Archimonocelis parastaresoi, 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 : 54-56

Archimonocelis parastaresoi sp. n.

( Figs. 2 B; 4 A–D)

Holotype: one whole mount, posterior part ( SMNH 6783). Frontal part processed for karyology.

Type locality: Apulia, Italy: Porto Cesareo (Lecce), in front of the harbour (lat. 40°14’59.44”N, long. 17°53’31.22”E), about 14 m deep, coarse silty sand, May 2005.

Etymology: the specific epithet reflects the similarity of the new species with Archimonocelis staresoi Martens & Curini-Galletti, 1993 .

Description. Similar to the previous species in size and general morphology. Cnidocysts ovoid, of different size classes: around 5 µm, 8–10 µm, and 23–25 µm; in addition, several large stenoteles, 23–30 µm long, were observed.

Male genital system. About ten testes located in one median row in front of the pharynx. The copulatory structures consist of one pair of seminal vesicles, a vesicula granulorum, a stylet surrounded by spines, and an accessory glandular organ provided with spines. The stylet is nearly straight, 80 µm long, and comparatively broad: its diameter is 13 µm. The straight proximal basis is provided with a thickened and distinctly inflated rim; the proximal opening is 26 µm wide. The stylet is acutely pointed distally, with a large, oblique opening (about 20 µm wide) (fig. 4 B). With 35 copulatory spines, arranged into a girdle. The two spines closer to the stylet are of the first order type, about 63 µm long, with a stalk about 7 µm broad. Distally, they widen into a recurve tip, provided with an obtuse subterminal tooth (maximum width about 9 µm). The second order spines differ markedly in size. Those closer to the first order spines are about 60 µm long, with a falcate apex and a very obtuse subterminal tip. The spines become progressively shorter, to about 30 µm long, and thinner farther on, with a smaller and slender apex, and a markedly more acute subterminal tooth.

With 18 accessory spines arranged into a girdle ( Figs 4 A, C). Similarly to the previous species, different groups of spines can be recognized:

A) 12 spines close to the copulatory organ, slender, with a slightly recurve apex and a very small and obtuse subterminal tooth. Spines closer to the copulatory organ are smaller and straighter, about 28 µm long; farther on, they become longer (up to about 45 µm) and broader (up to 3 µm), with a progressively more basal and obtuse subterminal tooth;

B) one pair of straight spines 45–50 µm long, slightly recurve apically, with a stalk 4 µm wide, attaining the maximum width (5.5 µm) just above the middle;

C) one pair of spines similar in morphology to the previous, but broader (stalk about 5 µm; maximum width: 7.5 µm) and larger (53–55 µm);

D) one pair of larger spines, 56 µm long, with a thin stalk (2 µm wide in the middle), provided with a pointed, conical apex, about 12 µm long and 6 µm wide at the basis.

Female genital system. Two 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. With a female pore posterior to the male pore.

Karyotype. Plates were unsuitable for karyometrical analysis. One plate (fig. 4 D) showed one large metacentric, and a few (3-4) acrocentric pairs.

Diagnosis. Archimonocelis species with two seminal vesicles and an accessory glandular organ. With a straight, tubular stylet, 80 µm long and 13 µm broad, with a large, oblique distal tip. With two falcate first order spines, 63 µm long, with an obtuse proximal tooth, and 33 second order spines 60–30 µm long; becoming shorter, thinner, and with a more acute subterminal tooth distally. With 18 accessory spines, 28–56 µm long, with two straight, broad spines, and one pair of large spines, with a conical apex.

Remarks. Although a single specimen was found, the peculiarities of its copulatory structures, and in particular of the spines of the accessory organ, warrant its description as a new species.

A. parastaresoi n. sp. was extracted from the same sediment as A. cygnicollis n. sp. The two species clearly differ for the shape and size of the stylet and spines (cf above).

A. parastaresoi n. sp. is similar to A. staresoi in general arrangement of the sclerotized structure (cf Martens & Curini-Galletti, 1993). This species, however, has a recurve stylet, longer (about 100 µm), much slen- der and thinner (to 5.5 µm wide), and with an obliquely truncated basis. Copulatory spines of first order are similar in size in the two species, and therefore proportionally smaller with respects to the size of the stylet in A. staresoi , with a slender, straighter apex. Second order spines are of more uniform length in A. staresoi , ranging 40–50 µm. Accessory spines of A. staresoi are shorter (20–33 µm); spines closer to the copulatory organ are similar to the new species; they progressively widen subterminally, with two distinctly larger and broader pairs ( Martens & Curini-Galletti, 1993). In A. parastaresoi n. sp. the comparable spines (pairs B and C in the species description above) are broader and widen just above the middle. Furthermore, the large, peculiarly shaped spines of pair D are absent in A. staresoi . The two species have also a different karyotype: A. staresoi has a set with n=5 and all acrocentric chromosomes ( Martens & Curini-Galletti, 1993).

The new species is similar to A. oostendensis for the shape of the stylet, which is however smaller (49–53 µm long); copulatory spines are 35–40 µm long. The accessory spines of A. oostendensis are only eight, with five spines comparable in shape to group A of the new species, but markedly smaller (18 µm long); and three spines markedly differing in shape: i) a broad, straight spine, similar to the distalmost spines of A. staresoi ; ii) a spine with a conical apex, similar to pair D in A. parastaresoi n. sp., but with a much broader, cylindrical stalk; iii) a spine slightly widening subterminally, and with a broad, cylindrical stalk. The species has furthermore a different karyotype, with n=6 ( Martens & Schockaert, 1981; Martens & Curini-Galletti, 1993).

Figures

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 4. Archimonocelis parastaresoi sp. n. A: sclerotized apparatus (holotype); B, C: details of copulatory structures and accessory spines; D: metaphasic plate from spermatogonia. Archimonocelis carmelitana Martens & Curini- Galletti, 1993, E: sclerotized apparatus from a karyological slide, showing companion spines (arrow). Scale = A – C: 25 µm; D: 10 µm; E: 50 µm.