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Research on Threatened Species


(1) Museo Nacional de Ciencias Naturales (CSIC), (2) Instituto de Acuicultura de Torre de la Sal (IATS-CSIC), (3) Instituto de investigación de la Generalitat de Catalunya (IRTA), Department of Agriculture, Fisheries, Food and the Natural Environment, (4) Universidad Autónoma de Madrid (UAM), (5) Journalist

Scientific progress on the conservation of Patella ferruginea

We are now half way through the time allotted for the FGCSIC’s first Proyectos Cero on Threatened Species. The moment has therefore come to report progress on the species and the work done in coordination and in parallel by all the teams and institutions involved.

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 Our project is a study of the limpet Patella ferruginea (Ribbed Mediterranean Limpet) with the aim of paving the way for the recovery of one of the few Mediterranean species considered to be in danger of extinction. The species is basically limited to a number of isolated locations on the coast of Andalusia and North Africa, and certain enclaves in Corsica and Sardinia. We are now half way through the time allotted for the implementation of the first of the Fundación General del CSIC’s Proyectos Cero projects on threatened species. The time has therefore come to report the progress during this period regarding this species and the work being carried out simultan­eously in coordination by all the teams and institutions involved, namely the Museo Nacional de Ciencias Naturales (MNCN-CSIC), Universidad Autónoma de Madrid (UAM), Instituto de Acuicultura de Torre de la Sal in Castellón (IATS-CSIC) and Generalitat de Catalunya’s Institut de Re-cerca Agro-Alimentária (IR-TA de Sant Caries de la Rápita in Tarragona).

The project’s overall object­ive is to develop working methods and a broad know­ledge base on which to draw in order to base efforts for the recovery of the species. One of the key aims is to obtain juvenile specimens in sufficient numbers using aquaculture techniques (both by recruiting them in artificial collectors and through controlled reproduction), in order to restore populations affected by natural catastrophes or repopulate sites from which the species has recently disappeared. From this general perspective, work is underway in parallel on three main lines, which although they take different approaches (and involve different methods) are complementary and represent different ways of addressing this same common goal. These lines aim to: 1) deepen our understanding of the basic aspects of the biology of the species that are of particular importance for population management and conservation; 2) understand the populations’ genetic structure and extent to which they are connected; and 3) run trials on the production of juveniles for their potential transfer to other zones.

Extraction of sperm for the controlled fertilisation of Patella ferruginea. / Photo: Paola Marin.

Research into techniques for the production of juveniles responds to the recommendations of the “Conservation strategy for the Patella ferruginea limpet in Spain,” published by the Ministry of the Environment, Rural and Marine Affairs, for the transfer of specimens to sites where it is in serious decline or for repopulation in the case of natural disasters (for example, an oil slick), given that this strategy advises against relocating adult specimens. However, in order to repopulate or reintroduce juveniles it is necessary to have a detailed knowledge of the genetic structure of the different natural populations, so as to be able to make the right decisions about the groups of specimens and sites suitable for transfer without altering the species’ genetic make-up. Moreover, it is also essential to acquire the maximum understanding pos­sible of the biology of this limpet species, not only in order to develop basic techniques for the transport, maintenance in controlled conditions, or acclimatisation of specimens, but also for to help manage the species in the natural environment. Significant progress has been made on all these lines of work, giving grounds for optimism about the successful achievement of the proposed objectives, despite the difficulty involved.

In parallel with these scientific and technical aspects, the project is also committed to disseminating the results of its work. A lot of effort is therefore also being put into designing a website and a variety of audiovisual materials on the progress of the research, so as to publicise the interim results and progress of the project.

Juveniles (2-3 mm) obtained at the Instituto de Acuicultura de Torre de la Sal in Castellón (IATS), resulting from a process of controlled reproduction / Photo: Juan B. Peña.

The field –or rather “sea”– work is mainly taking place on the Chafarinas islands, with the support of the staff and facilities of the National Parks Agency on the islands. Research is also being done there on the biology of P ferruginea, focusing particularly on its reproductive biology, its population dynamics, growth rate, recruitment, traffic displacements, and characteristics of its optimal habitat.

One of the aspects receiving most attention on the coast is the way the species reproduces and, specifically, the limpet’s ability to change sex between successive reproductive cycles, together with the factors that influence this process. Patella ferruginea reproduces just once a year. The gonads begin to mature between August and September, and the process completes during the autumn, as the water temperature drops. This culminates in November when, with the arrival of the first big storms, spawning takes place (synchronous release of both male and It has been found that the change in sex over the course of the limpet’s life can take place in both directions, both male to female and female to malefemale gametes into the environment) in a more or less generalised way. The “larvae” resulting from this external fertilisation look for a substrate to attach to after remaining afloat in the plankton for a few days. They then transform into tiny juvenile limpets which will go on to form the next generation of the species.

One of the much debated features of this species to date has been its mode of reproduction. It had been assumed that it was a protoandrous hermaphrodite species, i.e. that young specimens matured as males and then subsequently, after reaching a certain age or size, turned into females. However, our team’s work on the Chafarinas islands has found the species’ reproductive strategy to be much more complex. It has been found to be able to change sex in either direction at any point in its life, i.e. from male to female and vice versa, making its mode of reproduction a form of alternate hermaphroditism. The way this process works, and the factors determining it are still far from clear, and elucidating it is currently one of the objects of our research. In practice, to analyse these issues large sample sizes are needed, and techniques have to be developed taking novel approaches to avoid harming the organisms. The working protocols we are developing to determine specimens’ sex rely on biopsies, which pose little risk to the survival of the analysed limpet. Moreover, following sex changes between annual cycles also requires the identification of each of the spe­cimens using specific marking techniques, and in turn keeping a detailed photographic record of each spe­cimen. Marking also makes it possible to study the species’ growth rate. Our work on the ground is yielding new information about the seasonality of the growth rate, the existence of periods in which the shell erodes faster than it grows, and the high degree of variability between specimens as regards these aspects.

