Marina V. Malyutina

First insights into the biodiversity and biogeography of the Southern Ocean deep sea

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental features, including a very deep continental shelf and a weakly stratified water column, and are the source for much of the deep water in the world ocean. These features suggest that deep-sea faunas around the Antarctic may be related both to adjacent shelf communities and to those in other oceans. Unlike shallow-water Antarctic benthic communities, however, little is known about life in this vast deep-sea region. Here, we report new data from recent sampling expeditions in the deep Weddell Sea and adjacent areas (748–6,348 m water depth) that reveal high levels of new biodiversity; for example, 674 isopods species, of which 585 were new to science. Bathymetric and biogeographic trends varied between taxa. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. In other taxa, the shelf and slope assemblages were more distinct. Abyssal faunas tended to have stronger links to other oceans, particularly the Atlantic, but mainly in taxa with good dispersal capabilities, such as the Foraminifera. The isopods, ostracods and nematodes, which are poor dispersers, include many species currently known only from the Southern Ocean. Our findings challenge suggestions that deep-sea diversity is depressed in the Southern Ocean and provide a basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment.

Multiple origins of deep-sea Asellota (Crustacea: Isopoda) from shallow waters revealed by molecular data

The Asellota are a highly variable group of Isopoda with many species in freshwater and marine shallow-water environments. However, in the deep sea, they show their most impressive radiation with a broad range of astonishing morphological adaptations and bizarre body forms. Nevertheless, the evolution and phylogeny of the deep-sea Asellota are poorly known because of difficulties in scoring morphological characters. In this study, the molecular phylogeny of the Asellota is evaluated for 15 marine shallow-water species and 101 deep-sea species, using complete 18S and partial 28S rDNA gene sequences. Our molecular data support the monophyly of most deep-sea families and give evidence for a multiple colonization of the deep sea by at least four major lineages of asellote isopods. According to our molecular data, one of these lineages indicates an impressive radiation in the deep sea. Furthermore, the present study rejects the monophyly of the family Janiridae, a group of plesiomorphic shallow-water Asellota, and several shallow-water and deep-sea genera (Acanthaspidia, Ianthopsis, Haploniscus, Echinozone, Eurycope, Munnopsurus and Syneurycope).

Revision of Storthyngura Vanhöffen, 1914 (Crustacea: Isopoda: Munnopsididae) with descriptions of three new genera and four new species from the deep South Atlantic

Abstract The deep-sea genus Storthyngura (family Munnopsididae) is revised. Three new genera ( Rectisura, Sursumura and Vanhoeffenella ) and four new species ( Rectisura richardsoniae , Sursumura aberrata , Vanhoeffenella georgei , and V. moskalevi ) are described from deep-sea basins and trenches of the South Atlantic Ocean. Thirty-three previously described species are placed in new combinations with one of the new genera. Diagnoses are presented for the subfamily Storthyngurinae Kussakin (2003), the genus Storthyngura VanhIffen, and all new taxa. The accompanying Electronic Supplement offers a key to the six genera in the subfamily, and keys to species in Storthyngura and the three new genera.

Shallow-water northern hemisphere Jaera (Crustacea, Isopoda, Janiridae) found on whale bones in the Southern Ocean deep sea: ecology and description of Jaera tyleri sp. nov

The skeleton of a natural whale fall discovered in the Southern Ocean at 1,445 m was densely covered by one small, janirid isopod. Jaera tyleri sp. nov. is the first of its genus found in the southern hemisphere and in the deep sea and is described herein. Morphological and molecular investigations revealed the systematic position of this species new to science. Phylogenetic analysis of the 18S locus confirms that this species falls in a strongly supported monophyletic clade of Jaera species. The whale bone habitat of J. tyleri sp. nov. is quite different from those of other species of the genus Jaera. The analysis of bathymetric and distribution patterns of the Janiridae in general and Jaera specifically confirm the unusualness of the habitat for this isopod species. The abundance of J. tyleri sp. nov. on the whale bones and its absence from other nearby habitats suggests it to be a whale-fall specialist. The analysis of the size-frequency distributions of J. tyleri sp. nov. suggests multimodal population structure with continuous breeding activity throughout the year. The fecundity of the species is low but in line with reduced fecundity observed in polar and small-sized isopods.

First record of the deep-sea isopod family Dendrotionidae (Isopoda: Asellota) from the Northwest Pacific with description of two new species of Dendromunna

Two new abyssal species of Dendrotionidae are described: Dendromunna kurilensis sp. nov. from the Northwest Pacific Basin to the east of the Kuril–Kamchatka Trench and D. okhotensis sp. nov. from the Kuril Basin of the Sea of Okhotsk. The new species represent the first records of the family for the Northwest Pacific and the first records of the genus for the North Pacific. The new species differ from the remaining species of Dendromunna by the extremely long antennae and pereopods (antenna I is about 0.7–0.8 body length, article 4 of antenna II is about 0.6–0.7 body length, bases of pereopods are about 0.2–0.3 body length), the male pereopod I with concave lateral margins, short pereonite 1 (<0.03 body length), and the lack of mandibular palp. D. okhotensis sp. nov. differs from D. kurilensis sp. nov. by the more slender body, presence of stout setae on the pereonites 1–4 ventral surface, by different number of maxilliped retinaculae, and by number of spines of the mandibular spine row. The key to the species of Dendromunna is presented.

