Helobdella bolivianita SIDDALL, 2001, new species

Field: Agricultural and Biological Sciences (Life Sciences)

Helobdella bolivianita, new species Figures 4–7 HOLOTYPE (fig. 4): Free­living from Laguna Volcán, Departmento de Santa Cruz, Bolivia, 18°07′17"S, 63°38′88"W, 14 November 1999, hand collected M. Siddall and C. Specht; (deposited in Museo de Historia Natural Noel­Kempff Mercado, Santa Cruz, Bolivia, uncataloged); body length 15.4 mm, maximal width 2.6 mm, fixed in 10% formalin, stored in 70% ethanol. PARATYPES: Free­living from Laguna Volcán, Departmento de Santa Cruz, Bolivia, 18°07′17"S, 63°38′88" W, 14 November 1999, hand collected M. Siddall and C. Specht. Six mature specimens and 10 immature fixed in 10% formalin, stored in 70% ethanol (AMNH 4224, Annelida); one mature cleared in Hemo­D (AMNH 4225, Annelida); one dissected sexually mature, fixed in 10% formalin, stored in 70% ethanol (AMNH 4226, Annelida); one sectioned sexually mature, fixed in 10% formalin, mounted on 22 glass slides (AMNH 4227.1 through 4227.22, Annelida); seven sexually mature and 11 immature specimens fixed in 10% formalin, stored in 70% ethanol (Museo de Historia Natural Noel­Kempff Mercado, Santa Cruz, Bolivia, uncataloged); one sexually mature fixed and stored in 95% ethanol held at —80°C (AMNH 100009, Frozen Tissue Collection); six mature specimens and six juveniles fixed and stored in 95% ethanol (AMNH 4228); seven mature specimens and six juveniles fixed and stored in 95% ethanol (Museo de Historia Natural Noel­Kempff Mercado, Santa Cruz, Bolivia, uncataloged). ETYMOLOGY: Name refers to the combined violet and yellow appearance of this leech in the living state, which resembles a composite mineral, Bolivianite (or ametrine), a combination of amethyst and citrine unique to eastern Bolivia. DIAGNOSIS: This species is distinguished from other scutiferous species of the genus by having paired salivary glands at the base of the proboscis as well as diffuse salivary tissue in the parenchyma, subdivided annuli, six pairs of gastric caeca including diverticula, and six pairs of testisacs. FORM (fig. 4): Body lanceolate, broadest in posterior half; somites I through IV forming somewhat broadened head region; dorsum convex, with inconspicuous papillae in some; venter flat to slightly concave, without papillae; anterior sucker oval; mouth pore subterminal; caudal sucker circular, concave, directed ventrad, diameter smaller than width of posterior somites; middorsal nuchal glands and scute in VIIIa1/a2. EYES (fig. 4): One pair, punctiform to triangular, at junction of III and IV. ANNULATION (fig. 4): Somites I and II uniannulate; III and IV biannulate; V through XXIV triannulate each annulus subdivided; XXV and XXVI biannulate and subdivided, XVII uniannulate but no distinction from caudal sucker middorsally. COLOR AND PATTERN (fig. 4): When alive, anterior one­third of body appearing violet blending to yellow posteriad; chromatophores arranged in approximately 30 faint longitudinal arrays dorsally, and approximately 20 faint longitudinal arrays ventrally; dorsally one pair of solid paramedial lines from IV to XXIII or XXIV, becoming intermittent more posteriorly, a second pair of lines, fainter and more lateral from VII through XXIII, supramarginal lines fainter; ventrally two pairs of paramedial lines, the innermost being stronger. Anterior margin of oral sucker (I, II) considerably less pigmented than midbody somites. REPRODUCTIVE SYSTEM (figs. 5, 6): Male and female gonopores separated by one annulus, male at XII a1/a2, female at XII a2/ a3; six pairs of testisacs visible histologically at XIII/XIV through XVIII/XIX; sperm ducts exit parenchyma in XIII, extend posteriad to XVI, and fold back to XV or XIV such that if unfolded would reach XVI before returning anteriad, sperm ducts empty into atria anterioventrally without preatrial loops; atria piriform approximately at 45° to midline; ovisacs robust but simple, extending to XV. ALIMENTARY TRACT (figs. 5, 7): Proboscis slightly thicker at base than tip, in membranous sheath, base of proboscis at XII in relaxed state; salivary cells arranged both as a pair of glandular masses at base of proboscis and diffusely in parenchyma, ductules of the latter forming a bundle inserting into the former, oesophagus simple, not recurved; gastric chambers with digitiform caeca, six including postcaeca (diverticula), first five in XIV through XVII, postcaeca from XIX through XXIII or XXIV; intestine from XIX/ XX, four lobes but not pronouncedly caecate; anus at XXVI/XXVII. REMARKS: No other scutiferous species of leech is known to possess both compact salivary glands and diffuse salivary tissue. The presence of a nuchal scute on VIII is a clear synapomorphy (Light and Siddall, 1999) for a subset of species in the genus Helobdella, indicating that H. bolivianita is allied with the type species of the genus, Helobdella stagnalis (L.). In South America there are 11 known scutiferous species, most of which can be readily distinguished from H. bolivianita. Although Adaetobdella xenoica (Ringuelet, 1975) Sawyer, 1986, has compact salivary glands, six pairs of testisacs and a scute on VIII, it has seven crop chambers, a preatrial loop for each sperm duct, and no posterior crop diverticula and does not exhibit subdivided annuli (Ringuelet, 1975, 1978b). The most broadly distributed species of scutiferous leech in South America is Helobdella scutifera Blanchard, 1900, known from as far south as Tierra del Fuego (Moore, 1911) and as far North as Rio Grande do Norte, Brazil (Cordero, 1937a). Blanchard (1900) noted dorsal paramedial lines in some individuals of H. scutifera reminiscent of Glossiphonia complanata and superficially similar to those described here for H. bolivianita. However, H. scutifera has salivary cells diffusely arranged in the parenchyma, a very long proboscis extending to and folding back anteriorly at XIV, ovaries only as long as XIV, and sperm ducts that reach XIX (Blanchard, 1900; Weber, 1915; Ringuelet, 1978a). Helobdella diploides Ringuelet, 1948, although it lacks any observable pigmentation, exhibits subdivided annuli from VII through XXV and a scute in VIII similar to H. bolivianita. Otherwise it is unique in having exceedingly short sperm ducts, recurving anteriorly at XIV, and atria that are distinctly at right angles to the midline (Ringuelet, 1948). Helobdella godeti Weber, 1916, Helobdella simplex Moore, 1911, and Helobdella montevidensis Cordero, 1937, though scutiferous, do not have subdivided annuli and each has obvious dorsal papillation. The most similar species and one that individuals of H. bolivianita may previously have been confused with is Helobdella duplicata Moore, 1911, originally described from Patagonia but now attributed to a broader South American distribution. Helobdella duplicata has subdivided annuli, six pairs of gastric caeca including postcaeca, six pairs of testisacs, a scute in VIII, and a caudal sucker directed strongly ventrad (Moore, 1911). However, numerous features distinguish H. duplicata from H. bolivianita, most notably a lack of compact salivary glands, a transverse metameric pigmentation on annulus a1 of each somite, globular atria with anteriodorsal insertion of spermducts, ovaries that reach XVII, and the presence of pronounced lateral caeca of the intestine (Moore, 1911).