Key to the Freshwater Leeches of South America

modified from Sawyer, 1986


1 Well formed jaws with single row teeth (Monostichodontia)2*
- No teeth; jaws lacking or at most rudimentary12*

At least some species of Blanchardiella have rudimentary jaws with stylets.
2 Mid-body segments comprised of three or four annuli3*
- Segments comprised of five or more annuli5*
3 Segments three-annulate; three jaws (trignathous) 4*
- Segments four-annulate; two jaws (duognathous):
Land leech known only from Juan Fernandez Islands, off Chile (Ringuelet 1955).
Nesophilaemon skottsbergii (Johansson, 1924)
4 Gonopores separated by four annuli:
Sperm ducts linear in paramedial chamber; land leech known from provinces of Valdivia and Llanquihue, Chile (Ringuelet 1943; Richardson 1971c).
Mesobdella gemmata (E. Blanchard, 1849)
- Gonopores separated by five annuli:
Known from Parc Nacional Huapi, Rio Negro, Argentina (Ringuelet 1953a).
Mesobdella notohilica Ringuelet, 1953
5 Segments 10-annulate; terrestrail: Diestecostoma trujillensis Ringuelet, 1976e

Gonopores separated by 30 annuli; known from coastal Peru (Trujillo). See also key to Central American species of Diestecostoma.
- Segments five-annulate; aquatic6*
6 Gonopores on contiguous annuli, separated by 1/2 + 1/2 annuli (gonopores at XIIb2 and XIIa2):
Known from Argentina and Uruguay.
Oxyptychus inexpectatus Ringuelet, 1945
- Gonopores not on contiguous annuli; separated by at least 1.5 annuli7*
7 Gonopores separated by four complete annuli8*
- Gonopores separted by fewer than four annuli or by 1/2 + 2 + 1/2 annuli9*
8 Dorsum with 101 or 102 annuli; gonopores at XIIb1/b2 and XII/XIII:
Known from Ecuador (see Ringuelet 1981b).
Oxyptychus festai (Dequal, 1916)
- Dorsum with 103 or 104 annuli; gonopores at XI/XII and XIIb5/b6:
Known from eastern Brazil (Cordero 1936, 1937a,b): teeth reportedly 34-43 and with eight pairs testisacs. Closely related form, riopretensis Castro 1971, with 63-81 teeth and 10 pairs testisacs; known from Estado de Sao Paulo, Brazil
Oxyptychus brasiliensis (Pinto, 1920)
9 Gonopores separated by 3 + 1/2 anuuli; at XI/XII and XIIb510*
- Gonopores separated by 1/2 + 2 + 1/2 annuli or by 1 + 1/2 annuli 11*
10 Dorsum with 107-108 annuli; segments VII, four-annulate; VIII and XXIV, each five-annulate:
Known from Paraguay
Oxyptychus strenuus Ringuelet, 1948b
11 Gonopores separated by 1/2 + 2 + 1/2 annuli:
Known from Argentina, Uruguay (Cordero 1937b; Ringuelet 1968, 1981b) and nearby Brazil (Rio Grande do Sul) (Goulart 1963).
Oxyptychus ornatus (Weyenbergh, 1883)
- Gonopores separated by 1 + 1/2 annuli:
Known from Uruguay (Cordero, 1937b), Argentina (Ringuelet 1968), Brazil (Rio Grande do Sul) (Goulart 1963), and Venezuela (Ringuelet 1972b).
