ANATOMY OF PSEUDOTRITONIA THIELE, 1912 AND NOTAEOLIDIA ELIOT, 1905 (GASTROPODA: OPISTHOBRANCHIA: NUDIBRANCHIA) FROM SIGNY ISLAND, ANTARCTICA

Several species of nudibranch molluscs are abundant amongstthe rich benthic hard substratum communities found close tothe British Antarctic Survey base at Signy Island, in the Atlanticsector of the Antarctic. Over the austral summer 1992/1993,two of the authors (LWB and DKAB) were able to collect someof the lesser known species of Nudibranchia at depths between3 and 40 metres, using SCUBA. New information on morphologyand anatomy of two of these species, Pseudotritonia gracilidensOdhner, 1944 (Charcotiidae, Arminoidea) and Notaeolidia gigasEliot, 1905(Notaeolidiidae, Aeolidoidea) are presented in thispaper. The validity of the species Notaeolidia gigas is strengthened. (Received 9 February 1994; accepted 18 September 1994)     

Revision of the Antarctic genus Notaeolidia (Gastropoda, Nudibranchia), with a description of a new species

New material from the Atlantic sector of the Antarctic Ocean allows a revision of the Antarctic genus Notaeolidia Eliot, 1905. One new species (Notaeolidia schmekelae sp.n.) is described. N. depressa Eliot, 1905 and N. gigas Eliot, 1905, which arc poorly known, arc redescribed. N. rufopicta Thiele, 1912, N. robsoni Odhner, 1934, N. subgigas Odhner, 1944, N. alutacea Minichev, 1972 and N. flava Minichev, 1972 are synonymized with N. depressa. N. purpurea Eliot, 1905 is synonymized with N. gigas. The monogeneric family Notaeolidiidae Odhner, 1926. is characterized by the following autapomorphy: "nephroproct in front of the genital apertures". Too little is known to elaborate the phylogenetic position of the family Notaeolidiidae within the cladobranch Nudibranchia.     

The morphology and taxonomy of the Antarctic species of Tritonia Cuvier, 1797 (Nudibranchia: Dendronotoidea)

The external morphology and anatomy of the Antarctic nudibranchs Tritonia vorax Odhner, 1926, and Tritonia antarctica Pfeffer in Martens & Pfeffer, 1886, is redescribed in detail and compared with other nominal tritoniids from the Antarctic and Subantarctic waters. Tritonia appendiculata Eliot, 1905, T. challengeriana Eliot, 1907a, non Bergh, 1884, T. chalkngeriana Odhner 1926, non Bergh, 1884, and Marionia cmullata Vicente & Arnaud 1974, non (Couthouy, in Gould 1852), are shown to be synonymous with T. antarctica. Only Tritonia antarctica is a true High Antarctic species, with a distribution around the continental shelf, Antarctic Peninsula and South Georgia. T. vorax is confined to South Georgia and Subantarctic waters.     

Studies on the morphology and anatomy of the Antarctic nudibranch genera Pseudotritonia Thiele, 1912 and Telarma Odhner, 1934 with a discussion of the family Gharcotiidae Odhner, 1926 (Nudibranchia: Opisthobranchia)

The external morphology and anatomy of the Antarctic nudibranchs Pseudotritonia quadrangularis Thiele, 1912, P. gracilidens Odhner, 1944 and Telarma antarctica Odhner, 1934 are redescribed. Both genera, which were only known by two or one specimen, do not possess a cnidosac, but there is a terminal swelling at the termination of the digestive glandular ramifications in P. gracilidens. This sac is composed of cells with a large vacuole. A glandular stripe on the right side of the body above the genital openings, nephroproct and anal papilla is considered to be a synapomorphy for both genera. The validity of the family Charcotiidae and the affinities to the aeolid genus Notaeolidia Eliot, 1905 and taxa of the Arminacea are discussed.     

Two species of Drepanopus Brady (Copepoda Calanoida) with discrete ranges in the Southern Hemisphere

Morphological features, distributional records and developmentalstages of Drepanopus pectinatus Brady and D. forcipatus Giesbrechtindicate their close relationship but also corroborate the validityof their states as separate species with discrete ranges. D.pectinatus lives in inshore waters of the Crozet, Kerguelenand Heard Islands, south of the Antarctic Convergence. D. forcipatusoccurs along both the Pacific and thc Atlantic coasts of southernSouth America and around South Georgia. The distribution ofthe species in the former region, which includes the FalklandIslands, appears to be related to the extent of the continentalshelf and of the sub-Antarctic water; South Georgia lies southof the Antarctic Convergence. Significant morphometric differencesbetween both populations of D. forcipatus were found.     

