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

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

Opsin detection in the sea urchin Paracentrotus lividus and the sea star Asterias rubens

Vision in metazoans is permitted by opsin expression in photoreceptor cells. These opsins can be classified in two groups : the ciliary (c) and the rhabdomeric (r) opsins. Based on the r- and c-opsin sequences of the urchin Strongylocentrotus purpuratus, degenerate primers were designed and used to amplify opsin genes in the sea urchin Paracentrotus lividus and the sea star Asterias rubens by PCR. R-opsins sequences were obtained for P. lividus and A. rubens and compared to known echinoderm opsins. To complete the study, a commercial antibody, raised against the N-terminal domain of the rat rhodopsin was used to detect c-opsins in Western blot experiments. Putative c-opsins were detected in the oral and aboral integument of P. lividus. We also detected c-opsins in the aboral integument of A. rubens, but not in the oral integument nor in the podia. Furthermore, no antibody labeling was observed in extracts from the optic cushions known to contain r-opsins. In all eventualities, it is therefore likely that two types of opsins would co-occur in A. rubens and P. lividus as it is the case in S. purpuratus. In A. rubens, one opsin type would be located in the optic cushions and another in the aboral integument. This could support the idea that starfishes possess two types of vision: the optic cushions, involved in the immediate visual perception of the environment, and the aboral integument, certainly involved in a more diffuse photoreception

Genetic Diversity Trends in the Cultivated Potato: A Spatiotemporal Overview

International audienceSimple Summary Monitoring the change in genetic diversity over time and space in crop species is essential to facilitating further improvement. As the world's most important tuber crop for human consumption, and an ideal candidate to help address global food security, the cultivated potato deserves in-depth study in this regard. In this overview, some aspects of spatiotemporal diversity assessment in the cultivated potato are examined with the aim of promoting appropriate strategies for breeding programs in line with challenges relating to sustainable crop production. We investigated the changes in genetic diversity over time and space of the cultivated potato (Solanum tuberosum L.) for the period pre-1800 to 2021. A substantial panel of 1219 potato varieties, belonging to different spatiotemporal groups, was examined using a set of 35 microsatellite markers (SSR). Genotypic data covering a total of 407 alleles was analyzed using both self-organizing map (SOM) and discriminant analysis of principal components (DAPC) de novo and a priori clustering methods, respectively. Data analysis based on different models of genetic structuring provided evidence of (1) at least two early lineages that have been maintained since their initial introduction from the Andes into Europe in the 16th century, followed by later ones coming from reintroduction events from the US in the mid-1800s; (2) a level of diversity that has gradually evolved throughout the studied time periods and areas, with the most modern variety groups encompassing most of the diversity found in earlier decades; (3) the emergence of new genetic groups within the current population due to increases in the use of germplasm enhancement practices using exotic germplasms. In addition, analysis revealed significant genetic differentiation both among and within the spatiotemporal groups of germplasm studied. Our results therefore highlight that no major genetic narrowing events have occurred within the cultivated potato over the past three centuries. On the contrary, the genetic base shows promising signs of improvement, thanks to extensive breeding work that is gaining momentum. This overview could be drawn on not only to understand better how past decisions have impacted the current genetic cultivated potato resources, but also to develop appropriate new strategies for breeding programs consistent with the socio-economic and sustainability challenges faced by agrifood systems

Figure 6 in Four new species of Mesomyzostoma (Myzostomida: Annelida)

Figure 6. Mesomyzostoma botulus sp. nov. (A) Live adult being dissected from oral disc of host. (B) Juvenile stage with fi ve chaetigers. (C) Juvenile stage with four visible chaetigers and possible everted pharynx. (D) Larger specimens in life, one on left adult holotype (SAM E 3964) with possible everted pharynx. One on right paratype (SAM E 3409), arrow pointing to emergent chaeta visible via scanning electron micrograph (SEM) in E. (E) SEM view of paratype (SAM E 3409) showing only a single visible emergent chaeta. (F) Light micrograph of anterior end of juvenile specimen showing small hooks emerging from the body margin. (G) SEM view of smaller paratype on same stub (SAM E 3409) also showing only single visible emergent chaeta on its cylindrical body. (H) Micrograph of a parapodium digested in bleach showing the acicula. (I) Micrograph of a parapodium digested in bleach showing the emergent hook. (J) Detailed SEM view of the single emergent hook of larger paratype on stub SAM E 3409. Abbreviations: 1 – 5 refer to chaetigers; ac, acicula; ch, chaeta; h, hook; ma, manubrium; ph?, everted pharynx

Figure 1. Mesomyzostoma katoi Okada, 1933 in Four new species of Mesomyzostoma (Myzostomida: Annelida)

Figure 1. Mesomyzostoma katoi Okada, 1933. (A) Specimen alive, extracted from a pinnule of the crinoid host, Anneissia japonica. (B) Dorsal view of a complete specimen in life (SAM-E 3407), showing the translucent margin. (C) Ventral view of an incomplete specimen in life (SAM-E 3407), showing the digestive tube (through the translucent margin) and two chaetigers. (D) Scanning electron micrograph (SEM) side view of whole specimen (SIO-BIC A 4072) showing the thin body section and the notched margin with small parapodia and the lack of cirri; lateral organs are evident on body margin as small slits. (E) SEM view of a hook emerging from a parapodium. (F) SEM close up of body margin showing lateral organs as small slits. (G) SEM lateral view of the anterior end, showing the mouth and fi rst pair of very inconspicuous parapodia. Abbreviations: 1 – 5 refer to chaetigers; c, cloaca; ch, chaeta; dt, digestive diverticulae; lo, lateral organs; m, mouth; p, parapodium; pi, pinnule; sv, seminal vesicle; u, uterus