Parapraobdella lineata ( Sciacchitano, 1959 )

Phillips, Anna J., Oosthuizen, J. H. & Siddall, Mark E., 2011, Redescription, phylogenetic placement, and taxonomic reassignment of Mesobdella lineata (Sciacchitano, 1959) (Hirudinida: Arhynchobdellida), American Museum Novitates 2011 (3711), pp. 1-12 : 6-8

Parapraobdella lineata ( Sciacchitano, 1959)

Figures 1–3

REDESCRIPTION: Holotype, body length 6.4 mm, maximal width 3.7 mm; dissected. Body muscular. Dorsal surface with transversal bands of light olive green on two annuli and dark olive green on the following three annuli, repeated along the length of the body (figs. 2, 3A). Fifteen five-annulate midbody somites from X to XXIV; b1 and b6 diminutive falsely leading toward a triannulate appearance. Somites: I–III uniannulate, IV and V biannulate, VI biannulate with anterior annulus subdivided dorsally, VII triannulate with annulus b6 subdivided ventrally, VIII quadrannulate, IX quadrannulate with annulus a3 subdivided dorsally, X–XXIV five-annulate, XXV triannulate, XXVI biannulate, and XXVII uniannulate. Eyespots arranged dorsally in five pairs in a broad arch. Pair 1 anterior on somite III, remaining eyespots situated laterally on contiguous annuli of a pair on each annulus of somite IV and anterior annulus of somite V. Pairs 4 and 5 separated by one annulus (IVa3; fig. 3B). First two pairs of eyespots with pigment concentrated anterolaterally in eyespot, last three pairs with pigment concentrated posterolaterally in eyespot. Sensillae obvious in live condition, mostly obscure in preserved specimens. Nephropores 17 pairs on ventral surface situated bilaterally from somite VII to somite XXIII; in complete somites, just posterior to b2/a2 furrow and 17th pair in same position as others. Caudal sucker round, wider than the four most posterior somites without friction rays. Male gonopore at XI b5/ b 6 in furrow, female gonopore at XII b5/b 6 in furrow, five annuli between gonopores.

Jaws trignathous, monostichodont, no salivary papillae (fig. 3D). Jaws moderate in size, low, rounded. Teeth located in shallow open grooves, eight teeth per jaw. Dorsal lip of oral sucker with medial longitudinal furrow and nine sensillae, which are more pronounced in some specimens (fig. 3B). Oral velum absent. Pharynx short, terminating in somite VIII (fig. 3D). Internal muscular ridges, six arranged in dorsomedial and ventrolateral pairs, each pair fusing at base of each jaw. Esophagus narrow, lumen wide, tubular, tapering posteriorly to junction with crop. Pharynx terminating in somite VIII followed by an acecate compartment, which reaches up to the middle of somite IX. Crop from somite IX to somite XX, first 10 pairs of crop ceca simple and equal size, postceca not foliaceous extending bilaterally posterior to somite XVI. Intestine tubular, acecate, joining rectum at somite XXIV (fig. 3C). Rectum thin walled, tubular. Anus in furrow between last annulus and caudal sucker.

Internal male and female reproductive organs micromorphic. Male atrium bulbous, not extended into elongated penis or sheath (fig. 3E). Epididymis and ejaculatory bulbs absent. Vasa deferentia insert into dorsal median of male atrium. Vasa deferentia pass anterolaterally with two bends in an S-like shape before descending to testisacs. Vagina short. Common oviduct absent. Ovaries simple, bulbous.

HABITAT: Terrestrial. Associated with moist surroundings, such as vegetation by streams (Oosthuizen, personal obs.).

TYPE LOCALITY: Debegeni Falls (23°48′49.71″S 30°01′44.87″E), Limpopo Province, South Africa (previously Transvaal) .

REMARKS: Mesobdella lineata is not consistent with any other described genus and warrants the creation of a new genus. The species does not belong in the genus Mesobdella within Xerobdellidae : it is five-annulate, not three-annulate; it lacks the xerobdellid midventral nephridial pore; it does not have friction rays on the caudal sucker; the male atrium does not extend into a penis or sheath; it lacks epididymes ( Sawyer, 1986; Borda et al., 2008). Parapraobdella lineata differs from X. lecomtei : it does not have epididymes or defined ejaculatory bulbs, and it lacks a seminal receptacle and the associated accessory pore ( Borda et al., 2008). The species does not belong in the family Haemadipsidae : it lacks respiratory auricles; the eyespots are not arranged in the “haemadipsine” ocular arch; it has a caudal sucker that is round and lacks friction rays; the median reproductive apparatus is small compared to the highly robust apparatus typical of haemadipsids ( Sawyer, 1986; Borda et al., 2008). The species also does not belong in the family Hirudinidae : it does not have muscular ejaculatory bulbs adjacent to the epididymes; the male atrium is not extended into an elongated penis and sheath; it has eight teeth compared to 60–150 teeth seen in Hirudinidae ( Harding and Moore, 1927; Moore, 1938; Richardson, 1969). The species is not a macrobdellid: it does not have accessory glands, muscular ejaculatory bulbs, or annuli between the anus and the caudal sucker; it has one rather than two crop ceca per somite; it has eight teeth compared to the 30–60 teeth observed in macrobdellids ( Richardson, 1969; Phillips and Siddall, 2005).

The caudal sucker wider than the four most posterior somites of the body, possessing only eight teeth, micromorphic reproductive structures, and no postanal annuli all point to a placement of this genus and species within the family Praobdellidae along with, yet distinct from, the genera Praobdella , Myxobdella , Dinobdella , Limnatis , Limnobdella , Pintobdella , and Tyrannobdella ( Phillips et al., 2010) . Members of the genus Praobdella have more than five annuli between the gonopores, while P. lineata has exactly five annuli between the gonopores ( Sawyer, 1986). Whereas P. lineata has three jaws armed with eight small teeth and does not have a velar mouth, it is unlike Pintobdella chiapasensis (Caballero, 1958) , which has three jaws with six large teeth without a velum, and unlike Tyrannobdella rex ( Phillips et al., 2010) , which has only a single jaw with eight large teeth and a velum (Caballero, 1958; Phillips et al., 2010). The new genus Parapraobdella is distinct from Dinobdella ferox (Moore, 1927) , which does not possess teeth, and from the distichodont genera Myxobdella and Praobdella (Moore, 1927, 1938; Sawyer, 1986).

In Sciacchitano’s (1959) original description, he noted the presence of red papillae along the dorsal surface of the body. No such coloration of the papillae was observed in this study, and although the specimens examined here were preserved, several have retained their pigmentation. In addition, Sciacchitano (1959) described 40 black longitudinal lines on the ventral surface of the specimens he examined, but it seems that he was describing the internal longitudinal muscles of the body wall.