Poliquetos de fondos blandos en el Estrecho de Magallanes capturados durante la campaña oceanográfica italiana en febrero-marzo de 1991

Species composition, distribution and biogeography of polychaetes collected from the soft bottoms of the Straits of Magellan (South America) in February-March 1991 are reported. In 16 benthic samples, collected with different tools (Charcot and triangular dredges, van Veen grab), a total of 1132 individuals belonging to 119 taxa of polychaetes were collected; only 49 of the taxa found have been determined at species level. Eighteen species were recorded for the first time in the Straits of Magellan. Species richness was relatively high considering both the number of individuals collected, and the taxa known from previous studies on the area (182 species). The biogeographical analysis, conducted only on the 49 taxa classified at the species level, showed the dominance of Magellan-Antarctic-Subantarctic species (M-An-S 50%), followed by Magellan-American (M-Am 14%), Magellan-Antarctic (M-An 12%), Magellan-Subantarctic (M-S 6%), Cosmopolitans (C 10%), and also by a few species with disjunct distribution (D 8%). Values of the Sørensen similarity index among stations were very low (below 0.30) with a few exceptions. Both number of species and of individuals were higher in the Atlantic sector of the Straits, especially at some stations characterized by heterogeneous mixed sediments (gravels and pebbles) and biogenic debris (mollusc thanatocoenosis). The high number of species recorded, coupled with low similarity values among stations, suggests that the soft bottoms of the Straits of Magellan show, at medium scale, a highly diversified mosaic of different biotopes. This can be due to various factors which are expected to vary along the wide geographic area investigated, such as the wide bathymetric range sampled, the type of sampling gears used, and last but not least the occurrence of many different environmental situations along the Straits.En el presente trabajo se describen composición específica, distribución y biogeografía de los poliquetos recolectados en los fondos blandos del Estrecho de Magallanes (Sudamérica), durante los meses de febrero y marzo del año 1991. En 16 muestras bentónicas, recogidas con diferentes métodos (dragas Charcot, triangular y van Veen), se encontraron un total de 1132 individuos pertenecientes a 119 taxones de poliquetos. De éstos tan solo 49 han sido determinados a nivel de especie y a su vez 18 han resultado ser nuevas citas para el Estrecho de Magallanes. La riqueza específica encontrada fue relativamente alta, considerando tanto el número de individuos recolectados como los taxones conocidos gracias a estudios previos en el área (182 especies). El análisis biogeográfico, efectuado solamente sobre los taxones clasificados a nivel de especie (49), ha demostrado la dominancia de especies Magallano-Antártico- Subantárticas (M-An-S 50%), seguida por especies Magallano-Americanas (M-Am 14%), Magallano-Antárticas (M-An 12%), Magallano-Subantárticas (M-S 6%), Cosmopolitas (C 10%) y también por especies de distribución disjunta (D 8%). Los valores del índice de similaridad de Sørensen entre estaciones fueron muy bajos (inferiores a 0.3) salvo algunas excepciones. Tanto el número de especies como el número de individuos fueron más elevados en el sector atlántico del Estrecho, particularmente en algunas estaciones caracterizadas por sedimentos heterogéneos de tipo mixto (gravas y guijarros), y restos biogénicos (tanatocenosis de moluscos). El elevado número de especies descrito, combinado con los valores bajos de similaridad entre estaciones, sugieren que los fondos blandos del Estrecho de Magallanes presentan, a media escala, un mosaico altamente diversificado de biotopos diferentes. Esto puede ser debido a varios factores que son responsables de la variación a lo largo de la vasta área geográfica investigada, tales como el amplio rango batimétrico estudiado, el tipo de instrumentación de muestreo, y en último lugar pero no menos destacable, la presencia de muchas situaciones ambientales diferentes a lo largo del Estrech

