Unrecognized diversity of a scale worm,Polyeunoa laevis (Annelida: Polynoidae), that feeds on soft coral

A goal of taxonomy is to employ a method of classification based on phylogeny that captures the morphological and genetic diversity of organismal lineages. However, morphological and genetic diversity may not always be concordant, leading to challenges in systematics. The scale worm Polyeunoa laevis has been hypothesized to represent a species complex based on morphology, although there is little knowledge of its genetic diversity. Commonly found in Antarctic waters and usually associated with gorgonian corals (especially Thouarella), this taxon is also reported from the south-west Atlantic, Magellanic and sub-Antarctic regions. We employ an integrative taxonomic approach to examine the traditional morphological characters used for scale worm identification in combination with COI mitochondrial gene data and whole mtDNA genomes. Moreover, we consider P. laevis's association with Thouarella by examining data from the mMutS gene, a soft-coral phylogenetic marker. Analyses for P. laevis recovered 3 clades, two in Antarctic waters and one from the Argentina-Indian Ocean. Interestingly, genetic and morphological results show differences between specimens from South Argentina and the Antarctic region, suggesting that open ocean barriers might have limited gene flow from these regions. Bayesian phylogenetic analyses for Thouarella resulted in at least 12 lineages, although some of the lineages consist of only a single individual. Our results show different evolutionary histories for both species, confirming that association between these scale worms and their hosts is not restrictive. For both taxonomic groups, biodiversity in the Southern Ocean appears to be underestimated.     

Ecological studies of the nemertean fauna in an estuarine system of the northwestern Gulf of Mexico

The distribution and abundance of nemerteans in the brackish-water lakes of Sea Rim State Park, Texas, near the Louisiana border, were studied and compared with other macrobenthos during one year. Six of 93 macrobenthic species collected were nemerteans (0.9% of the total number of specimens). Only one species of nemertean, Carinoma sp., was consistently present. This species is the most ubiquitous and, probably, the most abundant nemertean in the estuarine systems of the Texas coast. Carinoma sp. was collected at Sea Rim from a salinity range of 0–21 ppt and at other Texas estuaries from 2–26 ppt. Preliminary experiments with Carinoma sp. as predator and as prey indicated that it feeds on polychaete worms and in turn is fed upon by white (Penaeus setiferus) and brown (P. aztecus) shrimp.     

On the identity of two Antarctic brooding nemerteans: redescription of Antarctonemertes valida (Bürger, 1893) and description of a new species in the genus Antarctonemertes Friedrich, 1955 (Nemertea, Hoplonemertea)

Nemerteans (ribbon worms) constitute an abundant and occasionally conspicuous group of benthic invertebrates in the Southern Ocean. Although recent work has confirmed that this group is far more diverse than previously recognized, the Antarctic nemertean fauna remains poorly understood when compared to other geographic regions. In most cases, the taxonomic information on the known nemertean fauna is incomplete for this region and/or has been inappropriately documented. As a consequence, many of the species described are considered species inquirendae. Among the nearly 50 species described so far for the Southern Ocean, two hoplonemerteans are known to brood eggs in cocoons: Amphiporus incubator Joubin, 1914 and Amphiporus michaelseni Bürger, 1895a. Here, we redescribe Antarctonemertes valida (Bürger, 1893), a senior synonym of A. michaelseni, and describe a new congeneric species, Antarctonemertes riesgoae sp. nov. Both species show a similar reproductive strategy by brooding their cocoons, and similar external appearance, but clearly differ in other aspects of their morphology, such as the cephalic coloration pattern and the number of proboscidial nerves. We provide novel information about their life habitus, reproductive behaviour, internal anatomy, and their phylogenetic placement within hoplonemerteans using one nuclear (28S rRNA) and two mitochondrial [cytochrome c oxidase subunit I (COI) and 16S rRNA] markers. We also provide a parsimony haplotype network using 16S rRNA, COI, and the internal transcribed spacer region 2 (ITS-2) showing a clear distinction between individuals of both species. Our results stress the need of combining molecular and morphological information when dealing with closely related species of nemerteans.     

