Publications

Lepisosteids or gars constitute a very special neopterygian group, with seven living species in two genera: Lepisosteus and Atractosteus. They live in freshwaters from the eastern part of North America and Central America. A new lepisosteid, Oniichthys falipoui gen. nov., sp. nov., is described on the basis of two well preserved specimens. Although the type locality is unknown, information provided by the fossil collector, the type of preservation of the specimen, and the nature of the attached matrix indicate, with confidence, that it comes from the Kem Kem beds of southern Morocco (fig. 1). The Kem Kem beds are rich fossiliferous horizons, exposed along the face of an escarpment extending from the north of Erfoud town to the Kem Kem area. The age of these outcrops is still debatable being considered as ?Albian in age [Forey and Grande, 1998] or regarded as Cenomanian, due to their elasmobranch assemblage [Sereno et al., 1996]. Oniichthys falipoui shows several derived characters of gars such as an elongated ethmoid region, an upper jaw formed by a chain of tooth-bearing bones, a joint between the quadrate and the lower jaw lying far forward, in front of the orbit and a large splint-like quadratojugal overlying the horizontal branch of the preopercle. O. falipoui shares with the primitive gar, Obaichthys decoratus, from the ?Albian Santana Formation of Brazil, the presence of toothed maxillaries, although in the Moroccan taxon, the maxillaries are anteriorly fused with infraorbitals. This structure confirms that, at least, some of the "infraorbital chain" bones bear maxillary teeth, fused to them during ontogeny. Discussion of characters leads to regard O. falipoui as more derived than Obaichthys, and to place it as the sister-group of Lepisosteus-Atractosteus.

The anatomy of the osteoglossomorph Palaeonotopterus greenwoodi Forey is redescribed on the basis of more complete material than used in the original description. This new material shows large rounded and attached parasphenoid tooth plates with a Plethodus -like histology. We are therefore able to associate some species ofPlethodus with a skull. Not all species of Plethodus may belong to the same kind of fish: specifically,Plethodus oblongus Dixon, which is known from articulated skull material, appears to be a very different kind of fish.Palaeonotopterus shows a mixture of notopterid and mormyroid characters. With notopterids Palaeonotopterus shares an elongate foramen for V+VII straddling the suture between prootic and pterosphenoid in the orbital wall, an auditory fenestra between the prootic and basioccipital (homoplastic with Hiodon), a sagitta with a prominent anterior process (inferred in Palaeonotopterus from the shape of the labyrinth cavity). With primitive mormyroids Palaeonotopterus shares a similar and distinctively shaped supraoccipital crest and a suture between the paraÍsphenoid and autosphenotic. A supraorbital branch of the otic sensory canal, formerly thought to be a character of notopterids, is present in mormyroids and therefore is interpreted as a character of notopterids+mormyroids.

During development, Hox gene transcription is activated in presomitic mesoderm with a time sequence that follows the order of the genes along the chromosome. Here, we show that Hoxd1 and other Hox genes display dynamic stripes of expression within presomitic mesoderm. The underlying transcriptional bursts may reflect the mechanism that coordinates Hox gene activation with somitogenesis. This mechanism appears to depend upon Notch signaling, as mice deficient for RBPJk, the effector of the Notch pathway, showed severely reduced Hoxd gene expression in presomitic mesoderm. These results suggest a molecular link between Hox gene activation and the segmentation clock. Such a linkage would efficiently keep in phase the production of novel segments with their morphological specification.

Large miliolid foraminifers of the subfamily Soritinae bear symbiotic dinoflagellates morphologically similar to the species of the "Symbiodinium" complex, commonly found in corals and other marine invertebrates. Soritid foraminifers are abundant in coral reefs and it has been proposed that they share their symbionts with other dinoflagellate-bearing reef dwellers. In order to test this hypothesis, we have analysed partial large subunit ribosomal DNA sequences from dinoflagellates symbionts obtained from 28 foraminiferal specimens, and compared them to the corresponding sequences of Symbiodinium-like endosymbionts from various groups of invertebrates. Phylogenetic analysis of our data shows that all soritid symbionts belong to the "Symbiodinium" species complex, within which they form seven different molecular types (Frl-Fr7). Only one of these types (Fr1) branches within a group of invertebrate symbionts, previously described as type C. The remaining six types form sister groups to coral symbionts previously designed as types B, C, and D. Our data indicate a high genetic diversity and specificity of Symbiodinium-like symbionts in soritids. Except for type C, we have found no evidence for the transmission of symbionts between foraminifers and other symbiont-bearing invertebrates from the same localities. However, exchanges must have occurred frequently between the different species of Soritinae, as suggested by the lack of host specificity and some biogeographical patterns observed in symbiont distribution. Our data suggest that members of the subfamily Soritinae acquired their symbionts at least three times during their history, each acquisition being followed by a rapid diversification and independent radiation of symbionts within the foraminiferal hosts.