Unpublished Mediterranean records of marine alien and cryptogenic species

Good datasets of geo-referenced records of alien species are a prerequisite for assessing the spatio-temporal dynamics of biological invasions, their invasive potential, and the magnitude of their impacts. However, with the exception of first records on a country level or wider regions, observations of species presence tend to remain unpublished, buried in scattered repositories or in the personal databases of experts. Through an initiative to collect, harmonize and make such unpublished data for marine alien and cryptogenic species in the Mediterranean Sea available, a large dataset comprising 5376 records was created. It includes records of 239 alien or cryptogenic taxa (192 Animalia, 24 Plantae, 23 Chromista) from 19 countries surrounding the Mediterranean Sea. In terms of records, the most reported Phyla in descending order were Chordata, Mollusca, Chlorophyta, Arthropoda, and Rhodophyta. The most recorded species was Caulerpa cylindracea, followed by Siganus luridus, Magallana sp. (cf. gigas or angulata) and Pterois miles. The dataset includes records from 1972 to 2020, with the highest number of records observed in 2018. Among the records of the dataset, Dictyota acutiloba is a first record for the Mediterranean Sea. Nine first country records are also included: the alga Caulerpa taxifolia var. distichophylla, the cube boxfish Ostracion cubicus, and the cleaner shrimp Urocaridella pulchella from Israel; the sponge Paraleucilla magna from Libya and Slovenia; the lumpfish Cyclopterus lumpus from Cyprus; the bryozoan Celleporaria vermiformis and the polychaetes Prionospio depauperata and Notomastus aberans from Malta

Distribución, diversidad y estacionalidad de los poliquetos en relación al recubrimiento de fanerógamas en fondos blandos litorales del Mar Tirreno (Italia)

