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In recent years, remote exploration around the Scotia Arc and waters off the Antarctic Peninsula yielded new records of Lithodidae suggesting our knowledge on their distribution is biased by our ability to sample areas with difficult access. In the present study, we used molecular methods to identify and report the occurrence of the deep-sea king crab Lithodes couesi, so far reported as a North Pacific lithodid, in the marine protected area (MPA) Namuncura/Burdwood Bank II, Southwestern Atlantic Ocean; more than 10,000 km away from its known distribution. Our finding suggests that the distributions of deep-water lithodid species are more extensive than they have been previously thought. We emphasize the need for a worldwide key to identify lithodid species, and prompt to barcoding specimens, at least those from poorly known species or remote locations, in order to corroborate their specific status. Finally, our study stresses the importance of MPAs in the conservation of biodiversity, as well as the processes involved in its evolution.

King crab fisheries constitute a highly profitable marine business in southern South America, where five fisheries for lithodids currently exist, two in Chile and three in Argentina. These fisheries mainly target Lithodes santolla, however in some localities the harvested morphospecies is Lithodes confundens, and in some others it constitutes a mixed fishery since it also captures Paralomis granulosa. Fishery products can be commercialized as frozen shredded or canned minced meat, making specific identification unfeasible since the morphological characters used in the identification are on the carapace, and consequently, not available in these processed products. Therefore, a potential for food fraud exists, since southern king crab meat (L. santolla/ L. confundens) could be replaced by the less expensive false southern king crab, i.e. P. granulosa. Furthermore, incongruence between morphological and genetic characters rendered the taxonomic status of both morphospecies of commercial Lithodes questionable, and stressed the need of implementing molecular methods to monitor the abundance and distribution, as well as the landings, of each genetic clade of L. santolla/ L. confundens. In the present study, we developed rapid and cost-efficient Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) tests that can aid in the identification of commercially important lithodids that inhabit waters off southern South America in cases where identification is not possible using morphological characters.

Munida gregaria (Fabricius, 1793) is one of the few species of squat lobsters (Anomura, Munididae) with two morphotypes, one with a post-metamorphic pelagic phase that eventually settles to the bottom ("gregaria") and a second that is exclusively benthic ("subrugosa"). This study provides the first information on the growth of the pelagic morphotype of M. gregaria and its relation with changes in morphology in southern South America. Specifically, we studied growth at molt and duration of the intermolt period in the laboratory and analyzed changes in morphology through growth by means of geometric morphometry techniques. Fifty squat lobsters were sampled from shoals in the Beagle Channel, Tierra del Fuego and kept in individual flasks during 29 months. The carapace of each exuvia was photographed and analyzed using 2D geometric morphometry analysis. Changes in shape associated with growth in the gregaria morphotype were gradual, adjusted to a linear function, and occurred mainly in the anterior portion of the carapace. After two years and at least eight molts, however, individuals of the gregaria morphotype were still clearly distinguishable from a typical individual of the subrugosa morphotype. These results suggests that once sexual maturity is attained, pelagic individuals of M. gregaria do not transform from gregaria to subrugosa, and retain the gregaria morphology. Fil: Diez, Mariano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Rojas Quiroga, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Pérez Barros, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Maimónides. Área de Investigaciones Biomédicas y Biotecnológicas. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y de Diagnóstico; Argentina Fil: Lezcano, Anibal Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Florentin, Olga Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

We investigated the taxonomic status of two sympatric morphospecies of squat lobsters from southern South America (Beagle Channel, Strait of Magellan, and Burdwood Bank), Munida gregaria and Munida subrugosa, by DNA sequence analysis of three mitochondrial (mt)DNA gene fragments [416 bp of 16S rDNA(165), 566 bp of cytochrome c oxidase subunit I(COI) and 418 bp of NADH dehydrogenase subunit 1 (ND1)]; and the nuclear rDNA internal transcribed spacer (ITS) 1 (883–952 bp). We obtained a total of 79 sequences from 32 individuals. The 16S sequences of all M. gregaria and M. subrugosa were invariant and identical, whereas COI and ND1 showed 12 and 15 variable sites, respectively. These polymorphisms were shared between morphospecies. Interspecific Tamura–Nei distances for COI and ND1 sequences were 0.0024 and 0.0032, respectively, and were not significantly different from intraspecific distances (Kruskal–Wallis tests: P = 0.58 and P = 0.69, for COI and ND1, respectively). Similar to the results obtained from the mtDNA sequences, no relationship was found between the ITS1 maximum parsimony tree topology and the morphologic classification of specimens in M. gregaria and M. subrugosa. We conclude that M. gregaria and M. subrugosa from southern South America may either represent a case of a dimorphic species, or a case of incomplete lineage sorting. The fact that these two morphospecies did not show fixed differences over a total of 1947 bp analysed reinforces the hypothesis of a single dimorphic species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 421–434.

