Apristurus iterum, a new shark discovered based on egg case morphology and sequence data obtained from a...

Area of Science:

• Marine Biology
• Ichthyology
• Genetics

Background:

• Deepwater catsharks (Apristurus) are poorly understood.
• New species descriptions are crucial for understanding chondrichthyan diversity.

Purpose of the Study:

• To describe a new species of deepwater catshark, Apristurus iterum, from northeastern Australia.
• To determine the phylogenetic relationships of the new species using molecular and morphological data.

Main Methods:

• Description based on a holotype specimen and 10 egg cases.
• Morphological analysis of egg case structures, focusing on longitudinal ridges.
• DNA extraction from formalin-fixed tissue, next-generation sequencing, and targeted mitochondrial genome alignment (COI gene).
• Maximum likelihood phylogenetic analysis.

Main Results:

• Apristurus iterum n. sp. is described, differentiated by unique, weakly T-shaped longitudinal ridges on its egg cases.
• Molecular data (COI gene fragment) successfully generated from the holotype.
• Phylogenetic analysis places A. iterum as a sister species to A. ovicorrugatus and A. nakayai, forming a new subgroup within the A. brunneus group.

Conclusions:

• Apristurus iterum represents a distinct new species of deepwater catshark.
• Combined morphological and molecular evidence supports its unique taxonomic status and phylogenetic position.
• The discovery highlights the importance of continued exploration and taxonomic research in Australian waters.