ChallenGen at the 2017 mid-year meeting of The Crustacean Society (TCS)

by Enrique Macpherson

Enrique Macpherson, Marta Pascual and Ferran Palero were members of the Organising Committee of the 2017 mid-year meeting of The Crustacean Society (TCS), of which EM was also the chair.

The meeting was organized by the Spanish Research Council (CSIC) and University of Barcelona (UB) and took place in Cosmocaixa, Barcelona, Spain, from 19th to 22nd June 2017. A total of 211 scientists from 34 countries attended the meeting. This symposium, with already some decades of existence, has given particular emphasis to the areas historically covered by the TCS meetings (ecology, fisheries, larvae, taxonomy, among many others topics). The meeting also included the “11th Colloquium Crustacea Decapoda Mediterranea” and the “5th Crustacean Larval Conference”.

The congress has been organized with parallel oral sessions and poster exhibitions, and included several invited plenary lectures made by world renowned crustacean researchers. Members of ChallenGen contributed with two oral presentations and ten posters (see Publications and Outreach: Conferences).

New paper published: Genetic diversity and demography of the red starfish

A beautiful specimen of the red starfish Echinaster sepositus.

by Alex Garcia-Cisneros

One of the most wonderful starfish of the Mediterranean suffered a large demographic expansion since the last maximum glacial period. However, its demographic expansion does not prevent it to have a weakness point: a low genetic diversity that might indicate the vulnerability of the species. These and more results were recently published by the ChallenGen team in a manuscript entitled “Low genetic diversity and demographic expansion in the red starfish Echinaster sepositus (Retzius 1816)” at the Scientific Reports.

The authors used both mitochondrial and nuclear markers to resolve the phylogeography and population genetics of the commonly named “red starfish” (Echinaster sepositus). The authors analysed samples from most of the distribution range of the species, with 15 localities distributed between both Mediterranean basins and the Atlantic Ocean.

Besides to demonstrate the low genetic diversity of the species compared with other echinoderms, the species showed a weak genetic structure within marine basins despite the a priori low dispersal potential of its lecithotrophic larva. The lecithotrophic larva in this species does not live more than few days before the settlement and therefore, it makes it difficult to connect distant or isolated populations. Furthermore, we found sharp differences in two Mediterranean localities, Cartagena and Livorno, that are located close to large marine harbours and coastal areas affected by industry, although our experimental design does not allow us to assess the effects of pollutants on the genetic structure.

Bar plots of the Bayesian clustering analysis obtained using STRUCTURE for different K values and based on the combination of both mitochondrial sequences (COI) and microsatellite loci.

Crossing Borders: Temporal genetic differentiation over oceanographic fronts

by Ferran Palero

A new paper from the CHALLENGEN team entitled “Temporal and spatial genetic differentiation in the crab Liocarcinus depurator across the Atlantic-Mediterranean transition” has been recently published in the JCR journal Scientific Reports.

Median joining haplotype network. Each circle represents a haplotype and its size is proportional to its frequency. Location acronyms are DELT (Delta de l’Ebre), VALE (València), ALAC (Alacant), WALB (Málaga) CADI (Cádiz).

Proportion of individuals assigned to the MED haplogroup in each location and sampled year from 1000 pseudoreplicates.

Spatial genetic studies often require sampling broadly separated areas, difficult to access simultaneously. Although comparing localities surveyed at different time periods might result in spurious genetic differentiation, there is a general believe on the stability of genetic structure through time, particularly if sampled localities are isolated or very distant. However, should we really expect stable genetic patterns in marine species? To test this important question, Marta Pascual and collaborators have assessed the time-variation of phylogeography patterns of the portunid crab Liocarcinus depurator across the Atlantic-Mediterranean transition. A partial fragment of the cytochrome oxidase I gene was sequenced in 366 individuals collected during three time periods from localities at both sides of each of the three main oceanographic discontinuities in the area: Gibraltar Strait, Almeria-Oran Front and Ibiza Channel. Although localities showed genetic fluctuations through time, a significant gradient was detected along the coast for all sampling periods. Significant inter-annual differences identified within the Alicante area, north of the Almeria-Oran Front, were associated with shifts in the relative contribution of Atlantic and Mediterranean water masses. The authors conclude that the persistence of a clinal pattern in the Atlantic-Mediterranean transition area despite local fluctuations suggests a complex balance of dispersal and selection.

