Choeradoplana cyanoatria, turralde, Giuly Gouvea & Leal-Zanchet, Ana, 2019

turralde, Giuly Gouvea & Leal-Zanchet, Ana, 2019, Why be original? Two new species of Choeradoplana resembling the type species of the genus in their external aspects (Platyhelminthes, Continenticola), ZooKeys 813, pp. 1-19 : 7-14

Choeradoplana cyanoatria sp. n. Figures 12, 13, 14, 15, 16, 17-18

Type-material.

Holotype: MZUSP PL.2144: leg. JAL Braccini, 2 June 2015, Três Barras (National Forest), state of Santa Catarina, Brazil - anterior tip: transverse sections on 17 slides; anterior region at the level of the ovaries: sagittal sections on 16 slides; pre-pharyngeal region: transverse sections on 7 slides; pharynx and copulatory apparatus: sagittal sections on 25 slides.

Diagnosis.

A species of Choeradoplana with dorsal surface covered by irregular small dark-brown flecks; pharynx bell-shaped; sperm ducts opening subterminally into prostatic vesicle; prostatic vesicle oval-elongate and folded, becoming funnel-shaped proximally and forming an elongate duct inside penis papilla; penis papilla, conical, long and almost symmetrical, with dorsal insertion shifted posteriorly, filling the whole atrium.

Description.

External features. Body elongate with parallel margins (Fig. 12), sub-cylindrical in cross section; anterior end expanded, posterior end slight pointed. Cephalic region (ca. 3 mm long) with two glandular cushions and a median slit in the ventral surface. Maximum length 20 mm when resting; 50 mm after fixation (Table 3). Mouth at median third of body; gonopore at posterior third of body (Table 3).

Live specimens with dorsal surface covered by irregular, small dark-brown flecks over all body length including cephalic region (Fig. 12). Yellowish ground colour visible on cephalic region, on body margins, as well as on thin, inconspicuous median stripe occurring along the anterior body half except for cephalic region. Ventral surface pale yellow. After fixation, dorsal pigmentation remains brownish; ventral surface becomes whitish with darker body margins.

Eyes absent on cephalic region (first 1.2 mm of body, corresponding to 2.4% of body length). After that, eyes initially monolobate and uniserial. Eyes become trilobate and plurisserial after 3 mm, becoming sparser towards posterior tip. No clear halos around eyes. Diameter of pigment cups between 24 µm and 32 µm in diameter.

Sensory organs, epidermis and body musculature. Sensory pits, as simple invaginations (15-18 µm deep), absent on anterior tip, occurring in a single row between 3% and 10% of body length.

Three types of glands discharge through whole epidermis of pre-pharyngeal region: rhabditogen glands with xanthophil rhammites (ventrally with smaller rhabdites) and cyanophil glands with amorphous secretion, as well as few xanthophil glands with coarse granular secretion (Fig. 13). Creeping sole occupies 89% of body width. Glandular margin absent. Glands discharging through anterior tip of body with similar arrangement as in other species of the genus.

Cutaneous musculature with usual three layers (circular, oblique, and longitudinal layers), with part of ventral longitudinal layer, as well as few muscle bundles of dorsal longitudinal layer, imbedded in mesenchyme (Fig. 13, Table 4). Longitudinal layer between five and eight times thicker than other two cutaneous layers in pre-pharyngeal region (Table 4). Cutaneous musculature as high paramedially as medially. Ventral musculature thinner than dorsal in pre-pharyngeal region. Mc:h 22% (Table 4). In cephalic region, cutaneous musculature with similar arrangement as in other species of the genus.

Mesenchymal musculature (Fig. 13) weakly developed, mainly composed of three layers: (1) dorsal subcutaneous, located mainly close to cutaneous musculature, with decussate fibres (2 fibres thick), (2) supra-intestinal transverse (2-4 fibres thick) and (3) sub-intestinal transverse (5-7 fibres thick). In cephalic region, mesenchymal musculature with similar arrangement as in other species of the genus.