Oxyptychus striatus Grube, 1851
12 Ovisacs simple, tubular, meeting in vicinity of female gonopore without forming distinct unpaired region (vagina)
Penis present or lacking
- Vagina present: unpaired female organs of hirudinid type, spheroid ovisacs with oviducts uniting into vagina
Penis present
13 Mid-body segments comprised of 10 or more annuli; caudal sucker lacking or rudimentary14*
- Mid-body segments five-annulate; distinct caudal sucker15*
14 Caudal sucker completely lacking:
Known only from Trinidad
Lumbricobdella schaefferi Kennel, 1886
- Caudal sucker rudimentary:
Known only from Venezuela
Lumbricobdella chamensis Dequal, 1917
15 Reproductive structures characteristic: male atrium firm muscular organ on anterior face of which is a bursa of similar size which receives paired tortuous ducts arising from small elongated ovisacs; male atrium with a small muscular region representing very short penis:
Very large predaceous land leech (up to 20 cm) from around Valdivia, Chile (Pinto 1923; Moore 1924b, 1931b). An unpaired bursa is also known in European land leech Xerobdella lecomtei, but is located at about XI/XII between male and female gonopores and not connected to ovisacs (Moosbrugger and Reisinger 1971) (cf. gastropores of Gastrostomobdella)
Americobdella valdiviana (Philippi, 1872)
- Male median region not associated with unpaired bursa16*
16 Eyes 4-5 paires in hirudinid arch; distinct unpaired male median region (penis)
Aquatic to amphibious species
- Eyes, if present, not in hirudinid arch
Terrestrial, primarily montane species; resembling earthworms
17 Eyes lacking altogether; in life reportedly vivid carmine red (Cylicobdella)
Pharynx with seven longitudinal folds: unpaird ventral and paired dorsolaterals, laterals and ventrolaterals; apparently not terminating anteriorly as small jaw-like structures.
- Eyes three or five (or nine) pairs; obscure grey (Blanchardiella)
Pharynx about 12 longitudinal folds terminating anteriorly as three jaw-like structures; in at least one species Blanchardiella fuhrmanni 'jaws' with two or three conical stylets (Ringuelet 1974). A complex of forms at least some of which are synonymous
18 Gonopores separated by two complete annuli in or near furrows between annnuli; segment IV, one-annulate:
Apparently = C. lumbricoides Grube 1871, which reportedly has an unpaired post-caecum (Kennel 1886). This remians unconfirmed and all subsequent Cylicobdella spp when dissected lack post-caeca. A very closely related form C. intermedia (Nonato, 1946), is common in central Argentina, Uruguay, Paraguay and southern Brazil, whereas the inadequately distinguished C. joseensis occurs in northern South America, from Venezuela to Peru (Ringuelet 1944d, 1945, 1968).
Cylicobdella joseensis (Grube and Oersted, 1859)
- Gonopores separated by 2 + 1/2 annuli or by 1/2 + 1 + 1/2 annuli; segment IV, two-annulate:
No post-caeca; common species of higher elevations (to 4100 m) of northern South America from the Guyanas to Peru, including northern Brazil and Trinidad (Kennel 1886; Moore 1944b; Ringuelet 1961, 1968, 1972b, 1980c, 1981a).
Cylicobdella coccinea Kennel, 1886
19 Eyes nine pairs, III-XI:
Gonopores as in B. fuhrmanni below; Arauca, Colombia; 4000 m. A related obscure species, Hypsobdella columbiensis (Weber, 1913), occurs in Ruiz, Colombia: eyes seven pairs of which two pairs each on annuli 4, 5, and 7 (variable); black mid-dorsal stripe; gonopores separated by three annuli
Blanchardiella adaiopthalma Ringuelet, 1980c
- Eyes 2-5 pairs20*
20 Eyes five pairs:
Costa Rica; a large related form (21.4 cm) recently found in Costa rica (Ringuelet 1981a).
Blanchardiella decemoculata (Dequal, 1917)
- Eyes 3-4 pairs 21*
21 Eyes four pairs (IV-VII), on annuli 4, 5, 7, and 9:
Gonopores as in following species; Tolma, Colombia (Ringuelet 1980c).
Blanchardiella octoculata Weber, 1913
- Eyes three pairs (IV - VI), occasionally two pairs:
Eyes on annuli 5, 6, and 8; or 5, 6, and 9; gonopores separated by two (or 2 + 1/2) complete annuli, at XIIb1/b2 and XIIa2/b5 (variable): anatomy: Ringuelet 1974, 1980c; type locality: Paramo Cruz Verde, Colombia (3600 m); known from Colombia to Venezuela (Ringuelet 1981a). This species is inadequatley distinguished from several closely related forms: peruana Ringuelet, 1961 from Peru; biolleyi Dequal, 1916 (gonopores: two annuli), festai Dequal, 1916 (gonopores: two annuli) and ecuadoriensis Dequal, 1916 (gonopores: 1/2 + 1/2 annuli), all three from ecuador; and cameliae Weber, 1913 (gonopores; 1/2 + 1 + 1/2, at XIIb2 and XIIb5) and tamboensis Weber, 1913, both from Colombia
Blanchardiella fuhrmanni Weber, 1913
22 Gonopores separated by 3.5 - 4 annuli:
Ovisacs tubular and reflected in XIII with very short oviducts; one pair testisacs between adjacent ganglia; ejaculatory bulbs narrow into a duct before entering base of penis; occurs in Rio Plata basin, in Argentina and Paraguay (Ringuelet 1953).