Polychaete distribution, diversity and seasonality were studied in relation to covering of the small phanerogams Cymodocea nodosa and Zostera noltii in shallow soft-bottoms off the island of Ischia (Tyrrhenian Sea, Italy). Samples were collected bimonthly from July 1988 to May 1989 from four stations, selected for seagrass meadows of different physiognomy and shoot density, and in a bare sandy bottom nearby, selected as a non-vegetated reference habitat. Two meadow compartments were considered: the leaf stratum and the sediment. A hand-towed net was used to sample vagile organisms living in the leaf stratum, while PVC corers were utilized for the sediment fauna. Stratification within the sediment was studied considering three layers (0-5 cm, 5-10 cm and > 10 cm deep). On the whole a total of 4640 individuals of polychaetes, belonging to 119 species, were collected; 4061 individuals and 115 taxa were found in the core-samples, and 579 individuals and 35 taxa in the net-samples. Polychaete diversity and abundance was higher in both meadow compartments and in all seasons in the station located in the meadow where more sheltered conditions occurred, high silt-clay and organic matter content in the sediment were observed. In addition, this is where higher shoot density, plant Leaf Area Index (LAI) and Leaf Standing Crop (LSC) were recorded. Whereas, lower diversity and higher patchiness (differences among core replicates) were always recorded in the less vegetated stations, and on the bare sandy bottom. The polychaete populations of the sediment layers showed their lowest diversity and abundances in summer. Whereas, the populations associated with the leaf stratum showed an opposite trend with higher development (number of species and individuals) in summer (July-September), consistent with the higher values of all the plant phenological parameters recorded (shoot density, LAI and LSC). In all stations and seasons, the polychaetes were concentrated (84% of the whole abundance) in the upper sediment layer (0-5 cm) and decreased strongly in the deeper sediment layers. Faunistic differences were recorded mainly between the leaf stratum and the sediment populations. The interstitial Syllidae Exogone naidina, Parapionosyllis elegans, Sphaerosyllis thomasi, dominated in the leaf stratum; while endofaunal forms, such as Neanthes caudata, Peresiella clymenoides, Heteromastus filiformis, Notomastus latericeus and Euclymene collaris, dominated at the sediment level. The differences in polychaete community structure observed between the sites studied can be explained by the coupling of abiotic conditions (in particular the reduced hydrodynamics and sediment features) and meadow structure and habitat complexity characterized by plant phenological features (e.g., shoot density, LAI, LSC). The seasonal and microdistributional (sediment and leaf stratum) patterns within each of the meadow stations are influenced by ecology and life history of single species, and probably by the higher predation pressure occurring in some seasons. These results suggest that at least for small-sized and less mobile organisms, like polychaetes generally, meadow structure, shoot density and other phenological plant features influence species composition and abundances both at large (between-meadows) and smaller (within-meadow) spatial scale.Se ha estudiado la distribución, diversidad y estacionalidad de poliquetos en la isla de Ischia (Mar Tirreno, Italia), en relación al recubrimiento de pequeñas matas de Cymodocea nodosa y Zostera noltii. Las muestras se recogieron cada dos meses desde julio de 1988 a mayo de 1989, en praderas con distinta distribución y densidad de matas y en otra estación sin matas como lugar de referencia. Se consideró tanto la fauna de las hojas de las fanerógamas como los sedimentos. La fauna vagil se recolectó mediante una red manejada a mano y el sedimento mediante cores de PVC de los que se consideraron tres estratos (0-5 cm, 5-10 cm, > 10 cm de profundidad). Se recolectaron 4640 individuos pertenecientes a 119 especies (4061 ind. de 115 taxa en los cores y 579 ind. de 35 taxa en las muestras de red). Las mayores densidades y mayor diversidad (tanto en el sedimento como en las hojas como estacionalmente) se observó en las praderas en zonas protegidas de las corrientes, con una mayor relación finos/arenas, contenido de materia orgánica, densidad de plantas, índice de cobertura de hojas (LAI) como el de biomasa de las mismas (LSC). La menor densidad y diversidad de poliquetos se observó en praderas con una menor densidad de matas y zonas más expuestas a las corrientes. La menor densidad de poliquetos en el sustrato arenoso se observó en verano mientras que en las hojas, el verano fué la mejor época. En todas las épocas del año y en todas las zonas prospectadas la densidad de poliquetos fué mayor (84 %) en los primeros 5 cm para decrecer fuertemente hacia los estratos inferiores. Las mayores diferencias faunísticas se observaron entre sedimento y hojas. Los Sílidos intersticiales Exogone naidina, Parapionosyllis elegans, Sphaerosyllis thomasi fueron dominantes en las hojas, mientras que en el sedimento dominaron, Neanthes caudata, Peresiella clymenoides, Heteromastus filiformis, Notomastus latericeus y Euclymene collaris. Las diferencias observadas entre la estructura de las comunidades de poliquetos estudiadas se pueden explicar por factores abióticos (hidrodinamismo y tipo de sedimento) conjuntamente con factores ligados a la heterogeneidad del hábitat debida a la morfología de las praderas. Las variaciones estacionales y las observadas en la microdistribución (entre sedimento y hojas) se explican por los propios ciclos de vida de las especies y por la depredación que reciben en algunas épocas del año. Los resultados obtenidos sugieren que para organismos como los poliquetos, la densidad de las matas de la pradera y sus características morfológicas determinan la densidad y diversidad de especies tanto, a gran escala (entre praderas) como, a pequeña escala (entre matas)

Biología reproductiva de Perkinsiana antarctica (Kinberg) (Polychaeta, Aabellidae) en el estrecho de