The use of genetic tools has a relevant role in fishery resource management and conservation, for example, when used in species delimitation. Morphological variation can occur as an adaptative or plastic response to environmental variation, and therefore, be mistakenly used as a criterion to delimit species. Particularly, Lithodes santolla and Lihodes confundens, two commercially important lithodid species from sub-Antarctic South America, are mainly differentiated by the number and size of spines on the carapace and pereiopods. However, variability in the size of spines of L. santolla has been reported. We evaluated whether these two morphospecies constitute reciprocally monophyletic clades at the molecular level using mitochondrial markers, and performed a detailed morphological analysis of the carapace to search for correspondence between genetic and morphological differences. The Bayesian phylogenetic reconstruction showed that L. santolla and L. confundens belong to two sister clades. However, individuals identified as L. santolla and L. confundens did not resolve as reciprocally monophyletic groups. Instead, one clade was formed by individuals belonging to both morphospecies and was widely distributed, while the other one was exclusively formed by L. santolla, and its members were only found near Puerto Montt and in the Beagle Channel. No morphological characters were found on the carapace that could differentiate individuals belonging to each genetic clade. Either if the two genetic clades constitute species or remnants of two species that are merging through introgression, they represent two evolutionary significant lineages, and measures should be taken to preserve both. Our study suggests the need to revise the use of the number of spines as a relevant taxonomic character in the taxonomy of Lithodes, and to implement molecular genetic methods to control fisheries. Fil: Pérez Barros, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Maimónides. Área de Investigaciones Biomédicas y Biotecnológicas. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y de Diagnóstico; Argentina Fil: Confalonieri, Viviana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Paschke, Kurt. Universidad Austral de Chile; Chile Fil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

Benthic decapod crustacean assemblages in the Beagle Channel are dominated by the galatheid crabs Munidasubrugosa and Munida gregaria. This study deals with the bathymetric and spatial distribution, density and diversity of the assemblage of decapod species that co-occur with Munida spp. in the Beagle Channel. A total of 131 samples were obtained using an epibenthic trawl from February 1999 to December 2000. They were taken monthly from two depth strata separated by the 40 m isobath (range: 4-262 m), and from three different sites: Bahia Lapataia, Ushuaia and Punta Segunda. Sixteen of the 36 recorded species of decapod crustaceans from the Beagle Channel were caught. Munidasubrugosa and M. gregaria contributed 94% to the total decapod material. Of the remaining 6%, Austropandalusgrayi (Caridea) was the most abundant species, constituting 43% of the non-galatheid decapod fraction. Some species, namely Paguruscomptus and Eurypodius spp., were characteristic of shallow waters ( 40 m). The average density and diversity of non-galatheid decapods varied with depth and location. Decapod diversity correlated positively with the density of algae and polychaete tubes. The influence of three-dimensional bottom structure on decapod diversity in the Beagle Channel is discussed.

Benthic decapod crustacean assemblages in the Beagle Channel are dominated by the galatheid crabs Munidasubrugosa and Munida gregaria. This study deals with the bathymetric and spatial distribution, density and diversity of the assemblage of decapod species that co-occur with Munida spp. in the Beagle Channel. A total of 131 samples were obtained using an epibenthic trawl from February 1999 to December 2000. They were taken monthly from two depth strata separated by the 40 m isobath (range: 4-262 m), and from three different sites: Bahía Lapataia, Ushuaia and Punta Segunda. Sixteen of the 36 recorded species of decapod crustaceans from the Beagle Channel were caught. Munidasubrugosa and M. gregaria contributed 94% to the total decapod material. Of the remaining 6%, Austropandalusgrayi (Caridea) was the most abundant species, constituting 43% of the non-galatheid decapod fraction. Some species, namely Paguruscomptus and Eurypodius spp., were characteristic of shallow waters ( 40 m). The average density and diversity of non-galatheid decapods varied with depth and location. Decapod diversity correlated positively with the density of algae and polychaete tubes. The influence of three-dimensional bottom structure on decapod diversity in the Beagle Channel is discussed. Los galateidos Munida subrugosa y M. gregaria dominan las capturas bentónicas en el Canal Beagle. En el presente trabajo se estudia la distribución batimétrica y espacial, la densidad y la diversidad del ensamble de crustáceos decápodos capturados junto con Munida spp. en el Canal Beagle. Entre febrero de 1999 y diciembre de 2000, se tomaron 131 muestras con una red epibentónica de arrastre en 2 estratos de profundidad separados por la isobata de 40 m (rango: 4-262 m), y en tres localidades: Bahía Lapataia, Ushuaia y Punta Segunda. Se registraron 16 de las 36 especies de decápodos citadas para el Canal Beagle. Munida subrugosa y M. gregaria constituyeron el 94% de los decápodos capturados. Del 6% restante, Austropandalus grayi (Caridea) fue la especie dominante y constituyó el 43%. Se observó una distribución batimétrica diferencial, con especies características de aguas poco profundas (< 40 m), como Pagurus comptus y Eurypodius spp., y otras de aguas profundas (>40 m), como Campylonotus semistriatus. La densidad y diversidad de los decápodos no galateidos varió con la profundidad y la localidad. La diversidad correlacionó positivamente con la densidad de algas y tubos de poliquetos. Se discute la influencia de la estructura tridimensional del fondo sobre la diversidad de decápodos en el Canal Beagle.

