Peracarida Research Articles

Endogenous origin of endo-β-1,4-glucanase in common woodlouse Porcellio scaber (Crustacea, Isopoda)

Because endogenous cellulases have been observed in arthropods, the potential ability to produce cellulose degrading enzymes was examined in the terrestrial isopod Porcellio scaber, an important decomposer of decayed plant material. cDNA fragments encoding portions of two novel endo-β-1,4-glucanase amino acid sequences were amplified by RT-PCR, and the amino acid sequences predicted were affiliated to endo-β-1,4-glucanases from other arthropods, where they cluster with endo-β-1,4-glucanases of decapod crustaceans. Hybridization in situ reveals the hepatopancreas to be the primary site of gene expression and provides direct evidence of the endogenous origin of endo-β-1,4-glucanase in P. scaber. Conservation of catalytically important amino acid residues suggests that both sequences translate into functional cellulases. Cellulolytic activity was detected in hepatopancreatic extract after separation by SDS-PAGE, which included CMC as substrate. This is the first evidence of endogenous cellulases in peracarid crustaceans and gives strong support for the involvement of isopod endo-β-1,4-glucanases in the degradation of cellulose in their diet.

Nest-building behavior by the amphipod Peramphithoe femorata (Kroyer) on the kelp Macrocystis pyrifera (Linnaeus) C. Agardh from Northern-Central Chile.

Many small arthropod herbivores from terrestrial and marine environments construct tubicolous nest-like domiciles on their host plants or algae by rolling up selected portions of the leaf or blade. Nests serve as both shelter and food, which results in conflicting needs for the grazers because feeding activity continuously destroys parts of the nests. While the nesting habit of ampithoid amphipods and other peracarid crustaceans is widely known, very little is known about the nest dynamics and how the conflict between shelter and food requirements is resolved. Herein we examined the nest-building behavior and nest occupancy of the kelp-dwelling amphipod Peramphithoe femorata on the giant kelp Macrocystis pyrifera. Domiciles on the distal-most part of the blades were occupied by amphipods and were steadily advanced toward the blade base. Since the blades grow from a basal growth meristem, blades and nests develop in opposite directions. Thus, the amphipods exploit the kelp growth pattern to maintain their nests in the medium-distal part of the blades. During a 2-week-long experiment, we observed that blade elongation equaled nest advancement during the first 8 days after nest construction. Thereafter, blade growth slowed down and was surpassed by nest advancement rates, possibly forcing amphipods to seek out new blades. Nest occupancy was generally short (1-4 days), but some amphipods resided longer (>4 days) in their nests. The sophisticated nest-building behavior of P. femorata and other ampithoids maximizes nest persistence, offers optimal protection against predators, and promotes feeding on nutritive or, alternatively, on less defended tissues.

Occurrence, diversity and community structures of peracarid crustaceans (Crustacea, Malacostraca) along the southern shelf of Greenland

The species composition of peracarids (Crustacea: Malacostraca) of the Greenland shelf between 60°N and 65°N was investigated by means of 10 qualitative epibenthic samples in relation to environmental factors. In total, 59,234 specimens were collected belonging to 219 species. The relative abundance was much higher on the western shelf (total of 41,594 specimens) than on the eastern shelf (total of 17,640 specimens with same effort). Three species were new to science, while five records were new for the investigated area. The species composition was dominated by amphipods (58%), while the relative abundances of isopods (25%), cumaceans (11%) and tanaidaceans (6%) were much lower. Diversity and evenness were similar in the eastern and the western areas. Multivariate analyses of the species relative abundances divided the peracarids into a southeastern and southwestern Greenland fauna. Based on a correlation analysis between faunal data and five environmental variables, the separation between the two areas was mainly based on sediment type. Species contributing most to the separation between eastern and western fauna included the amphipods Hardametopa nasuta, Photis reinhardi and Phoxocephalus holboelli, the isopods Pleurogonium spinosissimum, Iolella laciniata and Nannoniscus oblongus and the cumaceans Leucon cf. nasicoides and Campylaspis horrida. Species distribution patterns are discussed in the light of habitat and feeding preferences.