Population divergences despite long pelagic larval stages: lessons from crocodile icefishes (Channichthyidae)

Dispersal via pelagic larval stages plays a key role in population connectivity of many marine species. The degree of connectivity is often correlated with the time that larvae spend in the water column. The Antarctic notothenioid fishes develop through an unusually long pelagic larval phase often exceeding 1 year. Notothenioids thus represent a prime model system for studying the influence of prolonged larval phases on population structure in otherwise demersal species. Here, we compare the population genetic structure and demographic history of two sub‐Antarctic crocodile icefish species (Chaenocephalus aceratus and Champsocephalus gunnari) from the Scotia Arc and Bouvet Island in the Atlantic sector of the Southern Ocean to delineate the relative importance of species‐specific, oceanographic and paleoclimatic factors to gene flow. Based on 7 (C. aceratus) and 8 (C. gunnari) microsatellites, as well as two mitochondrial DNA markers (cytochrome b, D‐loop), we detect pronounced population genetic structure in both species (amova FSTs range from 0.04 to 0.53). High genetic similarities were found concordantly in the populations sampled at the Southern Scotia Arc between Elephant Island and South Orkney Islands, whereas the populations from Bouvet Island, which is located far to the east of the Scotia Arc, are substantially differentiated from those of the Scotia Arc region. Nonetheless, haplotype genealogies and Bayesian cluster analyses suggest occasional gene flow over thousands of kilometres. Higher divergences between populations of C. gunnari as compared to C. aceratus are probably caused by lower dispersal capabilities and demographic effects. Bayesian skyline plots reveal population size reductions during past glacial events in both species with an estimated onset of population expansions about 25 000 years ago.     

Benthic hydroids (Cnidaria, Hydrozoa) from off Bouvet Island (Antarctic Ocean)

Twenty-seven species of benthic hydroids have been found in a small collection from off Bouvet Island (Antarctic Ocean). The material was obtained during the XXI/2 German Antarctic expedition with R.V. Polarstern 2003–2004. Of the 27 species collected, 21 were unknown from those waters. Consequently, the number of known species of benthic hydroids from the area has risen to 32, representing a high diversity location for this group in the Southern Ocean considering the sampling effort made. All species, including those previously known from Bouvet waters, are considered with respect to geographical distribution.The present work is an addition to the special issue “Macrobenthic studies at Bouvet island”, presenting work carried out from on board RV Polarstern in 2003/2004 and published in Polar Biology 29 (2006)     

A shore-based preliminary survey of marine ribbon worms (Nemertea) from the Caribbean coast of Colombia

A checklist of benthic ribbon worm species from the Caribbean coast of Colombia is presented, including synonyms, distributions, a photographic record, and the main morphologic characters of each species for a rapid identification. This is the first research focused broadly on nemerteans in Colombia. 54 specimens of nemerteans were hand-collected from the rocky littoral of two different localities, and identified according to personal experience and specialist literature. 13 species were found; of which 11 represent new records for the country. These species belong to eight different traditionally used families: Tubulanidae, Valenciniidae, Lineidae, Amphiporidae, Cratenemertidae, Emplectonematidae, Drepanophoridae and Ototyphlonemertidae. The most common and abundant species was Dushia atra. The biodiversity of nemerteans in Colombia seems to overlap with the nemertean fauna from Florida and Brazil, explained by the convergence of the North Brazil Current, Guiana Current, Caribbean Currents and the Panama-Colombia Contracurrent in the sampled region. The results of this work suggest that the Caribbean coast of Colombia is a region with a high diversity of nemerteans, and provide important taxonomic data for environmental assessments and future biological research.     

