Abstract
The large, edible, and near-cosmopolitan brown mussel Perna perna (Linné, 1758) has a history of few and infrequent occurrences in Portugal since the Atlantic “climatic optimum” of the Holocene. Moreover, it is likely that some previous citations of Mytilus spp. from other Holocene deposits, including kitchen middens, may represent true Perna specimens. The species was recently found by Lourenço et al. (2012) in the south Portuguese coastal localities of Ilha do Farol and Vila Moura. Here, we summarize these and other previously published occurrences of P. perna in the areas of Armação de Pêra, Lagos and Aljezur, discussing morphologic, ecologic and biogeographic aspects of this species in the Portuguese fauna. The brown mussel is also known from archaeological records from Padrão I (Sagres – Vila do Bispo, Ancient Neolithic) and Arrifana (Aljezur, XII century). These chronologies are contemporaneous with the climatic warming intervals of the Atlantic Period (circa 8000-5000 BP) and “Medieval Warm Period” (circa 1000- 1200 AD). During these and other related intervals of warmer coastal surface waters, it is very likely that this subtropical “warm guest” colonized open marine rocky areas of the South and Southwest Portuguese coast, with settlement of stable and permanent populations.
 Ocorrências do mexilhão castanho anfiatlântico Perna perna (Linné, 1758) (Mollusca, Bivalvia) no sul de Portugal desde o “ótimo climático” Atlântico - O mitilídeo Perna perna (Linné, 1758), espécie comestível de dimensão apreciável e repartição quase cosmopolita, apresenta um historial escasso de ocorrências em Portugal desde o “ótimo climático” Atlântico do Holocénico. É provável, também, que algumas das ocorrências publicadas de Mytilus spp. noutros depósitos holocénicos, incluindo concheiros, possam corresponder a espécimes de Perna. Recolhas recentes na costa sul de Portugal, mencionadas por Lourenço et al. (2012) ampliam as ocorrências conhecidas às localidades de Ilha do Farol e de Vila Moura, em paralelo com citações mais antigas para Armação de Pêra, Lagos e Aljezur. Estas ocorrências são sumariadas no presente estudo, assim como discutidos aspetos de ordem morfológica, ecológica e biogeográfica relativos à presença desta espécie na fauna portuguesa. No registo arqueológico, o mexilhão castanho é conhecido nos arqueossítios de Padrão I (Sagres – Vila do Bispo, Neolítico Antigo) e Arrifana (Aljezur, século XII). Estas cronologias são coevas com os intervalos de melhoria climática do período Atlântico (circa 8000-5000 BP) e de finais da IdadeMédia (circa 1000-1200 DC). Durante estes e outros intervalos comparativos de melhoria das condições hidroclimáticas das águas superficiais costeiras, considera-se bastante provável que este “warm guest” subtropical tenha atingido, por diversas vezes, áreas não restritas do litoral rochoso do sul e sudoeste dePortugal, com o estabelecimento de populações estáveis e permanentes.
Highlights
The brown mussel Perna perna (Linné, 1758) is a well-known edible mollusc and an important food resource with economic impact in many low latitude coastal areas of South America, West and East Africa
The human exploitation of this intertidal bivalve has been revealed from the study of several African archaeological sites of various ages, often from kitchen middens (Jerardino & Marean, 2010; (1) Departamento de Ciências da Terra e Centro de Geofísica da Universidade de Coimbra – FCT; Largo Marquês de Pombal, 3001-401 Coimbra, Portugal. callapez@dct.uc.pt
These authors suggest that the recent Western Atlantic populations may have resulted from an exotic introduction initiated after 1500, by passive transport of individuals byssally attached to the hulls of slave ships in route from the West African coast
Summary
The brown mussel Perna perna (Linné, 1758) is a well-known edible mollusc and an important food resource with economic impact in many low latitude coastal areas of South America, West and East Africa. Like many warm water species, we can assume that the biogeographic range boundaries of this mussel have been repeatedly influenced by major changes in the hydroclimatic conditions of surface waters This was especially apparent during Pleistocene warming intervals, including the Post Würmian climatic optimum that culminated with the so called “Flandrian” transgression, when the effects of a worldwide millenary trend of sea-level rise caused large changes in the physiography and overall landscapes of the Portuguese coast (Granja & De Groot, 1996; Granja, 1998; Dias et al, 2000; Danielsen et al, 2011). Specimens of the brown mussel Perna perna have been found recently in rocky intertidal areas of central Algarve, in the southern Portuguese coast (Lourenço et al, 2012) These authors stated that this was the first find of this species in the European Atlantic coast. Posterior adductor muscle scar well marked and separated from the retractor one
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