Two species of Crustacea (Decapoda) associated with the fan mussel, pinna nobilis Linnaeus, 1758 (Mollusca, Bivalvia)

Abstract

During a study on the ecology and biology of the fan mussel, Pinna nobilis along the northern and eastern coasts of Tunisia, the presence of the shrimp, Pontonia pinnophylax and the crab, Nepinnotheres pinnotheres (Decapoda) associated with this bivalve, was recorded. The shrimp was collected only in the lagoon of Bizerte, whereas the crab was found exclusively at Stah Jaber (close to the fishing port of Monastir). P. nobilis was occupied by Pontonia pinnophylax in 23.3% of the samples and the associated shrimp population was dominated by males (63.6%). Shrimp couples were generally encountered inside the large pinnids, and the size of the shrimps increased with that of the host. P. nobilis was occupied by Nepinnotheres pinnotheres in 56.7% of the cases. The highest numbers of crabs were recorded in the oldest pinnids. The sex-ratio of the associated crab population was male-biased, 62.5% of the population being males. A morphological study of the two associated species revealed some features worth noting. In the female shrimp, distinguished by the right chela in the second pair of pereiopods being definitely larger than the left, the length of this appendage (both right and left) increased with individual size, but these two variables were found independent in the male shrimp. Concerning Nepinnotheres pinnotheres, the length of the two chelae of the first pair of pereiopods increased with that of the animal's body in both sexes. RÉSUMÉDans le cadre d'une étude sur l'écologie et la biologie de la grande nacre, Pinna nobilis, le long des côtes septentrionale et orientale de la Tunisie, nous avons observé la présence de la crevette Pontonia pinnophylax et du crabe Nepinnotheres pinnotheres (Decapoda) associés à ce bivalve. La crevette a été récoltée uniquement dans la lagune de Bizerte, tandis que le crabe a été trouvé exclusivement à Stah Jaber (près du port de pêche de Monastir). P. nobilis était occupée par Pontonia pinnophylax dans 23,3% des échantillons et la population était dominée par les mâles (63,6%). Des couples de crevettes se rencontraient généralement dans les grandes nacres et la taille des crevettes augmentait avec celle de l'hôte. P. nobilis était occupée par Nepinnotheres pinnotheres dans 56,7% des cas. Les nombres les plus élevés de crabes ont été relevés dans les nacres les plus âgées. La sex-ratio de la population de crabe associée était en faveur des mâles avec 62,5% de la population 1 ) Crustaceana 81 (4): 433-446 Also available online: www.brill.nl/cr 434 LOTFI RABAOUI ET AL.constituée de mâles. Une étude morphologique des deux espèces associées a révélé quelques faits qui valent la peine d'être notés. Chez la crevette femelle, que l'on distingue par la pince droite de la deuxième paire de péréiopodes nettement plus grande que la gauche, la longueur de cet appendice (à droite comme à gauche), augmente avec la taille de l'individu, mais ces deux variables sont indépendantes chez la crevette mâle. Chez Nepinnotheres pinnotheres, la longueur des deux pinces de la première paire de péréiopodes a...

Effects of the invasive macroalga <em>Lophocladia lallemandii</em> on the diet and trophism of <em>Pinna nobilis</em> (Mollusca: Bivalvia) and its guests <em>Pontonia pinnophylax</em> and <em>Nepinnotheres pinnotheres</em> (Crustacea: Decapoda)

“…The isotopic enrichment of the fan mussel guests in the present work was consistent with the estimated trophic level of the consumers (le loc 'h et al, 2008). The capacity for food selection may explain the differences in the contribution of the different food sources to their diets, since the morphology of both studied guests allows them to select food sources (Rabaoui et al, 2008). a previous study also demonstrated that the capacity for food selection generated variations in isotopic composition (decottignies et al, 2007).…”

“…differences in the percentage contribution between δ 13 C and δ 15 n signatures by food sources such as PoM and soM have been reported previously (sarà et al, 2004). The contributions to δ 15 n signatures of invaded versus non-invaded P. pinnophylax showed little variation, almost avoiding the effect of the red macroalga L. lallemandii (4.1% of real contribution), perhaps due to its capacity for food selection (Rabaoui et al, 2008). in invaded versus non-invaded P. nobilis, the food sources showed variations in their percentage contribution to the δ 15 n signatures, with L. lallemandii making a real contribution of 19.4% in P. nobilis located in the invaded seagrass meadows.…”

“…nobilis is the host of two species of crustacean decapods: the shrimp Pontonia pinnophylax (otto, 1821) and the pea crab Nepinnotheres pinnotheres (linnaeus, 1758) (Rabaoui et al, 2008). The decapods belonging to these genera also inhabit other organisms, such as mussels (sun et al, 2006), oysters (Mercado-silva, 2005;baeza, 2008), hydroids (Marin et al, 2007), holothurians (Peter and Manning, 2003) and ascidians (vicente, 1984).…”

“…The decapods belonging to these genera also inhabit other organisms, such as mussels (sun et al, 2006), oysters (Mercado-silva, 2005;baeza, 2008), hydroids (Marin et al, 2007), holothurians (Peter and Manning, 2003) and ascidians (vicente, 1984). Previous studies have highlighted the association between the fan mussel and P. pinnophylax (Calafiore et al, 1991;Richardson et al, 1997;Kennedy et al, 2001a;lagana et al, 2007), whereas only one study conducted by Rabaoui et al (2008) has addressed the association between the fan mussel and the pea crab N. pinnotheres.…”

Association between the Crab, Nepinnotheres pinnotheres (Linnaeus, 1758), and the Endangered Species Fan Mussel, Pinna nobilis (Linnaeus, 1758), from the Aegean Sea, Turkey

“…It is thought that N. pinnotheres live in P. nobilis as an impermanent refuge. Therefore, more than one male is encountered in the same P. nobilis (Rabaoui et al, 2008). At present, the population of P. nobilis is under significant threat on the Mediterranean coasts.…”