MORPHOLOGICAL AND GENETIC VARIATION IN THE ANTARCTIC LIMPET NACELLA CONCINNA (STREBEL, 1908)

Samples of the Antarctic limpet, Nacella concinna (Strebel,1908), were collected from four sites in the South Orkney Islandsand from Stromness in South Georgia during 1988. At three SouthOrkney sites, both littoral and sub-littoral samples of limpetswere taken. Shell dimensions were measured and littoral andsub-littoral limpets were shown to have significantly differentshell shapes. Foot and digestive gland tissues were subjectedto electrophoresis and five polymorphic loci {Es-1, lcd-1, lcd-2,Gpi, Got-1 and Pgm-1) and two monomorphic loci (Es-2 and Got-2)were scored. Genetic identities between littoral and sub-littoralforms and also between sites were calculated. At the loci scored,the littoral and sub-littoral forms were virtually identicaland this suggests that the shell shape differences between theforms are the result of environmentally induced phenotypic plasticity.However, significant genetic differences and some morphologicaldifferences were apparent between the sample of limpets fromSouth Georgia and all other sites. Genetic identity values suggestedthat the South Georgia and South Orkney N. concinna are geographicallyseparated populations of a single species rather than distinctsub-species. (Received 21 November 1990; accepted 17 April 1991)     

NORTH ATLANTIC SPURILLID NUDIBRANCHS, WITH A DESCRIPTION OF A NEW SPECIES, SPURILLA COLUMBINA, FROM THE ANDALUSIAN COAST OF SPAIN

The new species Spurilla columbina differs from its Europeancongeners in coloration and the shape of its cerata. Comparativedata derived from S. norvegica (Odhner, 1939), S. coerulescens(Laurillard, 1830) and S. verrucicornis (Costa, 1864) are tabulated. ^* T. E. Thompson died in a car accident 1 January 1990 (Received 10 January 1989; accepted 4 July 1989)     

EFFECT OF CONTROLLED TEMPERATURES ON GAMETOGENESIS IN THE GASTROPODS PHYSA ACUTA (PHYSIDAE) AND BULINUS TROPICUS (PLANORBIDAE)

The effects of a range of constant temperatures on gametogenesiswere investigated in two freshwater snail species which occursympatrically in the Umsin-dusi River, Natal, South Africa,Physa acuta (invasive) and Bulinus tropicus (endemic). Bothwere shown to be simultaneous hermaphrodites with slight protandry.An increase in temperature accelerated the process of gametogenesisbut P. acuta responded more rapidly to these changes than B.tropicus. This, coupled with the greater fecundity and shorterincubation period of P. acuta, gives it a reproductive advantageover the endemic species, providing a possible explanation forthe invasive's success in rapidly repopulating disturbed riverinehabitats. (Received 16 November 1990; accepted 1 May 1991)     

Reorganisation of the superfamily Lepocreadioidea Odhner, 1905 based on an inferred molecular phylogeny

Utilising phylogenetic estimates inferred from molecular sequences, the superfamily Lepocreadioidea Odhner, 1905 is re-organised, with the major family, the Lepocreadiidae, split into three separate families, the Lepocreadiidae Odhner, 1905, Aephnidiogenidae Yamaguti, 1934 and Lepidapedidae Yamaguti, 1958. These families have been widely recognised as subfamilies. Also recognised are the families Enenteridae Yamaguti, 1958, Gorgocephalidae Manter, 1966 and Gyliauchenidae Fukui, 1929. The constituent genera of these families are listed, some relying on molecular data and others on morphological similarity to molecularly-typed genera. Nine genera have not been placed in families and are considered incertae sedis.     

On the anatomy and zoogeography of Tritoniella belli Eliot, 1907 (Opisthobranchia,Nudibranchia) and the synonymy of T. sinuata Eliot, 1907

Summary Rich material of the genus Tritoniella (Opisthobranchia, Nudibranchia) from the Atlantic sector of the Antarctic Ocean demonstrates that the features of the internal anatomy are fairly constant in contrast to those of the external morphology and the cuticularized structures (radula and jaws). There are specimens intermediate between the two known species of the genus: T. belli Eliot, 1907 and T. sinuata Eliot, 1907. These specimens either show a combination of features characteristic for T. belli and T. sinuata, or of features which lie in between. Therefore T. sinuata is considered to be synonymous with T. belli. The monotypic genus Tritoniella has a circumpolar distribution with an extension of its range to the Subantarctic (South Georgia).     

