Kenneth Meland

Trophic ecology of deep-water fishes associated with the continental slope of the Eastern Norwegian Sea

Abstract In June 1995 and 1996 demersal fishes on the continental slope of the eastern Norwegian Sea were sampled to study distribution patterns and community structure. The diets of the more abundant slope species were characterised and linkages within the upper slope food web identified. Most of the smaller fishes fed on hyperbenthic crustaceans such as amphipods and mysids, while pelagic crustaceans and fish dominated the diets of larger fishes. Herring (Clupea harengus) and blue whiting (Micromesistius poutassou) were important prey items of Greenland halibut (Reinhardtius hippoglossoides), and were also eaten by Lycodes frigidus, Raja hyperborea, and roughhead grenadier (Macrounis berglax). At least for the latter three species this probably reflected scavenging. Few cases of predator-prey relationships between the typical slope fishes were found.

Global diversity of mysids (Crustacea-Mysida) in freshwater

In this article we present a biogeographical assessment of species diversity within the Mysida (Crustacea: Malacostraca: Peracarida) from inland waters. Inland species represent 6.7% (72 species) of mysid diversity. These species represent three of the four families within the Mysida (Lepidomysidae, Stygiomysidae, and Mysidae) and are concentrated in the Palaearctic and Neotropical regions. The inland mysid species distributional patterns can be explained by four main groups representing different freshwater invasion routes: (1) Subterranean Tethyan relicts (24 spp.); (2) Autochthonous Ponto-Caspian endemics (20 spp.); (3) Mysis spp. ‘Glacial Relicts’ (8 spp.); and (4) Euryhaline estuarine species (20 spp.). The center of inland mysid species diversity is the Ponto-Caspian region, containing 24 species, a large portion of which are the results of a radiation in the genus Paramysis.

MOLECULAR PHYLOGENY AND BIOGEOGRAPHY OF THE GENUS PSEUDOMMA (PERACARIDA: MYSIDA)

Abstract We used DNA sequences from 18S rDNA (808 bp) and COI mtDNA (599 bp) to infer evolutionary history of northern groups of the deep-sea mysid genus Pseudomma. The V4–V7 regions of 18S show an average of 1.31% sequence divergence between species. A secondary structure model is constructed and used in phylogenetic analyses to allow for different evolutionary rates in paired and unpaired nucleotide partitions. COI is observed as highly variable with uncorrected p-distance averaging 33%. Phylogenies for these sequences were estimated by maximum-likelihood, Bayesian, and maximum-parsimony analyses. More or less similar tree topologies were obtained for each gene with these methods. Pseudomma longisquamosum was placed in a basal clade, using Parapseudomma and Amblyops as outgroups, but the exact relationship of other basal taxa is less clear when results from the two genes are compared. An ancient presence of Pseudomma in the Tethys Sea is suggested by phylogenetic structure, molecular clock considerations, and present distributions. A well-supported Atlantic clade may have diverged from Indo-Pacific groups in the Miocene because of the closure of the Gibraltar Strait. More recent speciation events are proposed in the Norwegian Sea, and an Arctic intrusion from the North Pacific across the Bering Strait is suggested for the circumpolar species Pseudomma truncatum.

Phylogenetic evidence that both ancient vicariance and dispersal have contributed to the biogeographic patterns of anchialine cave shrimps

Cave shrimps from the genera Typhlatya, Stygiocaris and Typhlopatsa (Atyidae) are restricted to specialised coastal subterranean habitats or nearby freshwaters and have a highly disconnected distribution (Eastern Pacific, Caribbean, Atlantic, Mediterranean, Madagascar, Australia). The combination of a wide distribution and a limited dispersal potential suggests a large-scale process has generated this geographic pattern. Tectonic plates that fragment ancestral ranges (vicariance) has often been assumed to cause this process, with the biota as passive passengers on continental blocks. The ancestors of these cave shrimps are believed to have inhabited the ancient Tethys Sea, with three particular geological events hypothesised to have led to their isolation and divergence; (1) the opening of the Atlantic Ocean, (2) the breakup of Gondwana, and (3) the closure of the Tethys Seaway. We test the relative contribution of vicariance and dispersal in the evolutionary history of this group using mitochondrial genomes to reconstruct phylogenetic and biogeographic scenarios with fossil-based calibrations. Given that the Australia/Madagascar shrimp divergence postdates the Gondwanan breakup, our results suggest both vicariance (the Atlantic opening) and dispersal. The Tethys closure appears not to have been influential, however we hypothesise that changing marine currents had an important early influence on their biogeography.

Redescription of the North Atlantic Pseudomma species (Crustacea, mysidacea), with the addition of Pseudomma jasi n. Sp.

Abstract The Pseudomma G.O. SARS, 1870 species found associated with North Atlantic waters have often been subject to mis-identification. Methods for identifying the species P. affine G. O. SARS, 1870, P. frigidum HANSEN, 1908, P. kruppi W.M. TATTERSALL, 1909, P. nanum Holt & Tatiersall, 1906, P. roseum G.O. SARS, 1870, P. truncatum SMITH, 1879, and a new species Pseudomma jasi n.sp. have been developed, resulting in a complete redescription and an update of their distribution in the Norwegian Sea. A key to the north Atlantic Pseudomma species is also given. Body length variation alone is so great between populations of a single species, that characters directly correlated to size are found to be practically useless. Characters reliable in distinguishing specimens on the species level include setae number on the mandibular palps terminal segment, setae number on the maxillule and maxilla, and by outer setae number of the antennal scales apex. In adult individuals armature ofthe telsons apex was reliabl...