Caught in the act: an abyssal isopod collected while feeding on Komokiaceae

Protists such as Komokiaceae represent a huge, unexplored diversity in the abyss (Gooday et al. 1992). They likely play a key role in the food web and structuring of deep-sea benthos (Sokolova 1972), where isopods are abundant and diverse. Deep-sea isopods were initially classified as detritus feeders, but gut-content analyses (e.g. Svavarsson et al. 1993) revealed tests of hard-shelled Foraminifera, suggesting that some isopods, additionally or instead, prey upon protists. Isopod foraminiferivory was inferred also by means of fatty acid biomarkers (Würzberg et al. 2011). However, in a diverse taxon like Isopoda, feeding specialisation and plasticity can be expected, given temporal and spatial variations in food availabil i ty in the deep sea (Sokolova 1972). Hence, isopod feeding selectivity is likely complex, although it is not obvious from the often dominant materials in their guts: unidentifiable organic mucus, indicating that important food sources may be overlooked. Nevertheless, in addition to hard foraminiferan shells, some gut contents of Acanthocope and Betamorpha (Isopoda) were interpreted as remains of Komokiacea (Brökeland et al. 2010), a largely unexplored group of large-sized protists that often dominate the abyssal megabenthos. Vema-TRANSIT samples from the North Atlantic (see Supplementary material) contained a specimen of Betamorpha cf. profunda (Menzies & George, 1972) (ZMH K-45805) with parts of a komokiacean (cf. Lana Tendal & Hessler 1977) (Fig. 1) projecting out of the oral cavity. Between the mandible incisors, the komokiacean branches had been macerated to a pulp that can be further traced into the oral cavity and oesophagus, and is enriched in the stomach. To our knowledge, this is the first observation of an isopod directly feeding on a komokiacean. This evidence solidifies previous ideas of a komokiacean role in the diets of Betamorpha (Brökeland et al. 2010) and isopods in general. Given that both groups are abundant and diverse in abyssal settings, our observation yields the hypothesis that Komokiaceae may be an important food source for isopods. Communicated by C. Smith

New records of little known deep-sea Echinothambematidae (Crustacea: Isopoda: Asellota) with redescription ofVemathambema elongata Menzies, 1962 and description of a new species from the Argentina Basin

Abstract The family Echinothambematidae and the genus Vemathambema Menzies, 1962 are rediagnosed. A redescription of Vemathambema elongata Menzies, 1962 from the Angola Basin and the description of Vemathambema argentinensis sp. nov. from the Argentina Basin of the South Atlantic are presented. The new species can easily be distinguished from Vemathambema elongata by its larger opercular pleopods and deeper constrictions of pereonites two to four. Family Echinothambematidae Menzies, 1956Vemathambema elongata Menzies, 1962 (Fig. 1a, b) New material examined: German expedition “DIVA 1” (RV “Meteor” cruise 48/1): 22.7.2000, St. 338, 18°19.4′S 04°39.7′E, depth 5397 m, 1 female, 3.5 mm long; St. 340, 18°18.3′S, 04°41.3′E, depth 5395 m 1 female, 3.2 mm long; 28.7.2000, St. 348, 16°18.1′S 05°27.2′E, depth 5390 m, 1 juvenile female, 1.8 mm long. Russian Expedition RV “Akademik Kurchatov” (cruise 43): 13.1.1986, St. 4912, 26°45.1′S, 06°54.6′E, depth 4910 m, posterior part of male. Vemathambema argentinensis sp. nov. (Fig. 1c, d) Material examined: Russian expedition RV “Akademik Kurchatov” (cruise 43): 26.12.1985, St. 4893, 36°12′S 49°09′W, depth 4630 m. Holotype: male, 4.6 mm long, (Zoological Museum of Moscow University, ZMMU Mc 1322a). Paratypes: female allotype with oostegites on first pereopods, 4.7 mm long; 1 female, 4.2 mm; 2 adult males, 4.7 and 4.3 mm; 2 immature males in stage IV, 3.2 and 3.1 mm (see Wolff 1962); pleotelson of a male (ZMMU Mc 1322b-c). Description: All segments free. Body length more than 5 times width of pleotelson, more than 10 times width of narrowest part of pereon, anterior parts of tergites 3 and 4 about twice as wide as narrowest middle parts. Male pereopod 1 carposubchelate, length 0.25 of body length, carpus larger than ischium, propodus as long and half as wide as carpus. Operculum of female broad oval, 1.4 times as long as wide, 0.83 of pleotelson length. Male pleopod 1 length 0.9 of pleotelson length, 3 times as long as narrowest width, 2.6 times proximal width, and 2.1 times broadest distal sagittal part width; distolateral lobes bent dorsally, reaching 0.15 of total pleopod length, ventral and lateral margins with sparse setules. Male pleopod 2 protopod 3 times as long as wide in ventral view, truncated apically, proximomedial lobe length 0.15 of protopod length and 0.75 of protopod width; endite proximal article subequal in width to distal article, stylet very thin, curved, longer than protopod; exopod situated distally, longer than wide, covered apically with hair-like setae. Uropods uniramous, 0.4 of body length, tapering distally. Diagnosis: The new species is very similar to V. elongata, but can easily be distinguished by the relatively large operculum in both sexes. In a male of V. argentinensis sp. nov. it occupies almost the whole ventral area of the pleotelson, in V. elongata it covers only nearly 70% of the ventral area. Male pleopods 1 of the new species are more slender, distolateral lobes are less curved dorsally. All parts of pleopod 2 are more slender. The new species is distinguished also by a thinner body, pereonites 14 with more pronounced anterolateral projections which in pereonite 2 have the same shape as in the two following pereonites, without tubercles. The central constriction on pereonites 3 and 4 is narrower in the new species. Pereopod 1 is stouter, but we could examine it only in a male whereas for V. elongata the pereopod 1 is known only for a female, the difference could be due to sexual dimorphism. The epipod of the maxilliped in V. argentinensis sp. nov. is longer than in V. elongata in relation to the basis. The two first articles of antenna 1 are somewhat stouter in the new species. In males with the same size of pleotelson the uropods are shorter in the new species (the uropod/pleotelson length ratio is 2.2 in V. argentinensis sp.nov. and 2.9 in V. elongata).

