Cratera arucuia, Lago-Barcia & Carbayo, 2018

Lago-Barcia, Domingo & Carbayo, Fernando, 2018, Taxonomic revision of four species of the Neotropical land planarian genera Cratera and Geoplana (Platyhelminthes, Tricladida) with a description of two new species and an emendation of Cratera, Zootaxa 4500 (4), pp. 517-542 : 537-539

Cratera arucuia sp. n.

Synonymy

Geoplana sp. 2 ; Carbayo et al., 2013

Cratera sp. 2 ; Carbayo et al., 2013

Type material. Parque Estadual de Intevales , Ribeirão Grande, State of São Paulo, Brazil, (-24.2693, -48.4054) Holotype F2783 ( MZUSP PL 1048 ): F. Carbayo et al. coll., 29 July 2008, sagittal sections of region behind ovaries on 13 slides and horizontal sections on 5 slides; transverse sections of pre-pharyngeal region on 7 slides; sagittal sections of pharynx and copulatory apparatus on 14 slides. Paratype F2784 ( MZUSP PL 2112 ): F. Carbayo et al. coll., 29 July 2008, sagittal sections of copulatory apparatus and pharynx on 12 slides. Paratype F2696 ( MZUSP PL 2110 ): F. Carbayo et al. coll., 25 July 2008, sagittal sections of copulatory apparatus on 19 slides. Paratype F2724 ( MZUSP PL 2111 ): F. Carbayo et al. coll., 26 July 2008, transverse sections of cephalic region on 5 slides; sagittal sections of ovaries region on 4 slides; sagittal sections of region behind ovaries on 9 slides; sagtital sections of pre-pharyngeal region on 3 slides; sagittal sections of copulatory apparatus on 8 slides. Paratype F3094 ( MZUSP PL 2113 ): F. Carbayo et al. coll., 12 December 2008, transverse sections of cephalic region on 8 slides; sagittal sections of ovaries region on 20 slides .

Distribution: Only known from the type locality, Parque Estadual de Intervales, Ribeirão Grande, State of São Paulo, Brazil.

Etymology. The name arucuia is a free composition of the Tupi (indigenous Brazilian language) words aru (meaning back, opposite side) and cuia (meaning gourd, the dried shell of a cucurbit plant ( Tibiriçá, 1984)). It refers to the uncommon, dorsal location of the gourd or ovoid-like prostatic vesicle.

Diagnosis: Species of Cratera with dorsal coloration comprised of an orange median irregular stripe that can vary in size, lateral gray or black stripes and a gray marginal stripe on a whitish cream ground color. Dorsal eyes initiating in cephalic region. Proximal section of prostatic vesicle ovoid, extrabulbar and positioned dorsally above the penis bulb. Penis bulb strongly developed, extending 1.8 mm anteriorly to the penis. Ejaculatory duct not dilated distally. Very thick circular muscle surrounding ejaculatory duct, equivalent to 4 times the diameter of this duct in its proximal region, and 2 times the diameter in its distal region. Penis papilla projects into female atrium. Female:male atrial length ratio, 1.4. Common glandular duct present.

Description. External aspect. Preserved animals up to 42.5 mm long, and 3 mm wide (holotype). Body margins nearly parallel; anterior end rounded, posterior pointed. Dorsum strongly convex, ventral side slightly convex; body sides thin.

Dorsal ground color whitish cream. The median region presents a median stripe of irregular margins and variable width (8-30% of body width), constituted of orange small spots. This median stripe is absent on a variable portion of the anterior end ( Fig. 13A, B ), ranging from 1/10 to 3/4 of body length. An interval of ground color may separate this median line from dark gray or black lateral stripes, the external half of which is mottled with clear halos encircling eyes. These lateral stripes may vary in width (12%-32% of body width) ( Fig. 13C ). External to the lateral stripes and separated from them by an interval of ground color (17% of body width), is a marginal stripe of gray (12% of body width), with fading inner margin. These marginal stripes are also mottled with clear halos encircling eyes. Ventral surface whitish.