Cyclobdella glabra Weyenbergh, 1879
- Gonopores separated by 4-6 annuli (Orchibdella)
Ovisacs long and tubular reflected at about XV or XVI; ovisacs proper behind penis region, connected to long oviducts which meet at the female gonopores; ejaculatory bulbs, if present, enter penis base directly; two pairs testisacs between adjacent ganglia
23 Female gonopore at XIIIb1; first pair testisacs in anterior half of segment XV:
Known from Rio Plata drainage, Agentina; Uruguay and southern Brazil (Ringuelet 1981a).
Orchibdella pampeana Ringuelet, 1945
- Female gonopore at XII/XIII or 1/2 annulus anterior at XIIb5; first pair testisacs in posterior half of XIV24*
24 Ejaculatory bulbs present, subconical; epididymis little folded, from XII to XIII; base of penis (prostate) elongated:
Known from montane region of north-west Argentina
Orchibdella diaguita Ringuelet, 1978a
- Ejaculatory bulbs lacking; epididymus much folded, in XIV and/or XIII; base of penis globose:
Known from Andes of Peru
Orchibdella peruviensis Ringuelet, 1976c
25 Two pairs testisacs per mid-body segment; duct between epididymis and base of penis short and stout (Patagoniobdella)
Primarily alpine species
- One pair testisacs per mid-body segment; duct between epididymis and base of penis long and thin (Semiscolex)
Temperate species
26 Gonopores separted by 1/2 + 1 + 1/2 annuli; male at XIIb1 and female at XIIa2:
Known from Argentina Andes: primarily lakes in Neuquen Province
Patagoniobdella fraterna Ringuelet, 1976b
- Gonopores separated by at least 2.5 annuli27*
27 Gonopores separted by 2.5 - 4 annuli; female pore varying in position on or either side of XIIb5 or on XIIb6; male pore invariably at XIIb1:
Common in lakes of glacial origin in Patagonian Andes of Chile and Argentina (Moore 1911; Weber 1915; Ringuelet 1944d, 1945, 1958).
Patagoniobdella variabilis (Blanchard, 1900)
- Gonopores separated by about 6.5 annuli, male at XI/XII or anterior third of XIIb1; meale at posterior third of XIIIb2 or at XIIIb2/a2:
Known form Lago Nahuel Huapi, Argentina
Patagoniobdella ademonia Ringuelet, 1976b
28 Eyes located on annuli 2, 3, 4, 6, and 8 (segment IV with two annuli); third and fourth pair of eyes separated by a complete annulus; gonopores separted by 1/2 + 6 + 1/2 annuli:
Known from lower regions of Rio Plata, in Argentina and Uruguay (Ringuelet 1944d, 1968).
Semiscolex intermedius Ringuelet, 1942
- Eyes on annuli 2, 3, 4, 5, and 7 (IV with one annulus); third and fourth pair of eyes on contiguous annuli; gonopores separted by six or seven complete annuli29*
29 Gonopores separted by seven annuli:
Known from Buenos Aires, Uruguay, and neighbouring Brazil (Porto Alegre) (Ringuelet 1944d; Goulart 1963).
Semiscolex juvenilis Kinberg, 1867
- Gonopores separated by six annuli:
The most common hirudiniform of temperate South America, very widespread from central Argentina to Paraguay, Bolivia, Uruguay, and north-east Brazil (Ceara). Two related obscure forms from Brazil, zonatus Oka 1931 (gonopores separated by 5.5 annuli), and notatus Cordero 1937 (gonopores separated by eight annuli), are inadequately known.
