Erpobdella borisi Cichocka & Bielecki

Cichocka, Joanna M., Bielecki, Aleksander, Kur, Jarosław, Pikuła, Dorota, Kilikowska, Adrianna & Biernacka, Beata, 2015, A new leech species (Hirudinida: Erpobdellidae: Erpobdella) from a cave in the West Azerbaijan province of Iran, Zootaxa 4013 (3), pp. 413-427 : 420-422

Erpobdella borisi Cichocka & Bielecki n. sp.

( Figures 3–5 )

Type locality. IRAN, West Azerbaijan, Sahoolan cave (36°39”19’N, 45°57”11’E), entrances at 1780 m a. s. l. ( Fig. 1).

Holotype. Specimen collected on March 30th of 2012 from the Sahoolan cave; body length 25.37 mm, maximal width 5.10 mm, deposited at the Institute of Zoology of the Polish Academy of Sciences in Warsaw, Poland (catalogue number MIZ 1/2013/3), preserved in ethanol 75 %. ( Fig. 3 )

Paratype. Specimen collected on March 30th of 2012 from the Sahoolan cave; body length 24.80 mm, maximal width 5.00 mm, deposited in the first author’s collection, preserved in ethanol 75%.

Other material examined. One specimen, same locality and data of collection, deposited in the first author’s collection, body length 21.10 mm, maximal width 4.70 mm, preserved in ethanol 75%.

Etymology. The species is dedicated to Professor Boris Sket, former dean of the Biotechnical faculty and rector of the University of Ljubljana, currently, a scientific councilor, researcher of the faunistics of troglobites and speleology in general, author of descriptions of over a hundred new species and genera of invertebrates, mostly crustaceans and leeches. He has greatly contributed to consolidation of specialists dealing with biology and phylogenetics of Hirudinida.

External morphology. The values of the body form indices (obtained from mean values of particular parameters for each species) are as follows: L/D2 = 5.86, C1 1/d1 = 1.1, C1 1/D1 = 0.45, R1/M1 = 1.0, C1 1/C1 =1.43, L1/ D1 = 3.0, D1/N1 = 2.18, S1/S2 = 1.0, L2/D2 = 5.36, D2/N2 = 1.75, K1/K2 = 0.33, C1 2/d7 = 0.43, C1 2/D2 = 0.76, R2/M2 = 1.64, C1 2/C2 = 1.14, L2/L1 = 2.38, D2/D1 = 1.59, N2/N1 = 1.24, C1 2/ C1 1 = 2.37 ( Table 3 ). The largest preserved specimen measured 25.37 mm in length and 5.03 mm in width. Both anterior and posterior suckers are transversally elliptical and the posterior sucker is less narrow than the widest part of the body.

The colour of living specimens on the dorsal side of the body is light gray with dark, irregular spots. The ventral side is still lighter in colour with fewer spots ( Fig. 4 A,B). On the dorsal side, there is also a dark medial smudge with fairly distinct margins. The line is more visible in posterior rather than anterior part of the body. The colour originates from pigment cells that lay beneath the muscles layer.

There are no eyes or even trace of eye pigment ( Fig. 3 C).

In the post-clitellar region there are lateral keels. The complete somite is divided into 5 unequal annuli and it is typical of the ‘Dina’ species, as: b1, b2, a2, b5, b6 (c11+c12) ( Fig. 3 D).

The gonopores are separated by three annuli ( Fig. 4 A) in 2 specimens and 2.5 annuli ( Fig. 4 B) in one specimen. In two specimens the prominent male gonopore is situated in XII b1/b2, whereas in 1 specimen it is situated on annulus XII b2. The inconspicuous female gonopore of two specimens is situated in furrow XII b5/c11, and in one specimen it is situated on the beginning of the annulus c11.

Digestive system. The digestive system is constructed typically for erpobdellid leeches. The pharynx reaches the ganglion X and lacks jaws or stylets, but it has pseudognaths. The non-caecate crop is extended to XIX/XX segment where connects with the intestine. The intestine has also no caeca and opens with the anus on the dorsal side just before the caudal sucker.

Reproductive system. The testes are globular, numerous and form grape-like structures of testisacs ( Fig. 5 A).

They begin at ganglion XIX and reach close to the posterior sucker. The vas deferens ends at the ganglion XIX. Each of the sperm duct forms a pre-atrial loop that reaches ganglion XI ( Fig. 5 A). The atrium is located at the ganglion XII ( Fig. 5 B). The length of the male atrium is approximately 2/3 of a neurosomite. It has relatively wide cornua and a broad insertion in the atrial body. Atrial cornua are a little oblique and curved to the ventral side what is visible in lateral view after isolating the atrium ( Fig. 5 C, D). The bursa is as long as the atrial cornua ( Fig. 5 D). The ovisacs are paired, elongated convoluted structures, showing anteriorly a 1.5–2.5 somite-large ‘lateral’ loop and then lying medio-ventrally. They have 6.5 ns in length and they are arranged as loops, first they go posteriorly up to ganglion XIX and then turn back anteriorly up to the ganglion XII ( Fig. 5 A).

Habitat. Specimens of Erpobdella borisi n. sp. were found in the water part of the Sahoolan cave about 100 m from the entrance. The leeches were collected from the surface of clay sediments. However, abundant specimens of the species were observed in the water of the cave. Most probably, the species is a troglobiont or troglophile.

