Gianius camachoae Martínez-Ansemil sp. nov.

(Figs 1, 2)

Holotype. MHNUSC_10146: mature worm, incomplete (broken at segment XIV), unstained and whole-mounted in Canada balsam. Leg. Ana I. Camacho. Type locality. CAN002 De los Santos cave, Cantabria, Spain, –3.58453, 43.19491 (4 June 2002).

Paratypes. MHNUSC_10147_1–2: 1 mature and 1 immature specimen, unstained and whole-mounted in Canada balsam, from type locality (4 June 2002); MHNUSC_10147_3–5: 2 mature specimens (1 stained in haematoxylin and 1 unstained) and 1 immature stained in haematoxylin, whole-mounted in Canada balsam, CAN004 Covalagua cave (cueva del Agua), Cantabria, –3.61173, 43.22852 (7 June 2002); MHNUSC_10147_6–10: 2 mature specimens (1 stained in haematoxylin and 1 unstained) and 3 immature unstained, whole-mounted in Canada balsam, CAN022 Upwelling of the Bustablado stream, Cantabria, –3.61717, 43.27797 (14 Mars 2003); MHNUSC_10147_11: 1 mature specimen stained in haematoxylin and whole-mounted in Canada balsam, CAN034 Bustablado stream, Arredondo, Cantabria, –3.60441, 43.27404 (8 June 2002); MHNUSC_10147_12: 1 mature specimen stained in haematoxylin and whole-mounted in Canada balsam, CAN008 Arduengo cave (Cuviobramante), Cantabria, – 3.62032, 43.27576 (14 Mars 2003); MHNUSC_10147_13: 1 mature specimen stained in haematoxylin and whole-mounted in Canada balsam, CAN047 Asón stream, La Cubera, Cantabria, –3.60577, 43.25108 (20 January 2002). All leg. Ana I. Camacho.

Etymology. Named in honor of Dr.Ana Isabel Camacho (MNCN, Madrid, Spain), the leader of the PASCALIS project in Spain, who contributes greatly to the knowledge and development of the biospeleology.

Description. More than 2.6 mm long (all mature specimens are broken and lack posterior segments). Maximum number of segments (observed in immature specimens), 31. Diameter at segment V (slightly compressed specimens) 90–130 μm, at segment XI 100–180 μm. Clitellum 1/2 X–XII. Prostomium rounded, 42–58 μm long and 40–70 μm wide. Secondary annulation indistinct or slightly marked, up to VI. Somatic setae bifid, 26–35 μm long, with upper tooth shorter and thinner than lower (Fig. 2A); (2)3–5 setae per bundle anteriorly and 2–3 in the clitellar and postclitellar segments. Ventral setae of XI modified into bifid penial setae with short teeth, in number of 6–13 per bundle, 28–40 μm long and 1–1.5 μm thick, arranged comb-like, forming an open arc towards the sagittal plane and placed close to the male pores on their inner side (Figs 1A, B, 2D [ps]). One pair of male pores located in the posterior third of segment XI, in line with somatic ventral setae (Fig. 1A). One pair of spermathecal pores in segment XI; four of the ten specimens studied have an additional pair in XII (Fig. 2H), and one (from upwelling of Bustablado) has even additional spermathecal pores in X and XIII. All spermathecal pores are placed in the most anterior part of their respective segments, in line with somatic ventral setae (Figs 1A, 2H [sp]).

Pharyngeal glands in segments IV–VI, poorly developed. Chloragogen cells beginning in VI. Oesophageal appendages and diverticula absent. One pair of testes in segment X. One pair of ovaries in segment XI. Sperm sacs extending by segments (IX) X–XI(XII); mature eggs in segments XI–XII(XIII). Vasa deferentia twisted, shorter than atria, 45–60 μm long and around 3 μm wide, entering the apical (ental) end of the atria (Fig. 1A vd). Atria tubular to spindle-shaped, curved, 78–95 μm long and 12–16 μm maximum diameter, with a thin muscular outer layer (1–2 μm thick); atrial lumen frequently filled by spermatozoids; ectally, each atrium ends in a dilated spherical ampulla which is surrounded by a rather thin muscular layer (atrial bulb), 16–26 μm in diameter, acting as a pseudopenis in extrusion (Figs 1A, 2B–D, F–H [a, b, pp]). Two prostate glands per atrium, the anterior one large and placed near the entrance of vas deferens, and the posterior one small and placed close to the atrial bulb (Figs 1A, 2C, D [pr1, pr2]). Spermathecae of XI and XII filled with spermatozoids (Fig. 1A, D); spermathecae of X and XIII empty (Fig. 1C). Spermathecal duct muscular, conical and long (up to 30 µm) in XI, globular and short in XII and XIII, tubular and short in X; spermathecal ampulla tubular (up to 80 µm long, 10–20 µm in diameter) and directed forward (Figs 1A, C–D, 2B, E–H [sd, sa]).

Distribution and habitat. Caves, springs, phreatic and hyporheic habitats at the upper and middle parts of the Asón River basin, Cantabria, Spain. Alt. 161– 710 m.

Remarks. Following Erséus (1992a), the presence of elongated and curved atria, each with two prostate glands attached to proximal and distal ends, respectively, vasa deferentia entering apical ends of atria, slender spermathecae with short ducts, and small straight penial setae allocate the new species described above in the genus Gianius Erséus.

From the twelve species of Gianius currently known, Gianius camachoae sp. nov. is clearly distinguished by the presence of spermathecae in the atrial segment (segment XI), a character only shared with the marine species G. eximius Erséus, 1997 and G. urgorrii Martínez-Ansemil & Caramelo, 2025. Among other characters, G. camachoae sp. nov. clearly differs from these two species by the shape and structure of the spermathecae, ampullae elongate and ducts simple in the former, and ampullae globular and ducts bipartite in the two latter. G. crypticus (Rodriguez & Giani, 1989), described from the same geographical area (a cave in the upper part of the Clarin stream basin), appears as its most closely related species, although having exclusively a typical pair of spermathecae in the preatrial segment X. The variability in the number and location of the spermathecae observed in G. camachoae sp. nov. is high, but all specimens have, at least, one functional pair of spermathecae in the atrial segment. Furthermore, G. camachoae sp. nov. clearly differs from G. crypticus for at least two other characters, the atrial muscular layer (thin in the former; very thick in the later), and the atrial bulb (with a large lumen and surrounded by a relatively thin muscular layer in the former; heavily muscular in the later).