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).

Marcos Santos Silva,Fernando Carbayo

doi:10.3897/zookeys.910.39486

Abstract

In 2016, the type-material of ten of the 15 Brazilian land planarians (Platyhelminthes, Tricladida, Geoplanidae) described by Schirch (1929) was discovered deposited in the Museu Nacional do Rio de Janeiro (MNRJ). Schirch only described the external morphology of these species, all originally placed in the genus Geoplana. By the 1930s and 1950s Geoplana itatiayana, G. plana, and G. rezendei underwent taxonomic revision based on the study of non-type specimens. The remaining 12 species also underwent a taxonomic revision but only based on the literature. Current names of these species are Geoplana goettei, Pseudogeoplana arpi, Ps. blaseri, Ps. bonita, Ps. bresslaui, Ps. cardosi, Ps. doederleini, Ps. lumbricoides, Ps. obscura, Ps. riedeli, Ps. theresopolitana, and Ps. wetzeli. The species Geoplana maximiliani sensu Schirch (1929) was renamed as Ps. schirchi Ogren & Kawakatsu, 1990.The present study reports a taxonomic revision of seven of Schirch’s species using type material, namely Obama itatiayana, Pasipha plana, Pseudogeoplana arpi, Ps. bresslaui, Ps. doederleini, Ps. schirchi and Ps. wetzeli. Additional specimens of some of these species were also examined. Morphological data from histological preparations and from virtual sections were obtained through a non-destructive technique of X-ray computed microtomography (µCT). This approach resulted in the preservation of the entire body of at least one type-specimen of each species, and the holotype of Ps. bresslaui. Conspecificity of O. itatiayana and P. plana was confirmed, as previously reported in the literature. It is also proposed that Ps. bresslaui belongs to the genus Paraba, while the other species should remain in Pseudogeoplana, since type-specimens are either immature, poorly preserved or simply lost.

Highlights

Land planarians (Geoplanidae, Tricladida, Platyhelminthes) are free-living predators most diversified in intertropical forests
Four of these species were redescribed from new material: G. goettei, G. itatiayana, G. plana, and G. rezendei (Riester 1938, Marcus 1951, Froehlich 1955a)
The largest syntype or the holotype of each of Schirch’s species were processed for μCT (Table 1). These specimens were immersed in a solution of 0.3 % phosphotungstic acid (PTA) and 3 % dimethyl sulfoxide (DMSO) in 95 % ethanol for at least 30 days on a laboratory rocker to facilitate PTA penetration into the body (Fernández et al 2014)

Summary

Introduction

Land planarians (Geoplanidae, Tricladida, Platyhelminthes) are free-living predators most diversified in intertropical forests. Schirch (1929) described 15 new Brazilian species, which he placed in the genus Geoplana Stimpson, 1857 (Geoplaninae), viz., Geoplana arpi, G. blaseri, G. bonita, G. bresslaui, G. cardosi, G. doederleini, G. goettei, G. itatiayana, G. lumbricoides, G. obscura, G. plana, G. rezendei, G. riedeli, G. theresopolitana, and G. wetzeli. Type material of Schirch’s species has never been reexamined Later, four of these species were redescribed from new material: G. goettei, G. itatiayana, G. plana, and G. rezendei (Riester 1938, Marcus 1951, Froehlich 1955a). We inquired of the Brazilian Museu Nacional do Rio de Janeiro (MNRJ) concerning Schirch’s specimens and, contrary to expectations, were informed that the types of ten of Schirch’s species were housed in the museum, viz., Issoca rezendei, Obama itatiayana, Pasipha plana, Pseudogeoplana arpi, Ps. blaseri, Ps. bonita, Ps. bresslaui, Ps. doederleini, Ps. schirchi, and Ps. wetzeli. We tried to overcome the limitations regarding the resolution of μCT-derived images, as encountered in a previous taxonomic study of another land planarian (Carbayo et al 2016, Carbayo and Lenihan 2016)

Materials and methods

Paraba bresslaui Holotype

Findings

Discussion