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Located to the north of the Stevns Klint Peninsula (Denmark), Kulstirenden shows the transition from Cretaceous chalks to Danian carbonates across the Cretaceous – Paleogene (K/Pg) boundary. The K/Pg boundary at Kulstirenden is represented by the Fiskeler Member (Fish Clay), a streaked marl interval with a smectite rich, red oxidised layer at its base marking the boundary. The Fiskeler Member is important as it includes the iridium concentration linked to the bolide impact which may have caused the end-Cretaceous mass extinction and is at its maximum thickness at Kulstirenden (c.45 cm). Calcareous dinoflagellate cysts (Calciodinelloideae) have been investigated from within the fine fraction (45–125 μm) at Kulstirenden in order to understand the ecological implications of these enigmatic microfossils. Several species were found within the Fiskeler Member, including Orthopithonella collaris Wendler et al. (2001 , Rev. Palaeobot. Palynol. 115, 69–77). This species is of particular interest as it demonstrates reduced paratabulation and may indicate a transgressive period immediately after the K/Pg boundary event. O. collaris has been described as a morphotype formed under post-K/Pg environmental conditions and is, therefore, described as a “disaster” taxon that marks the K/Pg boundary at Stevns Klint. The distribution of this taxon is more extensive than previously documented, disappearing as carbonate sedimentation returned in the Cerithium Limestone Member of the Danian. Several calcareous microfossil specimens that were found cannot be associated with the dinoflagellates and display Bolboforma -like features. While the origins of Bolboforma are enigmatic, the current finding expands their stratigraphic range and suggests an appearance of this group of organisms found at Stevns Klint may give an insight into the inception of this group into the earliest Danian.

We used 20 species of coastal marine snails in the genus Cerithidea and Cerithium collected along the Pacific and Atlantic coasts of Central America to investigate the role of the rise of the Isthmus of Panama in the speciation of this group. Of particular interest was the identification of geminate species pairs presumably established by the disruption of gene flow across the isthmian barrier. Hypotheses of phylogenetic relationships were based on approximately 2.4 Kb of the mitochondrial cytochrome oxidase c subunit I gene, 16S ribosomal RNA gene and the nuclear 28S ribosomal gene. We identified four putative geminate species pairs out of the 20 species evaluated, but the level of sequence divergence among the pairs differed more than two-fold. A geminate pair, in which both species live in the high intertidal of mangrove habitats, exhibited less sequence divergence compared to other pairs occupying lower intertidal and subtidal habitats. Mangrove dwelling species were probably the last to be separated by the final closure of the Central American Seaway, and thus their divergence times correspond most accurately to the completion of the Isthmus.

The present work aims to assess the spatial distribution, analyze shell utilization, shell fitness and determine the effect of coexistence of two hermit crabs Calcinus latens and Clibanarius signatus on used shell resources in various habitats on the Red Sea Coast. Also, to determine the choice of shells and investigate the shell species preference of C. latens and C. signatus in the laboratory. The hermit crabs C. latens and C. signatus were found to occupy shells of 39 gastropod species. The most commonly occupied gastropod shells are those belonging to genera Strombus, Nerita, Cerithium and Planaxis. The results showed that crab individuals utilized mainly the shell with elongate aperture. Laboratory experiments showed that two crab species preferred shells of Strombus followed by Cerithium and Nerita when offered shells of nearly similar size (optimal). Crab individuals showed a significant preference for optimal sized shells when given suboptimal shells as an alternative choice. Also, the hermit crabs avoid damaged shells when given a choice of optimal sized damaged shell and optimal sized intact one. In addition, two hermit crab species chose shells of smaller than optimal size when given a choice of damaged optimal sized shells and smaller intact ones. On the other hand, field observations showed that most crab individuals lived in adequate sized shells. The present data conclude that shell selection by hermit crabs C. latens and C. signatus depends mostly on shell internal volume, shell quality and shell aperture size than other factors, because they provide a maximum protection for hermit crabs.

This study was designed to evaluate the effect of interference and exploitation competition in shell partitioning between two hermit crab species (Pagurus criniticornis and Clibanarius antillensis). Field samples revealed that shells of the gastropod Cerithium atratum were the main resource used by both hermit crab species and that Pagurus used eroded or damaged shells in higher frequency than Clibanarius. The exploitative ability of each species was compared between species in the laboratory using dead gastropod (Cerithium) baits to simulate predation events and signalize newly available shells to hermit crabs. Pagurus reached the baits more rapidly than Clibanarius, but this higher exploitative ability did not explain shell utilization patterns in nature. Another experiment evaluated the dominance hierarchy between these two hermit crab species and revealed that Clibanarius was able to outcompete Pagurus for higher quality shells in agonistic encounters. This higher interference competitive ability of Clibanarius in relation to Pagurus may explain field observations. Nevertheless, Pagurus may be responsible to enhance shell availability to other hermit crab species that have lower ability to find and use newly available shells. Differently, the poorer condition of shells used by Pagurus, the higher ability of this species to attend gastropod predation events and its higher consumption rate by shell-breaking crabs (Menippe nodifrons) may increase its predation risks, thus revealing the disadvantages of such an exploitative competitive strategy for hermit crabs.