Semiscolex similis (Weyenbergh, 1879)


Glossiphoniidae and Ozobranchidae
1 Eyes four pairs2*
- Eyes fewer than four pairs 3*
2 Gonopores separated by three (or 2.5) annuli:
Type locality: Colorado River, 25 km west of Pedro Luro, Buenos Aires; known host: fish Percichthys trucha
Theromyzon propinquum Ringuelet, 1947
- Gonopores separated by four annuli:
This species, which has usually been called T. tessulatum when found in South America (Blanchard 1892a, 1893a: Moore 1911; Oka 1932b), has not been adequately distinguished from T. tessulatum nor T. propinquum; type locality: Puerto Monti, Chile; type deposited in Santiago Museum. T. pallens is the type species for genus Theromyzon. Earlier finds 'T. tessulatum' in S.A. are T. propinquum (Ringuelet 1978c).
Theromyzon pallens Phillippi, 1867
3 Annulation reduced, mid-body segment basically two-annulate4*
- Mid-body segments basically three-annulate 8*
4 Margins of body with seven pairs of simple, undivided digitiform branchiae (Ozobranchidae):
Type locality: Villavicencio (Meta), Colombia; host: turtle Podocnemys vogli
Bogabdella ringueleti (Mane-Garzon, 1973)
- No lateral branchiae5*
5 Marsupium opening on venter at XVII/XVIII for brooding eggs:
Caudal sucker small, terminal; body thick, no papillae; gonopores at XI and XII (a1 + a2)/a3; (a1 + a2) larger than a3; seven pairs crop caeca; salivary glands diffuse; type locality: Jujuy in Argentinan Andes, 4000 m; host: amphibian Telmatobius (Ringuelet 1981b).
Maiabdella batracophila Ringuelet, 1980b
-No internal brood pouch6*
6 Anterior annulus about same size as posterior annulus in a segment, i.e. (a1 + a2) = a3; anterior annulus undivided:
Type locality: Rio Sao Francisco, Pernambuco, Brazil
Oligobdella brasiliensis Cordero, 1937
- Anterior annulus is larger than posterior annulus; anterior annulus subdivided at least on ventral side7*
7 Anterior annulus subdivided only on ventral side:
Type locality: Rio Miriti-Parana, trib. of lower Caqueta, Amazonian Colombia; host: crocodilian Paleosuchus trigonatus
Oligobdella columbiensis Ringuelet, 1972
- Anterior annulus subdivided both dorsally and ventrally:
Type locality: Rio Paran in Rosario, Santa Fe, Argentina; also at Lapango, Formosa, Argentina; and Rinco del Cerro, Montevideo, Uruguay; hosts: turtles Platemys, Phrynops and Hydromedusa and cayman Caiman sclerops (Ringuelet 1981b)
Oligobdella cheloniae Ringuelet, 1978a
8 Eyes one pair, never compound
If the one apparent pair of eyes is compound see key to North American species of Placobdella, which is also characterized by one pair mycetomes; species with these characteristics have not been documented for South America
- Eyes three pairs, in 'heteroclita' pattern:
Eyes on annuli 2/3, 3, and 5; mouth somewhat anterior at II/III; gonopores separated by one annulus; three pairs white sensory areas; type locality: Neuquen, Argentina; also Lago Gutierrez (Rio Negro) (Ringuelet 1978a). A. mesembrina is the only South American representative of this group of leeches so characteristic of Australia and South Africa.
Alboglossiphonia mesembrina (Ringuelet, 1949)
9 Gonopores at XI/XII and XIIa2/a3, separated by two primary annuli
Crop caeca seven pairs, large and lobed
- Gonopores at XIIa1/a2 and XIIa2/a3, separated by one annulus
Crop caeca typically 5-6, small and simple
10 Two pairs mycetomes in floor of pregenital region
Mouth pore terminal or subterminal; annuli a1 and a3 typically subdivided on venter
- Oesophageal region without the two pairs mycetomes as indicated above
Mouth pore central in oral sucker; annuli not subdivided
11 Salivary glands compact, two pairs:
Head blunt, not broadened but set off by deep furrow, Va2/a3, which demarcates posterior rim of sucker; uniform grey with papillae and preocular annuli white, lacking maculations (some with two obscure paramedial lines); on each a2 annulus four dorsal (and three ventral) pairs of small, white papillae which bear sensillae; proboscis with U-shaped crook, to XII/XIII; an unpaired 'gland' (? mycetome) at XII/XIII 'with long duct to base of proboscis'; sperm ducts with descending loops to XIII-XIV; size, 15 mm; caudal sucker small; type locality: Putabla, near Valdiviana, Chile; known from Chile, Argentina and Uruguay (Ringuelet 1944d, 1968); southern Brazil (Ringuelet 1981a).
