Identification of Macrourus species (Teleostei: Gadiformes) found near Prince Edward Islands in the Southern Ocean using molecular and morphological analyse.

Abstract

The genus Macrourus belongs to the family Macrouridae that consist mainly of deep-sea fish. Macrourus contains five species that have a polar distribution, with one species, M. berglax, found in the Atlantic Ocean, and the other four species, M. carinatus, M. holotrachys, M. whitsoni and M. caml, found in the Southern Ocean. The species found in the Southern Ocean are morphologically similar to each other and have overlapping distributional patterns, as a result there have been instances of misidentifications within this genus. Based on morphological characteristics, previous studies have grouped the Southern Ocean Macrourus species into two pairs, viz M. carinatus and M. holotrachys, and M. whitsoni and M. caml. Despite overlapping occurrence elsewhere, morphological studies conducted in the Prince Edward Islands (PEIs) located in the Southern Ocean, have identified only one Macrourus species, M. carinatus. Since there are known cases of species misidentification using morphological identification and distribution overlap within this genus, there is a need for a molecular study that will complement the morphological data. There are no published molecular studies that reviewed species identification in these islands. This study aimed to identify Macrourus specimens found near the PEIs using molecular and morphological analyses. This assessment was done by sequencing the cytochrome c oxidase subunit 1 gene, and by measuring and counting morphometric and meristic characters. The BLAST search which had a sequence similarity of 99 – 100%, showed that there are two species represented in this dataset which were identified as M. carinatus and M. holotrachys. This observation was supported by both the phylogenetic and haplotype network trees, which formed two distinct clades. On the other hand, the morphological data did not separate the two species, supporting previous studies that discovered high levels of morphological similarity between M. carinatus and M. holotrachys, which ultimately led to their grouping and/or misidentification. It can therefore be concluded that there are at least two Macrourus species inhabiting waters around PEIs, which are morphologically similar.