Stable-isotope and amino acid profiles of the New Zealand giant Pliocene oyster Crussostreu ingens

Mitchell, L., Curry, G.B. & Fallick, A.E. 1995 11 30: Stable-isotope and amino acid profiles of the New Zealand giant Pliocene oyster Crassostrea ingens .
Oxygen and carbon stable-isotope profiles and intracrystalline amino acid profiles (free and total) were determined for the New Zealand giant Pliocene oyster Crassostrea ingens by sampling annual growth increments along a sagittal section. These profiles reflect both ontogenetic and environmental change over the life-time of the oyster (approximately 20 years). There is a gradual increase in δ¹⁸O from the umbo towards the shell margin and a subsequent levelling-off about halfway along the shell. This pattern probably reflects a decrease in the growth rate of the oyster rather than a temperature effect. The δ¹³C profile initially increases sharply at the umbo and then gradually decreases towards the shell margin. This may be due to kinetic or metabolic effects associated with the development of a fast-growing juvenile into a slower-growing, sexually mature adult, or it may be due to the influence of ¹³C-depleted carbon derived from the oxidation of organic matter in the surrounding sediment. The amino acid profile reveals a gradual decrease in abundance from the umbo to the shell margin, indicative of a progressive increase in the relative amounts of inorganic carbonate to protein over the life of the oyster, that may also be a consequence of decreasing growth rate. Glycine and alanine are the two most common amino acids in both the free and total amino acid profiles: free (i.e. naturally hydrolysed) amino acids account for about three quarters of the total amino acids present. □ Biogeochemistiy, stable isotopes, amino acids, environment, ontogeny .     

Colloidal crystal-like structure of sporopollenin in the megaspore walls of Recent Selaginella and similar fossil spores

HEMSLEY, A. R., COLLINSON, M. E. & BRAIN, A. P. R., 1992. Colloidal crystal-like structure of sporopollenin in the megaspore walls of Recent Selaginella and similar fossil spores. TEM and SEM studies of iridescent fossil Erlansonisporites and Recent Selaginella spores reveal a wall composed of three regions. The central region consists of close-packed particles in a semi-crystalline arrangement. This organization is compared with that of aggregated Iridoviridae, prolamellar bodies, lipid micelles and precious opal. Our observations suggest that the structure of this wall region (and that of the remaining regions) can be explained by derivation from colloidal mixtures. It is concluded that colloids and their precursors may play a far more significant part in spore and pollen wall structure than was previously believed.     

Calcification in the Green Alga Halimeda: II. THE EXCHANGE OF CA2+ AND THE OCCURRENCE OF AGE GRADIENTS IN CALCIFICATION AND PHOTOSYNTHESIS

In Halimeda cylindracea and H. tuna segments, the concentrationof CaCO₃, MgCO₃, protein, and chlorophyll, as well as segmentvolume and wet and dry weight, increase with ‘age’i.e. from the apex of a branch downwards. Photosynthetic andcalcification rates decrease with age as does the degree oflight stimulation of calcification. Studies of the exchange of ⁴⁵Ca between the Halimeda thallusand the sea water under various conditions showed that mostof the Ca exchange is between the cell walls, the aragonitecrystals, and the intercellular space. The cell wall has twodistinguishable phases with half-times (t_0?5) of 200 and 35min while the CaCO₃ has a rapidly exchanging phase with a t_0?5of approximately 6 min. The t_0?5 of the exchange of Ca betweenthe intercellular space and the external medium is estimatedat about 6 min, on the basis of uptake studies. If the integrityof the barrier between the intercellular space and the externalsea water, created by the adpressed peripheral utricles is destroyedthe t_0?5 is smaller (<<3 min). These kinetic studies as well as comparative measurements ofcalcification rates by both isotopic and chemical methods showthat the ⁴⁵Ca method for measuring calcification rates overestimatesthe calcification rate, due to binding of ⁴⁵Ca in the cell wallsand retention of ⁴⁵Ca in the intercellular space. The ¹⁴C methodgives more accurate results and has the further advantage ofallowing simultaneous measurement of the photosynthetic andcalcification rate on the same segment.     

