In this report, we analyze the phylogeny of Pycnogonida using the three nuclear and three mitochondrial markers currently sequenced for studying inter- and intrafamilial relationships within Arthropoda: 18S and 28S rRNA genes, Histone H3, cytochrome c oxidase subunit 1 (CO1), 12S and 16S rRNA genes. We identify several problems in previous studies, due to the use of inappropriate sequences (taxonomic misidentification, DNA contamination, sequencing errors, missing data) or taxa (outgroup choice). Our analyses show that most markers are not powerful to study the phylogeny of sea spiders. The results suggest however a recent diversification of the group (Mesozoic rather than Paleozoic) and the early divergence of Austrodecidae, followed by Colossendeidae. Pycnogonidae and Rhynchothoracidae. Except Ammotheidae and Callipallenidae, all other families were recovered as monophyletic. Analyses of synonymous sites in CO1 sequences reveal an extreme heterogeneity of nucleotide composition within sea spiders, as six unrelated species show a reverse strand-specific bias. We therefore suggest that several independent reversals of asymmetric mutational constraints occurred during the evolution of Pycnogonida, as a consequence of genomic inversions involving either the control region or a fragment containing the CO1 gene. These hypotheses are supported by the comparison of two complete mitochondrial genomes of sea spiders (Achelia bituberculata and Nymphon gracile) with that of Limulus. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

MUSORSTOM 5, SALOMONBOA 3, SANTO 2006

The family Ammotheidae is the most diversified group of the class Pycnogonida, with 297 species described in 20 genera. Its monophyly and intergeneric relationships have been highly debated in previous studies. Here, we investigated the phylogeny of Ammotheidae using specimens from poorly studied areas. We sequenced the mitochondrial gene encoding the first subunit of cytochrome c oxidase (CO1) from 104 specimens. The complete nuclear 18S rRNA gene was sequenced from a selection of 80 taxa to provide further phylogenetic signal. The base composition in CO1 shows a higher heterogeneity in Ammotheidae than in other families, which may explain their apparent polyphyly in the CO1 tree. Although deeper nodes of the tree receive no statistical support, Ammotheidae was found to be monophyletic and divided into two clades, here defined as distinct subfamilies: Achelinae comprises the genera Achelia Hodge, 1864, Ammothella Verrill, 1900, Nymphopsis Haswell, 1884 and Tanystylum Miers, 1879; and Ammotheinae includes the genera Ammothea Leach, 1814, Acheliana Arnaud, 1971, Cilunculus Loman, 1908, Sericosura Fry & Hedgpeth, 1969 and also Teratonotum gen. nov., including so far only the type species Ammothella stauromata Child, 1982. The species Cilunculus gracilis Nakamura & Child, 1991 is reassigned to Ammothella, forming the binomen Ammothella gracilis (Nakamura & Child, 1991) comb. nov. Additional taxonomic re-arrangements are suggested for the genera Achelia, Acheliana, Ammothella and Cilunculus.

ATIMO VATAE, BATHUS 3, BIOPAPUA, GUYANE 2014, KARUBENTHOS 2012, KAVIENG 2014, MAINBAZA, PAKAIHI I TE MOANA, PAPUA NIUGINI, SANTO 2006

MADIBENTHOS

The marine biodiversity of the tropical northwestern Atlantic (TNWA) has been explored by many great naturalist expeditions. After more than one century of marine exploration, how well do we know its biodiversity? As a poorly studied taxon, sea spiders (Arthropoda: Pycnogonida Latreille, 1810) are excellent candidates to address this issue. Here, we report the results from the Madibenthos Survey conducted by the Muséum national d’Histoire naturelle (Paris) on the coasts of Martinique during Fall 2016, where sea spiders were collected during 138 sampling events by different methods. A total of 67 pycnogonid species, including 13 species probably new to science, were distinguished during this survey, whereas only 20 species were previously known from Martinique. Relying on an extensive and intensive sampling, the collection of pycnogonids from the Madibenthos Survey is one of the richest for TNWA. DNA barcoding based on 172 new CO1 sequences helped to discriminate species with inconspicuous diagnostic characters and pointed out 11 additional possible cryptic species. Richness estimators and species rarity indicate that the diversity of Martinique still remains underestimated. Results suggest that Martinique is not a hot spot for sea spiders and that similar levels of biodiversity might be expected in most other islands of the TNWA if similar sampling methods were applied. Finally, we show that the Caribbean and Atlantic coasts of Martinique harbor different sea spider faunas.