Dubinectes infirmus, a new species of deep-water Munnopsidae (Crustacea, Isopoda, Asellota) from the Argentine Basin, South Atlantic Ocean

Abstract Dubinectes infirmus sp. n., Munnopsidae, is described from the Argentine Basin, southwest Atlantic, at depths between 4586–4607 m. The new species is distinguished by a narrow rim of the pleotelson posterior margin which is not raising over its dorsal surface; article 3 of the antennula is subequal in length to article 2; distomedial lobes of male pleopod 1 are of same size as distolateral lobes; stylet of male pleopod 2 is subequal in length to protopod; uropod exopod is more than a half of endopod length. Some generic characters which are weakly pronounced in the new species or have different state are defined more precisely in the revised diagnosis of Dubinectes. The modified diagnosis of the genus, a key to the species of Dubinectes as well as the distribution of the genus are presented.

Revision of the genus Bathybadistes (Isopoda: Asellota: Munnopsidae), with descriptions of two new species from the southern hemisphere

The munnopsid isopod genus Bathybadistes Hessler & Thistle has undergone several rearrangements since its initialinception.ThisgenuswasoriginallyestablishedforBathybadisteshoplitisHesslerT he did not examine the other Bathybadistes species. The discovery of two new species of Bathybadistes has providedadditional information onthisgenus.Using newandexisting data,thepresentstudyusedphylogenetic methodsto test the validity and composition of Bathybadistes. Two outgroup and 15 ingroup taxa were analysed, including all nine speciesoriginallydesignatedasBathybadistes.TheresultofthisanalysissupportsthevalidityofBathybadistes.Echinozone appears tobeparaphyletic because thefourspeciesmoved tothisgenusbyKussakin (2003)donot alignthemselves withits type species, Echinozone coronata (Sars). Bathybadistes is rediagnosed and two new species, the first from the southern hemisphere, are described: Bathybadistes andrewsi, sp. nov. from ~3300-m depth off the west coast of New Zealand; and Bathybadistes fragilis, sp. nov. from ~4750-m depth in the eastern Weddell Sea, Antarctica.

New species of the deep-sea munnopsid genus Tytthocope (Crustacea, Isopoda, Asellota) from the South Atlantic and the Southern Ocean

In the benthic samples collected during the deep-sea expeditions ANDEEP from the Weddell Sea and DIVA from the Argentine Basin the isopod family Munnopsidae was the most specious and numerous. Among the collected munnopsids three new species of Tytthocope Wilson & Hessler, 1981 have been discovered. Tytthocope is one of six genera of the subfamily Eurycopinae. It differs from other genera of the Eurycopinae by having a strongly reduced pereonite 7 and inflated pleotelson. Until now the genus consisted of five described species: four of them are known from the northern Atlantic and only one species, T. sulcifrons (Barnard, 1920) was described from the southern Atlantic off the South Africa coast. The five known species of Tytthocope have been recorded from depths less than 1461 m. Descriptions of three new species of Tytthocope collected in the South Atlantic and Southern Ocean at depths between 1530-4608 m, T. divae sp. nov., T. fahrbachi sp. nov. and T. longitelson sp. nov. are presented in the paper. T. sulcifrons is redescribed herein based on the type material.