Niche segregation in sandy beach animals: an analysis with surface-active peracarid crustaceans on the Atlantic coast of Spain

Several species of sandy beach invertebrates regularly switch between burial in the sand during the day and surface activity at night to feed on stranded organic matter. Because all species consume essentially the same type of food (i.e., wrack) deposited over a restricted area, the potential for competition exists. Conversely, spatial and temporal segregation of surface activity behaviour is predicted to allow for niche separation. Here, we tested whether such behavioural niche separation occurs in three species of sympatric crustaceans (the talitrid amphipods Talitrus saltator (Montagu 1808) and Talorchestia brito Stebbing 1891, and the oniscoidean isopod Tylos europaeus Arcangeli 1938). We also assessed whether surface activity is modulated by weather, sea conditions and moon phases. Surface activity was measured over three consecutive moon phases on an exposed beach on the Atlantic Coast of Spain using pitfall traps along three transects from the foredunes to the swash. Adults of the amphipod T. saltator and the isopod T. europaeus overlapped spatially and temporally in their surface activity for most of the night. By contrast, the activity of T. brito was strongly disjunct in time and concentrated into significantly shorter bouts around dawn or dusk. Niche differentiation was also evident along the space axis, where T. brito occurred distinctly lower on the beach. Although several environmental factors (e.g., air and sand temperature, humidity, atmospheric pressure, wind speed and wind direction) were correlated with surface activity, this was highly variable amongst species, life stages, and synodic phases, and did not obscure the fundamental mosaic of spatio-temporal heterogeneity amongst species. Nocturnal feeding on beach wrack creates the potential for competition amongst sympatric crustaceans which can, however, be mitigated by behaviour patterns that separate consumers in time and space.

Effects of chronic trawling disturbance on the secondary production of suprabenthic and infaunal crustacean communities in the Adriatic Sea (NW Mediterranean)

Towing gears are known to produce several kinds of effects on benthic ecosystems. As small organisms and benthic species with faster growth rates and shorter life histories can withstand the fishing mortality and benefit from reduced competition or predation, trawl fishing can enhance their proliferation. Thus, trawl fishing can lead to biomass loss and production increase, since smaller specimens are more productive than bigger ones. In the present study we evaluate the effects, if any, of trawling on benthic crustacean macrofaunal production rates. Sampling was carried out in two neighbouring sites in the central Adriatic Sea (central Mediterranean), one affected by fishing activity and one not. Production and production/biomass (P/B) ratio of 13 species of peracarid and eucarid crustaceans were estimated using the Hynes size-frequency method. Estimates measured at both sites were compared in order to test the hypothesis that higher production and P/B values should occur in the fished area rather than in the unfished one. Our results indicated that the effects on the species are more complex than expected in regard to this hypothesis, and that they depend on the ecological and behavioural characteristics of the selected species.

Concentrated sodium chloride brine solutions as an additional treatment for preventing the introduction of nonindigenous species in the ballast tanks of ships declaring no ballast on board

Currently, seawater flushing is the only management strategy for reducing the number of viable organisms in residual sediments and water of ballast tanks of vessels declaring no ballast on board (NOBOB) that traffic ports of the eastern United States. Previously, we identified several species of freshwater and brackish-water peracarid crustaceans able to survive the osmotic shock that occurs during open-ocean ballast water exchange and, potentially, to disperse over long distances via ballasted ships and NOBOB vessels. We tested the efficacy of concentrated sodium chloride brine solutions as an additional treatment for eradicating the halotolerant taxa often present in the ballast tanks of NOBOB ships. The lowest brine treatments (30 ppt for 1 h) caused 100% mortality in several species of cladocerans and copepods collected from oligohaline habitats. Several brackish-water peracarid crustaceans, however, including some that can survive in freshwater as well, required higher brine concentrations and longer exposure durations (45-60 ppt for 3-24 h). The most resilient animals were widely introduced peracarid crustaceans that generally prefer mesohaline habitats but do not tolerate freshwater (required brine treatments of 60-110 ppt for 3-24 h). Brine treatments (30 ppt) also required less time to cause 100% mortality for eight taxa compared with treatments using 34 ppt seawater. Based on these experiments and published data, we present treatment strategies for the ballast tank biota often associated with NOBOB vessels entering the Great Lakes region. We estimate the lethal dosage of brine for 95% of the species in our experiments to be 110 ppt (95% confidence interval, 85-192 ppt) when the exposure time is 1 h and 60 ppt (95% confidence interval, 48-98 ppt) when the exposure duration is 6 h or longer.

