. nov. A. Digestive tract; B. Male reproductive system; C. Male and female reproductive systems. Abbreviations: pr = proboscis, sg = salivary glands, cc = crop caeca, pc = post-caeca, int = intestine.