Choeradoplana longivesicula, 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 : 3-7

Choeradoplana longivesicula sp. n. Figures 1-2, 3-7, 8, 9, 10-11

Type-material.

Holotype: MZUSP PL.2143: leg. JAL Braccini, 6 June 2015, General Carneiro ( Araucaria Natural Heritage Private Reserve), PR, Brazil - anterior tip: transverse sections on 24 slides; anterior region at the level of the ovaries: sagittal sections on 27 slides; pre-pharyngeal region: transverse sections on 8 slides; pharynx: sagittal sections on 31 slides; copulatory apparatus: sagittal sections on 25 slides. Paratype: MZU PL.00292: leg. I Rossi, 6 June 2015, General Carneiro ( Araucaria Natural Heritage Private Reserve), state of Parana, Brazil - anterior tip: transverse sections on 27 slides; anterior region at the level of the ovaries: sagittal sections on 24 slides; pre-pharyngeal region: transverse sections on 10 slides; pharynx: sagittal sections on 22 slides; copulatory apparatus: sagittal sections on 19 slides.

Diagnosis.

A species of Choeradoplana with dorsal surface covered by irregular small dark-brown flecks and thin median light stripe; pharynx bell-shaped; sperm ducts opening laterally into proximal wall of prostatic vesicle; prostatic vesicle tubular and unpaired, narrowing to open through tip of penis papilla as an ejaculatory duct; penis papilla cylindrical and almost symmetrical, filling entire common atrium; atrium oval-elongate and unfolded, without differentiation between male and female regions.

Description.

External features. Body elongate with parallel margins (Figs 1, 2), elliptical in cross section; anterior end expanded, posterior end slight pointed. Cephalic region (ca. 3 mm long) with two glandular cushions separated by a median longitudinal slit in the ventral surface. Maximum length 67 mm when crawling; 50 mm after fixation (Table 1). Mouth at median third of body; gonopore at posterior third of body (Table 1).

Live specimens with dorsal surface covered by dark-brown pigmentation constituted by irregular, small flecks. Yellowish ground colour visible on cephalic region, on body margins, as well as on thin median stripe occurring along the body except for cephalic region (Figs 1, 2). Ventral surface whitish before and after fixation. After fixation, dorsal pigmentation fades.

Eyes absent on anterior tip (first 1.5 mm of body, corresponding to 3% of body length). Afterwards, eyes initially monolobate and uniserial. Eyes become trilobate and plurisserial after 3 mm and sparser towards posterior tip. No clear halos around eyes. Pigment cups between 20 µm and 30 µm in diameter.

Sensory organs, epidermis and body musculature. Sensory pits, as simple invaginations (15-20 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 erythrophil glands with fine granular secretion (Figs 3, 4). Creeping sole occupies 82% 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), showing part of ventral longitudinal layer, as well as some muscle bundles of dorsal longitudinal layer, imbedded in mesenchyme (Fig. 3, Table 2). Longitudinal layer between four and eight times thicker than other two cutaneous layers in pre-pharyngeal region (Table 2). Cutaneous musculature as thick paramedially as medially. Ventral musculature slightly thinner than dorsal in pre-pharyngeal region. Ratio between cutaneous musculature and body height (mc:h) ca. 19% (Table 2). In cephalic region, cutaneous musculature with similar arrangement as in other species of the genus (Fig. 5).

Mesenchymal musculature (Fig. 3) weakly developed, mainly composed of three layers: (1) dorsal subcutaneous, located mainly close to cutaneous musculature, with decussate fibres (2-3 fibres thick), (2) supra-intestinal transverse (3-5 fibres thick) and (3) sub-intestinal transverse (4-6 fibres thick). In cephalic region, mesenchymal musculature with similar arrangement as in other species of the genus (Fig. 5).

Digestive System. Pharynx bell-shaped, ca. 6% of body length, occupies ca. 90% of pharyngeal pouch. Mouth slightly posterior to dorsal insertion next to end of median third of pharyngeal pouch (Fig. 7). Oesophagus absent.

Reproductive organs. Testes in one or two irregular rows on either side of body, located beneath dorsal transverse mesenchymal muscles, between intestinal branches (Fig. 3), begin slightly anteriorly to ovaries, in anterior third of body, and extend to next to root of the pharynx (Table 1). Sperm ducts dorsal to ovovitelline ducts, under or among fibres of sub-intestinal transverse mesenchymal musculature, in pre-pharyngeal region (Figure 3). They form spermiducal vesicles posteriorly to pharynx. Sperm ducts enter common muscle coat, ascend slightly and open laterally into proximal wall of prostatic vesicle. Intrabulbar prostatic vesicle, tubular and unpaired, traverses both penis bulb and papilla (Fig. 10), narrowing to open through tip of papilla as an ejaculatory duct (Fig. 11). Penis papilla, cylindrical and almost symmetrical, filling entire common atrium. Dorsal insertion of penis papilla slightly shifted posteriorly. Common atrium oval-elongate and unfolded, without differentiation between male and female atria (Figs 8, 9).

Prostatic vesicle lined with high pseudostratified epithelium with few ciliated cells, receiving numerous openings of glands with ill-stained, coarse granular secretion, sometimes containing an erythrophil core. In addition, sparse openings of other two types of glands occur throughout the epithelium of prostatic vesicle: cells with xanthophil, coarse granular secretion, and cell with amorphous, cyanophil secretion. Ejaculatory duct lined with columnar, densely ciliated epithelium. Both penis papilla and atrium lined with non-ciliated columnar epithelium, becoming cuboidal towards tip of papilla, showing a xanthophil apical region. Numerous glands of two types open through epithelial lining of penis papilla and atrium: one with xanthophil, coarse granular secretion and the other with amorphous, cyanophil secretion. In addition, a third type, with fine granular, erythrophil secretion, opens through epithelial lining of penis papilla. Muscularis of penis papilla (30-60 µm) composed of subepithelial layer with circular fibres followed by some longitudinal fibres; that of atrium composed of longitudinal and circular interwoven fibres (10-15 µm).

Vitelline follicles situated between intestinal branches, well developed. Ovaries ovoid, ca. twice longer than wide, measuring 0.2 mm in its antero-posterior axis. They are located dorsally to the ventral nerve plate, in anterior third of body. Ovovitelline ducts emerge laterally from median third of ovaries, then run posteriorly immediately dorsal to the nerve plate. Behind the gonopore, the ovovitelline ducts ascend posteriorly and medially inclined, and unite, dorsally to the female canal, forming the common glandular ovovitelline duct. Female canal relatively long and C shaped. This canal opens into bottom of posterior part of atrium, where a constriction occurs (Figs 8, 9).

Female canal lined with erythrophil, pseudostratified epithelium. Three types of glands open through the epithelium of female canal: abundant cells with finely granular, erythrophil secretion, cells with coarse granular, xanthophil secretion, and scarce cells with amorphous, cyanophil secretion. Muscularis of female canal composed of longitudinal and circular interwoven fibres (20-30 µm)

Gonopore canal almost vertical at the sagittal plane. Common muscle coat highly developed, especially at penis bulb (Figs 8, 9), with interwoven oblique, circular and longitudinal fibres.

Etymology.

The name is composed of the Latin adjective longus (long) and the Latin vesicula, alluding to the elongate prostatic vesicle.

Distribution.

known only from the type-locality, General Carneiro, Paraná, Brazil.