Helobdella socimulcensis ( Caballero, 1931 )

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 socimulcensis ( Caballero, 1931)

Figs 2 , 3 , 4

Helobdella moorei Caballero, 1933 – León, Guanajuato; Mexico.

Helobdella conchata Caballero, 1941 – Cuautla, Morelos Mexico.

Helobdella triserialis var. lineata Ringuelet, 1943 – Xochimilco, Mexico City (sensu Ringuelet 1981).

Neotype designation.

Mexico • A stained adult, mounted in a slide. 11.5 length and 4.5 maximum width at somite XIX; Xochimilco , Mexico City; 19°17'21"N, 99°06'31"W; Collected by G. T-C. CNHE 12299 .

Note.

According to Article 75.3 of the ICZN, a neotype is designated due to the absence or loss of the original type material. Caballero (1931) did not designate any specimen as part of the type series, and no specimens attributable to the original description of Glossiphonia socimulcensis , 1931 have been found in the CNHE or any other scientific collection. Furthermore, the nomenclatural act presented here is justified by the recognition of five lineages with specimens that exhibit morphological similarities to H. socimulcensis . In the absence of type material, meaningful comparisons are hindered. The neotype is designated from material collected from the type locality (Lake Xochimilco) and after ensuring a morphological correspondence with the original description. Finally, DNA sequences were obtained from specimens collected in the present study; these sequences have been validated and comply with the recommendations outlined by Kvist et al. (2010).

Material examined.

Mexico • Neotype and 20 adult specimens in total: 13 stored in ethanol, six mounted on slides and one processed for SEM; same data as for Neotype; CNHE 12298 . Mexico • 116 ethanol-preserved adult specimens; same data as for Neotype; collected by GT-C between April and November 2021; CNHE 13037 . Mexico • six adult specimens preserved in ethanol and one slide of an immature specimen; same data as for Neotype; Collected by Salas-Montiel and AO-F; CNHE 8860 . Mexico • One adult specimen; same data as for Neotype; collected by AO-F on February 2003; CNHE 4705 ( Oceguera-Figueroa 2007 . Mexico • two adult specimens; Lago de Tecocomulco , Hidalgo; 19°51'57"N; 98°23'51"W; collected by AO-F on 21 August 2004 CNHE 4704 . Mexico • “ Hellobdela conchata ” Holotype Cuautla , Morelos CNHE 1852 , and 2 adult paratypes; same data as for Holotype; CNHE 1853 .

Diagnosis.

Small leeches, 4–16 length and 1.5–9 width ( n = 115). Dorsal surface with ~ 34 brown stripes. Midline longitudinal paired stripes of solid color extend from Va 2 to the anus, separated by a distance approximately equal to that between eyespots; the stripes join each other at a 2 of each somite, creating a chain-like appearance. Three dorsal rows of longitudinal, dark brown-tipped papillae on a 2: one median and two lateral rows. In some specimens, an additional pair of marginal rows more prominent in the posterior third of the body. Papillae smaller than the width of individual annuli. Eyespots punctiform and well separated. Full body with 68 annuli. Esophagus slightly globular, spanning six annuli. Crop with five pairs of digitiform caeca, the last pair forming post-caeca. Testisacs in five intersegmental pairs.

Description.