Variability of Primary Production in an Antarctic Marine Ecosystem as Estimated Using a Multi-scale Sampling Strategy

A major objective of the multidisciplinary Palmer Long TermEcological Research (LTER) program is to obtain a comprehensiveunderstanding of various components of the Antarctic marineecosystem—the assemblage of plants, animals, ocean, seaice, and island components south of the Antarctic Convergence.Phytoplankton production plays a key role in this polar ecosystem,and factors that regulate production include those that controlcell growth (light, temperature, nutrients) and those that controlcell accumulation rate and hence population growth (water columnstability, advection, grazing, and sinking). Several of thesefactors are mediated by the annual advance and retreat of seaice. In this study, we examine the results from nearly a decade(1991–2000) of ecological research in the western AntarcticPeninsula region. We evaluate the spatial and temporal variabilityof phytoplankton biomass (estimated as chlorophyll-a concentration)and primary production (determined in-situ aboard ship as wellas estimated from ocean color satellite data). We also presentthe spatial and temporal variability of sea ice extent (estimatedfrom passive microwave satellite data). While the data recordis relatively short from a long-term perspective, evidence isaccumulating that statistically links the variability in seaice to the variability in primary production. Even though thismarine ecosystem displays extreme interannual variability inboth phytoplankton biomass and primary production, persistentspatial patterns have been observed over the many years of study(e.g., an on to offshore gradient in biomass and a growing seasoncharacterized by episodic phytoplankton blooms). This high interannualvariability at the base of the food chain influences organismsat all trophic levels.     

Biodiversity and biogeographic affiliation of Bryozoa from King George Island (Antarctica)

King George Island (KGI), which is located between the Antarctic and South American continents, may play a crucial role in the exchange of Bryozoa amongst the various Antarctic sectors and across the Polar Front. Knowledge regarding the biological diversity of this area could help us understand the evolution of the Antarctic ecosystem and its connectivity to the South American continent as well as the colonization ability of particular species. Here, we investigate the patterns of diversity and biogeographic affiliation of the cheilostome Bryozoa from KGI and the surrounding areas. Of 114 identified taxa from a depth range of 6–492 m, 26 species were reported for the first time in KGI. The most speciose genera were Camptoplites, Osthimosia, Smittina, and Cellarinella. Species richness at KGI consisted of 70% of the total bryozoans at the South Shetland Islands (SSI). Fifty-nine per cent of the bryozoans from KGI are endemic to Antarctica, which closely reflects the previously estimated endemism rate for bryozoans and other Antarctic taxa. Cluster analysis indicated that the strongest faunal links of SSI bryozoans were with Antarctic Peninsula assemblages, corresponding to the physical distance between both locations. The biogeographic similarities between SSI and South America confirm the broad trend of existing Antarctic–South American faunal links previously observed in bryozoans and many other taxa and indicate that SSI might be an important transitional zone between Antarctica and South America.     

Descriptions of digeneans from <Emphasis Type="Italic">Sardina pilchardus</Emphasis> (Walbaum) (Clupeidae) off the Algerian coast of the western Mediterranean,with a complete list of its helminth parasites

Five species of digeneans parasitic in the pilchard Sardina pilchardus (Walbaum), a little studied host, from off the Algerian coast of the western Mediterranean are redescribed. These are Parahemiurus merus (Linton, 1910) Manter, 1940, Aphanurus stossichii (Monticelli, 1891) Looss, 1907, Aphanurus virgula Looss, 1907, Lecithaster confusus Odhner, 1905 and Pronoprymna ventricosa (Rudolphi, 1819) Poche, 1926. One of these, A. virgula, is a new record for this host. One other digenean, Hemiurus luehei Odhner, 1905, was also recorded from this host. A complete checklist of the helminth parasites of S. pilchardus throughout its distributional range, comprising 104 host-parasite records of 39 taxa, is presented.     

Mixoscyphus antarcticus gen. nov., sp. nov. (Cnidaria, Hydrozoa, Sertulariidae), the first truly endemic genus of Antarctic benthic hydroids

A genus and species of Antarctic benthic hydroids new to science, Mixoscyphus antarcticus gen. nov., sp. nov., is described and figured. Its systematic position amongst allied genera of the family Sertulariidae is discussed. The studied material originates from the South Shetland Islands area (West Antarctica), which was collected by several Spanish and US Antarctic expeditions. Mixoscyphus gen. nov. currently represents the only complete endemic genus of Antarctic benthic hydrozoans. A discussion of other genera of benthic hydroids that are largely endemic to the Antarctic is also provided.     

