Pasipha plana (Schirch, 1929)

Silva, Marcos Santos & Carbayo, Fernando, 2020, X-ray microcomputed tomography applied to the taxonomic study of rare material: redescriptions of seven of Schirch's Brazilian species of land planarians (Geoplanidae, Platyhelminthes), ZooKeys 910, pp. 1-42 : 1

Pasipha plana (Schirch, 1929) Figures 10 , 11 , 12 , 13 , 14 , 15

Geoplana plana Schirch, 1929: 33. Type Locality: Teresópolis, Rio de Janeiro, Brazil.

Geoplana plana : E. M. Froehlich 1955a: 299.

Pasipha plana : Ogren and Kawakatsu 1990: 51.

Material examined.

Type material. Four syntypes collected by P. Schirch Coll (year unknown) in Teresópolis, State of Rio de Janeiro, Brazil. We received them on loan in 70 % ethanol with only a label reading 8915. Each syntype was given an additional identification with a letter, A-D. Three dimensional (3D) images and virtual sections of syntype MNRJ 220A were obtained by microcomputed tomography. Parts of the bodies of syntypes were histologically sectioned as follows. Syntype MNRJ 220A: Transverse sections of posterior extremity on 14 slides; remaining part of body preserved in 80 % ethanol. Syntype MNRJ 220B: Sagittal sections of copulatory apparatus on 156 slides; remaining part of body preserved in 80 % ethanol. Syntype MNRJ 220C: Horizontal sections of anterior extremity on 31 slides; horizontal sections of ovaries on 71 slides; transverse sections of pre-pharyngeal region on 35 slides; sagittal sections of pharynx on 94 slides; sagittal sections of copulatory apparatus on 124 slides; remaining part of body preserved in 80 % ethanol. Syntype MNRJ 220D: Preserved in 80 % ethanol.

Additional material examined: Specimen MZUSP PL XXXX, studied by E. M. Froehlich (1955a): Teresópolis, Parque Nacional da Serra dos Órgãos, State of Rio de Janeiro, Brazil (geographic coordinates not available), E. M. Froehlich et al., leg. 1953. Transverse sections of pre-pharyngeal region on two slides (S761-S762); sagittal sections of pharynx on one slide (S763); sagittal sections of copulatory apparatus on ten slides (S764-S773). F6484 (MZUSP PL XXXX): Parque Estadual da Pedra Branca, Rio de Janeiro, State of Rio de Janeiro, Brazil, -22.933, -43.447, Carbayo et al., leg. 9 Dec. 2014. Sagittal sections of copulatory apparatus on 101 slides; remaining part of body preserved in 80 % ethanol.

Diagnosis.

Species of Pasipha 60-70 mm long; dorsum with black brown dots on ivory ground color; eyes dorsal, occupying lateral band on each side of body, 44 % of body width; posteriormost testes between pharynx and copulatory apparatus; prostatic vesicle inverted U-shaped in lateral view, not bifurcated; ovovitelline ducts emerge from inner-dorsal side of ovaries; male atrium folded; length of male atrium to female atrium ratio, 8:1; female atrium as long as high.

External aspect.

Living adult (F6484) 70 mm in length and 10 mm wide. Fixed adults (F6484 and syntype C) 65-71 mm long, 6 mm wide, and 1.7 mm high. Elongated body, with margins approximately parallel; anterior and posterior extremities rounded. Dorsum slightly convex, ventral side flat. Ground color of the dorsum of living animals is ivory, richly ornamented with black brown dots (Fig. 10A, B, D, E ). Towards the body margins, these dots tend to anastomose into longitudinal striae. Striae are lacking in a thin medial stripe which is bordered on each side by an irregular line of the same color as the dots. Ventral side is sulfur yellow, with the anterior extremity light ivory and the pharyngeal region zinc yellow (Fig. 10C ). After 89 years or more in a preservative, the dorsal color of the four syntypes has turned ochre yellow and the dots faded to a terra brown color (Fig. 10D, E ); their ventral body surface has become olive yellow.

Monolobate eyes surround the anterior extremity of the body (Fig. 11A ). They also spread onto the entire dorsum except for a thin median line ~8 % of the body width (Fig. 11B ). Towards the posterior extremity, they become scarcer. Sensory pits are simple invaginations 25 µm deep, located ventro-marginally in a single row from the very anterior body tip up to at least 57 % of the body length (syntype C). Relative position of the mouth 69 % of body length, that of the gonopore 90 % in syntype C (68 %, and 91 %, in specimen F6484).

Internal morphology.

Creeping sole comprising 96 % body width. Abundant rhabditogen cells and glands producing erythrophil granules pierce dorsal and marginal epidermis; glands producing amorphous orangish-to-reddish secretion pierce marginal epidermis. Ventral epithelium is pierced by glands producing fine erythrophil granules. Glandular margin absent. Cutaneous musculature comprises three layers, namely a subepithelial circular layer, followed by a double diagonal layer with decussate fibers, and then a well-developed, innermost longitudinal layer (Fig. 12A, B ). Muscle fibers of the longitudinal layer (120 µm thick dorsally; 88 µm thick ventrally) are arranged into bundles with 30-50 fibers each. Cutaneous musculature thickness relative to body height at the pre-pharyngeal region, 13 %. Three parenchymal muscle layers present, all well-developed: dorsal layer of decussate diagonal fibers (60 µm thick), supraintestinal layer of transverse fibers (100 µm thick), and subintestinal layer with transverse fibers (65 µm thick; Fig. 12A, B ). Ventral nerve plate present.

Mouth situated at a distance from the root of the pharynx equivalent to 50 % of the pharyngeal pocket length. Pharynx collar-shaped (Fig. 12C ), with dorsal insertion very close to the end of the pharyngeal pocket. Esophagus absent. Outer pharyngeal musculature difficult to discern; apparently it consists of a one-fiber-thick subepithelial muscle layer (6 µm thick) of longitudinal fibers followed by an equally thick layer of circular fibers. Inner pharynx musculature consisting of a subepithelial layer of circular fibers (80 µm) in the anterior region of the pharynx; this circular layer is followed by scattered longitudinal fibers in the posterior region of the pharynx (syntype C).

Testes are ~300 µm in diameter and dorsally located between the supraintestinal parenchymal muscle layer and intestine. Anteriormost testes at a distance from the anterior extremity of the body equivalent to 29 % of body length; posteriormost testes are posterior to the pharynx, close to the prostatic vesicle, and at a distance equivalent to 85 % of the body length (syntype C).

Sperm ducts contain sperm in their distal region; a 60 µm thick circular muscle surrounds the distal region of these ducts. Sperm ducts run between the oviducts and onto the nerve plate. Lateral to the prostatic vesicle, efferent ducts curve forward and medially to communicate with the latero-proximal region of the prostatic vesicle (Fig. 13A ).

Prostatic vesicle extrabulbar, long and narrow, divided into an anterior half running dorsally, and a posterior half, running ventrally, so describing an inverted U-course. Initial portion of prostatic vesicle with folded wall and lined by a 12-30 µm high cuboidal-to-columnar ciliated epithelium which is pierced by abundant glands producing erythrophil (purple) granules (Fig. 13B, C ). Distal half lined with a 3 µm high epithelium that becomes 10 µm high in the section communicating with ejaculatory duct. This distal half pierced by numerous glands producing erythrophil (reddish) granules. Prostatic vesicle surrounded by variously oriented muscle fibers. This muscle is 200-400 µm thick around the proximal region, and thinner and less dense around distal region. Entire prostatic vesicle and its musculature are enveloped by a thin coat of muscle fibers, which are readily discerned from that of the common muscle coat.

Prostatic vesicle penetrates the ventral aspect of the common muscle coat and is continuous with the ejaculatory duct. This duct recurves dorsally before bending abruptly posteriorly to open into the anterior region of the male atrium (Fig. 13C ). Ejaculatory duct lined with a cyanophil, 10-12 µm high, ciliated epithelium, and is surrounded by a circular muscle (10-15 µm thick) of thin fibers (1 µm in diameter).

Male atrium a 5 mm long cavity (syntype C, 8 % of body length) with large folds along its dorso-anterior 3/4. Posterior quarter is large but with smaller folds. Male atrium lined with an 8-15 µm high epithelium, ciliated along the anterior 3/4 of its length, and with its free surface papillate (Fig. 15 ). This epithelium is pierced by glands producing erythrophil (reddish-to-purple) granules and which are abundant throughout the entire epithelium, with the exception of that lining the sphincter (Fig. 14A , see below), which is pierced by abundant glands producing erythrophil (reddish) granules, especially in its ventral region (Fig. 14B ).

Subepithelial musculature of male atrium consists of a 12 µm thick layer of circular and longitudinal muscle fibers, which sometimes intermingle and sometimes are arranged in two layers. This muscle continues with very abundant longitudinal and circular fibers located in the surrounding space delimited by the common muscle coat. A well-developed sphincter of circular muscle embraces the subterminal region of the male atrium. Dorsal region of the sphincter is posterior to the ventral (Fig. 14A, B ).

Ovaries ovoid-shaped, 500 µm in maximum length, and situated immediately above the ventral nerve plate (Fig. 12A ). They are at a distance from the anterior extremity equivalent to 22 % of the body length (syntype C). Ovovitelline ducts emerge from the inner-dorsal region of the ovaries. Posterior to the gonopore region, they curve medially and dorsally then join to form the common glandular ovovitelline duct, posteriorly to the female atrium. There are no shell glands discharging their secretion into the ovovitelline ducts (Fig. 13A ). Common glandular ovovitelline duct 120 µm long (syntype C) and runs dorsally to enter the female genital canal. This canal (800 µm long in syntype C) is a projection of the posterio-dorsal region of the female atrium, and runs posteriorly and ventrally. Common ovovitelline duct and female genital canal are lined by a ciliated epithelium which is surrounded by a 25 µm thick muscle comprising fine (~1 µm) circular and diagonal fibers.

Female atrium short and ample, roughly as long as high. Its posterior wall projects anteriorly, giving it a square shape. Epithelial lining 12-25 µm high. Female atrial epithelium pierced by glands producing erythrophil granules and surrounded by a muscle layer of longitudinal and circular fibers in some regions, and deccussate in others. Male atrium: female atrium ratio, 8:1.

Common muscle coat is comprised of interwoven circular and longitudinal muscle fibers. It is less developed in its posterior region and envelopes the male and female atria and the common glandular ovovitelline duct (Figs 13A , 15 ).

Distribution.

Areas covered with Atlantic forest in the municipalities of Teresópolis (-22.42, -43.01) and Rio de Janeiro (-22.93, -43.44), State of Rio de Janeiro, Brazil.

Remarks.

Schirch (1929) described only the external appearance of this species. Froehlich collected one specimen in the type locality and described its external and internal morphology (E. Froehlich 1955a). By comparing her specimen with the succinct original description, she considered that they are conspecific (E. Froehlich 1955a). Indeed, apart from the external aspect, the internal morphology of Froehlich’s specimen matches in all aspects that of the syntypes, especially the copulatory apparatus of syntypes A, B, and C, herein described for the first time. This similarity also applies to the specimen F6484, recently collected by us. Thus, it is safe to assume that the syntypes, Froehlich’s specimen and specimen F6484 are all conspecific.

Currently, the species is placed in Pasipha Ogren & Kawakatsu, 1990. The diagnosis of this genus was revised by Carbayo et al. (2013). Pasipha comprises 24 species (plus five5 species considered incertae sedis, see Carbayo et al. 2013). Regarding the external aspect, Pasipha plana can be distinguished from all congeners in that it displays dark dots which anastomose into longitudinal striae.

Regarding the internal aspect, Pa. plana shares only with Pa. cafusa (Froehlich, 1956), Pa. chimbeva (E. M. Froehlich, 1955a), Pa. oliveiroi (Froehlich, 1955b), Pa. pasipha (Marcus, 1951), Pa. penhana (Riester, 1938), Pa. pinima (E. M. Froehlich, 1955a), Pa. rosea (E. M. Froehlich, 1955a), Pa. splendida (Graff, 1899), Pa. tapetilla (Marcus, 1951) and Pa. velutina (Riester, 1938) a non-branched prostatic vesicle. However, among these eleven species, only in Pa. rosea , Pa. tapetilla and Pa. velutina is the length of the male atrium to the female atrium ratio> 3:1, as in Ps. plana . In Ps. plana , however, this ratio is as high as 8:1. Furthermore, differing from Ps. plana , in Pa. rosea the prostatic vesicle is more sinuous and elongate, and the length of the female atrium is twice that of its height (vs. roughly as long as high in Pa. plana ); in Pa. tapetilla , there is a barrel-shaped and muscular copulatory organ (vs. absent in Pa. plana ). Finally, in Pa. velutina there is a penis papilla-like annular fold in the proximal region of the male atrium (vs. absent in Pa. plana ).

Figures

Figure 10. Pasipha plana (Schirch 1929) A live specimen F 6484 in dorsal view B original drawing by Schirch (1929) C ventral view of live specimen F 6484 D set of all syntypes with anterior extremity to right E syntype B fixed in dorsal view.

Figure 11. Pasipha plana (Schirch 1929), specimen F 6484 in clove oil A dorsal anterior extremity B dorsal mid-body region.

Figure 12. Pasipha plana (Schirch 1929) A specimen F 6484 photomicrograph of a horizontal section of ovaries region B F 6484 photomicrograph of transverse section of pre-pharyngeal region C syntype A virtual section of a sagittal section of pharynx, pixel size: 12 µm.

Figure 13. Pasipha plana (Schirch 1929) A specimen F 6484 diagrammatic reconstruction of copulatory apparatus B photomicrograph of prostatic vesicle, ejaculatory duct, and male atrium in sagittal section C photomicrograph of distal portion of prostatic vesicle and of ejaculatory duct in sagittal section.

Figure 14. Pasipha plana (Schirch 1929). Specimen F 6484 A virtual sagittal section of copulatory apparatus, pixel size: 12 µm B photomicrograph of sagittal section of copulatory apparatus.

Figure 15. Pasipha plana (Schirch 1929). Syntype A virtual sagittal section of copulatory apparatus, pixel size: 12 µm.