Archimonocelis scopulicola, Curini-Galletti, Marco, Delogu, Valentina, Campus, Paolo & Casu, Marco, 2007

Curini-Galletti, Marco, Delogu, Valentina, Campus, Paolo & Casu, Marco, 2007, New species of the genus Archimonocelis Meixner, 1938 (Proseriata, Archimonocelididae) from southern Apulia (Italy), Zootaxa 1557, pp. 47-58 : 48-51

Archimonocelis scopulicola sp. n.

( Figs. 1 , 2 C, 3 A–C)

Holotype: one whole mount ( SMNH 6780).

Type locality: Apulia, Italy: Porto Cesareo (Lecce), Torre Scianuli (lat. 40°14’3.72”N, long. 17°54’35.77”E), about 7 m deep in pockets of sediments (mostly shell fragments) on a limestone cliff, May 2005.

Paratype. a specimen from the type locality, whole mount (rear portion) (ZMC-59); frontal half processed for karyology.

Etymology. the specific epithet refers to the habitat where the species was found (lat. scopulus = rocky cliff, and colere = to dwell).

Description. Comparatively small for the genus: the holotype, a fixed, contracted whole mount, is 3.7 mm long. Colourless and without pigmented eye-spots. With thin, cross shaped, calcareous spiculae, similar to those described for A. crucifera Martens & Curini-Galletti, 1993 , spread all over the body, and particularly evident in the cephalic region. Cnidosacs, containing numerous cnidocysts are well visible in living material, and arranged in a single median dorsal row. Cnidocysts consist of heteronemes of three different types: ovoid, around 5 µm in length; elongate, around 10 µm; and a few, very large and elongate cysts, about 30 µm long. Pharynx submedian, elongate, provided with numerous glandular cells ( Fig. 1 ).

Male genital system. Around ten testes arranged in one median line, from the ovaries to in front of the pharynx. The copulatory organ consists of one pair of seminal vesicles, a small bulb with the prostate vesicle (vesicula granulorum), and a stylet surrounded by 18 copulatory spines. The tubular stylet, 51 µm long in the holotype ( Fig. 2 C, 3 B), and 50 µm in the paratype ( Fig. 3 A), is straight and about 5 µm broad, with a slightly inflated proximal opening (8 µm in diameter), and an acuminate distal tip, provided with a very large and oblique distal opening, about 18 µm wide. The copulatory spines are arranged into a single girdle. Spines close to the stylet are 30–32 µm long and 1–1.5 µm broad, provided with a slightly falcate apex, and a small subterminal tooth. Away from the stylet, spines become progressively longer (up to 35 µm) and broader (up to 2 µm), with a distinctly falcate apex, and a more marked subterminal tooth (fig. 2C).

Female genital system. Limited observations could be performed on the living specimens. With two comparatively large ovaries, lying in front of the vitellaria, in the first third of the body. Vitellaria arranged in two lateral rows, from the ovaries to in front of the copulatory bulb. Most vitellaria are prepharyngeal, only 5 follicles per side are post-pharyngeal. Just posterior to the fusion of the oviducts, the female duct widens to form a small bursa. A vagina could not be detected on living specimens. The female pore opens posterior to the male pore; a genito-intestinal duct is present.

Karyotype. Chromosome number: n = 10 ( Fig. 3 C); FN =16. Chromosomes can be arranged in a regularly decreasing series: Chrom. I = r.l.: 13.95 + 0.28; c.i.: 30.91 + 4.91 (sm); Chrom. II = r.l.: 13.65 + 0.24; c.i.: 22.47 + 4.66 (st); Chrom. III = r.l.: 12.21 + 0.53; c.i.: 27.77 + 4.23 (sm); Chrom. IV = r.l.: 10.46 + 0.28; c.i.: 41.76 + 2.20 (m); Chrom. V = r.l.: 10.34 + 0.34; c.i.: 26.63 + 6.33 (sm); Chrom. VI = r.l.: 9.72 + 0.22; c.i.: 34.41 + 2.20 (sm); Chrom. VII = r.l.: 8.84 + 0.84; c.i.: 12.53 + 3.49 (st); Chrom. VIII = r.l.: 8.84 + 0.84; c.i.: 34.73 + 3.82 (sm); Chrom. IX = r.l.: 7.39 + 0.55; c.i.: 13.52 + 4.12 (st); Chrom. X = r.l.: 6.20 + 0.01; c.i.: 15.56 + 5.10 (st) (based on the measurements of two spermatogonial plates).

