Origins of the Greenland shark (Somniosus microcephalus): Impacts of ice-olation and introgression

Herein, we use genetic data from 277 sleeper sharks to perform coalescent-based modeling to test the hypothesis of early Quaternary emergence of the Greenland shark (Somniosus microcephalus) from ancestral sleeper sharks in the Canadian Arctic-Subarctic region. Our results show that morphologically cryptic somniosids S. microcephalus and Somniosus pacificus can be genetically distinguished using combined mitochondrial and nuclear DNA markers. Our data confirm the presence of genetically admixed individuals in the Canadian Arctic and sub-Arctic, and temperate Eastern Atlantic regions, suggesting introgressive hybridization upon secondary contact following the initial species divergence. Conservative substitution rates fitted to an Isolation with Migration (IM) model indicate a likely species divergence time of 2.34 Ma, using the mitochondrial sequence DNA, which in conjunction with the geographic distribution of admixtures and Pacific signatures likely indicates speciation associated with processes other than the closing of the Isthmus of Panama. This time span coincides with further planetary cooling in the early Quaternary period followed by the onset of oscillating glacial-interglacial cycles. We propose that the initial S. microcephalus–S. pacificus split, and subsequent hybridization events, were likely associated with the onset of Pleistocene glacial oscillations, whereby fluctuating sea levels constrained connectivity among Arctic oceanic basins, Arctic marginal seas, and the North Atlantic Ocean. Our data demonstrates support for the evolutionary consequences of oscillatory vicariance via transient oceanic isolation with subsequent secondary contact associated with fluctuating sea levels throughout the Quaternary period—which may serve as a model for the origins of Arctic marine fauna on a broad taxonomic scale

Distribution of haploniscids (Isopoda, Asellota, Haploniscidae) in Icelandic waters, with description of ~Haploniscus astraphes~ n. sp from the Iceland basin and the Southeast Atlantic Ocean

Ten species of Haploniscidae Hansen, 1916 were sampled in Icelandic waters during expeditions in the framework of the BIOICE project. Nine of these were known from the North Atlantic Ocean, i.e. Haploniscus aduncus Lincoln, 1985, H. ampliatus Lincoln, 1985, Haploniscus angustus Lincoln, 1985, H. bicuspis (Sars, 1877), H. foresti Chardy, 1974, H. hamatus Lincoln, 1985, H. spinifer Hansen, 1916, Antennuloniscus simplex Lincoln, 1985 and Chauliodoniscus armadilloides (Hansen, 1916). All but H. bicuspis and H. angustus were restricted to the Atlantic Ocean south of the Greenland-Iceland-Faeroe Ridge (GIF Ridge), while H. bicuspis occurred at considerable depth ranges both north and south of the GIF Ridge. A new species, Haploniscus astraphes n. sp., is described based on material from the Denmark Strait, North Atlantic and the Guinea Basin, South Atlantic. H. astraphes n. sp. belongs to a group of Haploniscus species closely related to the genus Antennuloniscus and shares several characters with species from that genus, especially the spine row on pleopod 1, the stout sensory seta on the carpus of pereopod 7 and characters of the antennae. H. astraphes n. sp. is characterized by a rectangular body shape, the straight frontal margin of the head and the strongly convex posterior margin of the pleotelson

New and little-known gnathiid isopod crustaceans (Cymothoida) from the northern Great Barrier Reef and the Coral Sea

Ten species of Gnathiidae (Crustacea, Isopoda, Cymothoida) including six new species, are reported from Lizard Island and nearby reefs, northern Great Barrier Reef and reefs of the Coral Sea (Chesterfield Reefs, Mellish Reef and Marion Reef): Gnathia wistari sp. nov. (Lizard Island region and Capricorn Group, southern Great Barrier Reef), Gnathia coralmaris sp. nov. (Mellish Reef), Gnathia varanus sp. nov. (Lizard Island group), Gnathia marionis sp. nov. (Marion Reef), Gnathia hamletgast sp. nov. (Chesterfield Reefs) and Elaphognathia australis sp. nov. (Chesterfield Reefs). New localities are reported for four other species: Gnathia aureamaculosa Ferreira and Smit, 2009 and Gnathia masca Farquharson and Smit, 2012 from Lizard Island and nearby reefs; Gnathia falcipenis Holdich and Harrison, 1980 and Gnathia variobranchia Holdich and Harrison, 1980 from Lizard Island, Wistari Reef, Heron Island and Chesterfields Reefs

Acoustic behaviour of northern bottlenose whales (Hyperoodon ampullatus) in Icelandic inshore waters

Northern bottlenose whales (Hyperoodon ampullatus) are among the deepest diving cetaceans, regularly foraging at depths >800 m. They are primarily found in offshore habitats, but occasionally they are also sighted within coastal waters. The drivers for these inshore movements remain unknown. Northern bottlenose whales use regular echolocation clicks and terminal ëbuzzes’ to find and capture prey, but they likely produce clicks for other functions like maintaining group cohesion. Between August and October 2022, a group of 3 northern bottlenose whales spent multiple weeks inshore within Eyjafjöròur in northern Iceland. Here we quantify the acoustic signals attributed to the whales and describe their usage. Acoustic recordings were conducted on three days in late August and revealed the production of regular clicking and buzz-like rapid click trains. Click rates of rapid click trains were slower than those documented for northern bottlenose whale foraging buzzes and may instead have served a communication function. One animal among the group showed consistent unusual behaviour with prolonged logging at the surface; this animal washed ashore dead nine days later without fresh prey in its stomach. Thus, the group likely moved inshore seeking shelter and used echolocation for communication, though a navigational function cannot be ruled out