Eyes are monolobulated, spread from anterior tip ( Fig. 13D ) to rear end of the body, and are distributed over dorsal surface to the maximum extent of about 37% of the body width in mid body, on either side. Towards the rear end, they become scarcer and are progressively distributed over a narrower band. Sensory pits as simple invaginations 30 µm deep, located ventro-marginally in a single row from very anterior tip to, at least the level of the ovaries (equal to 34% of body length). Relative mouth:body length and relative gonopore:body length variable depending on length of animals (in holotype and paratypes F3094, F2724 and F2696 these values are 62%, 66%, 70%, 81% for mouth; and 63%, 76%, 57%, 86% for gonopore, respectively). This pattern means that larger animals present mouth and gonopore in a relatively more anterior location.

Internal morphology. Creeping sole occupies 94% body width. Glandular margin present, composed of amorphous intensely-staining erythrophil glands, xanthophil glands and erythrophil granules, respectively. Cutaneous musculature with the usual three layers present in Geoplaninae : subepithelial circular (one fiber thick), diagonal with decussate bundles (10 µm thick) and an innermost longitudinal layer (50 µm thick), the latter more conspicuous and arranged in bundles. Cutaneous musculature as thick as 12% of body height. Parenchymal musculature composed of three muscular layers: a dorsal layer with diagonal decussate fibers (70 µm thick) and a supraintestinal layer (70 µm thick in holotype) and a subintestinal transverse layer (30 µm thick). Ventral nerve plate present.

Relative position mouth:pharyngeal pouch length, of 57%. Pharynx bell-shaped ( Fig. 13E ). Esophagus present, with 20% of pharynx length. Outer pharyngeal musculature consisting of a subepithelial layer (5 µm thick) of longitudinal muscle, followed by a layer (30 µm thick) of circular musculature. Inner pharynx musculature consisting of a subepithelial layer (40 µm thick) of longitudinal musculature followed by intermingled longitudinal and circular fibers (holotype).

Testes dorsal, located between supraintestinal parenchymal muscle layer and intestine. These testes extend from the level of the ovaries to shortly before root of pharynx. Laterally to the middle of penis bulb, sperm ducts bend dorsally above the level of the penis bulb, and subsequently bend anteriorly for a short length to open ventromedially into the extrabulbar portion of the prostatic vesicle. This extrabulbar portion is located above the penis bulb ( Figs. 14A, B ). These sperm ducts lined with a squamous ciliated epithelium, that becomes cuboidal distally and full of sperm. This epithelium is surrounded by a 8-15 µm thick circular muscle, at some points decussate. Penis bulb conspicuous, elongate and strongly developed, extending from 1.8 mm anterior to penis papilla (paratypes F2738, F2696), which represents half of the length of the copulatory apparatus. The bulb consists of decussate, tightly packed muscle fibers; the penis bulb is ectally continuous with the common muscle coat and entally with the muscle around the intrabulbar portion of the prostatic vesicle. The extrabulbar portion of the prostatic vesicle is gourd- or ovoid- shaped, and is placed above the penis bulb. From the ventro-anterior aspect of the extrabulbar portion, the prostatic vesicle continues as a canal that penetrates antero-dorsal section of the penis bulb. Inside the bulb, the prostatic vesicle is a dilated canal with slightly folded walls describing a curve as it runs initially ventrally, subsequently backwards and horizontally to advance into the anterior third or quarter of the penis papilla before continuing as the ejaculatory duct. Prostatic vesicle lined with a ciliated epithelium which is cuboidal in the extrabulbar portion, and columnar in the intrabulbar portion. Both epithelia are pierced by glands producing erythrophil granules. A tightly packed muscle of fibers variously oriented surrounds the prostatic vesicle. This muscle fibers are continuous with those of the penis bulb. Ejaculatory duct crosses the middle of the penis papilla. It is lined by a cuboidal, ciliated epithelium. This epithelium is surrounded by a conspicuous layer of circular muscle, tending to decussate muscle in some regions. This muscle layer is 80 µm thick in its proximal region and 10 µm thick in its distal region. In the proximal region, it constitutes a muscular cylinder with 300 µm in diameter, which represents four times the diameter of the ejaculatory duct (75 µm). Distally, the muscular cylinder is 50 µm in diameter, or twice that of the surrounded ejaculatory duct (25 µm). Penis papilla long, conical, with dorsal and ventral insertions at the same transverse plane. The papilla occupies whole of male atrium and most part of the female one ( Figs. 14A, B ). Papilla lined with a cuboidal epithelium. Glands producing cyanophil granules open through dorsal half of epithelium of penis papilla; the remaining papillar epithelium is crossed by glands producing erythrophil granules. The openings of these glands are specially abundant on distal half of the papilla. Subepithelial musculature of penis papilla consists of a dense 30µm thick layer of circular muscle, the innermost portion of which possesses intermingled longitudinal fibers ( Fig. 14B ). Male atrium not folded, lined by a cubic non ciliated epithelium, and underlain by a 10 µm thick layer of circular muscle, followed by a 20 µm thick layer of longitudinal muscle.

Ovaries ovoid, 300 µm in length, placed above the ventral nerve plate, and at a distance from anterior body tip equal to 34% of body length. Ovovitelline ducts emerge from dorso-lateral aspect of ovaries. Laterally to female atrium, they rise posteriorly and medially as they widen to double its own diameter, subsequently they narrow and unite dorsally to the common glandular ovovitelline duct ( Figs. 14A, B ). They receive shell glands into their distal, horizontal portion. Common glandular ovovitelline duct horizontal, as long as half of female atrium. This common duct opens to the female genital duct, an anteriorly oriented projection from postero-dorsal region of female atrium. Female atrium with a few longitudinal, lateral folds. The female atrium widens anteriorly to continue with the male atrium. Female:male atrial length, 1.4:1. Female atrium and female genital duct lined with a columnar 30µm high non-ciliated epithelium, the apical surface of which is erythrophil. This epithelium is crossed by two types of glands, producing erythrophil and xanthophil granules, respectively, the latter being scarcer. This epithelium and that of the female genital duct are surrounded by a thin, 10µm thick muscle layer of circular fibers with interwoven longitudinal fibers.

Remarks. Regarding the body aspect, Cratera arucuia sp. n. differs from all its congeners in the dorsal chromatic pattern. Cratera hina has a dorsal coloration somewhat resembling C. arucuia , but the former species lacks the marginal stripes of gray with fading inner margin. Pseudogeoplana tricolor ( Riester, 1938) is the only species in Pseudogeoplana Ogren & Kawakatsu, 1990 (a collective group for geoplaninid species whose internal morphology is unknown) also resembles the new species in that the dorsal colors are similar and distributed in longitudinal stripes. However, the dorsal color of P. tricolor consists of a median yellow line, flanked by two paramedian dark lines and externally to these, two orange marginal lines.

Regarding the internal morphology, C. arucuia is easily differentiated from its congeners, and even from all other species of Geoplaninae by the unique location of the prostatic vesicle above the penis bulb.

Figures

FIGURE 13. Cratera arucuia sp. n. (A): dorsal view of the paratype F3094. (B): dorsal view of the paratype F3135. (C): dorsal view of the paratype F2784 showing thinner lateral stripes. (D): dorsal view of the paratype F3135 showing eye distribution on anterior region. (E): photomicrograph of a sagittal section of the pharynx of paratype F2696.

FIGURE 14. Cratera arucuia sp. n. Holotype. (A): diagrammatic representation of the copulatory apparatus from sagittal sections. (B): photomicrograph of a sagittal section of the copulatory apparatus.