From pole to pole: the potential for the Arctic seastar Asterias amurensis to invade a warming Southern Ocean

Due to climatic warming, Asterias amurensis, a keystone boreal predatory seastar that has established extensive invasive populations in southern Australia, is a potential high‐risk invader of the sub‐Antarctic and Antarctic. To assess the potential range expansion of A. amurensis to the Southern Ocean as it warms, we investigated the bioclimatic envelope of the adult and larval life stages. We analysed the distribution of adult A. amurensis with respect to present‐day and future climate scenarios using habitat temperature data to construct species distribution models (SDMs). To integrate the physiological response of the dispersive phase, we determined the thermal envelope of larval development to assess their performance in present‐day and future thermal regimes and the potential for success of A. amurensis in poleward latitudes. The SDM indicated that the thermal ‘niche’ of the adult stage correlates with a 0–17 °C and 1–22.5 °C range, in winter and summer, respectively. As the ocean warms, the range of A. amurensis in Australia will contract, while more southern latitudes will have conditions favourable for range expansion. Successful fertilization occurred from 3 to 23.8 °C. By day 12, development to the early larval stage was successful from 5.5 to 18 °C. Although embryos were able to reach the blastula stage at 2 °C, they had arrested development and high mortality. The optimal thermal range for survival of pelagic stages was 3.5–19.2 °C with a lower and upper critical limit of 2.6 and 20.3 °C, respectively. Our data predict that A. amurensis faces demise in its current invasive range while more favourable conditions at higher latitudes would facilitate invasion of both larval and adult stages to the Southern Ocean. Our results show that vigilance is needed to reduce the risk that this ecologically important Arctic carnivore may invade the Southern Ocean and Antarctica.     

First record of lithodid crabs from Antarctic waters off the Balleny Islands

Four specimens of Neolithodes brodiei Dawson and Yaldwyn (1970) have been obtained for the first time from bottom trawls deployed in Antarctic waters off the Balleny Islands (about 67°S) in March 2004. The Lithodidae constitute the only anomuran crab family so far known to be able to thrive under high-Antarctic conditions, and lithodids in the Ross Sea have previously only been recorded off Scott Island. The new record of N. brodiei, commonly found in waters off New Zealand, clearly extends its geographic range into the Southern Ocean. The significance of this finding with respect to the biodiversity and distribution of the Lithodidae from the Southern Ocean is briefly discussed.This revised version was published online in November 2004 with corrections to Figure 2.     

Areas of endemism in the Antarctic – a case study of the benthic hydrozoan genus Oswaldella (Cnidaria,Kirchenpaueriidae)

Aim The aim of this study is to investigate areas of endemism within the distribution of Oswaldella species in the Southern Ocean, thereby testing previous hypotheses and proposing alternative scenarios for Antarctic evolution. Location Southern Ocean, Antarctic and sub-Antarctic waters of southern South America. Methods We prepared a database for the 31 currently known species of the Antarctic genus Oswaldella, which includes geographical locations gathered from published taxonomic studies as well as materials from museums and expeditions. A parsimony analysis of endemicity (PAE) was used to test hypotheses of distribution patterns. Results Four areas of endemism are hypothesized: southern South America, two high Antarctic areas (eastern and western) and a larger area, mainly in western Antarctica at lower latitudes and including insular areas (but not the Balleny Islands). Main conclusions The results support, in part, previous hypotheses for the Southern Ocean region, while providing more detailed resolution. The areas of endemism may reflect both historical and ecological processes that influenced the Antarctic biota. The Magellanic area reflects the well-known affinities of the Antarctic biota with that of South America and may be a consequence of dispersal through deeper (and colder) waters, followed by speciation. The second area, the largest one, encompasses most of the insular faunas and may also be associated with deeper waters formed since 43 Ma. The third area may be explained by the development of seaways in the circum-Antarctic region beginning 50 Ma. Finally, the fourth zone, with a very poor fauna, coincides with the opening of the Tasman Strait and the formation of the Australo-Antarctic Gulf, associated with a minor wind-driven current.     