External morphology. Body lanceolate, 3–16 length and 1.5–9 maximum width at somite XIX ( n = 115). Ground color pale yellow or cream; dorsal preocular zone unpigmented (Fig. 2 A – C ). Dorsal surface with ~ 34 stripes of longitudinal brown stripes (visible in stained specimens). A pair of solid midline stripes, separated by a distance equivalent to the distance between eyespots, extends from Va 2 to the anus at XXVII. The stripes join each other at a 2 of each somite, creating a chain-like appearance. The remaining 32 stripes (16 pairs) are slender extend from Va 2 or Va 3 (annuli 6 or 7) and continue to the anus (Fig. 2 A ). Dorsum with three longitudinal rows of dark brown-tipped papillae located in a 2 of each somite, one row median and two laterals. In some specimens, an additional pair of incomplete marginal rows may be present, papillae more prominent in the posterior third of the body, some papillae unpigmented (Fig. 2 A ). Median papillae row extends from X – XI to XXV – XXVI; lateral rows from XIII to XXVI (Fig. 2 C ). Papillae smaller than the width of an annulus. Dorsal white spots conspicuous, in three longitudinal rows metamerically arranged: one central and two laterals. White spots somewhat circular, approximately the size of an annulus and located in a 2, beside lateral rows of papillae. Median row of white spots from VIII to XXVI; lateral rows from XII or XIII. Eyespots punctiform at IV a 1 / a 2, well-separated. Anus dorsal, at XVII. Ventral surface whitish, without papillae. Mouth pore located at the anterior margin of the anterior sucker. Gonopores separated by a single annulus, male gonopore in XII a 1 / a 2, female gonopore in XII a 2 / a 3. In total, 68 annuli along the body. Annulation: I – II fused; III uni-annulate; IV bi-annulate; V – XXIV tri-annulate; XXV bi-annulate; XXVI and XXVII uni-annulate (Fig. 2 C ).

Internal morphology. Proboscis straight, not curved. 1.95 total length, extending from IX to XIV when retracted. Salivary glands diffuse in the parenchyma, extending from XI to XVII. Salivary ducts connect to the base of the proboscis at XIV. Esophagus enlarged, slightly globular, chamber-like, from XIIIa 3 to XV a 1. Crop with five pairs of digitiform caeca, the first four pairs laterally directed, with the first pair at XV; the fifth pair forming sinuous post-caeca from XIX to XXIII (Fig. 3 A ). Intestine with four pairs of caeca, the first three pairs directed slightly anteriorly and last pair directed posteriorly. Male atrial cornua laterally directed. Vas deferens with a short descending loop, reaching the first pair of testisacs or XIV (Fig. 3 B, C ). Five pairs of testisacs present, first pair between XIV and XV. Ovisacs simple, elongate, and not folded, extending to XVII or XVIII (Fig. 3 C ).

Reproductive information. No specimens with spermatophores attached to the body wall were observed at any time. In total, 18 of 116 specimens were found with five or six thin-walled cocoons attached to the ventral surface. The total number of eggs ranges from 20 to 100. The brooding area extended from XVIIa 2 to XXa 3 or XVIa 3 to XXI (Fig. 4 ). Egg diameter 306–479 μm (373, n = 29). Some specimens carried up to 69 embryos attached to ventral surface (Fig. 2 B ), easily lost during manipulation and fixation. The highest proportion of gravid or brooding individuals were collected between May and July.

Remarks.

The newly collected specimens collected in Xochimilco exhibit morphological traits consistent with the original description of H. socimulcensis , with two differences: a smaller maximum body length (10 vs 15) and higher number of annuli (68 vs 65). Regarding the difference in the number of annuli, Caballero (1931) considered that eyespots were located in somite I instead IV a 2. This difference in annuli numbering accounts for the apparent difference.

Figures

Figure 2. Helobdella socimulcensis from Xochimilco, Mexico. A. Dorsal view; B. Ventral view showing attached broods; C. SEM microphotograph showing somite numbering. Abbreviations: an = anus. Scale bar: 2 mm.

Figure 3. Helobdella socimulcensis from Xochimilco, Mexico City, Mexico. Internal morphology. A. Digestive system; B. Male reproductive system; C. Male and female reproductive systems. Abbreviations: Pr = proboscis; sg = salivary glands; cc = crop caeca; pc = post-caeca; int = intestine.

Figure 4. Helobdella socimulcensis from Xochimilco, Mexico. Ventral surface showing eggs attached. Scale bar: 500 μm.