Occurrence, infestation rate, and spatiotemporal distribution of the African pea crab (Afropinnotheres monodi) inhabiting Mediterranean mussels (Mytilus galloprovincialis) from southern Portugal

Abstract

The present study aimed to analyze the occurrence and prevalence, infestation rate and intensity, host–guest colonization pattern, morphometric relationships, and spatiotemporal distribution of the African pea crab (Afropinnotheres monodi) inhabiting the shell of Mediterranean mussels (Mytilus galloprovincialis) from the Algarve coast and Ria Formosa lagoon (southern Portugal). Sampling campaigns were performed with a trimestral periodicity in 2018–2019 and comprised 13 collecting sites distributed in the Ria Formosa, along the Algarve coast, and in an offshore mussel farm. Altogether, 10,109 individuals of M. galloprovincialis in a broad range of sizes (9.0–91.2 mm in shell length) were sampled, among which 571 host mussels (14.6–73.6 mm in shell length) contained a total of 598 individuals of A. monodi, corresponding to an infestation rate of 5.6% (prevalence rate of 5.9% due to multiple occurrences). The sample of pea crabs also covered an extensive range of sizes (1.7–14.5 mm in carapace width) and included eight juveniles, 163 males, and 427 females (82 hard females and 345 soft females, of which 128 were non‐ovigerous and 217 ovigerous). Overall, hard (13.9%) and soft (58.5%) females prevailed over males (27.6%), corresponding to female‐biased sex ratio of 1 male:2.6 females. In terms of infestation intensity, 95.4% of host mussels contained a single pea crab, with multiple infestations (two or three crabs inside a single mussel) being more frequent in the lagoon than along the coast. Morphometric relationships between host shell length and pea crab carapace width were highly correlated (r values ranged .218–.631), although there were no significant differences between sexes or female demographic categories and maturity stages. Overall, the present study provided further insights into the colonization of M. galloprovincialis by A. monodi.

Pea crabs (Pinnotheres pisum) colonisation of five commercial bivalve species from southern Portugal

“…Relationships between (A) bivalve host shell length and Pinnotheres pisum carapace width; (B) bivalve host total weight and Pinnotheres pisum total weight. Seed, 1969;Gam et al, 2008;Becker, 2010;Perez-Miguel et al, 2019a) and A. monodi preferring intertidal bivalve hosts (Drake et al, 2014;Perez-Miguel, 2018;Perez-Miguel et al, 2019a;Santos et al, 2022).…”

“…Pea crabs multiple infestations (more than one pinnotherid per bivalve host) were also quantified (e.g. Seed, 1969; Haines et al ., 1994; Perez-Miguel et al ., 2018; Cuesta et al ., 2020; Santos et al ., 2022). Smaller and sexually undifferentiated pinnotherids were classified as juveniles.…”

“…Pea crabs are small endosymbiotic crustaceans that colonise diverse marine invertebrates, being commonly found inside the mantle cavities of bivalves hosts such as cockles, clams, and mussels (e.g. Becker andTürkay, 2010, 2017;Drake et al, 2014;Perez-Miguel et al, 2019a;Cuesta et al, 2020;Santos et al, 2022). In European waters (Atlantic Ocean and targeted by commercial fisheries and recreational harvesting activities (e.g.…”

“…Pea crabs are small endosymbiotic crustaceans that colonise diverse marine invertebrates, being commonly found inside the mantle cavities of bivalves hosts such as cockles, clams, and mussels (e.g. Becker and Türkay, 2010, 2017; Drake et al ., 2014; Perez-Miguel et al ., 2019 a ; Cuesta et al ., 2020; Santos et al ., 2022). In European waters (Atlantic Ocean and Mediterranean Sea), five pea crabs species have been recorded, namely: Afropinnotheres monodi RB Manning, 1993; Nepinnotheres pinnotheres (Linnaeus, 1758); Pinnotheres bicristatus García Raso & Cuesta in Cuesta, García Raso, Abelló, Marco-Herrero, Silva & Drake 2019; Pinnotheres pectunculi Hesse, 1872; and Pinnotheres pisum (Linnaeus, 1767) (Becker, 2010; Becker and Türkay, 2010, 2017; Subida et al ., 2011; Marco-Herrero et al ., 2017, 2020; Cuesta et al ., 2019; Perez-Miguel et al ., 2019 a ).…”

“…Due to pinnotherids life strategy and colonisation of bivalve hosts, depending on the infestation degree, pea crabs might induce negative impacts on artisanal fisheries, recreational harvesting and aquaculture activities (e.g. Perez-Miguel et al ., 2018; Cuesta et al ., 2020; Marco-Herrero et al ., 2020; Santos et al ., 2022). Indeed, pea crabs can injure bivalve gills and affect filtering efficiency, leading to slower growth, maturation and condition index of their bivalve hosts (Christensen and McDermott, 1958; Sun et al ., 2006; Mena et al ., 2014; Yasuoka and Yusa, 2017; Cuesta et al ., 2020).…”