Home selection and regular welcome (and not so much) guests in Iberian Hermit Crabs
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1
Oceanographic Center of Vigo, Spanish Institute of Oceanography, Spain
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2
University of Cádiz, Spain
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3
Grupo de Estudo do Medio Mariño (GEMM), Spain
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4
Oceanographic Center of Cádiz, Spanish Institute of Oceanography, Spain
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5
University of Málaga, Spain
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6
Institute of Marine Sciences of Andalusia (ICMAN), Spain
Hermit crabs, known as paguroids, are relatively common along the shores of the Iberian Peninsula. They are easily recognizable due to their peculiar characters, as the soft twisted abdomen, usually protected inside a gastropod shell, although some species can use also sponges, bivalves, scaphopoda shells and even polychaeta tubes, among other objects. In other cases, they can also establish symbiotic relationships with a variety of Anthozoa species who serve as a refuge for them. By using of a wide range of objects and organisms to protect their body, hermit crabs create an optimal moving substrate for the settlement of other organisms, both on the outside of the shells and inside them.
In recent years, some interesting research about this matter has been released, increasing to a large extent, the knowledge about this interesting biological feature on hermit crabs, describing up to 550 symbiotic species of marine invertebrates permanently or temporarily associated with paguroids (Williams and McDermott, 2004, McDermott, 2010). However, there is very little information about these relations within the Iberian Peninsula framework.
As part of an ongoing taxonomic revision of the hermit crabs of the Iberian Peninsula, information on the associations they establish with other organisms is being collected. Samples included in this study, come from direct sampling by scuba diving mainly along the coasts of Galicia and Andalucía.
Fourteen species belonging to 6 different Phyla have been identified so far as frequent associates of at least 9 hermit crab species within the Iberian shores. The purpose of this work is to review the available information on the habitual tenants of the Iberian species of hermit crabs, adding new data obtained during this preliminary work, serving as a start point, baseline, for future revisions.
Two species of sponges are commonly found in Iberian waters associated with at least three different species of hermit crabs. Suberites domuncula (Olivi, 1792), is frequently found covering the shells occupied by Pagurus cuanensis and P. bernhardus, while Suberites pagurorum Solé-Cava & Thorpe, 1986, has been found associated with a wide range of species in other areas, although just two species have been registered as hosts in Iberian waters so far, P. cuanensis and Anapagurus hyndmanni. Both sponges are first records for Galicia.
The hydrozoan Hydractinia echinata (Fleming, 1828), build colonies over shells of hermit crabs on regular bases; although it can be found also on rocks, this behavior is by far less frequent. Polyps are disposed covering all the shell but tend to be placed in higher densities near the aperture of the shell. It doesn’t seem to show a great specificity regarding the species of hermit crab, although it can be found frequently associated with P. bernhardus. Due to the presence of the hydrozoa on the shell, the sea slug Cuthona nana has also been recorded feeding on them, temporarily associated with the community supported by the hermit crab presence.
Podocoryna carnea M. Sars, 1846 and Podocoryna exigua (Haeckel, 1880) are small hydrozoans living in colonies connected by a basal stolon. These species have preference for Nassarius shells, which can be occupied by a hermit crab. This relationship can be characterized therefore as “casual”, rather than specific symbiosis. However, colony structure changes depending on the substrate, with defensive polyps only present when the colony is placed on shells occupied by a hermit crab.
Adamsia palliata (O.F. Müller, 1776) has a predilection for gastropod shells of the genus Gibbula, and maintains a commensal relationship with hermit crabs, especially with Pagurus prideaux. It is exceptional to find this anemone on a shell inhabited by another species of hermit crab; the anemone feeds on the hermit’s leftovers, while the anemone offers protection with its cnidocytes. This anemone secretes a chitinous substance at its base that allows it to grow at the same rate as the hermit crab. It presents an ectoparasite, the amphipod Tryphosella sarsi.
Calliactis parasitica (Couch, 1842) is not an obligate symbiont and can be found on rocks or old empty shells. However, in most of the cases, they appear associated with shells occupied by hermit crabs, often P. bernhardus, since the crab is able to facilitate the transfer of the anemones from the old shell to the new one using their claws. The anemones feed on zooplancton, hermit’s leftovers and organic matter.
Hippoporidra lusitania Taylor & Cook, 1981 is an encrusting colonial bryozoan that can be found covering gastropod shells occupied by several species of hermits. So far, two Iberian species have been found associated with these colonies, Anapagurus curvidactylus and Cestopagurus timidus.
Neanthes fucata (Savigny, 1822), a polychaete worm, invades the hermit's shell (usually those of P. bernhardus) and remains inside poking up occasionally to remove the food from the crab claws. Its presence, although it does not cause great damage, doesn’t’ seem to bring any known benefits either.
Peltogaster paguri Rathke, 1842, Peltogastrella sulcata (Lilljeborg, 1859) and Clistosaccus paguri Lilljeborg, 1860 are parasitic cirripeds infecting each of them several species of hermit crabs, being the first found in P. bernhardus, P. cuanensis and A. chiroacanthus, the second in A. chiroacanthus, A. hyndmanni, A. laevis, P. cuanensis and P. prideaux and the last only in Diogenes pugilator so far.
The ectoparasite Athelges paguri (Rathke, 1843) can be found fixed to the abdomen of the hermit crabs. It has been recorded so far on P. bernhardus, P. cuanensis and A. laevis.
Pebrilla paguri Giard, 1888 is a suspension-feeding ciliate originally described on P. bernhardus, although it has been located on other species ever since.
These preliminary results, here summarized, are a starting point heading to a more complete description of this type of interactions in the near future, improving the knowledge about these unusual communities. At this moment, P. bernhardus holds the most diverse community of associates, but it may be due to the differences in sampling effort since P. bernhardus is one of the most common species in the sampled area.
Fig 1. From upper left to right, Athelges paguri, Neanthes fucata, Peltogaster paguri, Hydractinia echinata, Hippoporidra lusitania and Podocoryna carnea
Acknowledgements
We want to thank all the colleagues who in one way or another are collaborating with the compilation of examples and data for this work.
Keywords:
Hermit crabs,
Symbiosis,
Associates,
Iberian Peninsula,
Taxo nomy
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Poster Presentation
Topic:
Ecology, Biodiversity and Vulnerable Ecosystems
Citation:
Almón
B,
Pérez
J,
García-Isarch
E,
García-Raso
E and
Cuesta
JA
(2019). Home selection and regular welcome (and not so much) guests in Iberian Hermit Crabs.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00081
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Received:
23 Apr 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Mr. Bruno Almón, Oceanographic Center of Vigo, Spanish Institute of Oceanography, Vigo, Spain, brunoalmon2@yahoo.es