No abstract

No abstract

No abstract

The genus Beroe Browne, 1756 (Ctenophora, Beroidae) occurs worldwide, with 25 currently-described species. Because the genus is poorly studied, the definitive number of species is uncertain. Recently, a possible new Beroe species was suggested based on internal transcribed spacer 1 (ITS1) sequences from samples collected in Svalbard, Norway. Another species, Beroe ovata, was introduced to Europe from North America, initially in the Black Sea and subsequently (and possibly secondarily) into the Mediterranean and Baltic Seas. In areas where ctenophores have been introduced, they have often had significant detrimental ecological effects. The potential for other cryptic and/or undescribed Beroe species and history of spread of some species in the genus give reason for additional study. When alive, morphological hallmarks may be challenging to spot and photograph owing to the animals' transparency and near-constant motion. We sampled and analyzed 109 putative Beroe specimens from Europe, using morphological and molecular approaches. DNA analyses were conducted using cytochrome oxidase 1 and internal transcribed spacer sequences and, together with published sequences from GenBank, phylogenetic relationships of the genus were explored. Our study suggests the presence of at least 5 genetic lineages of Beroe in Europe, of which 3 could be assigned to known species: Beroe gracilis Künne 1939; Beroe cucumis Fabricius, 1780; and Beroe ovata sensu Mayer, 1912. The other 2 lineages (here provisionally named Beroe "norvegica" and Beroe "anatoliensis") did not clearly coincide with any known species and might therefore reflect new species, but confirmation of this requires further study.

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...