'Batracobdella' gemmata (Blanchard, 1900)
- Salivary glands diffuse:
No species with this combination of characters has been reported from South America, but is expected (but see Maiabdella batracophila above). The nature of any mycetomes needs detailed descriptions
Batracobdella sp
12 Distinct tubercles or papillae evident on venter13*
- Venter smooth15*
13 Each ventral annulus with 10-12 irregularly positioned papillae, including a pair of black paramarginal tubercles on a2:
Dorsum with 9-11 longitudinal rows of papillae; one dorsal pair of large paramarginal black spots on a2; head with anteriorly opened black V; known from Porto Alegre, Brazil; host: 'alligator' (Goulart 1963). An obscure related form, bistriata Pinto 1920, has ventral pair of dark paramedial lines; Minas Gerais, Brazil (Ringuelet 1981b).
Haementeria maculata (Weber, 1915)
- No paramarginal black spots on dorsum and venter14*
14 A mid-dorsal longitudinal row of tubercles located medially on each annulus (a1, a2, a3) of each mid-body segment; a pair of large tubercles located paramedial position on a2:
Venter typically numerous small, flat tubercles; on dorsum tubercles in supramarginal position on a1and a2; the supramarginal on a1, large paramedials on a2 and medial tubercle on a3 all together form a characteristic V; type locality: Surinam; also occurs from middle Argentina to Colombia (Ringuelet 1968, 1972e); host: turtle Platemys platicephala
Haementeria tuberculifera (Grube, 1871)
- Tubercles scarce or lacking at dorsal mid-line; tubercles not on each annulus a1, a2, and a3 at dorsal mid-line:
Conspicuous paired tubercles on venter: pair of intermediates on a1, pair of paramarginals on a2, and sometimes a smaller pair of paramedials on a3; dorsum with two pairs distinct tubercles on a2; total of 68 annuli; type locality: San Bernandino, Paraguay; known from north-eastern Brazil (Pernambuco) to Argentina (BA) (Ringuelet, 1968
Haementeria paraguayensis (Weber, 1915)
15 Each annulus with about 60 compound papillae, most abundant on lateral third of body; dorsal annuli not subdivided:
Dorsal annuli with about 20 areolae; no longitudinal pigment patterns; in life uniform olive-green very large, up to 50 cm; known from Amazonian Brazil and neighbouring French Guyana (Blanchard 1899d; Sawyer et al. 1981; Ringuelet 1980a); host: mammals (and reptiles).
Haementeria ghilianii de Filippi, 1849a
- Dorsal papillae much fewer, typically in seven longitudinal rows but not on every annulus in each row; dorsal annuli subdivided16*
16 Sensillae circular in outline:
Dorsal papillae variable, but small and scanty; size small, mature at 15 mm, but up to 32 mm; type locality: Isla Santiago, Prov. Buenos Aires; typically found on water plant Eichhornia azurea; host: Siluriformes fish Plecostomus and Sorubim lima
Haementeria eichhorniae Ringuelet, 1978a
- Sensillae bar-shaped17*
17 A mid-dorsal row of small salient tubercles on a2 annulus only; other tubercles lacking but two pairs conspicuous sensillae also occur on a2:
A thin medial and three paired equidistant longitudinal lines on dorsum; venter with pair fine longitudinal lines; type locality: Montevideo, Uruguay; host: frogs Leptodactylus ocellatus and Pseudis mantidactyla (Ringuelet 1980a, 1981b).
Haementeria molesta (Cordero, 1934)
- Distinct dorsal tubercles: annulus a2 with paired paramedial and intermediates; a3 with paired intermediates; small papillae sometimes located medially on a1 and paramarginally on a2:
Dorsum with seven longitudinal rows of dark, irregular pigmented maculae (stripes), mid-dorsal stripe uninterrupted; venter with paramedian dark stripes; known from Brazilian Highlands to Chile; common in Pampa region of Argentina where it feeds on diverse vertebrates (Ringuelet 1972a, 1981b; Souza 1980). Several Brazilian forms, inadequately distinguished from lutzi may key out here: lutzi Pinto 1920: seven longitudinal rows of tubercles; median tubercles reportedly only on a1; dark mid-line; type locality: Lassence, Minas Gerais, Brazil; and striata Oka 1932: dark median stripe; 10 black parallel stripes on each side, converging at each end: tubercles on each annulus at dorsal mid-line; Parana, Brazil; vizottoi Castro 1971: median tubercles confirmed to two consecutive annuli, a1 and a3; to 28 mm; Estado de Sao Paulo, Brazil.
Haementeria depressa (Em Blanchard, 1849) = Haementeria gracilis (Wyenbergh, 1883)
18 Salivary glands one pair semi-compact masses
An abscure form Desmobdella paranensis Oka, 1930, from Parana, Brazil, may be allied here; six-annulate; not tubercles; unicolour; six pairs testisacs; six pairs crop caeca; 36 mm
- Salivary glands diffuse24*
19 Proboscis long extending posteriorly to the level of XII/XIV or XIV21*
- Proboscis extneding posteriorly on to XII/XIII20*
20 Nuchal glands at dorsal mid-line at VIIIa1/a2:
Primary annuli not subdivided; dorsum unicolour with no papillae nor tubercles; salivary ductules looped before entering proboscis; crop caeca with seven chambers not true caeca; post-caeca absent; type locality: Cundinamarca, Columbia; host: fish Salmo irideus
Helobdella xenoica (Ringuelet, 1975)
- No nuchal gland:
Each annulus subdivided in posterior third, most markedly in genital and pregenital regions; in addition, a second furrow occurs in the anterior third of each annulus; tegument smooth, unicolour; crop with five variable chambers which may appear as diminutive caeca depending on state of feeding; plus short post-caeca to XX/XXI; caudal sucker small, subterminal; size small, less than 10 mm; type locality: San Bernardino, Paraguay
Helobdella longicollis (Weber, 1915) = Acritobdella longicollis
21 Crop caeca seven pairs; caudal sucker subterminal:
Dorsum with two obscure paramedial lines to extremities; no tubercles; proboscis thick, with U-shaped crook to XIV; crop caeca pairs 3-5 reduced to simple sacculations; post-caeca short, to XX/XXI; type locality: Lago Argentina, Argentina; also Chile (Conchi).
Helobdella dubia (Ringuelet, 1958), n. comb. = Batracobdella dubia
- Crop caeca 5-6 pairs; caudal sucker ventral 22*
22 Dorsum with three longitudinal rows of tubercles on annulus a2:
Crop caeca six piars; externally similar to Helobdella triserialis; type locality: Florencia Este (Formosa), Argentina
Helobdella chaquensis Ringuelet, 1978b
- Dorsum smooth without tubercles23*
23 Crop caeca six pairs; six pairs testisacs:
Last pair crop caeca horizontal, lacking descending portion; type locality: Lake Titicaca, Peru
Helobdella titicacensis (Ringuelet, 1959b)
- Crop caeca five pairs: five pairs testisacs:
Last pair crop caeca with short descending portion; anus behind XXVII; mouth at II/III; proboscis without crook; type locality: Tarapaca, Chile. A related form, malvinensis Ringuelet 1978b, is reported from Islas Malvinas, Rio Malo: anus at XXVI/XXVII; mouth at III; proboscis with a short crook
Helobdella cryptica Ringuelet, 1978b
24 Genital region with three ventromedial openings:
Male and female gonopores at XIIa1/a2 and XIIa2/a3, followed by a third opening at XII/XIII; female pore small and circular; the posterior-most opening large and oval; both open into a spacious female bursa; six pairs crop caeca, with descending post-caeca; male with extensive loop of sperm ducts; external appearance of Helobdella; type locality: Andahuaylas, Peru.
Tribothrynobdella andicola Ringuelet, 1978c.
