Helobdella atli Oceguera­Figueroa & León­Régagnon, 2005

Oceguera-Figueroa, Alejandro & Leon-Regagnon, Virginia, 2005, A new freshwater leech species of Helobdella (Annelida: Glossiphoniidae) from central Mexico, Zootaxa 976, pp. 1-8 : 2-6

Helobdella atli Oceguera­Figueroa & León­Régagnon , new species

External Morphology. Adults are mostly of a white­yellowish color, some of them slightly darker. On the dorsal surface, there is a middorsal line of papillae only found in a2 and a3 of each midbody somite. Body margins show small projections in a2 and a3 giving the organism a serrated appearance ( Fig. 1 ). Ventral surface white without papillae ( Fig. 2 ). Body length 7.5 mm, maximal width 2.3 mm. (n=20). Male gonopore situated on XII a1/a2, female gonopore on XII a2/a3. Genital pores separated by a single annulus. Anus located on the dorsal surface at XXVII ( Fig.3 ). One pair of eyes located on somite IV. A well defined nuchal scute occurs at VIII a1/a2 ( Fig. 4 ). Somites I­II fused. Somites III–IV fused or not well divided. Somite V biannulate, somites VI­XXIV triannulate, somites XXV–XXVI biannulate and somite XXVII uniannulate. Oral sucker somewhat triangular with mouth­pore subterminal. Caudal sucker smooth and directed ventrally in relaxed specimens.

Internal Morphology. The mouth pore is located on the anterior margin of the oral sucker. Proboscis in membranous sheath. Salivary cells arranged diffusely in parenchyma in somites XI–XIII. Ductules of the salivary cells forming a bundle inserting into the base of the proboscis in somite XIII. Oesophagus simple, not recurved. Mycetomes absent. Crop provided with six digitiform caeca in somites XIV–XIX; postcaeca or diverticula absent. Intestine with four caeca in somites XX­XXIII, the first two anteriorly directed and the last two pairs laterally directed ( Fig. 5 ). Six pairs of testisacs found intersegmentally from XIII/XIV to XVIII/XIX. Vas deferens with a long posterior extension, sometimes to the last pair of crop caeca in somite XIX. Ovisacs simple, not folded, very large, reaching somite XIX ( Fig. 6 ).

Etymology: atl means “water” in Nahuatl, a native dialect of the central region of Mexico, and refers to the environment where the leeches live.

Type Locality: Laguna de Totolcingo, Municipio de “El Carmen Tequexquita” Tlaxcala, México.

Other localities: Aljojuca, Puebla and Xochimilco, Mexico D.F.

Holotype: Colección Nacional de Helmintos ( CNHE 5208). Fixed in Formalin 4% and preserved in 70% ethanol. Length 6.2mm, width 2.1mm.

Paratypes: Colección Nacional de Helmintos. Five specimens ( CNHE 5209) one slide ( CNHE 5210)

American Museum of Natural History ( AMNH 5264 annelida)

Figures

FIGURE 1. Helobdella atli n. sp. from Totolcingo, Tlaxcala, Mexico. Dorsal view of the holotype.

FIGURE 2. Helobdella atli n. sp. from Totolcingo, Tlaxcala, Mexico. Ventral view of the holotype

FIGURE 3. Helobdella atli n. sp. from Totolcingo, Tlaxcala, México. Scanning electron microphotography of posterior part, showing the position of anus.

FIGURE 4. Helobdella atli n. sp. from Totolcingo, Tlaxcala, Mexico. Scanning electron microphotography of the anterior part, showing nuchal scute.

FIGURE 5. Helobdella atli n. sp. from Totolcingo, Tlaxcala, Mexico. Digestive system and testisacs.

FIGURE 6. Helobdella atli n. sp. from Totolcingo, Tlaxcala, Mexico. Reproductive system.