No abstract

Colour polymorphism is a widespread phenomenon in natural populations of several species. In particular, it is especially common on marine gastropod species from the genus Littorina. Recently, it has been argued that intrapopulation shell colour polymorphism in Littorina fabalis could be caused by negative frequency-dependent sexual selection via a mechanism of mate choice (indirectly estimated via negative assortative mating). Here we try to determine the existence of negative assortative mating in three species of the subgenus Neritrema (L. fabalis, L. obtusata, L. saxatilis) that share a similar shell colour polymorphism, in order to ascertain if this mechanism could represent an ancestral character in this subgenus that could be contributing to the maintenance of the colour polymorphism in each species.Here, we collected or reanalysed from previous studies a sample of mating pairs of the three species from seven locations from NW Spain and NE Russia and estimated assortative mating using the I PSI index. Our results show that all species and populations show a systematic tendency towards negative assortative mating when shell colour is grouped in the broad categories: 'light' and 'dark'. Although, a more detailed analysis of each colour individually suggests that shell colour may not be the main target of assortative mating, but perhaps physically linked to another trait or through pleiotropic effects. This hypothesis opens interesting new lines of research in Littorina snails.

No abstract

Colour polymorphism is a widespread phenomenon in natural populations of several species. In particular, it is especially common on marine gastropod species from the genus Littorina. Recently, it has been argued that intrapopulation shell colour polymorphism in Littorina fabalis could be caused by negative frequency-dependent sexual selection via a mechanism of mate choice (indirectly estimated via negative assortative mating). Here we try to determine the existence of negative assortative mating in three species of the subgenus Neritrema (L. fabalis, L. obtusata, L. saxatilis) that share a similar shell colour polymorphism, in order to ascertain if this mechanism could represent an ancestral character in this subgenus that could be contributing to the maintenance of the colour polymorphism in each species. Here, we collected or reanalysed from previous studies a sample of mating pairs of the three species from seven locations from NW Spain and NE Russia and estimated assortative mating using the IPSI index. Our results show that all species and populations show a systematic tendency towards negative assortative mating when shell colour is grouped in the broad categories: ‘light’ and ‘dark’. Although, a more detailed analysis of each colour individually suggests that shell colour may not be the main target of assortative mating, but perhaps physically linked to another trait or through pleiotropic effects. This hypothesis opens interesting new lines of research in Littorina snails.

In recent years, the immune response of mussels (Mytilus galloprovincialis) has been studied at the transcriptomic level against several bacterial infections. As a result, different immune mechanisms have been revealed, including both conserved essential innate pathways and particularities of the mussel immune response according to its nature and environment. However, there is often a lack of functional verification because mussels are a non-model species and because transcriptomic and proteomic information is not always well correlated. In the current study, a high-throughput quantitative proteomics study coupled to LC-MS/MS analysis using isobaric tandem mass tags (TMTs) for protein labeling was employed to study the mussel gill immune response to a Vibrio splendidus bath (waterborne) infection at a functional protein level. A total of 4,242 proteins were identified and quantified, of which 226 were differentially expressed (DEPs) after infection, giving to the study a depth that was lacking in previous proteomic studies of the bivalve immune response. Modulated proteins evidenced an important cytoskeletal disruption caused by bacterial infection. A conserved network of associated proteins was modulated, regulating oxidative stress and NF-kB inflammatory responses and leading to innate immunity effectors. Proteomic results were submitted to an integrated analysis with those obtained in a previous transcriptomic approach with the same infection. Half of all the quantified proteins had a concordant transcriptomic expression trend, but this concordance increased when focusing on the DEPs. The correlation was higher within the immune-related DEPs, and the activation of the conserved NF-kB pro-inflammatory pathway was the main response in both approaches. The results of both techniques could be integrated to obtain a more complete vision of the response.