- Genital region with only the two male and female openings 25*
25 Nuchal gland or brown plaque (= scute) at neck region (about VIIIa1/a2)
See also Adaetobdelloa xenoica above
- Nuchal gland or scute lacking 31*
26 Margins of mid-body annuli extended into short cylindrical appendages which are sharply digitate toward tips:
Diminutive papillae on all annuli; only about 7-10 larger ones in posterior part of body; ? nuchal gland; type locality: Lake Culebrillas, Ecuador; possibly also lives in Lake Titicaca, Peru (Ringuelet 1959b).
Helobdella festae (Dequal, 1916)
- Margins of annuli lacking conical appendages 27*
27 Annuli of segments VI to XXV subdivided equally to a distinct furrow28*
- Annuli of mid-body segments not subdivided29*
28 Vas deferens lacking a descending loop before differentiating into seminal vesicle:
Nuchal gland at VIIIa1, wide and prominent; sperm ducts to XIV; small leeches, brooding at less than 5 mm; type locality: Villarica, Paraguay
Helobdella diploides Ringuelet, 1948b
- Vas deferens sending a descending loop before abruptly enlarging into seminal vesicle:
Nuchal gland appearing as transverse, raised, unpigmented area; no scute; no metameric pigment pattern; type locality: Puntas Arenas, Patagonia, Chile; also occurs several locales in south Argentina (Ringuelet 1978a). Closely related forms with scutes instead of glands can be distinguished as follows: var. duplicata Moore 1911, without tubercles; var. tuberculata Ringuelet, 1958, with longitudinal row of low tubercles. Similar individuals with and without nuchal scute in Lago Argentina suggest these represent infraspecific forms (Ringuelet 1958).
Helobdella scutifera Blanchard, 1900
29 Chitinoid scute present at VIIIa1/a2; tubercles lacking 30*
- Nuchal gland appearing as raised, swollen area at VIIIa1/a2 (sometimes difficult to discern); small tubercles on every annulus at dorsal mid-line:
Pale brown with broad median dark area; 24 fine longitudinal dark lines; type locality: Chubut Prov., Argentina.
Helobdella simplex (Moore, 1911) = Helobdella montevidensis (Cordero, 1937)
30 Nuchal scute typically between annuli 12/13
The following species appears to be more common in South America, except in High Andes
Helobdella stagnalis L.
- Nuchal scute typically between annuli 14/15 (variable):
Closely resembles H. stagnalis from which it is unsatisfactorily distinguished; six pairs simple but permanent crop caeca, better developed than in H. stagnalis: post-caeca to XXII. Nuchal scute oval, subpyriform, as long as wide, uncommonly scute at annuli 13/14 or even 12/13; eyes on IV (a1 + a2), whereas eyes of stagnalis usually at III/IV; occurs in Mexico and throughout South America (Ringuelet 1972b), as well as South Africa (Sciacchitano 1960a, 1963b). A related form, H. godeti Weber 1916, is known only from Peruvian Andes (5000 m): scute typically between annuli 10/11; post caeca short, to XIX/XX
Helobdella adiastola Ringuelet, 1972b
31 Crop without caeca; no post-caeca32*
- Crop with caeca; post caeca may or may not be preent 33*
32 Head expanded; mouth pore central at III; seven pairs testisacs:
Body subcylindrical of uniform width; dorsum smooth; basically unicolour; caudal sucker small, subterminal; true crop caeca lacking (weak sphincters divide crop into obscure chambers). Type locality: Valdiviana, Chile
Helobdella michaelseni (Blanchard, 1900)
- Head not expanded; mouth pore somewhat anterior to centre, at II/III; six pairs testisacs:
Type locality: Pergamino, Buenos Aires Prov., Argentina. A similar form, votuporanguensis Castro 1971, but with post-caeca known from Brazil (Estado de Sao Paulo).
Helobdella obscura (Ringuelet, 1942)
33 Crop caeca lacking except for post-caeca which extends posteriorly to XIX:
Resembles G. michaelseni in body shape; six pairs testes; type locality: Charca, Cordoba, Argentina. Cf. G. elongata of North America: crop caeca short, to XX/XXI
Helobdella similis (Ringuelet, 1942)
- Crop with caeca
Malacophagous species
34 Dorsum uniformly coloured, lacking metameric pattern or tubercles
Post-caeca lacking or confined to segment XIX; vas deferns large
- Dorsal pigment pattern consisting of longitudinal pale stripes or metameric white spots; usually with 1-5 longitudinal rows of tubercles36*
35 Body subcylindrical; caudal sucker relatively large, terminal; eyes at IV (a1 + a2):
Last pair crop caeca resembling first five pairs, i.e. not descending; testes four pairs; type locality: Rio Uruguay at El Salto, Entre Rios; also known from Rio de la Plata, Punta Lara; apparently a permanent parasite in pallial cavity of snails Ampullaria spp.
