Duplominona hyperhystricina Curini-Galletti & Carcupino & Stocchino & Leasi & Norenburg 2020, n. sp.

Duplominona hyperhystricina Curini-Galletti n. sp.

(Fig. 4)

Holotype. Pacific Ocean: Achotines Bay (Lat. 7°24’54.59”N; Lon. 80° 10’25.33”W), intertidal, coarse sand with some silt, February 2016: one whole mount (USNM 1622576).

Paratypes. Same data as holotype, two whole mounts (USNM 1622577; USNM 1622578); two specimens sagittally sectioned (USNM 1622579; USNM 1622580).

Other material. Same data as holotype, two specimens observed alive, and prepared as semi-permanent mounts. Achotines Bay (Lat. 7°24’50.64”N; Lon. 80° 10’25.96”W), intertidal, fine sand with silt: one specimen sagittally sectioned (USNM 1622583). Gulf of Panama, Playa Venado (Veracruz, Panama)(Lat. 8°53’27.07”N; Lon. 79°35’44.16”W), intertidal in silty coarse sand, December 2011: one whole mount (USNM 1622581); one specimen sagittally sectioned (USNM 1622582). Gulf of Panama, Taboga Island (Lat. 8°48’5.06”N; Lon. 79°33’17.55”W), low intertidal in silty medium sand, December 2011, one specimen sagittally sectioned (USNM 1622584); three specimens observed alive and prepared as semi-permanent mounts.

Etymology. The name refers to the cirrus of the new species, which is similar but larger than that of Duplominona hystricina n. sp.

Description. A slender species (Fig. 4 A, C); about 2 mm long. Anterior tip with oily dots and dot-like rhabdoids; caudal tip pointed, with adhesive glands, and large rhabdoids. With a short pharynx at about mid-body.

Male genital system. With 10–15 testes in one row. Copulatory organ with a nearly spherical seminal vesicle, and well-developed prostatic vesicle. With a large spiny cirrus, lined by the inner muscular layer. The cirrus, 50–75 μm long in squeezed conditions, is provided with about 30 rows of densely packed spines (Fig. 4 B, D, E, H). Spines are slender, straight for most of their length, with a recurved distal tip; a degree of variability is apparent in the width of basis, and in the shape of the distal tip, that, in some spines, appears sharply bent, nearly angular (Fig. 4 F). Most spines range 8–10 μm long; distally, a few smaller spines, 1.5–4 μm long, are present. The distalmost part of the ejaculatory duct is unarmed: it is only seen in advanced stages of evertion of the cirrus (Fig. 4 B, D: ued), while it is hidden in specimens with more contract, inverted cirrus (Fig. 4 E, H).

Accessory organ 35–70 μm long, provided with a slender, pen-nib shaped stylet 18–30 μm long. It opens to the outside with its own pore, very close to female pore.

Female genital system. Ovaries just in front of the pharynx. Vitellaria extending from of anterior testes to copulatory organ. With a large vagina halfway between mouth and male pore. Vaginal duct wide, surrounded by a thick muscular layer, and lined internally by an irregular, apparently anucleated and degenerating epithelium. The vaginal duct narrows proximally and leads to a small, elongate bursa, surrounded by an epithelium of the resorbiens type. The female duct continues posteriorly and opens through the female pore, very close to the accessory organ pore. The distalmost portion of the female duct is surrounded by female glands.

Karyotype. With n=3. Karyotype formula: FN=4; Chromosome I: 44.68 ± 1.21; 44.53 ± 1.37 (m); Chromosome II: 35.21 ± 1.6; 10.34 ± 2.56 (a); Chromosome III: 19.37 ± 1.9; 8.83 ± 1.47 (a) (based on four plates, from two specimens from Playa Venado)(Fig. 4 I).

Diagnosis. Species of Duplominona with 10–15 testes. Large cirrus provided with 20–25 rows of slender spines with recurved distal tips, 8–10 μm long. Distalmost portion of ejaculatory duct unarmed. With a small bursa in front of the copulatory organ and external vagina; vaginal duct wide. Accessory organ stylet 18–30 μm long. Karyotype with one large metacentric pair and two pairs of heterobrachial chromosomes. Pore index: a: b: c: d = =12: 12: 6: 1.