The “East Pacific Barrier” has been recognized as the World’s largest marine biogeographic barrier. Munida gregaria is the only species of its family with transpacific populations; however, it still remains to be elucidated whether these two distantly located populations belong to the same species. In this study, we investigated the genetic cohesion of M. gregaria across the East Pacific Barrier by analyzing mitochondrial markers. Cytochrome oxidase subunit I and NADH dehydrogenase subunit 1 genes were sequenced for individuals from different areas, i.e., the southeast Pacific, the southern tip of South America, the southwest Atlantic, and the southwest Pacific. A median-joining network, pairwise F STs, genetic diversity statistics, and neutrality tests were computed. Our results, i.e., the absence of different haplogroups on both sides of the East Pacific Barrier and existence of shared haplotypes, showed that populations on both sides of this barrier belong to the same species. At a population genetic level, our results suggest that individuals from both regions have been connected, since although some differentiation was found between the southern tip of South America and the southwest Pacific, the southeast Pacific and southwest Atlantic showed no signs of differentiation from the southwest Pacific. In addition, our results provided evidence of a population expansion in southern South America during the Pleistocene. The role of Pleistocene glaciations and the Antarctic Circumpolar Current in shaping the distribution of sub-Antarctic marine invertebrates is discussed. Fil: Perez Barros, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Calcagno, Javier Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Confalonieri, Viviana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Gametogenesis and temporal variation in energy allocation to different organs were analyzed in Aulacomya atra from the Beagle Channel (Tierra del Fuego, Argentina). Our results show that A. atra presents an extended spawning period from late winter to spring when the lowest value of mantle-gonad index (MGI) and maximum number of spawned individuals were observed. The MGI in mature males increased as the energy density of the mantle-gonad (EDMG) decreased, indicating an increase in mass of lower energy values. In contrast, the MGI in mature females increased as EDMG increased, indicating an increase in mass of higher energy values. Consequently, males and females reached a similar energy content of the mantle-gonad (ECMG) by means of different strategies: males have gonads of larger size but with lower energy by unit of mass than females. Besides, we observed a decrease in the digestive gland index (DGI) in concordance with an increase in the MGI of mature individuals, and a trend towards the depletion of ED and EC in the digestive gland during gonadal maturation. Our results evidence the role of the digestive gland as an energy reservoir and a different energy allocation strategy between sexes during gonadal maturation. Se analizó la gametogénesis y la variación temporal en la asignación de energía a diferentes órganos de Aulacomya atra del Canal Beagle (Tierra del Fuego). El periodo de desove de A. atra se extendió desde el final del invierno hasta la primavera, cuando el MGI (Índice gónada-manto) resultó mínimo y el número de individuos desovados, máximo. En los machos maduros el incremento del MGI coincidió con un descenso en la densidad energética del manto-gónada (EDMG), lo que está relacionado con un aumento de masa con menor energía. En hembras maduras el incremento de MGI se relaciona con un aumento de masa con valores más altos de energía, que determina el aumento de la EDMG. Durante la maduración gonadal existen diferentes estrategias de asignación de energía en ambos sexos, aunque se alcanza similar contenido de energía en el manto-gónada; los machos mantienen gónadas más grandes, pero con menos energía por unidad de masa que las hembras. Además, en los individuos maduros desciende el valor del índice de la glándula digestiva (DGI), incrementa el MGI, y tiende a la depleción de la ED y del contenido energético, sugiriendo que este órgano actuaría como reservorio de energía. Fil: Pérez, Analía Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Maimónides; Argentina Fil: Boy, Claudia Clementina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Curelovich, Jessica Natalia. Universidad Maimónides; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pérez Barros, Patricia. Universidad Maimónides; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Calcagno, Javier Ángel. Universidad Maimónides; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Munida gregaria and M. subrugosa have been considered two different species for more than a century; however, after a recent molecular phylogenetic study, they are considered a single polymorphic species. Yet, the use of markers to diagnose species may be misleading when divergence between species is recent, since a speciation event may be obscured by the retention and stochastic sorting of ancestral polymorphisms. The morphs gregaria and subrugosa of Munida gregaria constitute an interesting case for the study of behavioural isolation since they are sympatric, breed at the same time of the year, and might have experienced a recent speciation. Mating behaviour observations and mate choice mating trials were conducted in order to investigate the potential existence of a behavioural prezygotic barrier to gene flow between these two morphs. Since factors involved in mate choice in galatheids are unknown, the four possible combinations of the two different morphs in trios were used to test for the existence of mate choice. Video recordings of all the possible trio combinations revealed that there was cross-attraction between males and females of different morphs. Females bearing partial broods participated in encounters as well as non-ovigerous females. The frequency and duration of homo- and heterotypic encounters were registered, and a reproductive isolation index was calculated for each variable for each trio. The isolation indexes calculated were not different from zero indicating random mating, and were not affected by the composition of the trio or the partial ovigerous condition of females. These results provided evidence of the absence of behavioural prezygotic barriers to gene flow between the morphs gregaria and subrugosa of M. gregaria. Fil: Perez Barros, Patricia. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolucion. Ecologia de Organismos Bentonicos Marinos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Calcagno, Javier Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