Geographic structure in the Southern Ocean circumpolar brittle star Ophionotus victoriae (Ophiuridae) revealed from mtDNA and single‐nucleotide polymorphism data

Marine systems have traditionally been thought of as “open” with few barriers to gene flow. In particular, many marine organisms in the Southern Ocean purportedly possess circumpolar distributions that have rarely been well verified. Here, we use the highly abundant and endemic Southern Ocean brittle star Ophionotus victoriae to examine genetic structure and determine whether barriers to gene flow have existed around the Antarctic continent. Ophionotus victoriae possesses feeding planktotrophic larvae with presumed high dispersal capability, but a previous study revealed genetic structure along the Antarctic Peninsula. To test the extent of genetic differentiation within O. victoriae, we sampled from the Ross Sea through the eastern Weddell Sea. Whereas two mitochondrial DNA markers (16S rDNA and COI) were employed to allow comparison to earlier work, a 2b‐RAD single‐nucleotide polymorphism (SNP) approach allowed sampling of loci across the genome. Mitochondrial data from 414 individuals suggested three major lineages, but 2b‐RAD data generated 1,999 biallelic loci that identified four geographically distinct groups from 89 samples. Given the greater resolution by SNP data, O. victoriae can be divided into geographically distinct populations likely representing multiple species. Specific historical scenarios that explain current population structure were examined with approximate Bayesian computation (ABC) analyses. Although the Bransfield Strait region shows high diversity possibly due to mixing, our results suggest that within the recent past, dispersal processes due to strong currents such as the Antarctic Circumpolar Current have not overcome genetic subdivision presumably due to historical isolation, questioning the idea of large open circumpolar populations in the Southern Ocean.     

The development of planktonic biogeography in the Southern Ocean during the Cenozoic