Reproductive biology and larval development of the polychaete Perkinsiana Antarctica (Kinberg, 1867) (Sabellidae) are described of a population sampled in October 1994 and March 1997 in the type locality of this species, the Straits of Magellan (Southern Chile). Perkinsiana antarctica is a simultaneous hermaphrodite. Eggs are present in the thorax and in the anterior part of the abdomen, while sperm cells occur in the posterior abdomen. Spermatids are grouped in tetrads; mature sperm cells present an oval nucleus (length of major axis about 3 µm) and the acrosome is about 2.5 µm long with a conoid shape. Mature eggs have a mean diameter of 235 µm; embryos and larvae are incubated within the branchial crown of specimens exceeding 10 mm in length. Hatching larvae have a mean length of 420 µm, with 4 segments, each bearing two notochaeta; two ocular spots and a well-developed prototroch are present at the anterior end. Both number of embryos and larvae per individual showed a relatively high range of variation (embryos from 54 to 374, mean=173; larvae from 18 to 222, mean=101). The features of reproductive biology in P. antarctica do not seem to be related to the size of the species itself, as P. antarctica represents one of the largest-sized sabellids that are brooding eggs, and producing a relatively high number of offspring. These reproductive and developmental traits seem more related to the colonization of harsh and selective habitats, such as the intertidal and shallow subtidal of the Subantarctic areas. Comparisons with the reproductive biology of other species of Perkinsiana demonstrate a high degree of variability within the genus regarding reproduction and the apparent lack of synapomorphies.Se describe la biología reproductiva y el desarrollo larvario del poliqueto Perkinsiana antarctica (Kinberg, 1867) (Sabellidae) en una población muestreada en octubre de 1994 y marzo de 1997 en su lugar tipo, el Estrecho de Magallanes (Chile meridional). P. antartica es un hermafrodita simultáneo. Los huevos se sitúan en el tórax y en la zona anterior del abdomen, mientras que las células espermáticas se encuentran en la parte posterior de éste. Las espermátidas están agrupadas en tetradas; las células espermáticas maduras presentan un núcleo oval (longitud del eje mayor aproximadamente de 3 µm) y un acrosoma de forma cónica con una longitud cercana a los 2,5 µm. Los huevos maduros poseen un diámetro de 235 µm; para aquellos individuos que superan los 10 mm de longitud los embriones y las larvas se incuban en el interior de la corona branquial. El primer estadio larvario presenta larvas de cuatro segmentos con una longitud media de 420 µm, cada segmento presenta dos notosedas; en el extremo anterior se encuentran presentes dos manchas oculares y una bien desarrollada prototroca. El número de embriones y larvas muestran un amplio rango de variación (embriones desde 54 a 374, media= 173; larvas desde 18 a 222, media=101). Las características de la biología reproductiva de P. antartica parecen no relacionarse con la talla intrínseca de la especie, ya que ésta posee una de las mayores tallas dentro del grupo de los sabélidos que incuban los huevos, y produce un número de descendientes relativamente alto. Estas características parecen más bien relacionarse con la colonización de hábitats muy extremos y selectivos, como por ejemplo el intermareal y submareal poco profundo de las áreas subantárticas. La comparación de la biología reproductiva de esta especie con otras del genero Perkinsiana demuestra un alto grado de variación dentro del género y una falta de synapomorfias

Posidonia bonsai: Dwarf Posidonia oceanica shoots associated to hydrothemal vent systems (Panarea Island, Italy)

[EN] Very small-sized shoots of the Mediterranean seagrass Posidonia oceanica, defined as “bonsai” shoots, were found in areas with most intense CO2 emissions and low pH associated with four vents systems off Panarea island (Aeolian Archipelago, Sicily, Southern Tyrrhenian Sea). Bonsai shoots were sampled in September 2021 and October 2022: Bottaro crater (8 m depth), Camp 7 (16 m and 21 m), Black Point (20 m) and Hot/Cold Points (10 m). They had 2–6 leaves, and adult-intermediate leaves were 5–21 cm long and 3.5–7 mm wide, with leaf shoot surface ranging 4.8 and 44.5 cm2, and shoot leaf biomass between 16 and 89 mg (d.w.). These values were all significantly lower (t-test p < 0.006–0.0001) than those measured in normal-sized shoots collected within the vents and in control sites not affected by gas emissions. Bonsai shoots had 86–89% lower leaf surface, and 61–75% lower leaf biomass than all normal-sized shoots measured. The sheath thickness of the bonsai shoots was very low (0.1–0.8 mm), and the temporal trend of sheath thickness along the rhizome (lepidochronology) showed an irregular pattern, without the clear cyclical seasonal variation typical of normal-sized shoots. The reasons of size reduction and lack of temporal cycle in lepidochronology are discussed in the light of plant acclimatization and the constraints imposed by the continuous exposure to the stressful conditions of seawater acidification and presence of phytotoxic gases (e.g. hydrogen sulfide) in the vents.We wish to thank the staff of the 5th and 6th School of scientific diving at Panarea (2021–2022) and the 2nd stage on Posidonia oceanica ecology at Salina (2022; founded by the Blue Marine Foundation), as well as the diving Amphibia coordinated by Andrea Fogliuzzi, for the support at sea and in the laboratory. Thanks to the ECCSEL NatLab Italy infrastructure of the OGS for the logistic support at Panarea. We wish to thank the anonymous reviewers, and the Editor B. van Tussenbroek, for the useful and constructive comments.Peer reviewe

FIGURE 1. Line drawings. A in Notes on the species of Perkinsiana (Polychaeta: Sabellidae) from Antarctica with the description of P. brigittae sp. nov.

