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On the genus Crossaster (Echinodermata: Asteroidea) and its distribution
Halldis Ringvold1, Truls Moum2
1Sea Snack Norway, Bergen, Norway.
Plos One
|January 8, 2020
Summary
Morphological and genetic analyses confirm Crossaster papposus and Crossaster squamatus are distinct starfish species. Their differing distributions in the Northeast Atlantic are linked to environmental conditions, supporting their taxonomic separation.
Area of Science:
- Marine Biology
- Echinoderm Taxonomy
- Molecular Phylogenetics
Background:
- Starfish (Asteroidea) are crucial marine keystone species, but morphological identification can be challenging.
- The common sunstar, Crossaster papposus, has a wide distribution, with a closely related species, C. squamatus, described from the Northeast Atlantic.
- Previous research has debated whether C. squamatus is a distinct taxon or an ecotype of C. papposus influenced by temperature.
Purpose of the Study:
- To assess differentiating morphological characters and distributions of C. papposus and C. squamatus in the Northeast Atlantic.
- To explore intraspecific diversity and interspecific genetic differentiation using DNA sequences.
- To determine the phylogenetic relationships of these taxa with other Crossaster species globally.
Main Methods:
- Morphological examination of specimens from Norwegian and Greenland waters.
- Analysis of distribution patterns based on research cruise data in the Northeast Atlantic.
- Mitochondrial and nuclear DNA sequencing for genetic differentiation and phylogenetic analysis.
Main Results:
- Field data indicate distinct distributions: C. papposus in temperate, shallow waters; C. squamatus on the shelf-break in colder waters.
- Molecular evidence reveals C. papposus as a diverse and geographically structured taxon.
- C. papposus and C. squamatus are confirmed as closely related but distinct taxa; C. papposus is also closely related to C. multispinus from the South Pacific.
Conclusions:
- Morphological and molecular data support the distinction between Crossaster papposus and Crossaster squamatus.
- Environmental factors likely drive the observed ecological separation of these two closely related starfish species.
- Phylogenetic analysis clarifies evolutionary relationships within the Crossaster genus, highlighting the distinctness of C. papposus and C. squamatus.
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