Two new species and a new genus of Calloporidae (Bryozoa: Cheilostomata) from the Southwest Atlantic

The family Calloporidae occupies a basal position in the classification of the Cheilostomata, the relatively simple callop- orid morphology seeming to be the basic pattern for the adaptive radiation of cheilostome bryozoans. The ovicells of the Calloporidae may be formed by the maternal zooid or the distal zooid, which can be an autozooid, a vicarious avicularium or a kenozooid. Examination of new calloporid material from the southern Patagonian shelf revealed the existence of two new species and a new genus. Kenoaplousina fissurata gen. nov., sp. nov. is characterized by its distinctive kenozooidal ooecium. The new genus is also deemed to include Aplousina grandipora Moyano, an allied species from the Chilean con- tinental slope. Alderina simplicissima sp. nov., is also described from the Magellanic region.Fil: López Gappa, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; ArgentinaFil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentin

Ecología y taxonomía de briozoos del Mar Argentino

En el ambiente acuático, todas las superficies sólidas representan posibles sitios de asentamiento para los organismos sésiles. Los sustratos duros suelen ser un factor limitante y su escasez regula la abundancia de muchas especies en ambientes que podrían serles favorables. Las algas marinas también suelen ser un sustrato adecuado para muchos epibiontes (especies asentadas sobre otros organismos) y en particular para los briozoos. En los últimos tiempos, el incremento en el número de descripciones de nuevas especies evidencia lo lejos que se está de conocer completamente la biodiversidad existente. También es importante entender los factores que determinan los límites geográficos de distribución de las especies, ya que éstos permiten analizar problemas ecológicos, evolutivos y de conservación.Fil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Algae as hosts for epifaunal bryozoans: Role of functional groups and taxonomic relatedness

Macroalgae build biogenic habitats which give shelter and provide a suitable physical environment for a great variety of organisms. Structural complexity of algal substrates may influence the composition of their attached epifauna. The aim of this study is to test whether the taxonomic relatedness of the algal hosts and the functional groups to which they belong influence the species richness and composition of their epifaunal bryozoans. We analysed 36 algal genera from the Atlantic coast of South America between 42°S and Cape Horn. Changes in bryozoan species richness (number of species) among different algal functional groups (filamentous algae, foliose algae, corticated foliose algae, corticated macrophytes) were non-significant. The composition of the epifaunal assemblages differed significantly only between filamentous and foliose algae. Sheet-like bryozoans (i.e. encrusting, pluriserial colonies) were more frequent on foliose than on filamentous algae, while runner-like species (i.e. uniserial stolons) were characteristic epibionts on filamentous thallii. Similarity of bryozoan assemblages increased with increasing taxonomic relatedness of their hosts. As most filamentous seaweeds analysed in this study are members of the Order Ceramiales, the influence of algal taxonomic relatedness and functional groups on the composition of their bryozoan assemblages can be viewed as two different aspects of the same phenomenon.Fil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentin

Macrofaunal assemblages associated with coralline turf: Species turnover and changes in structure at different spatial scales

Our aim was to analyse changes in species turnover and structure of macrofaunal assemblages associated with intertidal coralline algal turfs at 4 spatial scales along the coast of Argentina (southwestern Atlantic): provinces (∼106 m), localities (∼104 m), sites (∼10 2 m) and replicate quadrats (∼1 to 3 m). Corallina officinalis was by far the dominant algal species in most samples, but C. elongata and Jania rubens var. rubens were also frequent. Frond density was 3 times higher in the southern, cold-temperate Chubut province than in the northern, warm-temperate Buenos Aires province. Macrofaunal species richness, diversity and evenness were also significantly higher in samples from Chubut than in those from Buenos Aires, with 'province' explaining 86 to 98% of the variance in the analytical model. In total, 118 macrofaunal taxa belonging to 11 invertebrate phyla were found. Mytilid bivalves and polychaetes were the most important groups contributing to differences between provinces. Brachidontes roddguezii was extremely abundant in Buenos Aires province, while Rhynchospio glutaea and Perumytilus purpuratus were dominant in samples from Chubut. Changes in assemblage structure were significant at the scale of provinces, localities and sites in Patagonian localities. Measures of beta diversity showed that taxonomic turnover was correlated with distance between samples at scales of 10 4 m or higher, with the highest at the scale of provinces. Higher biodiversity in the Magellan assemblage than in warmer areas of the northern coast of Argentina may be related to the Pacific origin of the Magellan fauna, which entered the southwestern Atlantic during the Tertiary period.Fil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Egg-hull ultrastructure of Ischnochiton stramineus (Sowerby, 1832), a South American brooding chiton (Chitonina: Ischnochitonidae)

Se describe la ultraestructura de los huevos de Ischnochiton stramineus, una especie incubadora de América del Sur. Los huevos fueron hallados en los surcos paleales, donde se encuentran agrupados en masas de hasta 1.600 huevos. Los huevos están  redeados por una serie de placas perforadas, que presentan en su parte central una proyección enrulada. Se discute la morfología de estas cubiertas de los huevos, en el contexto de las presentes en otras especies de poliplacóforos incubadores.Fil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; ArgentinaFil: Zelaya, Diego Gabriel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

High density of the alien bryozoan Fenestrulina delicia in the fouling assemblage of a South American harbour (Argentina)

