On the genus Crossaster (Echinodermata: Asteroidea) and its distribution

Abstract

Several starfish (Echinodermata, Asteroidea) are keystone species of marine ecosystems, but some of the species are difficult to identify using morphological criteria only. The common sunstar, Crossaster papposus (Linnaeus, 1767), is a conspicuous species with a wide circumboreal distribution. In 1900, a closely similar species, C. squamatus (Dö derlein, 1900) was described from the NE Atlantic Ocean, but subsequent authors have differed in their views on whether this is a valid taxon or rather an ecotype associated with temperature variations. We assessed the differentiating morphological characters of specimens from Norwegian and Greenland waters identified as C. papposus and C. squamatus and compared their distributions in the NE Atlantic as inferred from research cruises. The field data show that C. papposus is found mainly in temperate and shallow waters, whereas C. squamatus resides on the shelf-break in colder, mixed water masses. Intraspecific diversity and interspecific genetic differentiation of the two putative species, and their phylogenetic relationships to several Crossaster congeners worldwide, were explored using mitochondrial and nuclear DNA sequences. The molecular evidence suggests that C. papposus is the more diverse and geographically structured taxon, in line with its wide distribution. C. papposus and C. squamatus are closely related, yet clearly distinct taxa, while C. papposus and C. multispinus H.L. Clark, 1916, the latter from the South Pacific Ocean, are closely related, possibly sister taxa. PLOS ONE | https://doi.org/10.1371/journal.pone.Solasteridae family appears in the fossil record during the Lower Jurassic and with fairly clear generic characters today, according to Blake [8]. Despite this, there have been several disagreements concerning the genera Solaster and Crossaster. Agassiz proposed two genera: Solaster Forbes, 1839 and Crossaster [9] (a genus already erected by Müller and Troschel in 1840), for the two species Solaster endeca (Linnaeus, 1771) and Solaster papposus (later Crossaster papposus) [10]. A number of researchers disagreed, e.g. Viguier, Danielssen and Koren [10], Fisher (in [5], and Mortensen [11]. E.g. Fisher considered Crossaster a junior synonym of Solaster, despite the different character of the marginals, the abactinal skeleton and spinelets. Today, both genera are accepted by Clark and Downey [5] and international expert groups [6].Crossaster papposus, being a common and widely distributed species in the North Atlantic, was recognised by Carl von Linné at an early point in history. Much later, in 1900, Döderlein described a variety that differed slightly from C. papposus, and he tentatively termed it Solaster papposus var. squamata (later Crossaster squamatus (Döderlein, 1900) [12]). However, researchers have been unable to reach a consensus on whether C. squamatus should be considered a valid taxon or rather a morphotype of C. papposus [e.g. 13, 14]. So far, discrimination between the papposus and squamatus varieties has been based on morphological ch...

The first records of sea star wasting disease in Crossaster papposus in Europe

“…An increase in seabed temperature fluxes, and the compounding effects of increased primary production and higher DOM concentrations [7,15], may lead to large SSWD outbreaks in larger more rugose asteroids. As a subtidal sea star [25][26][27], mass mortality events in C. papposus may have gone undetected. Many sea stars act as keystone predators responsible for regulating benthic invertebrate communities [28][29][30][31].…”

First record of the common sun star Crossaster papposus (L., 1767) in the Baltic Sea in over 100 years

“…The common sun star Crossaster papposus (L. 1767) is a conspicuous and distinctive species. The generic designation of this species has historically alternated between Solaster and Crossaster, both belonging to the family Solasteridae (Ringvold & Moum 2020).…”

“…Crossaster papposus shows a wide circumboreal distribution and is recorded mainly on the continental shelf in temperate waters (Ringvold & Moum 2020), but is also found at depths ranging from the low intertidal zone to 1200 m (Clark & Downey 1992). The species is widely distributed in the Pacific, the Atlantic Ocean and occurs all around the British Isles up to the southern North Sea (Djakonov 1950;Grainger 1966;Himmelman & Dutil 1991;Harms 1993;Carlson & Pfister 1999;Gaymer et al 2004).…”

The Common Sunstar Crossaster papposus—A Neurotoxic Starfish

“…The common sunstar is present around most of the British Isles [61] and has a broader circumboreal distribution [62]. The common sunstar is primarily predatory, feeding on most appropriately sized invertebrates that are available, but it also displays scavenging and cannibalistic feeding behaviours [18,[63][64][65][66][67].…”