Helobdella ampullariae Ringuelet, 1945
- Body flattened; lanceolate; caudal sucker ventral; eyes generally at Va2 (variable):
Last pair crop caeca confined to XIX, with very short descending portion; testes six pairs; type locality: north-east Buenos Aires Prov. (Isla Santiago) (Ringuelet 1944d, 1949), Uruguay, Argentina, and southern Brazil (Ringuelet 1981).
Helobdella hyalina Ringuelet, 1942
36 Dorsum lacking tubercles37*
- Dorsum with 1-5 rows of tubercles, nearly always on a
A complex of forms (see Ringuelet 1943c, 1968, 1976a); species inquir. deleted 2
37 Total of 66 annuli; caudal sucker relatively large, about one-half maximum body width:
Crop caeca not clearly demarcated; type locality: Peru: Lake Naticoche, also Lake Lavandera, 5140 m. A similar form, but with median row of tubercles, reported from Lake Titicaca (Ringuelet 1959bHelobdella peruviensis Weber, 1916
- Total of 69 or 70 annuli; caudal sucker small, less than one-half body width:
Crop caeca distinct; venter uniformly pale; posterior extension of vas deferens, abruptly meeting seminal vesicle which extends to XVI; small circular metameric pigment patches and fine longitudinal lines; type locality: Argentina: Tanti, Cordoba. A related form, araucana Ringuelet 1978a, occurs in glacial lakes at Neuquen, Argentina: no posterior extension of vas deferens which makes transition into seminal vesicle; irregular obscure pigment patches. Another form, columbiensis Weber 1913, occurs in Columbia (East Cordilleras, 2400 mm): venter with many small irregular patches of dark grey pigment; head on long neck.
Helobdella cordobensis (Ringuelet , 1942)
38 Only one median row of tubercles: Helobdella triserialis var. unilineata Ringuelet 1943c
- Dorsum with three or five distinct rows of tubercles 39*
39 Tubercles rounded, not pointed, of same colour as background; their bases occupy almost all the length of annulus; dorsum with vivid longitudinal striations:
Reproductive system distinct from H. triserialis (Ringuelet, 1978a): vas deferens with desending loop which meets abruptly the seminal vesicle complex, the latter large and extends to XIX; it reduces abruptly at XVI into sperm duct; known from central and north Argentina and Uruguay
Helobdella striata (Ringuelet, 1943c)
- Tubercles pointed, tinged with black or dark grey; their baes smaller than length of annulus 40*
40 Background colour uniform dark grey, almost black; tubercles intense black; metameric splotches white and rounded; five rows tubercles from pregenital or even cephalic region:Helobdella triserialis var. nigricans Ringuelet, 1943c
- Colour pattern not as above 41*
41 Dorsal tuberculation: median on annuli a1, a2, and a3; plus one, two or three rows on each side on a2 and a3:
Large species, to 32 x 9.5 mm; venter with four pairs longitudinal stripes; dorsum pale grey to straw-colour; mid-dorsal dark band on either side of which are five rows indistinct double stripes; type locality: Brazil: Rio Grande do Sul; known from north Brazil, Uruguay, and Central Argentina (Ringuelet, 1945, 1968).
Helobdella brasiliensis (Weber, 1915) = Placobdella taeniata Cordero, 1937
- Dorsal tuberculation variable, 1-5 rows nearly always on a2; tubercles generally beginning in genital region:
Type locality: Carelmapu, Chile (synonymies extensive: see Ringuelet 1942-1980. A complex of forms (see Ringuelet 1943c). Colour pattern variable, typically with white metameric spots bearing sensillae, or 5-7 longitudinal pale stripes alternating with darker stripes; vas deferens lacking descending portion; sperm ducts to XIII or beyond; hosts; snails; typical size 18 mm, extending to 25 mm
Helobdella triserialis (Em. Blanchard, 1849) s.s.