On the identity of broad-shelled mussels (Mollusca, Bivalvia, Mytilus) from the Dutch delta region

Late Quaternary (Eemian) deposits of the Netherlands contain shells that resemble those of living Mytilus galloprovincialis. Similar broad-shelled mytilids also occur in estuaries of the southwestern Netherlands together with slender individuals typical of M. edulis. We sampled living mussels along a depth gradient in the Oosterschelde to a) investigate whether a relation exists between shell shape and depth, b) test if the broad-shelled specimens might represent M. galloprovincialis (or a hybrid with M. edulis) and c) assess by inference if the Quaternary specimens might be attributed to M. galloprovincialis as well. In order to do so, we compared genetic (length polymorphism of Me 15/16, COIII sequences and AFLPs) and shell-morphological characteristics (juvenile L/W ratios and so-called Verduin parameters) of the same specimens. The obtained dataset indicates that all studied mussels from the Oosterschelde should be attributed to M. edulis, including those with broad shell outlines. No correlation of shell-morphology and depth-distribution was found. The worn and generally damaged state of the Eemian specimens precluded measurement of the Verduin parameters, while juvenile L/W ratios turned out not to be diagnostic. Therefore the shell characters examined in this study are insufficient to demonstrate the possible presence of M. galloprovincialis shells in Quaternary deposits of the Netherlands

The complete mitogenome of Cylindrus obtusus (Helicidae, Ariantinae) using Illumina next generation sequencing

Animal science

On the identity of broad-shelled mussels (Mollusca, Bivalvia, Mytilus) from the Dutch delta region

Late Quaternary (Eemian) deposits of the Netherlands contain shells that resemble those of living Mytilus galloprovincialis. Similar broad-shelled mytilids also occur in estuaries of the southwestern Netherlands together with slender individuals typical of M. edulis. We sampled living mussels along a depth gradient in the Oosterschelde to a) investigate whether a relation exists between shell shape and depth, b) test if the broadshelled specimens might represent M. galloprovincialis (or a hybrid with M. edulis) and c) assess by inference if the Quaternary specimens might be attributed to M. galloprovincialis as well. In order to do so, we compared genetic (length polymorphism of Me 15/16, COIII sequences and AFLPs) and shellmorphological characteristics (juvenile L/W ratios and socalled Verduin parameters) of the same specimens. The obtained dataset indicates that all studied mussels from the Oosterschelde should be attributed to M. edulis, including those with broad shell outlines. No correlation of shell-morphology and depth-distribution was found. The worn and generally damaged state of the Eemian specimens precluded measurement of the Verduin parameters, while juvenile L/W ratios turned out not to be diagnostic. Therefore the shell characters examined in this study are insufficient to demonstrate the possible presence of M. galloprovincialis shells in Quaternary deposits of the Netherlands.

A centuries old problem in nephtheid taxonomy approached using DNA data (Coelenterata: Alcyonacea)

The current centuries old classification of the family Nephtheidae is still mostly based on colony morphology. In this family the Indo-Pacifc genera Litophyton, Nephthea, Dendronephthya and Stereonephthya, and the Atlantic genus Neospongodes form a complex mix of closely related, poorly described species which cannot be recognized using only colony morphology. Attempts with the more modern approach of comparing skeleton composition (sclerites) have been only partly successful because of the extreme variation of sclerite forms present in these genera. The genus Chromonephthea Van Ofwegen, 2005, introduced for several species previously assigned to Dendronephthya, Nephthea and Stereonephthya, was established with sclerite morphology, but the true generic status of the majority of the nominal species of these genera remained unresolved. In an attempt to clarify the phylogenetic relationships between Litophyton, Nephthea, Stereonephthya and Chromonephthea fourteen specimens, unidentified but certainly belonging to these genera, have been used in molecular analyses. All analyses supported two clades, which could be related to the shape of the sclerites present in the polyp stalks. One clade contained the specimens with characters for Stereonephthya along with the Chromonephthea specimen as a sister group. The other clade had a 'true' Nephthea and Litophyton together with the specimens that could not be placed in any particular genus using the old classifi ca

A centuries old problem in nephtheid taxonomy approached using DNA data (Coelenterata: Alcyonacea)

The current centuries old classification of the family Nephtheidae is still mostly based on colony morphology. In this family the Indo-Pacifc genera Litophyton, Nephthea, Dendronephthya and Stereonephthya, and the Atlantic genus Neospongodes form a complex mix of closely related, poorly described species which cannot be recognized using only colony morphology. Attempts with the more modern approach of comparing skeleton composition (sclerites) have been only partly successful because of the extreme variation of sclerite forms present in these genera. The genus Chromonephthea Van Ofwegen, 2005, introduced for several species previously assigned to Dendronephthya, Nephthea and Stereonephthya, was established with sclerite morphology, but the true generic status of the majority of the nominal species of these genera remained unresolved. In an attempt to clarify the phylogenetic relationships between Litophyton, Nephthea, Stereonephthya and Chromonephthea fourteen specimens, unidentified but certainly belonging to these genera, have been used in molecular analyses. All analyses supported two clades, which could be related to the shape of the sclerites present in the polyp stalks. One clade contained the specimens with characters for Stereonephthya along with the Chromonephthea specimen as a sister group. The other clade had a 'true' Nephthea and Litophyton together with the specimens that could not be placed in any particular genus using the old classifi cation criteria. The consequences of these results for nephtheid classifi cation are discussed

On the identity of broad-shelled mussels (Mollusca, Bivalvia, <i>Mytilus</i>) from the Dutch delta region

Late Quaternary (Eemian) deposits of the Netherlands contain shells that resemble those of living Mytilus galloprovincialis. Similar broad-shelled mytilids also occur in estuaries of the southwestern Netherlands together with slender individuals typical of M. edulis. We sampled living mussels along a depth gradient in the Oosterschelde to a) investigate whether a relation exists between shell shape and depth, b) test if the broad-shelled specimens might represent M. galloprovincialis (or a hybrid with M. edulis) and c) assess by inference if the Quaternary specimens might be attributed to M. galloprovincialis as well. In order to do so, we compared genetic (length polymorphism of Me 15116, COIII sequences and AFLPs) and shell-morphological characteristics (juvenile L/W ratios and so-called Verduin parameters) of the same specimens. The obtained dataset indicates that all studied mussels from the Oosterschelde should be attributed to M. edulis, including those with broad shell outlines. No correlation of shell-morphology and depth-distribution was found. The worn and generally damaged state of the Eemian specimens precluded measurement of the Verduin parameters, while juvenile L/W ratios turned out not to be diagnostic. Therefore the shell characters examined in this study are insufficient to demonstrate the possible presence of M. galloprovincialis shells in Quaternary deposits of the Netherlands