Galapagetula cubensis Diez, Reygel & Artois sp. n.

(Fig. 17–19)

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Material and distribution. Observation on live specimens. One serially-sectioned specimen from Bueycabón (19°57’38”N; 76°57’28”W) (Type Locality), Santiago de Cuba, Cuba (November 18, 2017), designated holotype (FMNH https://id.luomus.fi/ KV.654), intertidal, scraping the upper 10 cm of the fine sand. One whole mount from Las Sardinas (19°56’24”N; 76°46’41”W), Santiago de Cuba, Cuba (June 22, 2016), fine, silty sand, 0.1 m deep, salinity 33 ‰, and two from El Masío (19°59’21”N; 76°16’35”W), Santiago de Cuba, Cuba (June 30, 2016), intertidal, upper 10 cm of the medium-coarse sand, salinity 33 ‰ (HU XIII.4.28– XIII.4.30) .

Etymology. The epithet refers to the occurrence of the new species in Cuba.

Diagnosis of Galapagetula cubensis sp. n. Species of Galapagetula with mouth sphincter. The copulatory bulb encompasses a prostate vesicle, a seminal duct, and the ejaculatory duct, which distally ends in a small and unarmed penis papilla. Prostate glands enter the male duct separately from the seminal duct, forming a divisa-type copulatory organ. Stalk of the resorptive bursa with a strong sphincter. Female duct lacking a sphincter. Common gonopore caudal.

Description. Live specimens about 1.5 mm long, translucent, with a pair of small eyes (Fig. 17A: e). Epidermis syncytial, 5–8 µm thick, fully ciliated. Cilia 5 µm long. The epidermis shows many vacuoles, some of which are empty, others are filled with a dark, granular secretion. The dark-stained rhabdites are 2–3 µm long.

The proboscis (Fig. 17A & 19A: pr, 17B) is of the typical koinocystidid construction (see Brunet 1972; Karling 1980), without a juncture sphincter. In live specimens it represents about 20% of the body length in live specimens. The exact number of fixators (Fig. 17B & 19A: pfix) and retractors (Fig. 17B: pret) muscles could not be determined. The cone retractors (Fig. 17B: cret) are well developed. A pair of ventral and a pair of dorsal integument retractors (Fig. 17B: iret) are present. Proboscis sheath surrounded by an external layer of longitudinal muscles. Several dilatators (Fig. 17B & 19A: dil) connect the proboscis sheath with the body wall. Most of these dilatators are very thin, except for some in the proximal half of the proboscis sheath. The proboscis pore (Fig. 17B & 19A: prp) is not surrounded by a sphincter. The proboscis sheath is lined by a nucleated and thick epithelium (Fig. 17B: pep). This epithelium is continuous with the epithelium covering the proboscis cone. Both epithelia contain oval to circular-shaped glands (reddish stained) (Fig. 17B & 19A: epg), albeit the sheath epithelium only in its most proximal part. Several proboscis glands lie just caudal to the proboscis: ventrally and dorsally there are coarse-grained basophilic glands (Fig. 17B: prg1), and in between them fine-grained eosinophilic (light-pink) (Fig. 17B: prg2) and medium-coarse-grained eosinophilic (dark-pink) (Fig. 17B: prg3) ones.

The pharynx (Fig. 17A & 19A–D: ph, 17B) is located at 30%. It has a diameter of about 15% of the body length. The prepharyngeal cavity is lined by a nucleated epithelium and is surrounded by a layer of longitudinal muscles. Additional circular muscles occur externally from the longitudinal ones in the distal half of the cavity. The mouth (Fig. 17B: m) can be closed by a sphincter (Fig. 17B: sph). Two types of glands open into the pharynx lumen: coarse-grained eosinophilic ones distally (Fig. 17B: phg1), and more to the middle part of the pharynx, additional coarse-grained basophilic glands occur (Fig. 17B: phg2).An epithelium lining the pharynx lumen was not observed. The musculature of the pharynx consists of a layer of longitudinal muscles outside of the septum (Fig. 17B: lm1), which is continuous with the longitudinal muscles surrounding the prepharyngeal cavity, and a thick circular layer just inside (Fig. 17B: cm1). The longitudinal muscles at the inside of the septum, observed in several species of Itaipusa, are not observed in this species. The pharynx lumen is surrounded by an inner circular muscle layer (Fig. 17B: cm2) and an outer longitudinal one (Fig. 17B: lm2). Internal strong longitudinal muscles are present (Fig. 17B: ilm). Radial muscles (Fig. 17B: rm) run between the septum and the wall of the pharynx lumen. The oesophagus (Fig. 17B & 19A: oe) is surrounded by the digestive parenchyma (Fig. 17B: dip). This parenchyma shows several nuclei and dark-stained vacuoles.

