Promesostoma panamaense, Diez & Monnens & Wuyts & Brendonck & Reygel & Schmidt-Rhaesa & Artois, 2023

Diez, Yander L., Monnens, Marlies, Wuyts, Arlien, Brendonck, Luc, Reygel, Patrick, Schmidt-Rhaesa, Andreas & Artois, Tom, 2023, Taxonomy and phylogeny of Dalytyphloplanida Willems et al., 2006 (Platyhelminthes: Rhabdocoela), with the description of a new family, a new genus, and sixteen new species from Cuba and Panama, Organisms Diversity & Evolution (New York, N. Y.) 23 (4), pp. 631-681 : 657-660

Promesostoma panamaense sp. n. Artois & Diez

(Figs. 13c–e and 15d)

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Material and distribution. Panama: Observations on live animals, whole mounted afterwards. Seven whole mounts, one of which is designated holotype ( ZMH, No. V13689 ) and the others paratypes (HU, No. V877–882 ), collected in Taboga (type locality), Taboga Island, Pacific side of Panama (9 December 2011); intertidal, fine sand with the alga Caulerpa sp. , salinity 30 ‰.

Etymology. Species named after its occurrence in Panama.

Diagnosis. Species of Promesostoma with eyes. Copulatory bursa present. Prostate vesicle located anterior to the pharynx, the seminal vesicle located beside the pharynx, and the male atrium with stylet caudal to the pharynx. Stylet~ 88 µm long and twisting 360° at about its proximal third; distal end rounded to oblique. Seminal vesicle oriented forward and prostate vesicle backward.

Description. The overall organisation is comparable to that of other species of the genus Promesostoma (see Luther, 1943; Ax, 1951, 1952; Karling, 1967). Measured on the whole mounts, the animals are 0.5–1.1 mm long (x = 0.8 mm; n = 4) translucent, with a pair of eyes (Fig. 13c: e). Anterior rhabdite tracts present (Fig. 13a: ar). The pharynx (Figs. 13c, d and 15d: ph) is located at 50–60%, and in the whole mounts is 82–102 µm in diameter (x = 94 µm; n = 3).

A pair of testes (Fig. 13c: t) is located anterior to the pharynx. The vasa deferentia open into a single seminal vesicle (Figs. 13c, d and 15d: sv), which is located beside the pharynx. Whether or not the seminal vesicle is surrounded by a muscle layer is unclear from the whole mounted material. From this vesicle, the seminal duct runs forward and opens into the prostate vesicle, which is located anterior to the pharynx. The prostate vesicle (Figs. 13c, d and 15d: pv) connects to the stylet through a relatively long duct. The stylet (Figs. 13c, d and 15d: st, 13e) is positioned caudal to the pharynx. It is 81–92 µm long (x = 88 µm; n = 7), with a proximal, funnel-shaped part 2–3 µm wide (x = 2 µm; n = 7), surrounded by a sphincter (Fig. 13d: sph). At about its proximal third the stylet makes a 360° turn. Its distal end is blunt, its opening sometimes appearing a bit oblique. The male copulatory bursa (Figs. 13c, d and 15d: mb; terminology of Karling, 1967) is located latero-proximally from the stylet, entering the male atrium at the level of the turn of the stylet.

The paired vitellaria (Fig. 13c: vi) extend laterally, between the brain and the caudal body end. The oval-shaped ovaries (Fig. 13c: ov) are located latero-caudal to the male atrium. A glandular structure (Fig. 13c: x), presumably part of the female system, is located between the ovaries. The common gonopore (Fig. 13c: cg) opens at 80%.