Laboratory work: inducing egg production Instituto de Acuicultura de Torre de la Sal (IATS) by modifying the temperature. / Photo: Javier Guallart.

Another important issue is the study of recruitment of P. ferruginea juveniles, in particular, the analysis of variations from one year to another. Recruitment is understood to mean the annual incorporation of new individuals in populations, and depends to a large extent on the success of the critical phase of the step from pelagic larva in the plankton to a crawling juvenile attached to the rock and its subsequent survival. The data available indicate that in the Chafarinas islands there is significant, albeit irregular, recruitment each year, much higher than that found in other locations, which is an indicator of the excellent state of conservation of the population on these islands. It is worth highlighting that recruitment was exceptional in 2011, possibly the best ever described for the species. Research is now focusing on determining the factors that can influence the variability of the success of recruitment from one year to the next, and the influence this can have on the dynamics of the species on a Young specimens have been obtained from larvae produced in the laboratorylarge scale. For this analysis a collaboration has been launched with a research group at IMEDEA in the Balearic islands, which specialises in modelling oceanographic and physiochemical factors in order to characterise changes in the waters of the Alborán Sea over the long term.

A number of floating collectors have been set up in the waters off the Chafarinas to gather “seeds” from the envir­onment. In aquaculture, “seeds” are juveniles that attach spontaneously to artificial surfaces. Designing the right type of collectors for P ferruginea juveniles to attach spontaneously, with characteristics facilitating the instal­lation of a sufficient number of these structures, would bring obvious advantages in terms of obtaining them. The main benefit would be that the juven­iles obtained, whose final destination would be to be transferred to other geographical zones if needed in an emergency, would present considerable genetic diversity, in line with the genetic mix of gametes that would occur the autumn spawning of the po­pulation of the Chafarinas Islands.

Ventral view of a 2mm-long juvenile obtained by controlled reproduction. / Photo: Javier Guallart.

The work aimed at controlled reproduction to obtain juven­iles of P ferruginea using aquaculture techniques is taking place in parallel and under different conditions at the Castellón and Tarragona centres. This involves developing or fine tuning a heterogeneous variety of techniques to address issues such as how to maintain adults ex situ, inducing egg laying, maximising the fertil­isation of gametes, following larval development, achieving the metamorphosis of swimming larvae until they attach to the substrate as post-larvae, and the subsequent growth of these juveniles under appropriate conditions. It is The specific objectives include obtaining juvenile specimens using aquaculture techniquesworth noting that the results obtained to date on these points have been more than satisfactory. It has been possible to reproduce the entire embryonic and larval cycle under laboratory conditions, and more importantly, juvenile specimens have been obtained from the larvae produced in the laboratory. It is precisely this progression by metamorphosis from larval phase in the water column to crawling juvenile on the substrate that is considered the most critical phase in the development of the life cycle of the species. Having managed to get beyond this phase under artificial conditions is a milestone that augurs well for the success of the project, enabling a methodology to complete the biological cycle and produce juvenile specimens by means of aquaculture techniques to be designed. To do so it is necessary to ensure that these small specimens or recruits survive and grow to sexual maturity.

A third important line of the project is the genetic study of the main populations of P ferruginea. This is being carried out at the Molecular Systematics Laboratory of the Museo Nacional de Ciencias Naturales [National Natural Sciences Museum]. The only genetic work published to date is based on universal molecular markers which, although they allow inferences to be made about the gene flow from the past, do not have sufficient resolution to determine the genetic status of today’s populations and how interconnected they are under current conditions. Our team previously designed specific micro-satellite markers for this species, which will be applied to their main populations, located in the Alboran Sea and the Algerian coast. Sufficient samples are currently available for Ceuta, the Chafarinas islands, and certain points on the coast of Morocco and Tunisia. It is hoped that future surveys will make it possible to complete the samples the study needs with material from Isla de Alborán, Algeria and vari­ous locations on the Andalusian coast.

The members of the research team, from left to right around the table: Marta Calvo, Juan B. Peña, Angel Luque, Eusebio Bonilla, Paola Martín, Josu Pérez, Javier Guallart, José Templado, Iván Acevedo and Annie Machordom. / Photo: MNCN-CSIC. photography service.

Lastly, the Autonomous University of Madrid is taking part in matching the research and results obtained to the recommendations of the “conservation strategy for the Patella ferruginea in Spain” and the precepts of the Law on Natural Heritage and Biodiversity, regarding the species in the Spanish Catalogue of Threatened Species. It is also responsible for preparing and correcting the texts of the various scientific papers and articles for non-specialist audiences.

In short, the results obtained so far have been positive in many respects, although challenges remain. Some of the most important achievements include, firstly, having managed to establish the conditions to adapt juveniles and adults to captivity and, secondly, practic­ally completing the larval development of the species, reaching metamorphosis to the crawling juvenile stage under laboratory conditions. Nevertheless, certain crucial issues still have to be addressed before the controlled reproduction of P ferruginea can be made a reality (i.e. to complete the cycle, in aquaculture terms).

In short, our objective is to establish, by means of a multidisciplinary approach, the theoretical, technical and practical frameworks for the adequate conservation of P ferruginea, so as to minimise its risk of extinction. With effort, ingenuity, and the essential research funding, we will be able to establish favourable conditions for the survival of a little known and undervalued species, which is highly threatened, but which could become a symbol of conservation of marine biodiversity.

Published in No. 09

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  • Lychnos. ISSN: 2171-6463 (Spanish print edition),
    2172-0207 (English print edition), 2174-5102 (online edition)
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