The darkness syndrome in subsurface-shallow and deep-sea dwelling Ostracoda (Crustacea)

Biosystematics and Ecology-Series. Año 1996, Vol. 1

On the need to renew the taxonomic system of the candoninae (non-marine Ostracoda, Crustacea). Reflexions from an analysis of data using the Yule Process

http://www.geoecomar.ro/website/publicatii-revista-geo-eco-marina.htm

Revision of the genus <i>Leucocythere</i> Kaufmann, 1892 (Crustacea, Ostracoda, Limnocytheridae) with the description of a new species and two new tribes

The main aim of the present contribution is to provide an unequivocal diagnosis of the genus Leucocyhtere. It appeared, however, that this could only be effected when embodied in a broader taxonomic framework. The subfamily Limnocytherinae is thus divided into four tribes: Limnocytherini, Dinarocytherini, Cytheridellini and Leucocytherini and diagnoses are provided for these taxa. The latter two are new to science while the rank of Dinarocyhterini was changed from subfamily to tribe. Three genera are lodged in the Leucocytherini: Leucocythere Kaufmann, 1892, Potamocythere Schornikov, 1986 and Ovambocythere Martens, 1989. The former, nominate, genus is characterized and its type species, L. mirabilis, is extensively redescribed. A comparative description of a limnocytheridinid with a somewhat similar appearance, Limnocythere (Limnocytherina) sanctipatricii, is offered. A second species of Leucocythere, L. algeriensis nov. sp., is described from a temporary pool in Algeria. L. baltica (Diebel) is retained as a third species in the genus. A large number of fossil records is reassessed. Most of the Asian fossils, previously assigned to Leucocythere, do not belong in this genus and a revision of their status appears urgent. Some remarks on the validity and position of Leucocytherella are also offered. L. mirabilis is a cold-stenothermic species, with a preference for oligotrophic waters and fine graine sediments. Its status in Europe can at present best be described as endangered, due to rapid degradation of suitable habitats. L. algeriensis nov. sp. and Ovambocythere milani Martens are probably both capable of producing dry resistant stages. This is thus far unique in Cytherids, but the exact taxonomic distribution of this feature remains as yet unknown. Some comments on the phylogeny and historical biogeography are presented. Leucocythere appears to be the more advanced group in the Leucocytherini, the other two genera show more plesiomorphic character states. It is here postulated that the three genera evolve by vicariance from a more widely spread ancestor: Leucocythere in Europe, Potamocythere in Asia and Ovambocythere in Africa. L. algeriensis from northern Africa is doubtlessly from Paleartic stock and its speciation from L. mirabilis must have occured fairly recently. A number of morphological peculiarities of L. mirabilis are discussed with special attention for the carapace and for those soft parts that are used for the mating process. In spite of the fact that many of the peculiarities appear maladaptive at first glance, it must be stressed that L. mirabilis thus far maintained itself very well in its environment, until recent anthropogenic pollution caused its extinction in many localities

IN MEMORY OF EMIL G. RACOVITZA (1868–1947) – HIS IDEAS REVERBERATE IN OUR SCIENTIFIC RESEARCH

The ideas of E. G. Racovitza which led to the development of biospelaeology (biospeology, is the term used by Racovitza and adopted here) are reviewed. We emphasize the important research programme named Biospeologica which allowed to implement practical investigations on the subterranean animals due to enthusiastic cooperative work of many scientists. It leads to the exploration of many caves and other hypogean habitats. It is stressed out that the aim of Racovitza’s efforts was to stimulate scientists to contribute with their research to the development of an encyclopedic view of the “Natural History of the Subterranean Domain”. Examples from our own research reflect such ideas. We adopted Racovitza’s views on the phylogenetic systematics, on the way to identify the relict aspect displayed by many subterranean animal groups. Also it is pointed out the importance of Racovitza’s ideas for reconstruction of the dynamic dispersion of homogeneous phylogenetic animal lineages in time and space. Such ideas help us to develop biogeographic scenarios which are important for understanding earth’s history. It is confirmed this way that the ambitious programme of Racovitza, became during the time a real research tradition that merits being pursued by young naturalists interested in solving exciting problems related to the origin and evolution of the subterranean domain and its ecosystems

Spatiotemporal distribution of microbial communities in a coastal, sandy aquifer system (Doñana, SW Spain)

This is the peer reviewed version of the following article: Velasco Ayuso, S. et al. Spatiotemporal distribution of microbial communities in a coastal, sandy aquifer system (Doñana, SW Spain). Geobiology 7 (2009): 66-81, which has been published in final format at http://dx.doi.org/10.1111/j.1472-4669.2008.00183.