The non-indigenous cheilostome bryozoan Fenestrulina delicia Winston, Hayward and Craig has been recorded for the first time in the southern hemisphere. It was found on experimental substrata submersed to study the fouling assemblage of Quequén Harbour (Argentina, southwest Atlantic), an estuarine environment. Its density on experimental panels was very high, reaching almost 5,000 colonies.m−2. The percentage of ovicellate colonies, however, was relatively low (mean ± SD: 5.2 ± 2.3 %, range: 1.6 – 9.9 %) due to the abundance of newly recruited zoaria. F. delicia was originally described for the Atlantic coast of the United States. It was later discovered in Alaska, Oregon and California, and has recently been reported as a highly invasive fouler along the Atlantic coasts of Europe. This species seems to have the potential to continue its dispersion by means of maritime traffic, or rafting on plastic debris, and become a stable component of this and neighbouring harbours in the area.Fil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

A new Antarctic Osthimosia (Bryozoa, Cheilostomata, Celleporidae) with dimorphic zooids

Osthimosia chaotica sp. nov., a new celleporid cheilostome bryozoan, is described from samples collected in the South Shetland Isles and the Antarctic Peninsula. It differs from other Antarctic and Subantarctic species of the genus Osthimosia in the absence of vicarious avicularia, the characteristic development of its peristome and the reduced size of the primary orifice of the ovicelled zooids compared to those of autozooids. The occurrence of sexual polymorphism in the Bryozoa is discussed. The new species lives on laminar and filamentous algae.Fil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

An unusual symbiotic relationship between a cyclostome bryozoan and a thecate hydroid

Previous examples of symbiotic associations between bryozoans and hydrozoans mainly involve cheilostome bryozoans and athecate hydroids belonging to the Family Zancleidae, in which only the hydrorhizal stolons become covered by a calcareous layer secreted by the bryozoan. The aim of this study is to describe an unusual symbiotic relationship between the cyclostome bryozoan Disporella densiporoides and the stolonal thecate hydroid Filellum bouvetensis (Family Lafoeidae) from Isla de los Estados, Southwest Atlantic. We found more than 120 chimney-like calcareous tubes covering most of the hydrozoan symbiont produced by only one bryozoan colony. Similar chimney-like tubes built by other cyclostome bryozoans have been attributed to the association with sedentary polychaetes or mistakenly interpreted as an ooeciostome, i.e. the aperture of a bryozoan reproductive polymorph. This is the first example of a symbiotic relationship in which most of the hydrozoan colony becomes covered by the bryozoan skeleton. The brood-chamber of D. densiporoides, previously unknown, is described and illustrated.Fil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

The distribution of colonies of the bryozoan Antarctothoa bougainvillei on the red alga Hymenena laciniata

The cheilostome bryozoan Antarctothoa bougainvillei (d'Orbigny) is the most frequent epibiont on the ribbon-like red alga Hymenena laciniata (Hooker f. & Harvey) Kylin in San Sebastián Bay (Tierra del Fuego, Argentina). Twenty-one thalli and 1,484 colonies were examined to analyse the relationship between both species. In most cases, number and area of colonies did not differ significantly at both sides of the thallus. Ancestrulae (i.e., founder zooids originating colonies by asexual budding) were mostly oriented facing the algal growing edge. Colonies were more frequent on central than on marginal zones of the thalli. The population of A. bougainvillei was mainly composed of very small colonies (<10 mm2). Larger colonies predominated and intraspecific competition was more intense near the basal portions of the thalli. Fecundity (number of ovicells) increased at a significantly higher rate in colonies with margins obstructed by conspecific neighbours than in free-growing colonies. Colonies were significantly larger on somatic than on reproductive algal tissues. As total and reproductive surfaces covered by colonies of A. bougainvillei were on average very low (4.43% and 0.53%, respectively), this epibiont is not supposed to produce a negative effect on H. laciniata.Fil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Recent discovery of non-indigenous bryozoans in the fouling assemblage of Quequén Harbour (Argentina, Southwest Atlantic)

The non-indigenous bryozoans Aspidelectra melolontha (Landsborough) and Amathia verticillata (Delle Chiaje) (= Zoobotryon verticillatum) are recorded for the first time in Argentina. They were found on experimental substrata submerged to study the fouling assemblage of Quequén Harbour (38°34.310′S, 58°42.814′W), an estuarine environment. Biflustra puelcha (d?Orbigny) comb. nov., Conopeum reticulum (Linnaeus), Conopeum seurati (Canu), Cryptosula pallasiana (Moll), Electra monostachys (Busk) and Schizoporella cf. errata (Waters) were also found in this association. Aspidelectra melolontha, a species native to Europe with only one record for San Francisco Bay (United States) based on unpublished data, is here reported for the first time for South America, and the affinity between this species and A. zhoushanica (Wang) is discussed. The presence of C. seurati in brackish water habitats of Argentina is confirmed. B. puelcha was previously unknown as a fouler in harbours. A. verticillata is a well-known marine fouler in many harbours and marinas worldwide. The southernmost record of this species on the Atlantic coast of South America was in Brazil. Thus, its distribution is herein expanded by 14° of latitude towards the south. In view of its great invasive potential, A. verticillata seems to have the ability to continue its dispersal and to become a stable component of this and neighbouring harbours.Fil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Liuzzi, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin