Cratera viridimaculata, Negrete, Lisandro & Brusa, Francisco, 2016

Negrete, Lisandro & Brusa, Francisco, 2016, First report of the genus Cratera (Platyhelminthes, Geoplanidae) in Argentina, with description of a new species and comments on the species of the genus, ZooKeys 610, pp. 1-12 : 2-8

Taxon classification Animalia Seriata Geoplanidae

Cratera viridimaculata sp. n. Figs 1, 2, 3, 4, 5, Tables 1, 2

Geoplana sp. 6 ( Negrete et al., 2014 in part)

Type material.

Holotype (Figs 1, 3-5). MLP–He 6944. Locality: Esmeralda Provincial Park (26°53'S, 53°52'W), Misiones Province, Argentina. 19 June 2013; cephalic region: transversal sections on 16 slides (6 µm thick); anterior region: sagittal sections on 30 slides (7 µm thick); anterior region at level of ovaries: sagittal sections on 20 slides (7 µm thick); pre-pharyngeal region: transverse sections on 6 slides (6 µm thick); pharynx: sagittal sections on 32 slides (7 µm thick); copulatory apparatus: sagittal sections on 32 slides (7 µm thick).

Paratype (Fig. 2). MLP–He 6489. Locality: San Antonio Strict Nature Reserve (26°03'S, 53°46'W), Misiones Province, Argentina. 30 October 2008; cephalic region and anterior region at level of ovaries: sagittal sections on 28 slides (8 µm thick); pre-pharyngeal region: transverse sections on 12 slides (8 µm thick); pharynx: sagittal sections on 31 slides (8 µm thick); copulatory apparatus: sagittal sections on 31 slides (8 µm thick).

Type locality.

Esmeralda Provincial Park (26°53'S, 53°52'W), in native subtropical forest. Misiones province, Argentina.

Diagnosis.

Species of Cratera of 50 mm in length; dorsal surface stippled with dark gray fine spots on a light olive green background; eyes dorsal; glandular margin present; CMI, 10-13%; pharynx cylindrical; prostatic vesicle extrabulbar, tubular and C-shaped, with proximal bifurcated portion.

Description.

External morphology. Body elongate with parallel margins. Anterior tip blunt and posterior end pointed (Figs 1, 2). Dorsal surface light olive green, stippled with dark gray fine spots, and body margins and cephalic region pigmented dark gray (Fig. 1). Ventral surface whitish with margins grayish. After fixation, the dorsal color pattern became paler with lighter gray fine spots. Eyes distributed from the anterior tip to the posterior end. They surround the cephalic region and extend uniserially on body margins along 1-2 mm from the anterior tip, continuing pluriserially over the dorsal surface, being surrounded by clear halos. Eyes occupy about 30% of body width on each side of the dorsal surface at pre-pharyngeal region. Behind the pharynx, they decrease in number and at the level of the copulatory apparatus become uniserial and marginal (Fig. 2). After fixation, the length of specimens is about 50 mm, maximum width ~4.5 mm, and maximum height ~1.5 mm. Mouth and gonopore located at a distance of 66-75% and 83-89% from the anterior tip, respectively (Table 1).

Internal morphology. Sensory pits, as simple invaginations ranging from 25 µm to 40 µm deep, contouring anterior tip and extending along body margins in a single irregular row. They occur at intervals of about 25-50 µm, and posteriorly become gradually spaced until they disappear at 5-6 mm from anterior tip. Three types of secretory cells discharge through dorsal epidermis (15 µm height) and body margins at pre-pharyngeal region: numerous rhabditogen cells with xanthophil secretion (rhammites), abundant cells with fine granular erythrophil secretion, and scarce cells with fine granular cyanophil secretion. Glandular margin composed of abundant fine gran ular erythrophil secretion and scarce fine granular xanthophil and cyanophil secretion (Fig. 3A, B). Ventral epidermis (25 µm height) ciliated on the creeping sole (90% of body width). Three types of secretory cells discharge their secretion through the creeping sole: rhabditogen cells (with rhabdithes), and abundant cells with fine granular erythrophil and cyanophil secretion. Cephalic region with the same types of secretory cells, discharging through dorsal and ventral epidermis but in less quantity, except cells with fine granular xanthophil secretion which are highly abundant mainly on body margins. No musculo-glandular specializations. Cutaneous musculature with the usual three layers present in the subfamily Geoplaninae: circular, oblique and longitudinal, the latter arranged in bundles and is the thickest (Table 1). Cutaneous Muscular Index (CMI) ranging from 10% to 13%. Parenchymatic musculature composed of a dorsal layer with oblique fibers, a supra-intestinal and a sub-intestinal transverse layers (Table 1) (Fig. 3A, B, D). Additionally, dorsoventral fibers located among intestinal branches (Fig. 3A). Parenchymatic Muscular Index (PMI) ranging from 8% to 9% (Table 1).

Pharynx cylindrical, 1.5-2.3 mm in length (3-4% of body length), with dorsal insertion located at the proximal third of pharyngeal pouch (3-3.2 mm in length) (Fig. 3C). Pharynx lined by ciliated cuboidal epithelium. Pharyngeal musculature of the planariid type comprising an outer musculature arranged in two layers: longitudinal subepithelial layer (5 µm thick) followed by a subjacent circular layer (5-10 µm thick). Pharyngeal lumen lined by ciliated columnar epithelium. Pharyngeal inner musculature comprised of circular subepithelial layer (75-90 µm thick) followed by a thinner longitudinal layer (10-20 µm thick). Pharyngeal glands constituted by three secretory cell types: abundant cells with fine granular erythrophil secretion, less abundant cells with fine granular cyanophil secretion and scarce cells with amorphous cyanophil secretion (Fig. 3C). Cell bodies of pharyngeal glands located in the surrounding parenchyma, mainly anterior to pharynx. Short esophagus (250-300 µm in length) lined by ciliated columnar epithelium, followed by a subepithelial circular layer (45-60 µm thick) and a subjacent longitudinal layer (5-15 µm thick). Esophagus: pharynx ratio, 13-17%.

Testes dorsal, mature, arranged in one irregular row on each side of the body, located between the supraintestinal parenchymatic muscle layer and intestinal branches (Fig. 3A). They extend immediately behind the ovaries to nearly the ventral root of pharynx (Table 2). Sperm ducts dorso-mediad to ovovitelline ducts, located among fibers of sub-intestinal transverse layer (Fig. 3D). Near the copulatory system, the lumen of sperm ducts is dilated and full of spermatozoa. They curve to the sagittal plane and communicate with the proximal paired portions of the prostatic vesicle (150-170 in length each) (Figs 4, 5A, B). Prostatic vesicle, extrabulbar, unpaired, tubular and C-shaped, spaced 5.2 mm from the pharyngeal pouch (Figs 4, 5A). Ejaculatory duct almost straight, except its proximal portion which is sinuous, opening through an expansion into the tip of the penis papilla (Figs 4, 5A). Male atrium with unfolded walls, housing a cylindrical penis papilla which occupies most of the atrium (Figs 4, 5A). Male atrium with ample communication with female atrium, without folds separating both atria (Figs 4, 5A).

Sperm ducts lined with ciliated cuboidal epithelium, coated by circular fibers (5 µm thick). Lining epithelium of prostatic vesicle columnar and ciliated, receiving abundant fine granular erythrophil secretion from glands with cells bodies located anterior to the prostatic vesicle. Muscularis of prostatic vesicle (15-20 µm thick) arranged in a circular layer interwoven with oblique fibers. Ejaculatory duct lined with ciliated columnar epithelium, which receives scarce fine granular erythrophil secretion, coated by circular fibers (2.5-5 µm thick). Penis papilla lined with non-ciliated columnar epithelium, strongly erythrophil (Fig. 5A). Epithelial lining of penis papilla receives abundant fine granular erythrophil secretion and less abundant amorphous erythrophil secretion (Fig. 5 A). Cell bodies of penis glands located in the parenchyma, outside the penis bulb. Muscularis of the penis papilla (5-10 µm thick) composed of circular fibers. Male atrium lined with non-ciliated columnar epithelium, followed by circular muscle layer (5-15 µm thick). The epithelial lining of the dorsal wall of the male atrium receives large amount of fine granular cyanophil secretion, and less abundant fine granular erythrophil secretion (Fig. 5A, B). The ventral wall receives fine granular erythrohil secretion and scarce cyanophil granules. Cell bodies of glands which discharge their secretions into the male atrium located in the parenchyma, external to common muscle coat.

Ovaries ovoid and distally elongate, measuring 500-600 µm in length, located just below the sub-intestinal parenchymatic muscle layer (Fig. 5C). Ovovitelline ducts emerge dorso-laterally from the middle third of ovaries, and run posteriorly between sub-intestinal parenchymatic muscle layer and nerve plate (Figs 3A, D, 5C). At the level of gonopore, ovovitelline ducts ascend, run to the sagittal plane and join in a short common glandular ovovitelline duct (Figs 4, 5A, B). The common ovovitelline duct is horizontal and located above the posterior region of the female atrium (Figs 4, 5A). Short female genital canal dorsoventrally oriented, connecting common glandular duct and female atrium (Figs 4, 5A). Female atrium funnel-shaped and without folded walls, shorter than the male atrium (Figs 4, 5A, Table 2).

Ovovitelline ducts lined with ciliated cuboidal epithelium, coated by circular fibers (2.5 µm thick). Ascending portions of ovovitelline ducts receive secretion from shell glands (Fig. 5B). Lining epithelium of common glandular ovovitelline duct columnar and ciliated, receiving abundant secretion from shell glands and amorphous cyanophil secretion (Fig. 5A). Cell bodies of these glands located posterior to the copulatory apparatus (Figs 4, 5A). Female genital canal lined with ciliated columnar epithelium, coated by circular fibers (5-10 µm thick). Female atrium lined by non-ciliated columnar epithelium, with nuclei located at different heights and giving a stratified aspect (Fig. 5A). Muscularis of female atrium composed of circular fibers mixed with some longitudinal fibers (10-15 µm thick). Female genital canal and female atrium receive abundant fine granular erythrophil secretion, and fine granular cyanophil secretion in less quantity. Common muscle coat poorly organized, composed of longitudinal and oblique fibers (5-10 µm thick) (Fig. 4).

Vitellaria well-developed in both specimens studied, located among intestinal branches (Figs 3 A–D, 5 A–C). Gonopore canal slightly anteriorly flexed, lined with ciliated columnar epithelium (Fig. 5A). Three types of secretory cells discharge their secretion through the gonopore canal: rhabditogen cells (with rhabdithes), abundant cells with fine granular erythrophil secretion and scarce cells with fine granular cyanophil secretion.

Etymology.

The specific name refers to the dorsal pigmentation of body, stippled with dark gray dots on a light green olive background (from lat. viridis = green, greenish; maculatus = maculated, spotted, splattered with dots).

Distribution.

Southern portion of the Interior Atlantic Forest ecoregion, Misiones Province, north-eastern Argentina. The new species was found in native subtropical forests, in two natural reserves: Esmeralda Provincial Park (26°53'S, 53°52'W) and San Antonio Strict Nature Reserve (26°03'S, 53°46'W).