Munida gregaria and M. subrugosa were originally described as two different species on the basis of several morphological characters, but recent studies evidenced that both former species constitute the same biological species, so hereafter they are referred to as two morphs of M. gregaria: `gregaria' and `subrugosa'. Notwithstanding their synonimization, the occurrence of two sympatric morphs represents an interesting case for the study of the processes involved in the maintenance of these two morphotypes in nature. We hypothesized that the distinct shapes of mouthparts of both morphs may be related to different feeding habits. Adults of M. gregaria, morphs `gregaria' and `subrugosa', were collected in the Beagle Channel by epibenthic trawling during November 2004. The trophic niche of both morphs highly overlapped. Both occupied the same trophic position in the food web of the Beagle Channel, showing the same feeding habits. As predators they fed mainly on crustaceans and algae, and as deposit feeders they ingested particulate organic matter and organisms associated with the superficial layer of the sediment. However, the relative abundance of crustaceans was higher in stomachs of `subrugosa' than in those of `gregaria', a higher proportion of stomachs of `gregaria' contained more algae than in `subrugosa', and a greater frequency of occurrence of unicellular preys was found in the diet of `gregaria'. Despite these differences, this study provided no evidences to support the existence of a trophic polymorphism between morphs of M. gregaria, at least based on the feeding habit of adults. Munida gregaria y M. subrugosa fueron originalmente descritas como especies diferentes, pero estudios recientes evidenciaron que ambas especies constituyen una misma especie biológica, y por tanto son referidas como dos morfos de M. gregaria: `gregaria' y `subrugosa'. A pesar de su reciente sinonimia taxonómica, la ocurrencia en simpatría de dos morfos representa un caso interesante para estudiar los procesos involucrados en el mantenimiento de los mismos en la naturaleza. Nuestra hipótesis es que las diferentes morfologías de los apéndices bucales de ambos morfos pueden estar relacionadas con hábitos alimentarios diferentes. Se capturaron adultos de M. gregaria, morfos `gregaria' y `subrugosa', en el Canal Beagle por medio de lances epibentónicos de arrastre en noviembre de 2004. La superposición dietaria entre los morfos resultó elevada. Ambos ocuparon la misma posición en la trama trófica del Canal Beagle y mostraron los mismos hábitos alimentarios. Como depredadores, se alimentaron principalmente de crustáceos y algas, y como depositívoros ingirieron materia orgánica particulada y organismos unicelulares bentónicos. Sin embargo, la abundancia relativa de crustáceos fue más alta en los estómagos de `subrugosa' que en los de `gregaria', una proporción más alta de estómagos de `gregaria' contenían más algas que los de `subrugosa', y se encontró una mayor frecuencia de ocurrencia de presas unicelulares en la dieta de `gregaria'. No obstante estas diferencias, este estudio no provee evidencias que respalden la existencia de un polimorfismo trófico entre los morfos de M. gregaria, al menos sobre la base del hábito alimentario de los adultos. Fil: Perez Barros, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Romero, Maria Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Calcagno, Javier Angel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina