MEPS 533:177-190 (2015)  -  DOI: https://doi.org/10.3354/meps11315

ABSTRACT: This study presents the first record of the recently colonizing lugworm species Arenicola defodiens in the Iberian Peninsula, and both A. defodiens and Arenicola marina in the Ria de Aveiro lagoon (northwest Portugal). We aimed firstly to provide a distinction between these 2 species, using combined morphological and genetic approaches, and secondly to determine their spatial distribution in the lagoon. Morphological characteristics such as annulation pattern, gill morphology, and faecal cast size enabled differentiation between both species, and we provide an updated taxonomic key for the valid species of the Family Arenicolidae known in the Iberian Peninsula. To confirm the distinction between A. defodiens and A. marina, 16S rDNA and COI gene sequencing analyses were performed. The percentage of nucleotide divergence between A. defodiens and A. marina was 13.5% for COI and 5% for 16S, and phylogenetic analyses showed that these are closely related species. Recent surveys conducted in Ria de Aveiro lagoon indicate that both species are dispersing throughout the system. Lugworm faecal casts were observed for the first time at 4 sites in 2009, and then at 7 sites in 2011. In 2014, A. marina was recorded at 2 intertidal sites of the Ria de Aveiro, which were characterized by very fine and medium sand. A. defodiens displayed a wider distribution, being reported at 13 intertidal and 5 subtidal sites where sediment characteristics ranged from mud to medium sand. A. marina densities ranged from 20.5 to 26.0 ind. m², higher than those recorded for A. defodiens, which did not exceed 3 ind. m². The expansion and the establishment of arenicolids in the Ria de Aveiro lagoon could be a result of the 2009-2010 and 2010-2011 cold winters. Possible consequences of the spread of these bioturbators in this lagunar ecosystem are discussed.

KEY WORDS: Arenicola defodiens · Arenicola marina · Iberian Peninsula · Arenicolidae · 16S · COI