Octodrilus tergestinus

Octodrilus tergestinus (Michaelsen, 1910)

(Figure 4A,B)

Octolasium mima vAr. tergestina MIchAELsEn, 1910 MITT. MUs. HAMbUrg, 27: 73.

Octolasium (Octodrilus) mima: OModEo 1956 Arch. ZooL. ITAL., 41: 177 (pArT).

Octolasium mima vAr tergestina: KArAMAn 1972 BIoL. VEsTn., 20: 102.

Octodrilus rucneri (PLIsko & ZIcsI, 1970): ZIcsI 1981 OpUsc. ZooL. (BUdApEsT), 27–28: 66 (MIsIdEnTIfIcATIon).

Octodrilus tergestina: ZIcsI 1982 AcTA ZooL. HUng., 28: 439.

Octodrilus tergestinus: ZIcsI 1986 OpUsc. ZooL. (BUdApEsT), 22: 108.

Octodrilus tergestinus: MršIć 1991 Monogr. EArThw. BALkAns: 417.

Material examined. Cerreto 1 (MH 032866), 2 (MH 032867): Cerreto, Grimalda, Croatia, 15/05/2016, leg. Maurizio G. Paoletti. Judrio 2 (MH 032874): Judrio river, Medea, Udine, Italy, 18/02/2016, leg. Maurizio G. Paoletti. Medea 3 (MH 032876), 6 (MH 032878): Colle di Medea, Medea, Udine, Italy, 18/02/2016, leg. Maurizio G. Paoletti. Moruzzo 1 (EWITA361-15): Moruzzo, Udine, Italy, 11/11/2015, leg. Luca Dorigo. Muzzana 5 (MH 032880): Coda Manin woodland, Muzzana del Turgnano, Udine, Italy, 22/11/2014, leg. Luca Dorigo. Ospo 4 (EWITA348-15): Ospo river at Muggia, Trieste, Italy, 06/02/2015, leg. Maurizio G. Paoletti. Podlaka 1 (MH 032881), 2 (MH 032882): Banjšice-Podlaka, Slovenia, 09/04/2016, leg. Tommaso Barcaro, Angelo L. Dreon & Maurizio G. Paoletti. (Altogether ten specimens).

Diagnosis. Large worms, 200–500 mm by 10–15 mm. Colour brown on dorsum with darker midsegment stripes and pale on ventrum (much darker than Oc. mimus). Male pores on 15 small. Clitellum on ½29, 30–½44, 44, ½45; tubercles on 30–44, ½45. Nephridiopores irregularly alternate between b and above d. Two pairs of testes enclosed in perioesophageal testis sacs in 10, 11. Vesicles in 9–12, those in 11 sometimes smaller. Spermathecae seven or eight pairs, in 5/6, 6/7–12/13.

Remarks. Oc. tergestinus clearly differs from Oc. mimus by its much darker pigmentation, longer clitellum and tubercles. However, the clitellar organs are definite only in completely adult specimens (Zicsi 1981) and examining preadult or subadult worms might lead to incorrect identification. It is also worth noting that the number of spermathecae shows some variation as well. In our specimens it is usually 7 pairs in 6/7–12/13, however, sometimes an extra pair also appears in 5/6. In this respect Oc. tergestinus clearly differs from Oc. rucneri which has the eighth pair of spermathecae in 13/14.

Zicsi (1981) reported Oc. rucneri from Italy, Versa. Unfortunately we were not able to find the specimen reported in this paper (Z/6851) but found a later collection from the very same place. This material (HNHM/12809) was identified by Zicsi as Oc. tergestinus which is the correct identification.

On our molecular tree Oc. tergestinus is represented by four unresolved subclades including Oc. istrianus which shows an intermediate clitellar position between Oc. mimus and Oc. tergestinus (½29–42, ½28, 29–40, 41 and ½29, 30–44, ½45 respectively). The status of these subclades needs further investigations.