The gonads and atrial organs are located in the caudal fourth of the body. The pair of testes (Fig. 17A: t) is ventral. The vasa deferentia each form a seminal vesicle (Fig. 17A & 18: sv), and these fuse at the point where they enter the copulatory bulb (Fig. 17A & 19B–C: cb). At the same point, also the prostate glands (Fig. 17A, 18 & 19D: pg) open into the copulatory bulb. The copulatory bulb encompasses the free prostate vesicle (Fig. 18 & 19B–D: pv), the seminal duct (Fig. 18 & 19D: sd) and the male duct, which ends in an unarmed penis papilla (Fig. 17A, 18 & 19B: pp). The rest of the space of the copulatory bulb is filled with parenchymatic tissue, which appears syncytial (Fig. 18 & 19B: np). The seminal vesicles and the seminal duct are lined by a nucleated epithelium. The copulatory bulb is surrounded by a thick coat of circular muscles, which gradually becomes thinner distally and eventually disappears toward the penis papilla. The prostate vesicle opens proximally into the ejaculatory duct (Fig. 18: ed), next to the opening of the seminal duct (Fig. 18: sd), hence the copulatory organ is of the divisa type (see Karling 1956 for details). The prostate vesicle consists of a number of a coarse-grained eosinophilic glands. A connection with these prostate glands and the ones entering the copulatory bulb could not be observed, but as nuclei are only found in the extracapsular parts it is most likely that both are part of the same glandular system. The male duct is lined by a nucleated epithelium and surrounded by a layer of longitudinal muscles. Distally, the epithelium is thicker, and the male duct forms the penis papilla, which protrudes into the male atrium (Fig. 18: ma). Only the distal part of the male atrium seems to be surrounded by muscles, which are longitudinal; no muscles were seen around the proximal part.

The vitellaria (Fig. 17A & 19A–D: vi) extend along both sides of the body from behind the pharynx up to the level of the copulatory bulb. The elongated ovaries (Fig. 17A: ov) are located on either side of the copulatory bulb. The oocytes are organised in a row, increasing in diameter from the most proximal to the most distal one. The oviducts (Fig. 18: od) open into the female duct, which distally is a bit swollen (Fig. 18 & 19C–D: fd). Both the oviducts and the female duct are lined by a nucleated epithelium. Distally, the female duct is surrounded by a thin lon- gitudinal muscle layer. It enters the female atrium through the latter’s rostro-ventral wall (Fig. 17A, 18 & 19B: fa). Two bursae open into the female atrium. A resorptive bursa (Fig. 18 & 19B–C: b1) opens rostrally into the female atrium and contains degraded material. It is lined by a nucleated epithelium. Its distal, tubiform part (bursal stalk) is surrounded by thin longitudinal muscles. A well-developed sphincter occurs at the place where this bursa opens into the female atrium (Fig. 18: sph1, 19B–D: sph). A second, muscular bursa [Fig. 18 & 19D: b2; accessory bursa in the terminology of Reygel et al. (2011)] opens dorsal-rostrally into the female atrium. It is lined by a nucleated epithelium and surrounded by a layer of longitudinal muscles. The female atrium is lined by a nucleated epithelium and surrounded by an internal layer of longitudinal muscles and an external layer of very strong circular muscles (Fig. 19C: cm). The uterus (Fig. 17A, 18 & 19B–C: ut) is lined by a nucleated epithelium and by a longitudinal muscle layer. Coarse-grained basophilic (Fig. 18 & 19B: ubg) and fine-grained eosinophilic (Fig. 18 & 19B: ueg) glands open into the distal part of the uterus. Proximally and distally from these glands sphincters are present (Fig. 18: sph2 & sph3). The common genital atrium (Fig. 18: ca) is lined by a nucleated epithelium and by a longitudinal muscle layer. It opens to the outside through the common gonopore, which is situated exactly terminally (Fig. 17A, 18 & 19D: cg). The gonopore is surrounded by a sphincter (Fig. 18: sph4).