Calcareous deposits, mainly consisting of mollusc shell accumulations, which have been dated by the U/Th disequilibrium method, mark the shorelines of paleolake highstands in the Great Chotts Area of Southern Tunisia. The 5 sites studied consist of discontinuous accumulations of fossils of marine-like organisms e.g.: Cerastoderma glaucum, Melania tuberculata, Melanopsis praemorsa, Cerithium rupestre. U/Th isochron plots and age frequency histograms for 39 shell samples are reported here. Limited variations for U content and 234U/238U activity ratios (AR) of shells support the hypothesis of closure of the geochemical system with respect to this element. It is remarkable that 234U/238U AR of shells collected in Chott Fejej or Chott Jerid are clustered around different values, reflecting probably different groundwater recharge from the Continental Intercalaire (CI) or Complexe Terminal (CT) aquifers. Furthermore waters collected near Wadi el Akarit show 234U/238U AR values comparable to those observed for shells. 14C determinations made on aliquots of some of these samples suggested an age distribution between 18 and 34 ka BP. The U/Th data of these 39 shell samples imply that 4 distinct flood episodes of these lakes occurred at about 30, 95–100, 130–150 and 180–200 ka. For the episode centred around 30 ka, the frequency histogram of ages shows a multimodal age group that could represent the existence of several humid pulses rather than a unique event. Moreover, the comparison of δ13C and δ18O with those of older humid Pleistocene phases, when very large palaeolakes have been recorded, suggests that these young carbonate shells are not related to a true highstand lake. It is suggested that they represent a period of less humid climatic conditions with carbonate accumulation in minor water ponds in which intensive biological activity could have taken place. It should be noted that this period was less arid than the present.

Paleogene sedimentation in the Alpes Maritimes and Alpes de Haute Provence regions is composed of one complete sedimentary sequence. This sequence begins with the continental Formation from Microcodium and continues with the Cerithium layers, the Calcaires Nummulitiques and the Marnes Bleues, which are overlaid by the turbidites of the Gres d’Annot Formation. Sedimentation starts in the Nummulites perforatus zone close to the base of ‘the Truncorotaloides rohri zone (P 14) and ends in the Cassigerinella chipolensis–Pseudohastigerina micra zone (P 18) and the NP21 zone in the upper part of the Gres d’Annot. More biomarkers were used in order to define a more detailed local biozonation (biozones AMP 1 to AMP 7). Four local zones were also defined by the last occurrence of Nummulites millecaput and N. perforatus–N. ptukhiani and then by the first appearance of N. retiatus (AMGF 1–4). The evolution of benthic foraminiferal assemblages shows an increase in bathymetry from the internal platform in the Cerithium layers to the calcareous platform with large foraminifers, then to the external platform and the deep offshore environment of the Marnes Bleues and Gres d’Annot. Low faunal diversity in the Gres d’Annot together with the predominance of agglutinated species indicates a poorly oxygenated, organic rich and turbidite environment. Seven steps (SD 1 to SD 7) in the Eocene marine transgression are shown from East to West by detailed local biozonation and sequence analysis. Gres d’Annot sedimentation is also diachronous, beginning within the Truncorotaloides rohri zone (P 14, AMP 1) in the East and ending within the Pararotalia opima opima zone (P 20, middle Rupelian) in the West (Barreme). Small foraminifer Paleogene fauna from the Alpes Maritimes and Alpes de Haute Provence was studied from 400 samples. It is composed of 378 species. Two new taxa are proposed: Fissurina niceana n. sp. and Globocassidulina alpina n. sp. The species from the Escarene and Gorbio neighborhood described by M. von Hantken (1884) were re-examined.

The Albian section of Gabal Manzour, Maghara area, north Sinai is highly fossiliferous. Besides the foraminifers, Orbitolina in particular, macroinvertebrates are very common and highly diversified. These are represented by corals, gastropods, bivalves, cephalopods and echinoids. Serpulids are also recorded. Eighty genera including 127 species, were identified. Of these eight genera and eight species are reported for the first time in the Lower Cretaceous of Egypt. Nine new species are established. Six of them are gastropods viz., Solariella douvillei, Cerithium manzourensis, Cerithium abbassi, Drepanocheilus abbassi, Bittium mahmoudi and Tylostoma canaliculata. Crassatella manzourensis, Venilicardia faragi and Liopistha albiana are three new bivalve species. Generally, the faunal assemblages recovered from the studied section have Tethyan affinities. They indicate rather warm waters of normal to slightly hypersaline conditions, that represent a shallow, near shore environment in which the water depth did not exceed 100 m.

