Helobdella paranensis

External morphology

Body elongate-oval, depressed, 36 mm in length and 10 mm in maximum width. Annuli smooth, without tubercles. Mouth situated on the anterior lip of the capitulum, which is formed by segments I through IV. Two eyes located on the second annulus (somite III). Gonopores separated by annulus XII (b3 + b4); the male gonopore is located at XII b2/(b3 + b4), and the female at XII (b3 + b4)/b5. Somites I through V possess an indeterminate number of annuli; somite VI is 3-annulate. Somite VII is 3-annulate, with the VIIth annulus (b5 + b6) subdivided; VIII consists of 3 annuli, the first and last of which are subdivided: (b1 + b2) – a2 – (b5 + b6); IX is 5-annulate, with a2 being twice the size of b1, b2, b5, and b6. From X through segment XXII, each somite bears 6 similar annuli dorsally—namely, b1, b2, b3, b4, b5, and b6. Ventrally, the somites possess 5 annuli: 2 anterior ones (b1 and b2), the subdivided neural annulus (b3 + b4), and 2 posterior ones (b5 and b6). On the dorsal aspect, segments XXIII and XXIV each bear 3 subdivided annuli; XXV is 2-annulate, with the second annulus being much narrower. These are followed by 3 annuli corresponding to segments XXVI and XXVII, with the anus situated between the first two. In alcohol, the coloration is a uniform grayish hue—slightly lighter on the ventral aspect—devoid of any spots, bands, or striations.

Internal morphology

The crop is provided with 6 lateral pairs of simple caeca, and the intestine features the customary 4 pairs of caeca. Six pairs of testes are present.

Habitat & range

Habitat

Freshwater

Region

South America

Recorded from

Uruguay, Brazil