The First Danish Deep-Sea Expedition on the Ingolf: 1895 and 1896

The Danish Ingolf Expedition took place in the summer months of 1895 and 1896, with C. F. Wandel as captain, a man with long experience in hydrographical work in the Arctic. The other scientific participants were the zoologists H. Jungersen, W. Lundbeck and H. J. Hansen during the 1895 cruise; C. Wesenberg-Lund replaced Hansen during the 1896 cruise. C. H. Ostenfeld was the botanist and M. Knudsen the hydrographer. The Ingolf (see Figure 1) was a naval cruiser. In both years the voyages were hindered by ice that had moved much further south than normal, even closing most of the Denmark Strait. In 1895, the best results were obtained south of Iceland and in the Davis Strait; in 1896 south and east of Iceland and as far north as Jan Mayen Island. A total of 144 stations were completed, all with soundings, trawlings and (for the first time) continuous hydrographical work associated with the deep-sea trawling (bottom measurements of temperature, salinity, chlorine contents and specific gravity). Eighty of the stations were deeper than 1,000 m. There were more than 800 hydrographical measurements, with about 3,300 registrations recordings added on the basis of the measurements. 138 gas analyses were performed on board with samples from the surface and the sea bottom. The main result of the expedition was the final demonstration of probably the most important threshold boundaries in the world: the Wyville Thompson Ridge from East Greenland to Scotland with maximum depths of 600 m, separating the fauna in the Norwegian and Polar Sea to the north, always with negative below-zero temperatures except close to the Norwegian coast, from the fundamentally different general Atlantic deep-sea fauna to the south of the ridge with positive temperatures. The results are published in the Ingolf Report, with fifteen volumes containing forty-three papers by nineteen Danish authors and fourteen papers by six foreign authors. The sieving technique was excellent—due to an apparatus designed by H. J. Hansen that kept the animals under water until preservation and using the finest silk for sieving. In this way, the expedition collected more smaller animals than had been acquired by previous deep-sea expeditions. Hansen's studies of the peracarid crustaceans and parasitic copepods and Lundbeck's report on the sponges were particularly noteworthy. The 130 photographs taken on board and on land by the ship's doctor William Thulstrup represent a cultural/historical treasure.

Size variations of the amphipod crustacean Melita palmata in two Adriatic lagoons: Goro and Lesina

1 - Body length of the peracarid crustacean Melita palmata (Montagu, 1804) was measured in two Adriatic lagoons, Goro and Lesina, in order to verify the relationships between body size and ecological conditions. 2 - The size class distribution was unequal in the two lagoons. Two distinct generations were observed at Goro, one including small or medium sized juveniles and the other medium or large sized adults; most of the Lesina specimens, instead, had medium-sized bodies and the population size dispersion was lower. 3 - Mean adult sizes were significantly different among stations and between lagoons. 4 - Larger sizes were observed in stations at higher salinity, under direct seawater influence, whereas adult individuals of smaller size were present in more confined stations.

Diversity and temporal variation of peracarid fauna (Crustacea: Peracarida) in the shallow subtidal of a sandy beach: Playa América (Galicia, NW Spain)

AbstractPeracarids (Crustacea: Peracarida) are an important component of soft‐sediment faunas and are considered good indicators of quality of water and sediments. Nevertheless, little is known about diversity of peracarid crustaceans on the shallow subtidal sediments of Playa América, a sandy beach in the Ensenada de Baiona (Galicia, NW Spain). Therefore, the peracarid fauna of its shallow subtidal zone was studied in a fine‐sand site at 4‐m depth from February 1996 to February 1997. Monthly sampling yielded a total of 4753 individuals belonging to 60 species. Amphipods were dominant in number of individuals and species followed by cumaceans. The assemblage showed a stable composition in species through the year and was numerically dominated by a few species, namely the amphipods Siphonoecetes kroyeranus and Microprotopus maculatus and the cumacean Pseudocuma longicorne. These species showed large monthly fluctuations in abundance, with maximal values between summer and autumn.

Assemblages of peracarid crustaceans in subtidal sediments from the Ría de Aldán (Galicia, NW Spain)

Peracarid crustaceans inhabit many marine benthic habitats and are good indicators of environmental conditions. There is, however, a lack of information about diversity and distribution of peracarid crustaceans on the shallow subtidal sediments of the Galician rias. In the summer of 1997, 27 subtidal stations were sampled in the Ria de Aldan, a ria on the southern margin of the mouth of the Ria de Pontevedra (Galicia, NW Spain). A total of 16,191 peracarid individuals were collected, comprising 125 species belonging to five orders. Amphipods were dominant in number of species and individuals, followed by isopods and cumaceans. Multivariate analyses of these data indicated that depth and sediment granulometry were major determinants of distribution and composition of peracarid assemblages in the ria.