Deep-sea drilling at high latitudes of the Southern Hemispheres has provided almost the only available data to evaluate the biogeographic development of the planktonic biota in the Southern Ocean during the Cenozoic (65 m.y. to Present Day). Paleontological investigations on Deep Sea Drilling Project (DSDP) materials have shown that the development of Cenozoic planktonic biogeography of the Southern Ocean is intimately linked with the evolution of the Southern Ocean water masses themselves. During the Cenozoic, this has included the development of the Circum-Antarctic Current system as obstructing land masses moved apart, the refrigeration and later extensive glaciation of the continent, and the development of the Antarctic Convergence (Polar Front) with related oceanic upwelling.Almost all evolution of calcareous planktonic microfossils has occurred outside of the Antarctic—Subantarctic region followed by limited migration into these water masses. Virtually no endemism occurs amongst calcareous microfossil groups at these latitudes. In contrast, conspicuous and widespread evolution has occurred within the siliceous microfossil groups especially during the Neogene. Low diversity and differences in stratigraphic ranges of Antarctic calcareous microfossils makes them only broadly useful for correlation. Relatively higher diversities within the Subantarctic provide a firmer basis for more detailed correlation, although the ranges of fossils are often different than at lower latitudes because of different paleoceanographic and paleoclimatic controls. Within the Antarctic water mass south of the Antarctic Convergence, siliceous microfossilsbiostratigraphy, oxygen isotopic stratigraphy and magnetostratigraphy, provide the only firm basis for correlation with low-latitude sequences.Eocene (55-38 Ma) sediments contain abundant calcareous microfossils even closely adjacent to the continent. Antarctic calcareous planktonic microfossils of this age exhibit relative high diversity, although this is lower than assemblages of equivalent age at middle and low latitudes. Within the Subantarctic region, Eocene planktonic foraminifera exhibit strong affinities with those in the temperate regions. Biogeographic differences exist between various sectors of the Southern Ocean related to biogeographic isolation preceding the development of the Circum-Antarctic Current. Subantarctic calcareous nannofossil assemblages of Paleocene and Eocene age exhibit higher diversity than Oligocene and Neogene assemblages. Siliceous microfossils are poorly represented or at best poorly known.One of the most dramatic changes in Southern Ocean planktonic biogeography occurred near the Eocene/Oligocene boundary (38 Ma). Since then, Antarctic planktonic foraminiferal assemblages have exhibited distinct polar characteristics, marked in particular by low diversity, and this event thus reflects the initiation of the Antarctic faunal and floral provinces. Profound paleoceanographic changes at this time, which triggered the biogeographic crisis, appear to be related to the initiation of widespread Antarctic sea-ice formation, and rapid cooling of deep and intermediate waters, in turn associated with increased Antarctic glaciation. During the Oligocene, planktonic microfossil diversity was low in all groups throughout the world's oceans. In Antarctic waters, the early Oligocene foraminiferal fauna is monospecific (Subbotina angiporoides), while in the later Oligocene two species (S. angiporoides and Catapsydrax dissimilis) were recorded. Calcareous nannofossil assemblages are of low diversity compared with the Eocene. Subantarctic foraminiferal faunas of Oligocene age display much higher diversity than those in the Antarctic, but early and middle Oligoceae faunas still exhibit the lowest diversities for the entire Cenozoic. Siliceous assemblages remain relatively inconspicuous in most regions of the Southern Ocean.The Paleogene-Neogene transition (22 Ma) is marked by a major change in the global planktonic biogeography, i.e. modern patterns developed in which permanent, steep faunal and floral diversity gradients existed between tropical and polar regions; a gradient which has persisted even during the most severe glacial episodes. Oligocene assemblages of low diversity and almost cosmopolitan distribution were replaced by distinctive belts of planktonic assemblages arranged latitudinally from the tropics to the poles. The establishment of the steep planktonic diversity gradients and latitudinal provinces near the beginning of the Neogene almost certainly were linked to the development of the Circum-Antarctic Current in the late Oligocene which effectively separated high- and low-latitude planktonic assemblages. These fundamental global circulation and biogeographic patterns have persisted through the Neogene.During the Neogene (22 Ma to Present Day), Antarctic calcareous microfossil assemblages exhibit persistent low diversity and high dominance, while Subantarctic assemblages are of much greater diversity. The beginning of the Neogene (= beginning of Miocene) heralded the development of the high-latitude siliceous microfossil assemblages towards their present-day dominant role. Siliceous biogenec productivity began to increase. These changes were linked to the initial development and later intensification of circulation associated with the Antarctic Convergence and Antarctic Divergence. The Antarctic Convergence sharply separates dominantly siliceous assemblages to the south from calcareous assemblages to the north. Radiolarian assemblages became more endemic. Relatively warm early and middle Miocene conditions are reflected by slightly higher diversity of planktonic foraminifera and by the presence, in the northern Subantarctic, of conspicuous discoasters in early Miocene sediments. In Antarctic waters, calcareous nannofossils become unimportant as biogenic elements after the middle Miocene.The latest Miocene ( 5 m.y. ago) was marked by northward movement of the Antarctic Convergence, corresponding expansion of the Antarctic water mass, and low diversity of calcareous assemblages. Pliocene planktonic foraminifera seem to be largely monospecific in Antarctic and southern Subantarctic sequences. During the Quaternary, Antarctic waters reached a maximum northward expansion and exhibit highest siliceous biogenic productivity for the Cenozoic. In the Subantarctic, Quaternary foraminiferal diversities are much higher than in Pliocene sequences. Although calcareous nannofossil diversity may be high, only a few species are abundant. Large northward shifts of Antarctic and Subantarctic water masses have occurred during the Quaternary although no southward penetrations have occurred much beyond that of the present day. Several radiolarian and foraminiferal species disappeared or appeared at or close to a number of paleomagnetic reversals during the last 4 m.y. These faunal events, which provide valuable datums, do not seem to be associated with major climatic changes.     

Filling biodiversity gaps: benthic hydroids from the Bellingshausen Sea (Antarctica)