Large miliolid foraminifers bear various types of algal endosymbionts including chlorophytes, dinoflagellates, rhodophytes, and diatoms. Symbiosis plays a key role in the adaptation of large foraminifera to survival and growth in oligotrophic seas. The identity and diversity of foraminiferal symbionts, however, remain largely unknown. In the present work we use ribosomal DNA (rDNA) sequences to identify chlorophyte endosymbionts in large miliolid foraminifera of the superfamily Soritacea. Partial 18S and complete Internal Transcribed Spacer (ITS) rDNA sequences were obtained from symbionts of eight species representing all genera of extant chlorophyte-bearing Soritacea. Phylogenetic analysis of the sequences confirms the previous fine structure-based identification of these endosymbionts as belonging to the genus Chlamydomonas. All foraminiferal symbionts form a monophyletic group closely related to Chlamydomonas noctigama. The group is composed of seven types identified in this study, including one previously morphologically described species, Chlamydomonas hedleyi. Each of these types can be considered as a separate species, based on the comparison of genetic differences observed between other established Chlamydomonas species. Several foraminiferal species share the same symbiont type, but only one species, Archaias angulatus, was found to bear more than one type.

Large miliolid foraminifers of the subfamily Soritinae bear symbiotic dinoflagellates morphologically similar to the species of the "Symbiodinium" complex, commonly found in corals and other marine invertebrates. Soritid foraminifers are abundant in coral reefs and it has been proposed that they share their symbionts with other dinoflagellate-bearing reef dwellers. In order to test this hypothesis, we have analysed partial large subunit ribosomal DNA sequences from dinoflagellates symbionts obtained from 28 foraminiferal specimens, and compared them to the corresponding sequences of Symbiodinium-like endosymbionts from various groups of invertebrates. Phylogenetic analysis of our data shows that all soritid symbionts belong to the "Symbiodinium" species complex, within which they form seven different molecular types (Frl-Fr7). Only one of these types (Fr1) branches within a group of invertebrate symbionts, previously described as type C. The remaining six types form sister groups to coral symbionts previously designed as types B, C, and D. Our data indicate a high genetic diversity and specificity of Symbiodinium-like symbionts in soritids. Except for type C, we have found no evidence for the transmission of symbionts between foraminifers and other symbiont-bearing invertebrates from the same localities. However, exchanges must have occurred frequently between the different species of Soritinae, as suggested by the lack of host specificity and some biogeographical patterns observed in symbiont distribution. Our data suggest that members of the subfamily Soritinae acquired their symbionts at least three times during their history, each acquisition being followed by a rapid diversification and independent radiation of symbionts within the foraminiferal hosts.

Large miliolid foraminifers bear various types of algal endosymbionts including chlorophytes, dinoflagellates, rhodophytes, and diatoms. Symbiosis plays a key role in the adaptation of large foraminifera to survival and growth in oligotrophic seas. The identity and diversity of foraminiferal symbionts, however, remain largely unknown. In the present work we use ribosomal DNA (rDNA) sequences to identify chlorophyte endosymbionts in large miliolid foraminifera of the superfamily Soritacea. Partial 18S and complete Internal Transcribed Spacer (ITS) rDNA sequences were obtained from symbionts of eight species representing all genera of extant chlorophyte-bearing Soritacea. Phylogenetic analysis of the sequences confirms the previous fine structure-based identification of these endosymbionts as belonging to the genus Chlamydomonas. All foraminiferal symbionts form a monophyletic group closely related to Chlamydomonas noctigama. The group is composed of seven types identified in this study, including one previously morphologically described species, Chlamydomonas hedleyi. Each of these types can be considered as a separate species, based on the comparison of genetic differences observed between other established Chlamydomonas species. Several foraminiferal species share the same symbiont type, but only one species, Archaias angulatus, was found to bear more than one type.

Embryonic stem (ES) cells are fully pluripotent in that they can differentiate into all cell types, including gametes. We have derived 35 ES cell lines via nuclear transfer (ntES cell lines) from adult mouse somatic cells of inbred, hybrid, and mutant strains. ntES cells contributed to an extensive variety of cell types, including dopaminergic and serotonergic neurons in vitro and germ cells in vivo. Cloning by transfer of ntES cell nuclei could result in normal development of fertile adults. These studies demonstrate the full pluripotency of ntES cells.

Axons of olfactory sensory neurons expressing a given odorant receptor converge to a few glomeruli in the olfactory bulb. We have generated mice with unresponsive olfactory sensory neurons by targeted mutagenesis of a cyclic nucleotide-gated channel subunit gene, OCNC1. When these anosmic mice were crossed with mice in which neurons expressing a given odorant receptor can be visualized by coexpression of an axonal marker, the pattern of convergence was affected for one but not another receptor. In a novel paradigm, termed monoallelic deprivation, axons from channel positive or negative neurons that express the same odorant receptor segregate into distinct glomeruli within the same bulb. Thus, the peripheral olfactory projections are in part influenced by mechanisms that depend on neuronal activity.