Effect of osmotic shock as a management strategy to reduce transfers of non-indigenous species among low-salinity ports by ships

Open-ocean ballast-water exchange (BWE) is currently the most common treatment used to reduce the ballast transfer of organisms and the subsequent risk of invasions among coastal ecosystems. Freshwater or estuarine organisms remaining after BWE often experience high mortality, due to osmotic shock caused by high-salinity exposure. We conducted 70 salinity tolerance experiments on 54 different taxa to measure mortality rates of freshwater and estuarine organisms after exposure to oceanic seawater (34 psu), simulating both flow-through (F-T) and empty-refill (E-R) BWE methods. We focused especially on larval and adult crustaceans from freshwater and mesohaline habitats adjacent to ports of the Baltic Sea, North Sea, Great Lakes, Chesapeake Bay, and San Francisco Bay. Animals from oligohaline habitats (0-2 psu) experienced the highest mortality: all individuals died in 82% of the F-T treatments and 88% of the E-R treatments. The effectiveness of both treatment types decreased with animals from low-salinity (2-5 psu, 100% mortality in 27% of F-T and 46% of E-R treatments) and mesohaline habitats (5-18 psu, 100% mortality in 40% of F-T and 52% of E-R treatments). In 43% of cases among all salinity categories, empty-refill treatments required less exposure time to cause significant mortality than flow-through treatments. Invertebrates that exhibited significant survivorship were most often peracarid crustaceans including widely introduced species of mysid shrimps and amphipods. Although salinity shock does not completely prevent the transfer of all low-salinity biota, BWE provides a useful management tool to reduce species transfers, especially considering the combined effects of removal and mortality.

The Amphipod Pilot Species Project (AMPIS), a novel Dutch-Chinese taxonomic initiative (Peracarida, Amphipoda): a description of the project

AMPIS is a comprehensive database of pictures and illustrations of the morphology of a collection of selected amphipod pilot species. All macro- and micro-characters of the entire body surface are systematically recorded. A pilot species in AMPIS is represented by a large number of illustrations and scanning electron micrographs accessible via a series of increasing magnification steps. Functional morphological interpretations will be made based on the inventories. Explanatory video recordings concerning specific behaviour will be added. This unique vertical database, first of its kind, will be complementary to the many overlapping horizontal database projects that have been developed or are under construction. AMPIS will meet a demand for a framework of more detailed information of the highly complex morphology of amphipods. It is an entirely new approach towards taxonomic research. AMPIS is the result of a cooperation between the Zoological Institute of the Chinese Academy of Sciences, the Radboud University of Nijmegen, and the University of Amsterdam, the last two partners from the Netherlands. The project is funded by the China Exchange Programme of the Royal Netherlands Academy of Sciences. AMPIS est une base de donnees d'images et d'illustrations de la morphologie d'une collection d'especes selectionnees d'amphipodes. Tous les macro- et micro-caracteres de la surface du corps dans son entier sont systematiquement enregistres. Une espece pilote dans AMPIS est representee par un grand nombre d'illustrations et de microphotographies realisees en microspopie electronique a balayage via une serie de grossissements successifs. Les interpretations en morphologie fonctionnelle seront realisees a partir des inventaires. Des enregistrements videos explicatifs sur le comportement specifique seront ajoutes. Cette base de donnees unique, vertical, la premiere du genre, completera les multiples projets de base de donnees horizontales, qui ont ete developpees ou sont en construction. AMPIS repondra a la demande pour une structure d'information plus detaillee sur la morphologie hautement complexe des amphipodes. C'est une approche entierement nouvelle de la recherche taxonomique. AMPIS est le resultat d'une cooperation entre l'Institut de Zoologie de l'Academie des Sciences de Chine, l'Universite Radboud de Nijmegen et l'Universite d'Amsterdam, ces deux dernieres des Pays-Bas. Le projet est finance par le «Programme d'echange avec la Chine» de l'Academie Royale des Sciences des Pays-Bas.

