Unique morphologies of <i>Encheliophis vermiops</i> (Carapidae) with revised diagnosis of the genus

Encheliophis vermiops was first briefly described in 1990 on the basis of three specimens. This study validates this species and provides previously unrecorded useful characters to realise the identification: (1) the forward orientation of the palatine teeth, (2) the enlarged teeth of the third basibranchial, (3) the particularly well-developed pharyngeal apparatus, (4) the unpigmented band along the base of anal fin and (5) the insertion of the primary sonic muscle on the parasphenoid. Moreover, the particular morphology of Encheliophis vermiops forces us to reconsider the diagnosis of the genus

Interspecific variation of calls in clownfishes: degree of similarity in closely related species

Clownfishes are colorful coral reef fishes living in groups in association with sea anemones throughout the Indo-Pacific Ocean. Within their small societies, size hierarchy determines which fish have access to reproduction. These fishes are also prolific callers whose aggressive sounds seem to play an important role in the social hierarchy. Agonistic interactions being involved in daily behaviour suggest how acoustic communication might play an important role in clownfish group. Sounds were recorded and compared in fourteen clownfish species (some of which have never been recorded before) to evaluate the potential role of acoustic communication as an evolutionary driving force. Surprisingly, the relationship between fish size and both dominant frequency and pulse duration is not only species-specific; all the specimens of the 14 species are situated on exactly the same slope, which means the size of any Amphiprion can be predicted by both acoustic features. The number of pulses broadly overlaps among species, whereas the pulse period displays the most variation even if it shows overlap among sympatric species. Sound comparisons between three species (A. akallopisos, A. ocellaris and A. frenatus) having different types of teeth and body shape do not show differences neither in the acoustic waveform nor in the power spectrum. Significant overlap in acoustic features demonstrates that the sound-producing mechanism is highly conservative among species. Differences in the calls of some species are due to size dimorphism and the sound variation might be in this case a by-product. This morphological constraint does not permit a consideration of acoustic communication as the main driving force in the diversification of clownfishes. Moreover, calls are not produced to find mate and consequently are less subject to variations due to partner preference, which restricts the constraints of diversification. Calls are produced to reach and defend the competition to mate access. However, differences in the pulse period between cohabiting species show that, in some case, sounds can help to differentiate the species, to prevent competition between cohabiting species and to promote the diversification of taxa

Fixed, Free, and Fixed: The Fickle Phylogeny of Extant Crinoidea (Echinodermata) and Their Permian-Triassic Origin

Although the status of Crinoidea (sea lilies and featherstars) as sister group to all other living echinoderms is well-established, relationships among crinoids, particularly extant forms, are debated. All living species are currently placed in Articulata, which is generally accepted as the only crinoid group to survive the Permian–Triassic extinction event. Recent classifications have recognized five major extant taxa: Isocrinida, Hyocrinida, Bourgueticrinina, Comatulidina and Cyrtocrinida, plus several smaller groups with uncertain taxonomic status, e.g., Guillecrinus, Proisocrinus and Caledonicrinus. Here we infer the phylogeny of extant Crinoidea using three mitochondrial genes and two nuclear genes from 59 crinoid terminals that span the majority of extant crinoid diversity. Although there is poor support for some of the more basal nodes, and some tree topologies varied with the data used and mode of analysis, we obtain several robust results. Cyrtocrinida, Hyocrinida, Isocrinida are all recovered as clades, but two stalked crinoid groups, Bourgueticrinina and Guillecrinina, nest among the featherstars, lending support to an argument that they are paedomorphic forms. Hence, they are reduced to families within Comatulida. Proisocrinus is clearly shown to be part of Isocrinida, and Caledonicrinus may not be a bourgueticrinid. Among comatulids, tree topologies show little congruence with current taxonomy, indicating that much systematic revision is required. Relaxed molecular clock analyses with eight fossil calibration points recover Articulata with a median date to the most recent common ancestor at 231–252 mya in the Middle to Upper Triassic. These analyses tend to support the hypothesis that the group is a radiation from a small clade that passed through the Permian–Triassic extinction event rather than several lineages that survived. Our tree topologies show various scenarios for the evolution of stalks and cirri in Articulata, so it is clear that further data and taxon sampling are needed to recover a more robust phylogeny of the group

Genetic Impact of a Severe El Niño Event on Galápagos Marine Iguanas (Amblyrhynchus cristatus)