MADIBENTHOS

The marine biodiversity of the tropical northwestern Atlantic (TNWA) has been explored by many great naturalist expeditions. After more than one century of marine exploration, how well do we know its biodiversity? As a poorly studied taxon, sea spiders (Arthropoda: Pycnogonida Latreille, 1810) are excellent candidates to address this issue. Here, we report the results from the Madibenthos Survey conducted by the Muséum national d’Histoire naturelle (Paris) on the coasts of Martinique during Fall 2016, where sea spiders were collected during 138 sampling events by different methods. A total of 67 pycnogonid species, including 13 species probably new to science, were distinguished during this survey, whereas only 20 species were previously known from Martinique. Relying on an extensive and intensive sampling, the collection of pycnogonids from the Madibenthos Survey is one of the richest for TNWA. DNA barcoding based on 172 new CO1 sequences helped to discriminate species with inconspicuous diagnostic characters and pointed out 11 additional possible cryptic species. Richness estimators and species rarity indicate that the diversity of Martinique still remains underestimated. Results suggest that Martinique is not a hot spot for sea spiders and that similar levels of biodiversity might be expected in most other islands of the TNWA if similar sampling methods were applied. Finally, we show that the Caribbean and Atlantic coasts of Martinique harbor different sea spider faunas.

MADIBENTHOS

This study presents the inventory of sea spiders (Pycnogonida) sampled during the Madibenthos Expedition in Martinique (West Indies). Species were discriminated leaning on morphological and molecular data. A total of 761 specimens are classified in 72 species, 16 genera and nine families. Thirteen new species are described: Ammothella dirbergi sp. nov., A. krappi sp. nov., Tanystylum boucheti sp. nov., T. ingrallis sp. nov., Ascorhynchus iguanarum sp. nov., Eurycyde kaiouti sp. nov., Nymphon dorlis sp. nov., N. ludovici sp. nov., N. martinicum sp. nov., N. timons sp. nov., Anoplodactylus madibenthos sp. nov., Pycnogonum cesairei sp. nov. and Rhynchothorax sidereus sp. nov. We describe a neotype for Anoplodactylus micros Bourdillon, 1955 from the type locality. Martinique now includes 79 species of sea spiders, mostly endemic to the Tropical Northwestern Atlantic, cosmopolitan or shared with the South America Atlantic coast. Some species are potentially introduced. However, our knowledge of the distribution of species found in Martinique is probably biased by the scarcity of diagnostic morphological characters. Also, nine potentially cryptic species (discriminated on genetic data alone), are identified, shedding light on the overlooked diversity of sea spiders in the Tropical Northwestern Atlantic. Therefore, we call for a more widespread use of barcoding in sea spiders.

MADIBENTHOS

The phylogeny of sea spiders has been debated for more than a century. Despite several molecular studies in the last twenty years, interfamilial relationships remain uncertain. In the present study, relationships within Pyc­ nogonida are examined in the light of a new dataset composed of 160 mitochondrial genomes (including 152 new sequences) and 130 18S rRNA gene sequences (including 120 new sequences), from 141 sea spider mor­ phospecies representing 26 genera and 9 families. Node congruence between mitochondrial and nuclear markers was analysed to identify the most reliable relationships. We also reanalysed a multilocus dataset previously published and showed that the high percentages of missing data make phylogenetic conclusions difficult and uncertain.

ATIMO VATAE, BICOSE, BIOCAL, BIOMAGLO, BIOPAPUA, CEAMARC-AA, EXBODI, GUYANE 2014, ILES DU SALUT, KANACONO, KANADEEP, KARUBENTHOS 2012, KAVIENG 2014, MADIBENTHOS, MAINBAZA, MIRIKY, MONTROUZIER, MUSORSTOM 4, MUSORSTOM 8, PAPUA NIUGINI, SALOMONBOA 3, TARASOC, Walters Shoal