Global diversity of spelaeogriphaceans & thermosbaenaceans (Crustacea; Spelaeogriphacea & Thermosbaenacea) in freshwater

Spelaeogriphaceans and thermosbaenaceans are two orders of eyeless, unpigmented peracarid crustaceans represented by very few species from subterranean waters. Spelaeogriphaceans occur only in continental waters, either running or still, in limestone or sandstone caves, or in calcrete aquifers. The four species known are limnic except one occurring in slightly brackish water loosely associated with an endorheic basin. The Thermosbaenacea are primarily marine, with only 18 species recorded in limnic conditions or in brackish inland waters whose salinity does not derive from dilution of seawater. They occur in limestone caves, the interstitial medium associated to alluvial deposits, or in thermo-mineral springs. Spelaeogriphaceans are found on the southern continents, in ancient cratons not affected by sea transgressions at least since the Early Cretaceous, when Gondwana started to breakup. The former integration of these terranes into Gondwana suggests that the penetration of spelaeogriphaceans in continental waters took place previous to the fragmentation of this super continent (starting ca. 140 Ma), and that their current distribution pattern was driven by continental drift. The distribution of the Thermosbaenacea matches precisely the area covered by the ancient Tethys Sea or its coastlines. They are most probably relicts of a once widespread shallow-water marine Tethyan fauna stranded in interstitial or crevicular groundwater during marine regressions.

Slope and deep-sea abundance across scales: Southern Ocean isopods show how complex the deep sea can be

How animals are distributed in the world's largest surface environment, the deep sea, is poorly understood. The ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) III cruise probed richness and abundance of one group, peracarid crustaceans (isopods, amphipods, cumaceans, tanaidaceans, mysidaceans), as a model of deep-sea fauna across Southern Ocean (SO) sites. Analysis of samples from the ANDEEP cruises reveals SO isopods to be highly abundant, rich and endemic as many other taxa in the region are known to be. Samples taken across three spatial scales include sites tens, hundreds and thousands of kilometers apart, sites stretching from the Southern Cape Basin (South Atlantic) to continental Antarctica and including depths from 1030 to 5000 m. Across these spatial scales we investigated ecological success (abundance) of peracarids at order, family, and species levels. Remarkably no significant relationship was found between abundance and spatial scale at any taxonomic level. That is, the variability in abundance at major regional scale is no different to that across just tens of kilometres. Most taxa were represented in only a few samples, but we suggest most inhabitants of the deep Weddell Sea environment to be very patchy rather than rare. Separate plots of family, genus, and species abundance by sample number revealed this to be true—nearly all genera and species are an order of magnitude more abundant than ‘background’ levels in just one or two samples. Our isopod and amphipod samples reveal the Atlantic sector of the SO, one of the most dynamic and important regions influencing the global deep-sea environment, to be highly complex. Our study suggests that, at least with regard to the study taxa and area, the typical comparisons of regions that are made by ecologists miss the scale at which crucial ecological variability happens. Even without ice scours creating topographical complexity (as on the shelf) the deep Weddell Sea is clearly complex at scales smaller than that measured to date.

Introduction of the Ponto-Caspian Bloody-red Mysid Hemimysis anomala into the Lake Michigan Basin

Hemimysis anomala G.O. Sars, 1907, a mysid species native to the Ponto-Caspian region, was discovered during fall 2006 in the Lake Michigan basin. Large numbers of individuals formed aggregations (averaging 1,540 ± 333 individuals/m2) in a shallow docking basin connected to the channel linking Lake Michigan and Muskegon Lake. The population included females (63%), males (35%), and juveniles (2%). The global invasion pattern in H. anomala is similar to that in another Ponto-Caspian peracarid crustacean, Echinogammarus ischnus. As with E. ischnus, the expansion of H. anomala in North America is anticipated.

Composition and distribution of the peracarid crustacean fauna along a latitudinal transect off Victoria Land (Ross Sea, Antarctica) with special emphasis on the Cumacea