Digestive system. Pharynx bell-shaped, as long as 7% of body length, occupies almost entire pharyngeal pouch. Mouth almost at the same transversal level as dorsal insertion in the beginning of median third of pharyngeal pouch (Fig. 14). Oesophagus absent.

Reproductive organs. Testes in two or three irregular rows on either side of body, located beneath dorsal transverse mesenchymal muscles, between intestinal branches (Fig. 13). They begin slightly anteriorly to ovaries, in anterior sixth of body, to just the root of the pharynx (Table 3). Sperm ducts dorsal to ovovitelline ducts, medially displaced, under or among fibres of sub-intestinal transverse mesenchymal musculature, in pre-pharyngeal region (Fig. 13). They form spermiducal vesicles posteriorly to pharynx. Sperm ducts enter common muscle coat, recurve, and open subterminally into prostatic vesicle. Intrabulbar prostatic vesicle, oval-elongate and folded, becoming funnel-shaped both proximally and distally (Fig. 17). Inside penis papilla, prostatic vesicle narrows and forms an elongate duct that opens through tip of the papilla. Penis papilla, conical, long and almost symmetrical, filling the whole atrium. The dorsal insertion of the penis papilla is posteriorly shifted (Figs 15, 16). Folded atrium without anatomical or histological differentiation between male and female regions. Close to papilla insertions, longitudinal folds represent part of papilla wall.

Prostatic vesicle and proximal third of ejaculatory duct receive abundant openings of cells with coarse granular, erythrophil secretion, besides sparse amorphous, cyanophil secretion, besides a third type of gland containing heavy cyanophil granules. Distal two thirds of ejaculatory duct receives openings from numerous glands with amorphous, cyanophil secretion. Muscularis of ejaculatory duct thin (5µm) composed of longitudinal fibres. Abundant glands with densely distributed, coarse granular, xanthophil secretion and numerous glands with amorphous, cyanophil secretion open through epithelial lining of penis papilla, besides sparse erythrophil glands through lining of penis papilla. Numerous glands with amorphous, cyanophil secretion and scattered glands with erythrophil, fine granular secretion open through epithelial lining of the atrium, which is cyanophil. Muscularis of penis papilla (40-80µm) composed of subepithelial layer with circular fibres followed by layer with longitudinal fibres, both layers well developed. Posteriorly to the gonopore, necks of cyanophil glands concentrate subepithelially; subepithelial muscle fibres of atrium scattered among these cell necks (Fig. 18).

Vitelline follicles, situated between intestinal branches, well developed. Ovaries ovoid, 1.5 times longer than wide, measuring 0.3 mm in its antero-posterior axis. They are located dorsally to the ventral nerve plate, in anterior sixth of body. Ovovitelline ducts emerge laterally from median third of ovaries, and run posteriorly immediately above nerve plate. Behind gonopore, the ovovitelline ducts ascend posteriorly and medially inclined, uniting to form a common glandular ovovitelline duct. This duct is situated dorsally to the relatively long, C shaped female canal, which opens into the atrium (Figs 15, 16).

Shell glands of two types: with coarse granular, erythrophil secretion, as well as with coarse granular, xanthophil secretion, the cells bodies of which occur among cell bodies of cyanophil glands. Towards female canal, the lining epithelium becomes pseudostratified and erythrophil. Two types of glands open through the epithelium of the female canal: erythrophil glands with finely granular secretion and cyanophil glands with amorphous secretion both sparsely distributed. Muscularis of female canal (20-40µm) composed of interwoven circular and longitudinal fibres.

Gonopore canal vertical at the sagittal plane. Common muscle coat highly developed, especially at penis bulb (Figs 15, 16), with interwoven oblique, circular and longitudinal fibres.

Etymology.

The name is a composite of the Latin adjective cyano (blue) and the Latin atria, referring to the abundant cyanophil secretion opening through the atrium.

Distribution.

Known only from the type-locality, Três Barras, Santa Catarina, Brazil.