THE DISTRIBUTION OF SOME ANTARCTIC NUDIBRANCHS (OPISTHOBRANCHIA)

The circumpolar distribution of the four revised species ofdoridacean nudibranchs: Aegires albus, Bathydoris hodgsoni,B. clavigera and Austrodoris kerguelenensis, is demonstrated,taking into consideration the known data from the literatureand new localities from the Atlantic sector of the Antarctic.A. albus and B. hodgsoni are restricted to the High AntarcticZone. A. kerguelenensis is widely distributed in the High Antarcticand Subantarctic Zone, whereas localities of B. clavigera arerestricted to the High Antarctic Zone and the Atlantic sectorof the Subantarctic Zone. (Received 13 November 1986;     

Extinction and recolonization of maritime Antarctica in the limpet Nacella concinna (Strebel, 1908) during the last glacial cycle: toward a model of Quaternary biogeography in shallow Antarctic invertebrates

Quaternary glaciations in Antarctica drastically modified geographical ranges and population sizes of marine benthic invertebrates and thus affected the amount and distribution of intraspecific genetic variation. Here, we present new genetic information in the Antarctic limpet Nacella concinna, a dominant Antarctic benthic species along shallow ice‐free rocky ecosystems. We examined the patterns of genetic diversity and structure in this broadcast spawner along maritime Antarctica and from the peri‐Antarctic island of South Georgia. Genetic analyses showed that N. concinna represents a single panmictic unit in maritime Antarctic. Low levels of genetic diversity characterized this population; its median‐joining haplotype network revealed a typical star‐like topology with a short genealogy and a dominant haplotype broadly distributed. As previously reported with nuclear markers, we detected significant genetic differentiation between South Georgia Island and maritime Antarctica populations. Higher levels of genetic diversity, a more expanded genealogy and the presence of more private haplotypes support the hypothesis of glacial persistence in this peri‐Antarctic island. Bayesian Skyline plot and mismatch distribution analyses recognized an older demographic history in South Georgia. Approximate Bayesian computations did not support the persistence of N. concinna along maritime Antarctica during the last glacial period, but indicated the resilience of the species in peri‐Antarctic refugia (South Georgia Island). We proposed a model of Quaternary Biogeography for Antarctic marine benthic invertebrates with shallow and narrow bathymetric ranges including (i) extinction of maritime Antarctic populations during glacial periods; (ii) persistence of populations in peri‐Antarctic refugia; and (iii) recolonization of maritime Antarctica following the deglaciation process.     

Descriptions of Wardula bartolii n. sp. (Digenea: Mesometridae) and three newly recorded accidental parasites of Boops boops L. (Sparidae) in the NE Atlantic

Four species of digeneans parasitic in the bogue Boops boops from the Spanish coast of the NE Atlantic are described. All are new records for this host, but one species is new and the other three are considered to be accidental parasites. Wardula bartolii n. sp. (Mesometridae) is distinguished from its two congeners on the basis of a range of morphometrical features, such as the post-ovarian extent of the uterus, the relative length of the attachment organ, the position of the pharynx and vitelline fields, and the absence of anterior caecal diverticula. The other three species are Lecithaster confusus Odhner, 1905, Aponurus laguncula Looss, 1907 (Lecithasteridae) and Accacladium serpentulum Odhner, 1928) (Accacoeliidae).     

The Synthesium Brachycladiidae Odhner, 1905 (Digenea) association with hosts based on nuclear and mitochondrial genes

Synthesium pontoporiae, exclusive parasite of the endangered dolphin, Pontoporia blainvillei, is endemic and restricted to the South Atlantic and belongs to the Brachycladiidae family Odhner, 1905. The study of this family has been limited by the difficulty of accessing the parasites from their marine mammal hosts and as a consequence there is a paucity of genetic information available. Herein we present a genetic analysis using 18S rDNA sequences of S. pontoporiae and S. tursionis and the ND3 mtDNA sequence of S. pontoporiae. The genetic analysis of 18S rDNA sequences of brachycladiids and acanthocolpids determined two major clusters associated with their definitive hosts, marine mammals and fishes, respectively. Considering the tree topology of brachycladiids ND3 mtDNA gene, two clusters were defined, one with the Synthesium species. This work contributes with fundamental genetic information on S. pontoporiae, and suggests a Brachycladiidae genetic evolution related to their hosts.