FIELD STUDIES OF HOMING IN THE PULMONATE SLUG LIMAX PSEUDOFLAVUS (EVANS)

Excursions of Limax pseudoflavus (Evans) were recorded over9 days using time lapse cinematography. Excursions were madeat night, ending before sunrise, and were significantly morefrequent in wet than in dry weather. The homes of these slugsare species rather than population or individual specific. Animalstended to home upwind but the direction in which they left homewas not significantly correlated with wind direction. Trailfollowing may be involved in homing. All but one example ofhoming may be interpreted in terms of distant chemoreception,rheotaxis and trail following. Using these mechanisms alonea slug's best strategy for feeding and homing is discussed. (Received 15 March 1979;     

A new large philisid (Mammalia,Chiroptera, Vespertilionoidea) from the late Early Eocene of Chambi,Tunisia

Abstract: Among the new dental remains from the late Early Eocene of Chambi (Kasserine area, Tunisia) is a large‐sized upper molar of a new bat species, Witwatia sigei nov. sp. (Chiroptera, Vespertilionoidea, Philisidae), described herein. The locality of Chambi has revealed evidence for an early appearance of two modern microchiropteran superfamilies in Africa: Dizzya exsultans, a Philisidae, which is considered to be an archaic Vespertilionoidea, and an indeterminate Rhinolophoidea. In addition to D. exsultans, the new species, W. sigei, is the second representative of the Philisidae in this locality. W. sigei extends back to the late Early Eocene the occurrence of the genus Witwatia, which was previously only reported from the early Late Eocene of the Fayum (BQ‐2, Egypt). By analogy with the largest extant microbats, the large size of Witwatia suggests a tendency to the opportunistic diet of this taxon, thereby contrasting with the strict insectivory characterizing primitive bats found in other continents in the same epoch.     

Developmental patterns of the crocodilian and avian columella auris: reappraisal of interpretations of the derivation of the dorsal hyoid arch in archosaurian tetrapods

The morphogenesis of the crocodilian and avian columella auris is analysed, using Alligator and Struthio as models that are studied in detail, and Crocodylus, Gallus, and Coturnix as models for comparative purposes. This investigation was undertaken to address controversies emanating from previous studies concerning the identity of archosaurian hyal elements, and to clarify confounding nomenclature that has been used for both topographic and phylogenetic purposes. We found that confusion in the identification of the reptilian and avian hyoid arch derivatives is attributable to: (1) redundant and/or inconsistently applied topographical terminology; (2) mixing of topographical and phylogenetic terminology; (3) interpretation in a recapitulatory framework; and (4) failure to consider that developmental pathways of recent archosaurians (reptilians and birds) might be divergently modified. Our analysis identifies errors in previous interpretations, misinterpretations of prior work, and histological observations that have been idealized. The most controversial issues are addressed – the derivation of the supracolumellar process; the concept of the laterohyal component; and segmentation of the distal part of the reptilian and avian columella auris. Based on new data, we suggest that the osteichthyan infrapharyngohyal, suprapharyngohyal, epihyal, and ceratohyal are not applicable terms for reptilian and avian columellar components from a phylogenetic perspective, and should not be used as topographical terms either. We further propose that the original morphogenetic program of the hyoid arch has been overwritten in newly derived evolutionary pathways of crocodilians and birds, in which a new functional and morphological patterning of the hyoid arch, as a specific sound‐transmitting apparatus, have evolved. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 384–410.     

Opening Pandora's box: comparative studies of genetic mating systems reveal reproductive complexity

Genetic analyses of realized reproductive success have fundamentally changed our understanding of mating behaviour in natural systems. While behavioural ecologists have long been interested in what factors influence mating behaviour, early studies were limited to direct observations of matings and thus provided an incomplete picture of reproductive activity. Genetic assessments of parentage have revolutionized the study of reproductive behaviour, revealing that many individuals engage in extra‐pair copulations ( Griffith et al. 2002 ) and that social mating partners frequently invest substantial resources into raising offspring that are unrelated to one or both of them ( Avise et al. 2002 ). While these findings have changed the way we think about reproductive behaviour, most investigations of genetic parentage have been restricted to single populations at a single point in time, obscuring spatial and/or temporal variation in mating behaviour and limiting our ability to determine how environmental changes can lead to shifts in mating strategies. In this issue of Molecular Ecology, Mobley & Jones (2009) compare genetic mating behaviour across five populations of Syngnathus floridae ( Fig. 1 ), a widespread species of pipefish distributed along the Gulf‐ and Atlantic Coasts of North America. The authors document how genetic mating behaviour varies across space in S. floridae and identify correlations between reproductive variation and particular ecological characteristics. Mobley & Jones’ paper is one of an increasing number of studies which address the question of how ecological variables influence mating behaviour, and highlights how our understanding of mating system variation and evolution is likely to expand through the wider application of high‐throughput parentage assessment in a comparative context.

Figure 1 Open in figure viewer PowerPoint A pregnant male dusky pipefish (Syngnathus floridae) in its natural habitat. Photo credit: Joe O’Hop.