Systematic position. Phenetic analysis based on 19 indices of the model of leech body form shows Erpobdella borisi n. sp. to be most similar to E. [= D.] stschegolewi and E. [= E.] lineata ( Fig. 6 ). Phylogenetic analysis based on COI gene sequences (uncorrected p-distance = 0.158) positioned Erpobdella borisi n. sp. in sister relation to the clade containing E. [= D.] japonica (uncorrected p-distance = 11.51%), E. [= E.] octoculata (uncorrected pdistance = 12.71%) and E. [= E.] testacea (uncorrected p-distance = 13.06%) ( Fig. 7 A). The same result was obtained in parsimony analysis of combined morphological and molecular data set (length = 758, CI = 0.5435, RI = 0.3651; Fig. 7 B).

Remarks As a result of detailed comparisons with related species, Erpobdella borisi n. sp. is explicitly different at the morphometric, morphological and COI gene sequence levels.

Morphometry: Considering morphotypes of all the analyzed species and also of other genera, in its body form Erpobdella borisi n. sp. is most similar to E. [= D.] stschegolewi and E. [= D.] lineata ( Fig. 6 ). Almost identical characteristic in these species are: C1 1/d1, R1/M1, C1 2/C2,, and very similar characteristics are: C1 1/D1, K1/K2, C1 2/D2, N2/N1. It differs from E. [= D.] stschegolewi in following characteristics: L/D2, C1 1/C1, L1/D1, D1/N1, S1/S2, L2/D2, D2/ N2, C1 2/d7, R2/M2, L2/L1, D2/D1, C1 2/C1 1.

Morphology: In non-metric characteristics Erpobdella borisi n. sp. is most similar to the following group of species: E. [= E.] octoculata , E. [= D.] japonica , E. [= E.] testacea , E. [= E.] nigricolllis and E. [= E.] monostriata. However, it does not form a sister relationship with any of these five species. This confirms the distinctness of Erpobdella borisi n. sp. ( Fig. 7 B).

Erpobdella borisi n. sp. is most similar to E. [= E.] octoculata ; they have the following characters in common (excluding genus-level characters): spots and lack of paramedian lines in the coloration of dorsal side, male gonopore on annulus and female in furrow, gonopores separated by 2.5 annuli, and short relatively wide atrial cornua.

The new species differs from E. [= E.] octoculata in the following characters: single wide median line on dorsal side (in E. [= E.] octoculata lack of median line), lack of eyes (in E. [= E.] octoculata there are four pairs of well visible eyes), fifth annulus in mid-body somite longer than other (in E. [= E.] octoculata all five annuli in midbody somite are of equal length), ovisacs have 6.5 ns in length (in E. [= E.] octoculata ovisacs have about 5 ns in length). The length of the male atrium is approximately 2/3 of a neurosomite (in E. [= E.] octoculata the atrium is almost 1 ns long). The atrium in Erpobdella borisi n. sp. is visibly narrower than in E. [= E.] octoculata and atrial cornua have a broad insertion in the atrial body, while in E. [= E.] octoculata this structure is slander. An angle between atrial cornua is slight (in E. [= E.] octoculata it is obtuse), thus the atrium of Erpobdella borisi n. sp. seem to be slim while the atrium of E. [= E.] octoculata is rather large. The bursa is not big and it is as long as atrial cornua (in E. [= E.] octoculata the bursa is about two times longer than the atrial cornua).

Barcodes: Characteristic attributes generated from the results obtained in these analyses occurred at 26 of 645 nucleotide positions (Table 5). Twenty six diagnostic characters were found for the clade Erpobdella borisi n. sp. + E. [= E.] octoculata + E. [= D.] japonica + E. [= E.] testacea . Private characters occur at 8 position only for E. borisi n. sp. (151, 256, 383, 418, 421, 499, 535, 601). Additionally, at position 181 ‘C’ diagnoses Erpobdella borisi n. sp. found on E. [= E.] testacea , and at position 512 ‘T’ diagnoses Erpobdella borisi n. sp. found on E. [= E.] octoculata .

Figures

FIGURE 3. External morphology of Erpobdella borisi n. sp. A. Dorsal view. Scale bar: 1.70 mm. B. Ventral view. Scale bar: 1.70 mm. C. Anterior part of the body. Scale bar: 0.33 mm. D. Annulation of the mid-body segment. Scale bar: 0.33 mm.

FIGURE 4. Ventral view of Erpobdella borisi n. sp. with male (M) and female (F) gonopore separated by (A) 3 annuli and (B) 2.5 annuli. Scale bar: 0.30 mm.

FIGURE 5. Reproductive system of Erpobdella borisi n. sp. A. Dorsal dissection with the atrium (a) and ovisacs (o) visible. Scale bar: 1.30 mm. B. Dorsal view of atrium. Scale bar: 0.58 mm. C. Lateral view of atrium. D. Ventral view of atrium. Scale bar: 0.32 mm.

FIGURE 6. Diagram of similarity for 10 species of Erpobdellidae based on mean values of 19 body proportion indices according to the geometric model of leech body form using Ward’s method, Manhattan distance.

FIGURE 7. Phylogenetic position of Erpobdella borisi n. sp. within erpobdellid leeches. A. Result of Bayesian inference based on COI gene sequences; number above branches indicate the posterior probabilities. B. One of the most-parsimonious trees based on morphological characters and COI gene sequences; numbers above branches indicate bootstrap support (values less than 50 % are not shown).