The El Niño-Southern Oscillation (ENSO) is a major source of climatic disturbance, impacting the dynamics of ecosystems worldwide. Recent models predict that human-generated rises in green-house gas levels will cause an increase in the strength and frequency of El Niño warming events in the next several decades, highlighting the need to understand the potential biological consequences of increased ENSO activity. Studies have focused on the ecological and demographic implications of El Niño in a range of organisms, but there have been few systematic attempts to measure the impact of these processes on genetic diversity in populations. Here, we evaluate whether the 1997–1998 El Niño altered the genetic composition of Galápagos marine iguana populations from eleven islands, some of which experienced mortality rates of up to 90% as a result of El Niño warming. Specifically, we measured the temporal variation in microsatellite allele frequencies and mitochondrial DNA diversity (mtDNA) in samples collected before (1991/1993) and after (2004) the El Niño event. Based on microsatellite data, only one island (Marchena) showed signatures of a genetic bottleneck, where the harmonic mean of the effective population size (Ne) was estimated to be less than 50 individuals during the period between samplings. Substantial decreases in mtDNA variation between time points were observed in populations from just two islands (Marchena and Genovesa). Our results suggests that, for the majority of islands, a single, intense El Niño event did not reduce marine iguana populations to the point where substantial neutral genetic diversity was lost. In the case of Marchena, simultaneous changes to both nuclear and mitochondrial DNA variation may also be the result of a volcanic eruption on the island in 1991. Therefore, studies that seek to evaluate the genetic impact of El Niño must also consider the confounding or potentially synergistic effect of other environmental and biological forces shaping populations

From commensalism to parasitism in Carapidae (Ophidiiformes): heterochronic modes of development?

Phenotypic variations allow a lineage to move into new regions of the adaptive landscape. The purpose of this study is to analyse the life history of the pearlfishes (Carapinae) in a phylogenetic framework and particularly to highlight the evolution of parasite and commensal ways of life. Furthermore, we investigate the skull anatomy of parasites and commensals and discuss the developmental process that would explain the passage from one form to the other. The genus Carapus forms a paraphyletic grouping in contrast to the genus Encheliophis, which forms a monophyletic cluster. The combination of phylogenetic, morphologic and ontogenetic data clearly indicates that parasitic species derive from commensal species and do not constitute an iterative evolution from free-living forms. Although the head morphology of Carapus species differs completely from Encheliophis, C. homei is the sister group of the parasites. Interestingly, morphological characteristics allowing the establishment of the relation between Carapus homei and Encheliophis spp. concern the sound-producing mechanism, which can explain the diversification of the taxon but not the acquisition of the parasite morphotype. Carapus homei already has the sound-producing mechanism typically found in the parasite form but still has a commensal way of life and the corresponding head structure. Moreover, comparisons between the larval and adult Carapini highlight that the adult morphotype “Encheliophis” is obtained by going beyond the adult stage reached by Carapus. The entrance into the new adaptive landscape could have been realised by at least two processes: paedomorphosis and allometric repatterning

Evidence for cospeciation events in the host–symbiont system involving crinoids (Echinodermata) and their obligate associates, the myzostomids (Myzostomida, Annelida)

Although molecular-based phylogenetic studies of hosts and their associates are increasingly common in the literature, no study to date has examined the hypothesis of coevolutionary process between hosts and commensals in the marine environment. The present work investigates the phylogenetic relationships among 16 species of obligate symbiont marine worms (Myzostomida) and their echinoderm hosts (Crinoidea) in order to estimate the phylogenetic congruence existing between the two lineages. The combination of a high species diversity in myzostomids, their host specificity, their wide variety of lifestyles and body shapes, and millions years of association, raises many questions about the underlying mechanisms triggering their diversification. The phylogenetic relationships, inferred using a three-genes dataset (18S rDNA, 16S rDNA, and COI) and two-genes dataset (18S rDNA, and COI) for the myzostomids and crinoids, respectively, were congruent with the literature. The overall congruence between the two phylogenies was statistically significant according to topology-based, distance-based, and data-based approaches: a significant pattern of cophylogeny was found, though not perfect probably resulting from occasional host switches, duplications or extinction events. A minimum of 8 cospeciation events was estimated, which is significantly higher than it would have been expected due to chance alone

Unique morphologies of Encheliophis vermiops (Carapidae) with revised diagnosis of the genus

Abstract Encheliophis vermiops was first briefly described in 1990 on the basis of three specimens. This study validates this species and provides previously unrecorded useful characters to realise the identification: (1) the forward orientation of the palatine teeth, (2) the enlarged teeth of the third basibranchial, (3) the particularly well-developed pharyngeal apparatus, (4) the unpigmented band along the base of anal fin and (5) the insertion of the primary sonic muscle on the parasphenoid. Moreover, the particular morphology of Encheliophis vermiops forces us to reconsider the diagnosis of the genus