The Bellingshausen Sea constitutes the third largest sea in the Southern Ocean, though it is widely recognized as one of the less-studied Antarctic areas. To reduce this lack of knowledge, a survey to study the biodiversity of its marine benthic communities was carried out during the Bentart 2003 and Bentart 2006 Spanish Antarctic expeditions. The study of the hydroid collection has provided 27 species, belonging to ten families and 15 genera. Twenty-one out of the 27 species constitute new records for the Bellingshausen Sea, raising the total number of known species to 37, as also do nine out of the 15 genera. Candelabrum penola, Lafoea annulata, and Staurotheca juncea are recorded for the second time. Most species belong to Leptothecata. Sertulariidae with 13 species (48%) is by far the most speciose family, and Symplectoscyphus with seven species (26%), including S. bellingshauseni sp. nov. and S. hesperides sp. nov., the most diverse genus. Considering the whole benthic hydroid fauna of the Bellingshausen Sea, 18 species (69%) are endemic to Antarctic waters, either with a circum-Antarctic (12 species, 46%) or West Antarctic (6 species, 23%) distribution, 23 (88%) are restricted to Antarctic or Antarctic/sub-Antarctic waters, and only three species have a wider distribution. Bellingshausen Sea hydroid fauna is composed of a relatively high diversity of typical representatives of the Antarctic benthic hydroid fauna, though with a surprisingly low representation of some of the most diverse and widespread Antarctic genera (Oswaldella and Schizotricha), what could be related to the fact that its shelf-inhabiting hydroid fauna remains practically unknown.     

Effects of ocean acidification on Antarctic marine organisms: A meta‐analysis

Southern Ocean waters are among the most vulnerable to ocean acidification. The projected increase in the CO₂ level will cause changes in carbonate chemistry that are likely to be damaging to organisms inhabiting these waters. A meta‐analysis was undertaken to examine the vulnerability of Antarctic marine biota occupying waters south of 60°S to ocean acidification. This meta‐analysis showed that ocean acidification negatively affects autotrophic organisms, mainly phytoplankton, at CO₂ levels above 1,000 μatm and invertebrates above 1,500 μatm, but positively affects bacterial abundance. The sensitivity of phytoplankton to ocean acidification was influenced by the experimental procedure used. Natural, mixed communities were more sensitive than single species in culture and showed a decline in chlorophyll a concentration, productivity, and photosynthetic health, as well as a shift in community composition at CO₂ levels above 1,000 μatm. Invertebrates showed reduced fertilization rates and increased occurrence of larval abnormalities, as well as decreased calcification rates and increased shell dissolution with any increase in CO₂ level above 1,500 μatm. Assessment of the vulnerability of fish and macroalgae to ocean acidification was limited by the number of studies available. Overall, this analysis indicates that many marine organisms in the Southern Ocean are likely to be susceptible to ocean acidification and thereby likely to change their contribution to ecosystem services in the future. Further studies are required to address the poor spatial coverage, lack of community or ecosystem‐level studies, and the largely unknown potential for organisms to acclimate and/or adapt to the changing conditions.     

Status of the Nemertea as prey in marine ecosystems

Nemerteans are predators of a wide variety of animals, but little is known of their role as prey for other animals. The presence of toxins in the tissues and secretions of these worms has led to the assumption usually suggested that they are ingested only rarely. However, analysis of a Food Habits Data Base from the United States National Marine Fisheries Service, compiled for fishes collected in the Atlantic Ocean from the Canadian border to Cape Hatteras, North Carolina (1973–1990), showed that nemerteans were recovered from the stomachs of 27 species of fishes in 14 families. They were found in 223 of 26 642 (0.84%) fish stomachs examined in the laboratory, but only in 0.09% of 58 812 fish examined in the field. Among species in the former category, for which 1000 were examined, the winter flounder, Pseudopleuronectes americanus(Walbaum), and the yellowtail flounder, Limanda ferruginea (Storer), had the greatest frequency of nemerteans, 71 of 1545 (4.6%) and 33 of 1045 (3.2%), respectively. These nemerteans were identified as Nemertea, Cerebratulus sp. or Micrura sp., but it is likely that they were all of a Cerebratulus-like type. Nemerteans have also been recorded from the guts of eight additional species (including four additional families) of fishes collected from the western Atlantic Ocean, Gulf of Mexico, eastern Pacific Ocean (Washington, Alaska), North Sea and Indian Ocean off South Africa. The black-bellied plover, Pluvialis squatarola(L.), semipalmated plover, Charadrius semipalmatus Bonapart and the herring gull, Larus argentatus Pontoppidan are the only three species known to feed on nemerteans (Cerebratulus lacteus (Leidy) and Paranemertes peregrina Coe by the black-bellied plover and C. lacteus by the other species). Several species of nemerteans are known to ingest other nemerteans, and several arthropods, a squid, and a few other invertebrates also feed on these worms. On the other hand, careful laboratory studies have shown that some members of the Palaeonemertea, Heteronemertea and Hoplonemertea, when fed to various species of fishes, crustaceans (Astacidea, Anomura, Brachyura and Amphipoda) and a polychaete, were rejected, usually violently. There is a history of using large nemerteans, e.g. Cerebratulus lacteus and Polybrachiorhynchus dayi, as bait by sport fishermen in the United States and South Africa. The incongruity of successfuly using these toxic animals to catch fish is discussed in relation to conclusions on the importance of nemerteans as prey in the marine environment.     