The following study was the first to describe composition and structure of the peracarid fauna systematically along a latitudinal transect off Victoria Land (Ross Sea, Antarctica). During the 19th Antarctic expedition of the Italian research vessel “Italica” in February 2004, macrobenthic samples were collected by means of a Rauschert dredge with a mesh size of 500 μm at depths between 85 and 515 m. The composition of peracarid crustaceans, especially Cumacea was investigated. Peracarida contributed 63% to the total abundance of the fauna. The peracarid samples were dominated by amphipods (66%), whereas cumaceans were represented with 7%. Previously, only 13 cumacean species were known, now the number of species recorded from the Ross Sea increased to 34. Thus, the cumacean fauna of the Ross Sea, which was regarded as the poorest in terms of species richness, has to be considered as equivalent to that of other high Antarctic areas. Most important cumacean families concerning abundance and species richness were Leuconidae, Nannastacidae, and Diastylidae. Cumacean diversity was lowest at the northernmost area (Cape Adare). At the area off Coulman Island, which is characterized by muddy sediment, diversity was highest. Diversity and species number were higher at the deeper stations and abundance increased with latitude. A review of the bathymetric distribution of the Cumacea from the Ross Sea reveals that most species distribute across the Antarctic continental shelf and slope. So far, only few deep-sea records justify the assumption of a shallow-water–deep-sea relationship in some species of Ross Sea Cumacea, which is discussed from an evolutionary point of view.

The complete mitochondrial genome of the common sea slater, Ligia oceanica (Crustacea, Isopoda) bears a novel gene order and unusual control region features

BackgroundSequence data and other characters from mitochondrial genomes (gene translocations, secondary structure of RNA molecules) are useful in phylogenetic studies among metazoan animals from population to phylum level. Moreover, the comparison of complete mitochondrial sequences gives valuable information about the evolution of small genomes, e.g. about different mechanisms of gene translocation, gene duplication and gene loss, or concerning nucleotide frequency biases.The Peracarida (gammarids, isopods, etc.) comprise about 21,000 species of crustaceans, living in many environments from deep sea floor to arid terrestrial habitats. Ligia oceanica is a terrestrial isopod living at rocky seashores of the european North Sea and Atlantic coastlines.ResultsThe study reveals the first complete mitochondrial DNA sequence from a peracarid crustacean. The mitochondrial genome of Ligia oceanica is a circular double-stranded DNA molecule, with a size of 15,289 bp. It shows several changes in mitochondrial gene order compared to other crustacean species. An overview about mitochondrial gene order of all crustacean taxa yet sequenced is also presented. The largest non-coding part (the putative mitochondrial control region) of the mitochondrial genome of Ligia oceanica is unexpectedly not AT-rich compared to the remainder of the genome. It bears two repeat regions (4× 10 bp and 3× 64 bp), and a GC-rich hairpin-like secondary structure. Some of the transfer RNAs show secondary structures which derive from the usual cloverleaf pattern. While some tRNA genes are putative targets for RNA editing, trnR could not be localized at all.ConclusionGene order is not conserved among Peracarida, not even among isopods. The two isopod species Ligia oceanica and Idotea baltica show a similarly derived gene order, compared to the arthropod ground pattern and to the amphipod Parhyale hawaiiensis, suggesting that most of the translocation events were already present the last common ancestor of these isopods. Beyond that, the positions of three tRNA genes differ in the two isopod species. Strand bias in nucleotide frequency is reversed in both isopod species compared to other Malacostraca. This is probably due to a reversal of the replication origin, which is further supported by the fact that the hairpin structure typically found in the control region shows a reversed orientation in the isopod species, compared to other crustaceans.

The effects of temperature on peripheral neuronal function in eurythermal and stenothermal crustaceans

