Pseudogeoplana doederleini (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

Pseudogeoplana doederleini (Schirch, 1929) Figures 23 , 24

Geoplana doederleini Schirch, 1929: 33. Type Locality: Baixo Guandu, Espírito Santo, Brazil.

Pseudogeoplana doederleini : Ogren and Kawakatsu 1990: 153.

Material examined.

Type material. Three syntypes collected by P. Schirch Coll in 1917 at Baixo Guandu, State of Espírito Santo, Brazil. We received them on loan with only a label reading 8914. Each syntype was given an additional identification with the letters A, B, and C. Three dimensional (3D) images and virtual sections of syntype MNRJ 211A were obtained through microcomputed tomography. Syntype MNRJ 211A: Preserved in 80 % ethanol. Entire body of syntype MNRJ 211B was histologically sectioned as follows: transverse sections of anterior extremity on 12 slides; horizontal sections of ovaries on five slides; transverse sections of pre-pharygeal region on nine slides; sagittal sections of pharynx on 17 slides; sagittal sections of post-pharynx on 17 slides. Syntype MNRJ 211C: preserved in 80 % ethanol.

Description.

All three specimens were rigid and shrunk, with longitudinal cracks (Fig. 23C ). Syntype A is 30 mm long, ~3 mm wide (Fig. 23A, B ), and 1 mm high; syntype B, 26 mm, 2 mm, and ~0.8 mm, respectively. Elongated body, with parallel margins; anterior and posterior extremities rounded, body sides rounded (Fig. 23A, B, E ). Dorsum convex, ventral side convex in some regions, concave in others, the latter probably an effect of dehydration. Ground color of the dorsum beige with yellow olive pigment dots, which are absent in some areas (Fig. 23A ). This aspect contrasts with original description and drawing by Schirch (Fig. 23D ). Ventral side beige. Eyes monolobate, surround anterior extremity of the body (Fig. 23E ). Posterior to this region, eyes were not observed. Relative position of mouth: body length, 61 % (syntype B). Poor quality of the histological and virtual sections (Fig. 24A, D ) did not permit the investigation of further morphological details. µCT-derived images did not provide enough contrast for the internal organs and, consequently, we could not obtain any useful virtual section.

Remarks.

The body color is somewhat different from the original description ( Schirch 1929), since the longitudinal stripes have disappeared after 100 years in preservative. Both the size and form of the body, and the eye distribution pattern agree with the original description. The specimens showed signs of having been accidentally dehydrated (body roughened and rigid) and thus were immersed in Sandison’s solution for five days for tissue rehydration ( Sandison 1955). Nonetheless, histological sections of syntype B are of very poor quality, the pharynx and copulatory apparatus are poorly differentiated, and the epithelia are indistinct. µCT derived images are also of very poor quality; the preparation of the specimen for µCT scanning was preceded by the rehydration of the specimen in Sandison’s solution (1955). Even so, the electron-dense contrast agent (PTA) did not penetrate the body and hence the internal organs remained transparent under the X-ray. This failure has been demonstrated by other authors (e.g., Metscher 2009, Fernández et al. 2014). Based on histological sections and µCT derived images of the type material, the species cannot be determined. Therefore, the species is retained in Pseudogeoplana .

Figures

Figure 23. Pseudogeoplana doederleini (Schirch 1929) A syntype A fixed in dorsal view B virtual µCT reconstruction of the body of syntype A C three syntypes D original illustration of G. doederleini by Schirch (1929) E anterior extremity of syntype A in clove oil.

Figure 24. Pseudogeoplana doederleini (Schirch 1929). Photomicrographs of syntype B. Sections showing poor quality histological sections. A Transverse section of anterior region B horizontal section of anterior half of body C sagittal section of pharyngeal region D virtual sagittal section showing pharyngeal region, pixel size: 5 µm.