Diagnosis. Archimonocelis species with two seminal vesicles. With a straight, tubular stylet, about 50 µm long, with a straight, slightly inflated proximal aperture and an acuminate distal tip, provided with a large, oblique, distal opening. With a girdle of 18 copulatory spines 30–35 µm long, 1–2 µm broad, shorter and narrower proximal to the stylet, and provided with a falcate apical tip and a subterminal tooth, more marked in the spines away from the stylet. With n=10.

Remarks. Archimonocelis scopulicola n. sp. belongs to the group of species lacking accessory spines. Most species of this group are provided with two first order copulatory spines, distinctly larger and broader than the rest of the spines (see, i.a., A. crucifera Martens & Curini-Galletti, 1993). Besides the new species, in eight Archimonocelis species the first order spines are absent, and copulatory spines differ slightly in size and morphology. Among these, A. bathycola (Westblad, 1952) and A. carmelitana Martens & Curini-Galletti, 1993 have many more (around 100) copulatory spines than the new species, while A. hasanuddin Martens & Curini-Galletti, 1989 and A. helfrichi Karling, Mack-Fira & Dšrjes, 1972 possess four spines only ( Martens & Curini-Galletti, 1993).

A. koinocystis Karling, 1966 , from the coast of western Norway ( Karling, 1966a), has one seminal vesicle only, and its copulatory spines present distinctly falcate distal tips, proportionally much longer than in the new species (about one third of the length of the whole spines), with a much more marked and elongate basal tooth.

A. rhizophoralis Martens & Curini-Galletti, 1989 , from northern Australia has 12 copulatory spines, arranged in two groups: six are needle-like, without subterminal tooth, and six are falcate, with a subterminal tooth (Martens & Curini-Galletti, 1989). The stylet (65 µm long), and the spines (45–53 µm) are slightly longer than in the new species. The chromosome number is n=5 ( Martens & Curini-Galletti, 1993).

A. mediterranea Meixner, 1938 , from western Mediterranean, has a stylet similar in size and morphology to the new species. Copulatory spines are fewer, arranged in two concentric rings: six larger spines (about 36 µm long) form the outer girdle, and six smaller spines (about 30 µm) form the inner girdle; in addition, two spines, about 45 µm long, lie close to the stylet. The chromosome number is n=12, with a distinctly larger metacentric pair ( Martens & Curini-Galletti, 1993), absent in the new species.

A. monicae Martens & Curini-Galletti, 1993 , from northern Red Sea, has a slightly larger stylet (up to 65 µm long), and fewer (11–16) and longer (45–60 µm) copulatory spines. Furthermore, it lacks a bursa. A. monicae is a very large Archimonocelis : living specimens can reach, in extension, up to 20 mm in length. The chromosome number is n=7, with two large metacentric pairs ( Martens & Curini-Galletti, 1993).

Figures

FIGURE 1. Archimonocelis scopulicola sp. n. A: general organisation of a live animal; B: recostruction of the sclerotized apparatus (based on the holotype); C: genital organs in the living animal. Scale = 25 µm.

FIGURE 2. Reconstruction (based on holotypes) of the sclerotized apparatus of A. cygnicollis sp. n. (A) and A. parastaresoi sp. n. (B). Scale = 50 µm.

FIGURE 3. Archimonocelis scopulicola sp. n. A, B: sclerotized apparatus (A: paratype; B: holotype); C: metaphasic plate from spermatogonia. Archimonocelis cygnicollis sp. n. D: sclerotized apparatus, holotype; E: detail of stylet, paratype; F: bivalents from male spermatocytes. Scale = A, B, E: 10 µm; C, F: 5 µm; D: 20 µm.