From Naples 1963 to Rome 2013 - A brief review of how the international research group on Ostracoda (IRGO) developed as a social communication system

The 1st International Symposiumon Ostracoda (ISO) was held in Naples (1963). The philosophy behind this symposiumand the logical outcome of what is nowknown as the International Research Group on Ostracoda (IRGO) are here reviewed, namely ostracodology over the last 50 years is sociologically analysed. Three different and important historic moments for the scientific achievements of this domain are recognised. The first one, between about 1963 and 1983, is related to applied research for the oil industry aswell as to the great interest in the better description of the marine environment by both zoologists and palaeontologists. Another important aspect during this period was thework by researchers dealing with Palaeozoic ostracods,who had their own discussion group, IRGPO. Gradually, the merger of this latter group with those dealing with post-Palaeozoic ostracods at various meetings improved the communication between the two groups of specialists. A second period was approximately delineated between 1983 and 2003. During this time-slice, more emphasis was addressed to environmental research with topics such as the study of global events and long-term climate change. Ostracodologists profited also from the research "politics" within national and international programmes. Large international research teams emerged using new research methods. During the third period (2003-2013), communication and collaborative research reached a global dimension. Amongst the topics of research we cite the reconstruction of palaeoclimate using transfer functions, the building of large datasets of ostracod distributions for regional and intercontinental studies, and the implementation of actions that should lead to taxonomic harmonisation. Projects within which molecular biological techniques are routinely used, combined with sophisticated morphological information, expanded now in their importance. The documentation of the ostracod description improved through new techniques to visualise morphological details, which stimulated also communication between ostracodologists. Efforts of making available ostracod information through newsletters and electronic media are evoked

Palaeoenvironmental and diagenetic reconstruction of a closed-lacustrine carbonate system - the challenging marginal setting of the Miocene Ries Crater Lake (Germany)

Chemostratigraphic studies on lacustrine sedimentary sequences provide essential insights on past cyclic climatic events, on their repetition and prediction through time. Diagenetic overprint of primary features often hinders the use of such studies for palaeoenvironmental reconstruction. Here the potential of integrated geochemical and petrographic methods is evaluated to record freshwater to saline oscillations within the ancient marginal lacustrine carbonates of the Miocene Ries Crater Lake (Germany). This area is critical because it represents the transition from shoreline to proximal domains of a hydrologically closed system, affected by recurrent emergent events, representing the boundaries of successive sedimentary cycles. Chemostratigraphy targets shifts related to subaerial exposure and/or climatic fluctuations. Methods combine facies changes with δ13C–δ18O chemostratigraphy from matrix carbonates across five closely spaced, temporally equivalent stratigraphic sections. Isotope composition of ostracod shells, gastropods and cements is provided for comparison. Cathodoluminescence and back‐scatter electron microscopy were performed to discriminate primary (syn‐)depositional, from secondary diagenetic features. Meteoric diagenesis is expressed by substantial early dissolution and dark blue luminescent sparry cements carrying negative δ13C and δ18O. Sedimentary cycles are not correlated by isotope chemostratigraphy. Both matrix δ13C and δ18O range from ca −7·5 to +4·0‰ and show clear positive covariance (R = 0·97) whose nature differs from that of previous basin‐oriented studies on the lake: negative values are here unconnected to original freshwater lacustrine conditions but reflect extensive meteoric diagenesis, while positive values probably represent primary saline lake water chemistry. Noisy geochemical curves relate to heterogeneities in (primary) porosity, resulting in selective carbonate diagenesis. This study exemplifies that ancient lacustrine carbonates, despite extensive meteoric weathering, are able to retain key information for both palaeoenvironmental reconstruction and the understanding of diagenetic processes in relation to those primary conditions. Also, it emphasizes the limitation of chemostratigraphy in fossil carbonates, and specifically in settings that are sensitive for the preservation of primary environmental signals, such as lake margins prone to meteoric diagenesis

Islands beneath islands: phylogeography of a groundwater amphipod crustacean in the Balearic archipelago

<p>Abstract</p> <p>Background</p> <p>Metacrangonyctidae (Amphipoda, Crustacea) is an enigmatic continental subterranean water family of marine origin (thalassoid). One of the species in the genus, <it>Metacrangonyx longipes</it>, is endemic to the Balearic islands of Mallorca and Menorca (W Mediterranean). It has been suggested that the origin and distribution of thalassoid crustaceans could be explained by one of two alternative hypotheses: (1) active colonization of inland freshwater aquifers by a marine ancestor, followed by an adaptative shift; or (2) passive colonization by stranding of ancestral marine populations in coastal aquifers during marine regressions. A comparison of phylogenies, phylogeographic patterns and age estimations of clades should discriminate in favour of one of these two proposals.</p> <p>Results</p> <p>Phylogenetic relationships within <it>M. longipes </it>based on three mitochondrial DNA (mtDNA) and one nuclear marker revealed five genetically divergent and geographically structured clades. Analyses of cytochrome oxidase subunit 1 (<it>cox1</it>) mtDNA data showed the occurrence of a high geographic population subdivision in both islands, with current gene flow occurring exclusively between sites located in close proximity. Molecular-clock estimations dated the origin of <it>M. longipes </it>previous to about 6 Ma, whereas major cladogenetic events within the species took place between 4.2 and 2.0 Ma.</p> <p>Conclusions</p> <p><it>M. longipes </it>displayed a surprisingly old and highly fragmented population structure, with major episodes of cladogenesis within the species roughly correlating with some of the major marine transgression-regression episodes that affected the region during the last 6 Ma. Eustatic changes (vicariant events) -not active range expansion of marine littoral ancestors colonizing desalinated habitats-explain the phylogeographic pattern observed in <it>M. longipes</it>.</p