Checklist / Glossiphoniidae / Helobdella / Helobdella gemmata
Helobdella gemmata
· Glossiphoniidae
External morphology
Body broad, with a transversely oval cephalic lobe composed of eight annuli (I to Va2). Annuli simple, not subdivided. Two eyes located on annulus III (a1–a2). Gonopores separated by two annuli: the male gonopore is located at XI/XII, and the female at XIIa1/a2. On each middle, or neural, annulus (a2), there are four dorsal and three ventral pairs of sensillae situated upon small segmental papillae. Anus located posterior to XXVII. Somites I and II are uniannulate; III and IV are biannulate; V is triannulate—though on its ventral aspect it appears biannulate, as the furrow between Va2 and Va3 is deeper than adjacent furrows and serves to delimit the cephalic lobe; somites VI through XXIV are triannulate; XXV and XXVI are biannulate; and XXVII is uniannulate. The mouth is situated within the concavity of the acetabulum (sucker), at the level of somite IV. In life, the coloration is a dark violet-gray, unblemished by spots, with white preocular rings. Against this dark background, the white segmental papillae stand out in sharp relief. The ventral aspect is much lighter—a milky violet-gray. The specimens from Córdoba feature two dark gray lines that, originating very close to the eyes, traverse the entire body as far as the cotyle, at a short distance from the midline.
Internal morphology
The pharynx descends as far as XI/XII, whereupon it ascends along a recurrent path—forming a distinct loop—to reach the ganglion of somite XI. At its base, it receives the ducts of the compact, globose salivary glands, each of which consists of a dense cluster of cells. Four of these glandular masses encircle the base of the pharyngeal sac at somite XI, while the fifth mass is situated more posteriorly, at the level of XI/XII; this latter mass possesses a long duct which, together with the shorter ducts of the other glands, empties into the base of the pharynx. The esophagus is a slender tube that originates from the base of the pharyngeal sac at somite XI—situated on a plane inferior to the pharynx itself—and continues through somite XII, at the posterior boundary of which it opens into the crop. Midgut or crop extending from XIII to XIX, featuring 7 pairs of lobed lateral ceca—with the exception of the first pair, which is simple. The pair of post-ceca in segment XIX descends, bearing 3 secondary lateral lobes, as far as the level of ganglion XXII. There are six pairs of testes, ranging from XIII/XIV to XVIII/XIX. The vas deferens on each side ascends as an extremely fine, whitish thread as far as segment 53 XI, where it turns toward the midline and abruptly widens into the epididymis on its respective side. This spermatic duct is a whitish, slender, and rather delicate tube with an opaque, rough surface. It descends to the beginning of somite XIV (one duct being longer than the other), from where it ascends to the level of ganglion XII—retaining its characteristic features throughout—and there opens into the ejaculatory duct on its side, following a constriction. The spermiducts on the left side exhibit curves and loops, whereas those on the right side are straighter. The ejaculatory ducts are of the same caliber as the spermatic ducts but are more robust, with a smooth, glossy surface. They ascend in a curve to a point slightly above ganglion XI, where each bends and descends to open into the atrial horn on its side, following a strong constriction. The atrial horns are globose, forming an obtuse angle that opens caudally. The ovarian tubes are slender, extending as far as segments XV and XVI, with curved tips.
Habitat & range
- Habitat
- Freshwater
- Region
- South America
- Recorded from
- Uruguay, Chile, Argentina
Junior synonyms
Batracobdella gemmata