To determine whether neuronal function in Antarctic crustaceans is adapted to the low and narrow range of temperatures at which these animals live, we have compared conduction velocities in the peripheral nervous systems of two temperate species, the decapod Carcinus maenas and the isopod Ligia oceanica, and two Antarctic species, the isopod Glyptonotus antarcticus and the amphipod Paraceradocus gibber. Neuronal conduction velocity differs among the species in the order C. maenas > G. antarcticus > P. gibber > L. oceanica. When measured at the normal environmental temperatures characteristic of each species, conduction velocity of the Antarctic peracarid P. gibber is greater than that of its similar sized temperate relative L. oceanica, demonstrating complete thermal compensation. The temperate decapod C. maenas has a higher thermal dependence of neuronal conduction velocity than either of the Antarctic species, G. antarcticus and P. gibber, but the temperate L. oceanica does not. These data, when collated with published values, indicate that peracarid crustaceans (L. oceanica, G. antarcticus and P. gibber) have lower neuronal conduction velocities and a lower thermal dependence of neuronal conduction velocity than do other arthropods, irrespective of habitat. There is a linear dependence of conduction velocity on temperature down to -1.8 degrees C in all three species. Our data extend by more than 10 degrees the lower range of temperatures at which conduction velocities have been tested systematically in previous studies. The upper thermal block of neuronal conduction is similar in C. maenas, G. antarcticus, P. gibber and L. oceanica at 24.5, 19.5, 21.5 and 19.5 degrees C, respectively. This suggests that failure to conduct action potentials is not what determines the mortality of Antarctic invertebrates at approximately 10 degrees C. The excitability of axons in the leg nerve of G. antarcticus is not affected by temperatures ranging from -1.8 to +18 degrees C. The responses of sensory neurones activated by movements of spines on the leg, however, are strongly modulated by temperature, with maximal responses at 5-10 degrees C; well above the normal environmental temperature range for the species. The responses fail at 20-22 degrees C. The number of large diameter axons (which produce the fast action potentials recorded in this study) is the same in L. oceanica and G. antarcticus, but the median axon diameter is greater in L. oceanica than G. antarcticus. In G. antarcticus, however, there are glial wrappings around some large (>5 microm diameter) axons that may increase their conduction velocity. Such wrappings are not found in L. oceanica.

Levantamento de Mollusca, Crustacea e Echinodermata associados a Sargassum spp. na Ilha da Queimada Pequena, Estação Ecológica dos Tupiniquins, litoral sul do Estado de São Paulo, Brasil

Neste trabalho foi realizado o primeiro levantamento da macrofauna de fital da ilha da Queimada Pequena, focalizando o registro das espécies de moluscos, crustáceos e equinodermos associados a Sargassum spp. Para a amostragem da macrofauna associada, foram coletadas aleatoriamente 6 frondes de Sargassum localizadas a 6 m de profundidade, usando-se equipamento de mergulho autônomo. As frondes foram envolvidas em sacos de tecido com malha de 200 mm, mraspadas do substrato, colocadas em recipientes com uma solução de formaldeído 10% e levadas ao laboratório para remoção e identificação da fauna. Quarenta e um táxons foram identificados, havendo dominância de crustáceos peracáridos. Em relação aos Mollusca, a composição específica foi diferente em relação àquela observada na costa norte do estado de São Paulo. Das 16 espécies de moluscos encontradas, apenas os gastrópodes dos gêneros Anachis e Odostomia e os bivalves dos gêneros Musculus e Modiolus são representantes da fauna associada à Sargassum comuns às duas regiões do estado de São Paulo, embora representantes do gênero Fissurela já tenham sido relatados na região de Santos em associação à alga Amphiroa fragilissima. A ocorrência do bivalve exótico Isognomon bicolor também foi confirmada. Os dados obtidos sugerem que a fauna de moluscos pode realmente ser distinta na região norte e sul do estado. No entanto, são necessários estudos mais extensos para confirmar esses resultados e para subsidiar futuras estratégias de manejo dessa unidade de conservação.

Evolution of Antarctic biodiversity in the context of the past: the importance of the Southern Ocean deep sea

Present day Southern Ocean benthic biodiversity is the result of climatic changes based on the break-up of Gondwana in the Cretaceous and the Cenozoic and the physiological potential of the fauna to cope with the climatic deterioration. Though many taxa survived the thermal drop in ocean bottom temperatures, zoogeographic ranges changed and some faunal elements even became extinct, e.g. benthic decapods and teleost fish, opening up new ecological niches and the potential for enormous adaptive radiations within some taxa, like the amphipods and isopods (peracarid crustaceans) and notothenioid fish. Ice-sheet extensions and retreats might have enhanced speciation processes as well as eurybathy. Biodiversity on the Antarctic shelf is high within the polychaetes, molluscs, and echinoderms, and within the amphipods and isopods possibly due to the Cenozoic extinction of the benthic decapods. Moreover, some shelf areas are characterized by accumulations of large suspension feeders like poriferans, bryozoans, ascidians, gorgonians, and hydroids. Palaeoclimatic changes also caused that many taxa of the modern, present day Southern Ocean benthic organisms are characterized by gigantism, slow metabolism, longevity, and a reduced number of offspring combined with late maturation. However, our biological knowledge is mainly confined to Southern Ocean shelf organism; we do not know much about the composition, biodiversity and zoogeography of the Southern Ocean deep sea animals. On this background the deep sea expeditions ANDEEP were born and the background and first results of these are presented herein.