Despite the Alicante population from 2007 had a larger proportion of Atlantic haplotypes, an overall genetic cline remains stable across the 3-year sampling period.

ChallenGen Project and CEAB at the XIV Firamar

by Maria Casso

Last weekend, the 20th-21st July, the Centre for Advanced Studies of Blanes (CEAB - CSIC) participated at the XIV Firamar of Sant Pol de Mar. The Firamar is a fair of artisans and activities related to the sea, like many research projects developed at the CEAB. Our ChallenGen Project, which is developed partially at the CEAB, got involved in the event.

As a member of the ChallenGen Project and the CEAB, I stayed in our stand at the fair during Saturday afternoon, explaining the work researchers conduct at the CEAB about invasive species, climate change, conservation, ecology and biodiversity. It was really nice to see how interested are many people on our job!

The stand of the CEAB at the Firamar, with some visitors during Saturday afternoon. Children could paint their own real balloon fish!

Monitoring ascidians in the Venetian Lagoon

by Maria Casso

A wood pile dolphin, full of benthic organisms, and half eaten by wood-boring species.

Marco and the fog during the sampling.

The Benthic Ecology research group from the Istituto di Scienze Marina, ISMAR (Consiglio Nazionale delle Ricerche, CNR), placed in the Venetian Lagoon, is hosting me for a 3 months research stay. They focuses on ecology of coastal transitional ecosystems, specially benthic communities. More recently, they are interested on wood-boring marine organisms (shipworms and gribbles). This is very important in a place like the Venetian Lagoon as it has a large wooden maritime cultural heritage.

The aim of my stay in Venice is to study the invasive ascidians, which grow on top of those wooden marine structures. To do this, yesterday we went to a field trip around the Venetian Lagoon with Davide Tagliapietra, Marco Sigovini and Irene Guarneri. It was foggy in the beginning but more sunny at the end of the sampling. The objective of the field trip was to determine the distribution of some invasive ascidians and to collect samples for aquaria experiments.

New paper published

by Xavier Turon

New paper published in Frontiers in Zoology: “Feeding cessation alters host morphology and bacterial communities in the ascidian Pseudodistoma crucigaster”, by Susanna López-Legentil, Xavier Turon and Patrick M. Erwin.

This article is the result of yet another collaboration between the projects ChallenGen and MarSymbiOmics. We have coupled electron microscopy and 16S rRNA gene tag pyrosequencing to investigate the bacterial communities associated with the colonial ascidian Pseudodistoma crucigaster, a species endemic to the Mediterranean Sea that has a life cycle with two phases: actively-filtering (active) and non-filtering (resting) forms.

Active (A) and resting (B) colonies of Pseudodistoma crucigaster. The active form has functional siphonal apertures for filtering water, while the resistance form has all apertures sealed by a glassy cuticle.

Resting colonies exhibited a reduced branchial sac (feeding apparatus) and a thickened cuticle. Electron microscope images also suggested higher abundance of colonizing microorganisms on surfaces of resting colonies. Accordingly, bacterial sequences associated with environmental sources (sediment and biofilms, >99 % similarity) were detected exclusively in resting colonies. Bacterial communities of P. crucigaster colonies (active and resting) were dominated by 3 core taxa affiliated (>94 % similarity) with previously described symbiotic Alphaproteobacteria in marine invertebrates. Shifts in rare bacteria were detected when ascidians entered the resting phase, including the appearance of strictly anaerobic lineages and nitrifying bacterial guilds.

These findings suggest that physical (thickened cuticle) and metabolic (feeding cessation) changes in host ascidians have cascading effects on associated bacteria, where modified oxygen concentrations and chemical substrates for microbial metabolism may create anaerobic microhabitats and promote colonization by environmental microorganisms.

Network of bacterial OTUs in three active and three resting samples of Pseudodistoma crucigaster, with edges coded by specificity.