The structure and evolution of Ordovician conodont apparatuses

Multielement taxonomy was instituted for Ordovician conodonts over a decade ago, and probably a majority of the multielement genera have been defined or are well understood. The present systems of notation for elements within apparatuses are inadequate and cumbersome. A new notation scheme is proposed which applies a single-letter code to the position in the apparatus occupied by certain element morphotypes. The taxonomic status of all known Ordovician conodont genera is reviewed (appendix) using the new notation, and a new scheme to classify conodont apparatuses is presented. Five main apparatus types (I-V) and seventeen subtypes (IA-IC, etc.) are defined. Within these groups, all known Ordovician conodont genera can be accommodated, and probably few new groups are required to include all other conodont genera. The apparatus types and subtypes are defined on the basis of symmetry, curvature, and number of the element types, with a clear distinction being made between the first and second transition series. Certain homologous relationships, both between and within many apparatus types, are noted. The evolution of the five major types, and the subtypes, is traced through the Ordovician. The pattern of evolution suggests that the types and subtypes recognized are probably natural biologic groupings, largely reflecting phylogenetic change.     

Correlation of shape and habit with sediment grain size for selected species of the bivalve Anadara

Burrowing ability was experimentally determined for a range (3–150 g) of sizes of the blood ark, Anadara ovalis , in sieved sediments ranging from very coarse sand (-1 φ) to silt (>4 φ). Small individuals (<5 g) could penetrate the complete range of sieved sediments, but the ability to reburrow apparently decreases with size (age) so that adults larger than 50 g can only reburrow in fine sands (2.5–3.0φ). This semi-infaunal species has a length/height ratio of 1.16 and is most commonly found in sand. The infaunal A. cheninitzi and A. braziliana , with L/H values of 1.10 and 1.18, respectively, are also most common in sands. The ovate (L/H ratio = 1.07–1.25) forms of the Pliocene A. trilineata from the Kettleman Hills of California are inferred to have been infaunal, based on the absence of muricid boreholes and the infrequent occurrence of epizoans. Ovate specimens are restricted to fine sands (2–3φ) in the Etchegoin and San Joaquin Formations, sediment textures into which the adults could probably reburrow. Elongated shell morphotypes (L/H = 1.5–1.67) have muricid boreholes and epizoans concentrated posterodorsally on the inferred exposed portion of the shells in life position. Populations of elongated shells were associated with gravelly, sandy and silty sediments, as is the living epibyssate A. lienosa (L/H = 1.72) and A. transversa (L/H = 1.48).□ Anadarids, burrowing, epifounal, infaunal, Pliocene, sediment influence .     

Pollen in the guts of Permian insects: first evidence of pollinivory and its evolutionary significance

Uniquely preserved pollen was extracted from intestines of fossil insects from the Lower Permian of the Urals. A species of Hypoperlidae, an extinct family ancestral to bark-lice, bugs and plant-hoppers, and two species of Grylloblatida, a predominantly Permian group with a few extant representatives related to stoneflies, contain protosaccate taeniate grains of several pollen genera well known as dispersed microfossils and occasionally found in sporangia of conifers, peltasperms and glossopterids. This is so far the earliest direct evidence of pollinivory, a major factor of plant-insect coevolution. The partly digested pollen grains reveal infratectal reticulum and other structural details of evolutionary significance. It is suggested that the peculiar taeniate pollen of worldwide distribution in the Permian might simultaneously evolve in several groups of Paleozoic seed plants in relation to pollinivory that, by altering the rnicropyle load and thereby the pollen/ovule ratio, could also affect ovuliferous structures. Thus pollinivory might impel rapid diversification of gymnosperms in the Permian. The pollinivorous Hypoperlidae, which have evolved in the direction of ovulivory, might initiate insect pollination in the process.     

UNTERSUCHUNG DES CHEMISCHEN AUFBAUS VON MITTELKAMBRISCHEN OSTRACODENSCHALEN

A microprobe investigation demonstrated that the shell substance of archaeocope ostracodes consists mainly of calcium phosphate and contains subordinate quantities of iron and carbonaceous matter. The relative content of calcium phosphate increases towards the outer surface of the shell; the content of carbonaceous matter decreases in this direction.     

Trochonerilla mobilis gen. et sp.n., a meiofaunal nerillid (Annelida, Polychaeta) from a marine aquarium in Moscow

A nerillid species new to science is described from the marine aquarium system of Moscow Zoo. Trochonerilla mobilis gen. et sp.n. is characterized by eight chaetigerous segments, three antennae, absence of palps, parapodia with two bundles of simple chaetae and pygidium with two anal cirri. In contrast to other eight-segmented nerillids, Trochonerilla mobilis are very active and mobile animals. They are also able to swim through the water column by means of the strong ring of cilia on the first chaetigerous segment. Their geographical origin is unknown.     

Intraspecific selective survival within variably uniplicate Late Devonian brachiopods

The central fold of the Late Devonian brachiopods Cyrtospirifer monticola, Cleiothyridina devonica, Rugaltorostrum madisonense, Sinotectirostrum banffense and Trifiodorostellum dunbarense (Three Forks Formation, Central Idaho) varies intraspecifically from nearly rectimarginate or weakly developed to chevron-shaped. Frequency of central fold morphotypes through succesSjve size classes indicates selective survival in favor of variants with a strongly developed central fold, although morphotypes with the most extremely developed central fold never numerically dominate the larger size classes of any species. Differential mortality among the morphotypes can be attributed to: (1) less resistance to shell fracture by morphotypes with weakly developed uniplicae which were preferentially culled out of the population by durophagous predators, (2) less efficiency of weakly uniplicate morphotypes in the generation of nutrient-bearing eddies against the downcurrent inhalant margins. Failure of the morphotypes with the most strongly developed uniplicae to numerically dominate adult (largest) size classes is attributed to the hydrodynamic instability of such shell geometries on current-scoured substrates.     

Impact of parasitic mite infection on a terrestrial snail

Summary

Although parasitic infections have been shown to be critical for growth, reproduction and survival of many vertebrates, little is known about the impact of parasites on invertebrate hosts and particular on molluscs. Therefore, it is of interest how parasites may affect their invertebrate hosts and how hosts can manage the detrimental effect of infections. In the present study, the naturally widespread parasitic mite Riccardoella limacum, which has been suggested to play an important role in the ecology of the land snail Arianta arbustorum, was artificially transferred to A. arbustorum. We experimentally examined the effect of the parasite on the food consumption, shell growth, and survival of its host. Surprisingly, we found minor impacts in some traits, i.e. we found that infected and uninfected snails similarly completed their shell growth, attained sexual maturity, and allocated equal energy into their albumen glands. However, infected snails consumed less and showed a significantly higher mortality after winter than uninfected snails.     

Isolation of five polymorphic microsatellite markers in Utetheisa ornatrix (Lepidoptera: Arctiidae)

We isolated five polymorphic microsatellite markers for the arctiid moth Utetheisa ornatrix as part of an effort to investigate the role of inbreeding in the degree of polyandry seen in natural populations of the moth. We tested the primers on 105 individuals collected from scrub habitat in central Florida. These microsatellite loci provide a new research tool for understanding the population structure and reproductive behaviour of U. ornatrix.