Temporal variation in abundance of the egg predator Carcinonemertes epialti (Nemertea) and its effect on egg mortality of its host,the shore crab,Hemigrapsus oregonensis

An outbreak of the nemertean, Carcinonemertes epialti, was observed on Hemigrapsus oregonensis during October, 1982 at Campbell Cove, Bodega Harbor, California. Mean worm intensity (296 worms/crab) was the highest recorded for this nemertean egg predator on H. oregonensis. During the outbreak, male crabs were found to harbor more worms than both non-ovigerous and ovigerous females. Crab egg mortality was substantial; 83% of the ovigerous females experienced 75–100% brood mortality. The seasonal peak in worm abundance coincided with the seasonal low in crab reproduction at this locality. A method for estimating the impact of C. epialti on H. oregonensis natality was developed using crab size and fecundity, and worm prevalence and intensity. For a non-outbreak sampling period, a mean of 5.6% egg mortality was experienced by infested crabs for the period selected. Thus, brood mortality during the outbreak was much greater than that experienced at non-outbreak periods. Heavy fishing pressure on some commercially important crab species has been suggested as a possible factor inducing worm outbreaks and facilitating their continued persistence. These observations suggest that fisheries are not necessarily responsible for the outbreaks of nemerteans on commercially important crab species. However, fishing pressure may still be a sufficient condition to promote nemertean outbreaks.     

Genome‐wide SNP data reveal improved evidence for Antarctic glacial refugia and dispersal of terrestrial invertebrates

Antarctica is isolated, surrounded by the Southern Ocean and has experienced extreme environmental conditions for millions of years, including during recent Pleistocene glacial maxima. How Antarctic terrestrial species might have survived these glaciations has been a topic of intense interest, yet many questions remain unanswered, particularly for Antarctica's invertebrate fauna. We examine whether genetic data from a widespread group of terrestrial invertebrates, springtails (Collembola, Isotomidae) of the genus Cryptopygus, show evidence for long‐term survival in glacial refugia along the Antarctic Peninsula. We use genome‐wide SNP analyses (via genotyping‐by‐sequencing, GBS) and mitochondrial data to examine population diversity and differentiation across more than 20 sites spanning >950 km on the Peninsula, and from islands both close to the Peninsula and up to ~1,900 km away. Population structure analysis indicates the presence of strong local clusters of diversity, and we infer that patterns represent a complex interplay of isolation in local refugia coupled with occasional successful long‐distance dispersal events. We identified wind and degree days as significant environmental drivers of genetic diversity, with windier and warmer sites hosting higher diversity. Thus, we infer that refugial areas along the Antarctic Peninsula have allowed populations of indigenous springtails to survive in situ throughout glacial periods. Despite the difficulties of dispersal in cold, desiccating conditions, Cryptopygus springtails on the Peninsula appear to have achieved multiple long‐distance colonization events, most likely through wind‐related dispersal events.     

