Reproductive strategies of benthic invertebrates in the Kara Sea (Russian Arctic): adaptation of reproduction modes to cold water

Abstract

Many benthic invertebrates in the boreo-Atlantic region reproduce via pelagic larvae. Past investigations in polar areas suggested a greater predominance of species lacking a pelagic phase. In this study, the reproduction strategies of the main 88 species of the Kara Sea were investigated. Field observations were supplemented by literature studies (reproduction period and strategy, biogeographical affiliation). Larvae of 44 meroplanktonic species were identified, but adult forms of only 23 of these species are known from the region. For the other 21 larval types, adults were not present in the Kara Sea but have previously been recorded in the adjacent Barents Sea. Larval transport processes are thus potentially important for the import of species into the region. High numbers of species of temperate origin were common, and had a strong influence on the overall reproduction patterns of the region. The southern Kara Sea was mainly dominated by 2 groups: highly mobile crustaceans, which are obligate non-pelagic developers, and non-motile organisms with primarily pelagic reproduction modes. We propose that reproduction patterns are strongly influenced by the highly variable environmental conditions of the Kara Sea which, via ice-scouring and the high input of freshwater from the 2 adjacent rivers, regularly lead to a local depletion of the benthic species. The input of warm freshwater from the rivers enhances the survival of species with a boreal biogeographical distribution, which additionally contributes to the high number of species with pelagic development that were found. Overall, the reproduction modes of benthic invertebrates in the Kara Sea are thus strongly governed by the local environmental conditions characteristic of the region.

An Externally Brooding Acorn Worm (Hemichordata, Enteropneusta, Torquaratoridae) from the Russian Arctic

“…In most years, the ice cover persists for about 9 months (October through June). Much of the Kara Sea is shallower than 50 m, and its southern region is complexly influenced by seasonal input of river water from the Russian mainland (e.g., Vetrov and Romankevich, 2011;Kozlovskiy et al, 2011), which (Fetzer and Arntz, 2008). By contrast, oceanographic conditions in the northwestern part of the Kara Sea fluctuate less markedly.…”

Brooding and Species Diversity in the Southern Ocean: Selection for Brooders or Speciation within Brooding Clades?

“…This notion was persuasively reinforced by Thorson (1936Thorson ( , 1950, who focused on gastropods in the Northern Hemisphere, and Mileikovsky (1971), who termed it "Thorson's rule." Both Thorson (1936) and Mileikovsky (1971), however, recognized many exceptions, and subsequently, with more information and reanalyses of earlier data, the generality of Thorson's rule weakened substantially (Pearse et al, 1991;Clarke, 1992;Hain and Arnaud, 1992;Pearse, 1994;Young, 1994;Stanwell-Smith et al, 1999;Arntz and Gili, 2001;Schluter and Rachor, 2001;Absher et al, 2003;Sewell, 2005;Vázquez et al, 2007;Fetzer and Arntz, 2008). We now know that many of the most abundant species in Antarctic waters, especially those in shallow water, have pelagic larvae as in other areas of the world.…”

Recent distribution of Echinodermata species in Spitsbergen coastal waters

“…Singletons, which were single individuals in the whole collection, included two sea cucumbers (Acanthotrochus mirabilis and Cucumaria frondosa), one brittle star (Gorgonocephalus eucnemis) and four starfish (Hippasteria phrygiana, Hymenaster pellucidus, Poraniomorpha tumida, and Pteraster obscurus, Table 2). The majority of the species found have wide borealarctic distributions (75%), with only six species described as true Arctic cold water species (Acanthotrochus mirabilis, A. sundevalli, Hymenaster pellucidus, Ophiopleura borealis, Poliometra prolixa and Poraniomorpha tumida; Table 3), (Brattegard and Holthe 2001;Sirienko 2001;Fetzer and Arntz 2008). The dominant functional groups were deposit feeders (10 species) and carnivores (12 species, Table 3).…”

“…Table 3 Species composition and basic characteristics including food guilds (sus -suspension feeders, df -deposit feeders, car -carnivores, omni -omnivorous, sca -scavengers, and herb -herbivorous), habitat (m -mud bottom, mg -muddy gravel, r -rocky bottom, s -sand, ms -mixed sediments, si/ssi -silt, sandy silt, sb -soft bottom, and vs -variety of substrates) and zoogeographic rank (A -arctic, B -boreal, BA -boreal-arctic, and C -circumboreal). The data were compiled from Connor et al (1997), Piepenburg (2000), Fetzer and Arntz (2008) …”