Cadmium, Co, Cr, Cu, Fe, Mn, Ni, and Zn were measured by atomic absorption spectroscopy in the digestive gland of the marine gastropods Cerithium vulgatum, Monodonta spp., Murex trunculus, Conus mediterraneus , and Patella coerulea , sampled during different seasons at four sites near a ferro-nickel smelting plant and two control sites on the east coast of Greece. Near the smelter there were higher concentrations of all metals in Cerithium (except Cu) and Murex , and of Ni and Co in Monodonta , compared with the control sites, which indicated that the plant contaminated the environment. The animals from the contaminated area showed marked differences in concentrations which were associated both with the genera and the sites, while there were no consistent seasonal variations.

An intertidal Pleistocene sandflat community is analyzed in terms of community structure, survivorship, inferred biomass distributions, predation patterns, and trophic structure. The distributions of the first-level consumers was controlled by substrate grain size. The distributions of the predators mirrored the concentrations of their prey. Because of differing burrowing abilities, the Libertad infauna produced a community stratification. This property concentrated large segments of biomass at different levels within the substrate. This mechanism buffered biospace-related competition. When similar interspecific depth habitation zones overlapped, one or the other taxon was density limited. Survivorship curves constructed from size-frequency data and the function D = S 1n ( T +1) demonstrated that Lucina approximata experienced constant mortality; Chione califonniensis had a well-developed bimodality of age distributions and Tagelus californianus had increasing population mortality. These contrasting mortality patterns were related to depth of habitation and substrate stability. The internal volumes displaced by a growth series of selected taxa were used to estimate biomass distributions. In terms of biomass, the dominant community members had largest volumes in juveniles — a characteristic of a stable population. Other accessory taxa had large volumes in adults — a property of stationary populations. Theodoxus lutteofasciatus had constant mortality, Cerithium stercusmuscarum, Nassarius tiarula and Natica chemnitzii had curves similar to Chione . Predation patterns demonstrated that two trophic subwebs existed among the predators. Muricanthus nigritus, Hexaplex erythrostomus and Melongea patula preyed on Ostrea palmula, Megapitaria squalida and Cerithium. Natica consumed the juveniles of Chione, Lucina, Nassarius and Theodoxus . The annelid predators Conus regularis, Acteocina inculta and Bulla gouldiana composed a third subweb, not attacked by any molluscan carnivore. The highest predation rate occurred in Nassarius , the lowest among the deep infauna. Differing food preferences by predators served as a stabilizing mechanism maintaining community homeostasis by providing alternative food reserves. It was shown that bore-hole loci changed through ontogeny in selected taxa. Likewise, borehole patterns differed slightly on right and left valves of the same prey species. In general predation rates declined rapidly with advancing age. Highly localized borehole sites were found in Theodoxus, Natica and Nassarius — the prey of Natica . Cerithum , the prey of Muricanthus , had less localized borehole loci. This suggests the latter's predator was less “sensitive” to prey- “induced” responses for selective manipulation. The Libertad community declined when the substrate closed to recruitment by the accumulation of the shells from previous generations.

Sense receptors of the juvenile aspidogastrid Lobatostoma manteri infecting the digestive gland of the prosobranch snail Cerithium moniliferum were examined by transmission electron microscopy. At least eight types of presumptive sense receptors, some uniciliate and some non-ciliate, are described. Some of the receptors occur in thousands. This is the greatest variety of receptors ever described from a parasitic stage of a platyhelminth by electron microscopy.

The temporal and spatial distribution of major plant and animal species were investigated for 4 years in south Biscayne Bay including Card Sound, Florida, a subtropical estuarine lagoon. This was part of a larger study including chemical, physical and geological investigations. The major species of plants were Thalassia testudinum Banks ex Konig, turtle grass, Laurencia poitei (Lamour.) Howe, a red macroalga and the green algae Penicillus capitatus Lamarck and Halimeda incrassata (Ellis) Lamour. Standing crop and production of plant material taken bi-weekly is given in detail for 16 stations in Card Sound for the 4-year period and for eight stations in Biscayne Bay for a 1-year period. The major animal species were not equally distributed; in the near-shore Thalassia community, species of Pagurus, Neopanope, Hippolyte, Cerithium, Bulla, Prunum and Modulus were dominant. In mid-bay, where patchy Thalassia plus green algae occurred, Thor and Chondrilla were the dominant animals. Near the fringing islands, where tidal flow caused more oceanic conditions, the community was dominated by sponges, urchins and corals. This highlights the structural differences in what is now termed the “ Thalassia community”. Comparisons with other known Thalassia communities are made.