Unmasking Antarctic mollusc lineages: novel evidence from philinoid snails (Gastropoda: Cephalaspidea)

Since its introduction, the genus Philine has epitomized numerous mollusc snails with strong morphological convergence. Recently, a molecular analysis including a wide taxon sampling split this group into four non-sister families. Although they are especially diverse in cold and deep waters, no comprehensive studies are available for the Antarctic counterparts. Here, our morpho-anatomical and molecular data suggest major changes in the systematics of the group. From the eight known species, two are synonymized, Antarctophiline amoena with A. alata, and A. gouldi with A. gibba, and two are transferred to the genus Antarctophiline, namely A. apertissima comb.n. and A. falklandica comb.n. Two new species are described, A. easmithi sp.n. and A. amundseni sp.n. from different depths in the eastern Weddell Sea. The elusive P. antarctica from the Ross Sea was found in the Weddell Sea and Waegelea gen.n. is erected to place this species. Both phylogenetic and morphological data support the erection of Antarctophilinidae fam.n. to embrace most of the Philinoidea species described in the Southern Ocean. Only two species of Philinidae are found in Antarctic waters, Spiraphiline bathyalis gen. et sp.n. from bathyal depths in the Weddell Sea and S. kerguelensis comb.n. from the Kerguelen Islands. In light of the new data provided for all described species and the phylogenetic framework proposed herein, we briefly discuss the diversification and biogeographical patterns of Antarctic philinoid snails. Overall, antarctophilinid species seem to have restricted and grossly nonoverlapping distributions suggesting allopatric speciation connected possibly to geographical or bathymetric isolation.     

A new species and new records of lithodid crabs (Crustacea: Decapoda: Lithodidae) from the Crozet and Kerguelen Islands area (Subantarctica)

Four species of lithodid crabs from waters (240–2,005 m) in the Crozet and Kerguelen Islands area were studied. One new species, Neolithodes duhameli, is described. Three other species, N. capensis Stebbing, Paralomis anamerae Macpherson and P. birsteini Macpherson are reported for the first time from these localities. The new species, N. duhameli (620–1,500 m), is the fourth representative of the genus in Subantarctic waters and belongs to the group of species possessing a carapace, chelipeds and walking legs covered with numerous spinules or spiniform granules in addition to spines. However, the new species is distinguishable from others in the genus by the long, strong spines on the carapace and pereiopods. The finding of two species of Paralomis clearly extends their geographic ranges in the Southern Ocean: P. anamerae was previously known only in waters of the Falkland Islands and the circumpolar distribution of P. birsteini is supported. The observation of N. capensis also extends its previously described range from South Africa, in the Cape region, to Subantarctic waters. As a result of this study, 14 species of the family Lithodidae are now known from Antarctic and Subantarctic waters; and most can be considered endemic to these waters.     

Cryptic mitochondrial lineages in the widespread pycnogonid Colossendeis megalonyx Hoek, 1881 from Antarctic and Subantarctic waters

Colossendeis megalonyx Hoek, 1881 is a widespread and abundant pycnogonid in the Southern Ocean which has also been reported from the South Atlantic and South Pacific Oceans. Its strictly benthic lifestyle is expected to promote genetic differentiation among populations and ultimately facilitate speciation. On the other hand, the reported eurybathy and unknown larval stages of this species may allow Colossendeis megalonyx to maintain genetic continuity between isolated shallow-water habitats by active dispersal through the deep sea or by passive rafting on floating substrates. Thus, it remains unknown whether and to which extent geographically separated populations of Colossendeis megalonyx maintain gene flow in the Southern Ocean. We sampled 96 specimens of Colossendeis megalonyx from three stations in the Atlantic Sector of the Southern Ocean and one station from the South American continental shelf (Burdwood Bank). The genetic structure of nominal Colossendeis megalonyx as well as its phylogenetic position within the genus Colossendeis were assessed using a fragment of the cytochrome c oxidase subunit 1 gene. Our data strongly support that nominal Colossendeis megalonyx consists of at least five cryptic and one pseudocryptic mitochondrial lineages, four of which appear to be geographically restricted. Two lineages occurred at locations separated by more than 1,000 km in the Antarctic, thus indicating high levels of gene flow or recent colonization. No haplotype sharing across the Polar Frontal Zone was observed. Our results strongly suggest that cryptic speciation occurred within the genus Colossendeis. The wide biogeographic distribution range of Colossendeis megalonyx and perhaps that of other Antarctic pycnogonids should therefore be regarded with caution.