Cratera aureomaculata, Rossi, Ilana & Leal-Zanchet, Ana, 2017

Rossi, Ilana & Leal-Zanchet, Ana, 2017, Three new species of Cratera Carbayo et al., 2013 from Araucaria forests with a key to species of the genus (Platyhelminthes, Continenticola), ZooKeys 643, pp. 1-32 : 15-21

Cratera aureomaculata sp. n.

Material examined.

Holotype: MZUSP PL.1692: leg. J. L. A. Braccini, 3 June 2015, Três Barras ( Três Barras National Forest), state of Santa Catarina, Brazil - anterior tip: transverse sections on 19 slides; anterior region at the level of the ovaries: sagittal sections on 56 slides; pre-pharyngeal region: transverse sections on 14 slides; pharynx: sagittal sections on 35 slides; copulatory apparatus: sagittal sections on 31 slides.

Diagnosis.

Species of Cratera with dorsal ground colour yellowish covered by brownish pigmentation in cephalic region and blackish pigmentation constituting irregular flecks over rest of dorsum; eyes dorsal with clear halos; pharynx cylindrical; prostatic vesicle unpaired with proximal portion displaced ventrally, laterally expanded and T-shaped; penis papilla conical and symmetrical with ventral insertion posteriorly displaced.

Description.

External features.Body elongate with parallel margins and dorsal surface slightly convex; anterior tip rounded and posterior tip obtuse (Fig. 42). When creeping, maximum length 55mm. After fixation, maximum length 46mm. Mouth and gonopore located at posterior fourth of body (Table 5).

Live specimens with dorsal ground colour yellowish, covered by brownish pigmentation in cephalic region. Behind cephalic region, blackish pigmentation constitutes irregular flecks over dorsal surface, larger laterally and more concentrated towards posterior tip (Figs 42-43). Ventral surface light grey with yellowish margins; cephalic region (nearly anterior 1/8th of body length) brownish with darker margins.

Eyes monolobate, initially uniserial, surround anterior tip (Figs 44-45). After first millimetre of body, eyes become larger and spread onto dorsal surface, occupying maximum width of approximately one-third of body width on either side of body. Eyes remain dorsal, but less numerous towards posterior tip (Figs 44, 46). Some eyes over dorsal flecks surrounded by inconspicuous clear halos (Figs 45-46). Diameter of pigment cups 20-40 µm.

Sensory organs, epidermis and body musculature.Sensory pits (Figs 47-48), as simple invaginations (30-60 µm deep), contour anterior tip and occur ventromarginally in irregular, single row in anterior third of body. Creeping sole occupies whole body width in pre-pharyngeal region (Fig. 52).

Three types of glands discharge through whole epidermis of pre-pharyngeal region: abundant rhabditogen cells with xanthophil secretion (rhammites), cyanophil glands with amorphous secretion and xanthophil glands with fine granular secretion (Figs 51-52). Glandular margin (Figs 49-50) visible after anterior 1/16th of body. At least four types of glands constitute glandular margin: xanthophil and erythrophil glands, both with coarse granular secretions, besides few xanthophil and cyanophil glands with fine granules. Glands discharging through anterior tip of body similar to those of pre-pharyngeal region (Figs 47-48).

Cutaneous musculature with usual three layers (circular, oblique and longitudinal layers); longitudinal layer with thick bundles (Figs 49-52, Table 6). Thickness of cutaneous musculature between four and five times that of epidermis (Table 6). Ventral musculature thicker than dorsal at sagittal plane in pre-pharyngeal region (Table 6). Musculature becoming progressively lower towards body margins. In relation to body height, cutaneous musculature slightly thinner in pre-pharyngeal region than in cephalic region (Figs 47-48), especially ventral musculature (Table 6); thickness gradually diminishes towards anterior tip.

Mesenchymal musculature (Figs 49, 51-52) well developed, mainly composed of three layers: (1) dorsal subcutaneous, located close to cutaneous musculature, with decussate fibres variously oriented (3-5 fibres thick), (2) supra-intestinal transverse (8-14 fibres thick) and (3) sub-intestinal transverse (8-18 fibres thick). Mesenchymal musculature less developed in cephalic region (Fig. 47) than in pre-pharyngeal region.

Digestive system.Pharynx cylindrical, approximately 4% of body length, occupies 90% of pharyngeal pouch. Pharyngeal dorsal insertion slightly shifted posteriorly. Mouth in median third of pharyngeal pouch (Fig. 53). Oesophagus short with folded wall. Oesophagus: pharynx ratio 24%.

Pharynx and pharyngeal lumen lined by ciliated, cuboidal epithelium with insunk nuclei. Pharyngeal glands constituted by four secretory cell types: numerous erythrophil and xanthophil glands, both with fine granular secretion and cyanophil glands with amorphous secretion, as well as less numerous xanthophil glands with coarse granular secretion. Outer pharyngeal musculature (6-12 µm thick) comprised of thin subepithelial layer of longitudinal muscles, followed by layer of circular fibres. Inner pharyngeal musculature (60-110 µm thick) comprises thick subepithelial layer of circular fibres, followed by layer of longitudinal fibres. Outer and inner muscle layers gradually become thinner towards pharyngeal tip. Oesophagus lined by ciliated, cuboidal to columnar epithelium with insunk nuclei. Musculature of oesophagus (30-50 µm thick) composed of thick layer with circular fibres, followed by layer of longitudinal fibres.

Reproductive organs.Testes in one irregular row in either side of body, located beneath dorsal transverse mesenchymal muscles (Figs 49, 51), begin slightly behind anterior third of body and extend to near root of pharynx (Table 5). Sperm ducts medial to ovovitelline ducts, among fibres of sub-intestinal transverse mesenchymal musculature, form spermiducal vesicles posteriorly to pharynx. Distally, spermiducal vesicles bend to enter laterally into proximal expanded portion of prostatic vesicle (Fig. 55). Prostatic vesicle extrabulbar, unpaired, located near common muscle coat, with ample proximal portion and tubular distal portion. Proximal portion laterally expanded and T-shaped, displaced ventrally in relation to distal portion and located closer to ventral epidermis than to dorsal epidermis (Figs 55-57). Ejaculatory duct with slightly sinuous proximal portion and expanded distal portion (Figs 57, 58). Male atrium without folds. Penis papilla conical and symmetrical with ventral insertion posteriorly displaced (Figs 55-56, 58, Table 5).

Sperm ducts lined with ciliated, cuboidal epithelium and coated with thin muscularis (about 3 µm thick) constituted of interwoven circular and longitudinal fibres. Prostatic vesicle lined with ciliated, tall columnar epithelium (Fig. 57). Muscularis of prostatic vesicle (8-20 µm thick) comprises interwoven circular, longitudinal and oblique fibres. Ejaculatory duct lined with ciliated, columnar epithelium (Fig. 58). Muscle coat of ejaculatory duct thin (about 6 µm), mainly constituted of circular fibres. Numerous glands with fine granular, mixed secretion (cyanophil external part and erythrophil internal core) empty into both prostatic vesicle and ejaculatory duct; erythrophil glands with fine granules open into ejaculatory duct. Penis papilla and male atrium lined with non-ciliated, columnar or pseudostratified epithelium (approximately 40 µm thick). Erythrophil glands with fine granules, as well as cyanophil glands with amorphous secretion open through penis papilla and male atrium, besides xanthophil glands through penis papilla (Figs 56-58); cyanophil glands concentrate their numerous openings at dorso-lateral wall of male atrium (Figs 55-57). Muscularis of penis papilla (nearly 10 µm thick) and male atrium (5-10 μm thick) composed of subepithelial circular layer, followed by longitudinal layer.

Vitelline follicles (Figs 49, 51, 54) situated between intestinal branches. Ovaries oval-elongate (Fig. 54), two times longer than wide (approximately 200 µm in diameter), located dorsal to ventral nerve plate, in anterior third of body (Table 5). Ovovitelline ducts emerge dorsally from median third of ovaries and run posteriorly immediately above nerve plate. Ascending portion of ovovitelline ducts located at level of gonopore. Common glandular ovovitelline duct short, located dorsally to median third of female atrium. Female genital duct dorso-anteriorly curved (Figs 55, 59). Female atrium funnel-shaped. Length of female atrium about half that of male atrium (Figs 55-56, 59, Table 5).

Ovovitelline ducts and common ovovitelline duct lined with ciliated, cuboidal to columnar epithelium and covered with intermingled circular and longitudinal muscle fibres (approximately 5 μm thick). Abundant shell glands with erythrophil secretion, besides cyanophil glands, empty into common glandular ovovitelline duct as well as into distal third of ascending portion of ovovitelline ducts (Figs 55-56, 59). Epithelial lining of female genital duct and atrium with irregular height and stratified appearance (30-120 µm thick); epithelial cells with some lacunae (Figs 56, 59). Abundant cyanophil glands with amorphous secretion and erythrophil glands with fine granules empty into female duct and atrium. Muscularis of female duct and atrium (8-20 μm thick) composed of interwoven circular and longitudinal fibres.

Male and female atria with ample communication, without separating folds (Figs 55-56). Common muscle coat thin along both male and female atria, thicker dorsally than ventrally, composed of circular, longitudinal and oblique fibres. Gonoduct anteriorly inclined, lined with ciliated columnar epithelium. Numerous cyanophil glands with amorphous secretion, besides rhabditogen glands, open into gonoduct. Muscularis of gonoduct comprised of subepithelial layer of circular fibres, followed by longitudinal layer.

Etymology.

The specific name is a composite of the Latin adjective aureus (golden) and the Latin noun macula (spot), referring to the colour pattern with yellowish ground colour covered by black irregular flecks.

Distribution.

Known only from its type locality.