Promesostoma roseapharynx sp. n. Diez, Reygel & Artois ( Figs. 14a–c and 15e )

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Promesostoma sp. 3 in Diez et al. (2023)

Material and distribution. Cuba: Observations on live animals. Three whole mounts from Las Sardinas (type locality) (21 June 2017), one of which is designated holotype ( ZMH, No. V 13690) and the others paratypes (HU, No. 883–884); on the alga Dictyota menstrualis covered with silty sand, 0.5 m deep, salinity 32‰. Two whole mounts and one specimen used for molecular analyses from Chivirico (March 16, 2017) (HU XIX.4.13– XIX.4.14); on the alga Halimeda sp. covered with silt, 0.6 m deep, salinity 35‰. Seven whole mounts from Bueycabón (February 6 & 21, & May 25, 2018) (HU XIX.4.15– XIX.4.21); on algae ( V. pachynema covered with red filamentous algae, Amphiroa fragilissima , G. rugosa , and G. acerosa ), 0.5 m deep, salinity 32‰. Etymology. Species named after the pinkish glands of the pharynx observed on live animals. Lat. roseus: pink.

Diagnosis. Species of Promesostoma with eyes. Male copulatory bursa present. Curved stylet situated beside the pharynx,~ 177 µm long, with the proximal funnel bent over ~ 180°. Tubular part of the stylet ~ 2 µm wide and ends in a sharp and oblique tip. Seminal vesicle situated caudally and laterally from the pharynx, oriented forward. Prostate vesicle anterior to the pharynx, directed backwards.

Description. The overall organisation is comparable to that of other species of the genus Promesostoma (see Luther, 1943; Ax, 1951, 1952; Karling, 1967). Measured on the whole mounts, the animals are 0.6–1 mm long (x = 0.8 mm; n = 3), translucent, with a pair of eyes ( Fig. 14d : e). Adenal rhabdite tracts present anteriorly ( Fig. 14a : ar). The pharynx ( Figs. 14a and 15e : ph) is located at 50%, 105–136 µm in diameter (x = 119 µm; n = 4), measured on the whole mounts, containing pinkish glands in live animals.

A pair of testes ( Fig. 14a : t) is located anterior to the pharynx. The vasa deferentia open into a large seminal vesicle situated caudal to the pharynx. On the whole mounts it was not possible to infer whether or not the seminal vesicle is surrounded by a muscle layer. The seminal vesicle ( Fig. 14a, b : sv) is oriented forwards and opens into the prostate vesicle ( Figs. 14a, b : pv), which itself is located anterior to the pharynx and oriented backwards. The male duct ( Fig. 14b : md) receives the stylet and the male copulatory bursa ( Figs. 14a, b : mb; terminology of Karling, 1967). The curved stylet ( Figs. 14a, b and 15e : st, 14c) lies next to the pharynx. It is 168–189 µm long (x = 177 µm; n = 12), with a proximal funnel bent over ~ 180°. This funnel is 9–15 µm long (x = 12 µm; n = 7) and 6–8 µm wide proximally (x = 7 µm; n = 7). A sphincter surrounds the base of the funnel. The tubular part of the stylet is 2–3 µm wide (x = 2 µm; n = 12), and distally ends in a sharp, oblique tip. The proximal half of the stylet is surrounded by a sheath of circular muscles.

The paired vitellaria ( Fig. 14a : vi) extend laterally from the eyes to the caudal body end. The oval-shaped ovaries ( Fig. 14a : ov) are located caudal to the pharynx. The common gonopore opens at 70–75%.

Figures

Fig. 14 a–c, Promesostoma roseapharynx sp. n. d–e, Promesostoma toryne sp. n. a, d Body organisation. b Sche- matic reconstruction of the male genital structures. c, e Stylet (from the holotype). Structures oriented with the anterior end toward the top of the plate

Fig. 15 Male genital structures in the new species of Promesos- toma (from the holotype). a Promesostoma baculum sp. n. b Promesostoma cubanum sp. n. c Promesostoma cubitum sp. n. d Promesostoma panamaense sp. n. e Promesostoma roseaphar- ynx sp. n. f Promesostoma toryne sp. n. a, d–e Structures oriented with the anterior end toward the left side of the plate. b, c, f Structures oriented with the anterior end toward the top of the plate