Effects of the parasitic pea crab Afropinnotheres monodi Manning, 1993, on commercial bivalve species of the Iberian Peninsula: results of the AFROBIV project.
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1
Institute of Marine Sciences of Andalusia (ICMAN), Spain
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2
University of Málaga, Spain
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3
Andalusian Institute for Research and Training in Agriculture, Fisheries, Food and Ecological Production (IFAPA), Spain
Afropinnotheres monodi Manning, 1993 is one of the many African crustaceans that have been recorded on the coasts of the Iberian Peninsula. This crab belongs to the Pinnotheridae, a family that comprises 303 species of small marine brachyuran decapods. Pinnotherids live as symbionts in other invertebrates, very often in the paleal cavity of bivalve molluscs. The main objective of this project has been to determine the effect of A. monodi on bivalves of commercial interest in the Iberian Peninsula, especially mussels (Mytilus galloprovincialis) and cockles (Cerastoderma spp.), which are the two species presenting the highest degree of infestation by this crab. In this study the distribution of A. monodi has been researched in the Gulf of Cádiz, and beyond its known limits (the south of Portugal and Strait of Gibraltar) to monitor its process of geographic expansion. Relevant aspects of its biology, that affect its reproductive success and dispersive capacity, have been also studied experimentally in order to predict the potential evolution of this species in the Iberian Peninsula.
The current limits of the distribution of A. monodi have been determined by analysing samples from 69 localities between Gijón (Atlantic) and Sant Carles de la Ràpita (Mediterranean). Its current distribution in the Atlantic extends to the town of Cascais (Portugal), and in the Mediterranean, to the Caleta de Vélez (Spain). In parallel, the current distributions of three native pinnotherid species (Nepinnotheres pinnotheres, Pinnotheres pectunculi, and Pinnotheres pisum) on the coasts of the Iberian Peninsula have been updated. The information obtained has enabled confirmation of the distribution and hosts of several species, and the extension of their distribution of others. For each of the five European species of pinnotherids (including A. monodi and the recently-found new species Pinnotheres bicristatus), sequences of three genetic markers (16S, Cox1, and H3) have also been obtained, both to improve the accuracy in the identification of these crabs and to detect possible new species. To determine the optimal values and the limits within which A. monodi can lives (respect to water temperature and salinity), experiments have been carried out in thermo-regulated culture chambers, at 5, 10, 15, 20, 25 and 30 °C, in both the larval (mobile) and adult (symbiont) phases. The complete development of larvae was successfully completed at 20 and 25 °C, but the highest rate of survival until the megalopa was observed at 25 °C. In a second experiment at 25 °C (optimal temperature), when larvae were cultured at salinities of 15, 25, 36 and 45, the maximum survival until reaching the megalopa phase occurred at a salinity of 25. In the case of adults, the results showed that all the demographic categories (males, hard females and soft females) can survive at the 6 temperatures tested except for the lowest temperature (5 °C). In addition, survival after 42 days of culture was always high (98.8% at 15 °C, 100% at 20 °C, 88.5% at 25 °C and 91.2% at 30 °C), except at 10 °C (survival of 69.4%). To estimate experimentally the effect of temperature on the fecundity of this species, ovigerous females were cultured at the 4 temperatures at which survival was high (> 88%). The effective fecundity decreases gradually as the temperature increases between 15 (95.94%) and 30 °C (3.23%).
Finally, field samplings were carried out to estimate the degree of infestation and the condition index of A. monodi hosts. The bivalve target species, M. galloprovincialis and Cerastoderma edule, are of commercial interest for mussel and shellfish farming, and they have been sampled in three natural beds of the Gulf of Cádiz: Bay of Cádiz, and Carreras and Piedras river estuaries. The average prevalence of A. monodi infestation in cockles ranged from 4.0% in the Bay of Cádiz to 51.4% in the Carreras estuary; in the case of mussels, from 30.5% in the Bay of Cádiz to 45.4% in the Carreras estuary. In bivalves infested by A. monodi, we have estimated a condition index reduction of around 15% in the case of mussels, and of 3% in the case of cockles. In general, these studies demonstrate an energy disadvantage in infested mussels (with respect to non-infested mussels), suggesting that this infestation would cause negative commercial effects in the bivalve aquaculture.
The habitat of the Andalusian populations of A. monodi coincides with those found at the Galician rias, where the most important mussel production in Europe is developed. In the case of a future infestation of this area, this parasitic crab could cause economic losses in the mussel raft cultures. For the moment, mussels infested by A. monodi have never been found in the Andalusian culture facilities. However, we found A. monodi in intertidal mussels less than 5 mm in length. Mussels of these sizes can be transported to be used as seeds in culture facilities; it could be dangerous practice since infested mussel-seeds may contaminate previously unaffected sites.
Currently, there is not enough evidence to consider this species as invasive; however, since it is not known how it has reached peninsular waters, it would be advisable to catalogue it as an allochthonous species. The thermal limits of survival of this African pinnotherid indicate its possible establishment in Galician rias, areas of special relevance for mussel farming. From this study, it has become clear that A. monodi is a parasitic species for the bivalves that infests, especially in the case of mussels, and that the species is currently in a period of expansion along the coasts of the Iberian Peninsula.
Keywords:
pea crab,
Mussel (Mytilus galloprovincialis),
Cerastoderma edule,
Aquaculture,
Parasitism
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Poster Presentation
Topic:
Global Change, Invasive Species and Conservation
Citation:
Cuesta
JA,
Perez-Miguel
M,
García Raso
JE,
Navas
JI and
Drake
P
(2019). Effects of the parasitic pea crab Afropinnotheres monodi Manning, 1993, on commercial bivalve species of the Iberian Peninsula: results of the AFROBIV project..
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00103
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Received:
14 May 2019;
Published Online:
27 Sep 2019.
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Correspondence:
Dr. Jose A Cuesta, Institute of Marine Sciences of Andalusia (ICMAN), Puerto Real, Spain, jose.cuesta@icman.csic.es