FIGURE 1. Line drawings. A) Abdominal chaeta type A, B) abdominal chaeta type B, C) abdominal chaeta type C, D) collar and anterior thorax, dorsal view, E) same, ventral view, F) same, lateral view, G) posterior abdomen, H–I) dorsal and ventral lips, J) thoracic uncinus, K–L) abdominal uncini, M–O) companion chaetae, P) thoracic narrowly-hooded chaeta, Q) thoracic paleate chaeta, R) abdominal narrowly-hooded chaeta. A–C) redrawn from Fitzhugh (1989), D–R) Perkinsiana brigittae sp. nov. Holotype (D–G, J–R). Paratype (H–I). Scale bars: A–C (not scaled); D–I (1 mm); J–R (20 µm). Abbreviations: (apr) anterior peristomial ring, (dl) dorsal lip, (ll) lateral lamella, (mr) mid-rib, (vl) ventral lip

Extreme pH Conditions at a Natural CO2 Vent System (Italy) Affect Growth, and Survival of Juvenile Pen Shells (Pinna nobilis)

© 2015, Coastal and Estuarine Research Federation. Predicted pH decreases in ocean surface waters of ~0.3–0.5 and 0.7–0.8 pH units (for 2100 and 2300, respectively) are expected to negatively affect calcification processes and physiological performances of many marine organisms. Here we evaluated the response of important parameters such as growth, mortality, oxygen consumption, and mineralization of transplanted Pinna nobilis juveniles in the naturally acidified waters of a CO2 vent system. Our field experiments show a general decrease of physiological responses of juveniles for the studied parameters along a decreasing pH gradient, even if significant effects are only observed under pH values of 7.6 units (“extreme” pH). In particular, the mortality rate increased from 10–30 % over the study period at control conditions to 60–70 % at extreme pH values. We conclude that near-future decreases in pH (decreases of 0.3–0.5 pH units) may not have a significant effect on performance of P. nobilis juveniles, while predicted longer-term decreases (decreases of 0.7–0.8 pH units) could affect the survival of the species. The combination of laboratory experiments with the assessment of naturally acidified environments can provide further insights into the threshold pH affecting the performance of vulnerable marine species.This research was supported by the MedSeA project (www.medsea-project.eu, contract number 265103 of the Framework Program 7 of the European Union), and ESTRESX (ref. CTM2012-32603), funded by the Spanish Ministry of Economy and Competitiveness. L.B. was supported by JAE pre-DOC fellowship and I.E.H. by a JAE-DOC fellowship (CSIC, Spain)Peer Reviewe

Quantitative analysis of soft-bottom polychaetes of the Bellingshausen Sea and Gerlache Strait (Antarctica)

The basin off the Bellingshausen Sea, in contrast to other better known areas such as the Antarctic Peninsula and the Ross and Weddell Seas, has been little investigated due to remoteness and the prevalence of ice for most of the year. The present study focuses on an analysis of polychaetes collected from soft bottoms of this sea and off the west coast of the Antarctic Peninsula (Gerlache Strait) by means of a box-corer (25 × 25 cm) in two intensive surveys carried out during austral summers of 2002–2003 and 2005–2006 (BENTART-03 and BENTART-06). Three different polychaete assemblages were determined from the classification and ordination analyses of sampling stations based on the Bray-Curtis similarity index. One group of stations encompassed the deep stations from the shelf of the Bellingshausen Sea, the second one the shallower stations from the same area and the third one those stations located near the coast of Peter I Island and Gerlache Strait, off the Antarctic Peninsula. The environmental variables involved in segregating these groups were several sedimentary features (redox potential, gravel content) and depth. The present study provides further support to previous ones that considered the shelf of the Bellingshausen Sea as a differentiated region within the Southern Ocean, clearly distinct to the adjacent Weddell and Scott Seas and the Antarctic Peninsula.Publicado