# First case of a reversed Parabothus taiwanensis Amaoka & Shen, 1993 from Taiwan (Pleuronectiformes: Bothidae), with first evidence of situs inversus viscerum in bothid

## TL;DR

This paper reports the first reversed (dextral) specimen of Parabothus taiwanensis from Taiwan and the first case of reversed internal organs in the Bothidae family.

## Contribution

First evidence of situs inversus viscerum in the Bothidae family and the second reversed case in this family.

## Key findings

- No differences in meristic and morphometric characters between dextral and sinistral specimens.
- Situs inversus viscerum was confirmed in the dextral Parabothus taiwanensis specimen.
- This is the sixth record of reversed internal organs in flatfishes.

## Abstract

Reversed condition is rarely found in most flatfishes in natural environment, except for some certain species. The mechanism controlling the reversals in flatfishes has been studied in some cultivated species, whereas some have only few cases for the entire family and remain unclear. Here, we report the first record of a dextral (reversed) specimen of Parabothus taiwanensis Amaoka & Shen, 1993 collected off southwestern Taiwan recently. It represents the second reversed case ever recorded in Bothidae. We aim to provide a detailed description of this dextral specimen and compared to the sinistral (normal) specimens collected from the vicinity.

Specimens were fixed in 4% formaldehyde and transferred to 70% ethanol for preservation. Meristic and morphometric characters were examined for both dextral and sinistral specimens. Dissections were made on specimens to confirm the position of internal organs. Lastly, X-radiographs were taken to elucidate the osteological features.

As a result, no differences of both meristic and morphometric characters were observed between the dextral and sinistral specimens. Nevertheless, situs inversus viscerum is discovered in the dextral specimen for the first time in Bothidae and the sixth record within flatfishes.