Developmental constraints on limb growth in domestic and some wild canids

The domestic dog varies remarkably in limb size. Presumably, such differences in limb size stem from inequities in postnatal specific growth rate. I test this hypothesis by examining the postnatal growth of limb bones (40–250 days post-partum) in four dog breeds of dramatically different adult size; Lhasa Apso, Cocker Spaniel, Labrador Retriever and Great Dane. The results show that the limb bones of these four breeds have similar specific growth rates throughout most of postnatal development. Thus, proportionate differences in limb bone length are established during perinatal growth (0–40 days post-partum) or before birth.
Comparisons of postnatal growth in the Great Dane and two wild canids of dramatically different leg length, the Bush dog ( Speothos venaticus ) and the Maned wolf ( Chrysocyon brachyurus ) also show a near congruency of specific growth rate curves. However, despite these similarities, the adult limb proportions of small dogs and small wild canids are different. Dogs also differ from wild canids in the relative variability of gestation time. All dogs have a similar gestation period of 60–63 days which is independent of birth weight, whereas the two are directly related in wild canids. I suggest that small dogs may differ in limb proportions from small wild canids because the latter have a shorter gestation period. Thus, the relative invariability of gestation time in domestic dogs may act as a fundamental constraint on their morphologic variability.     

Boring Late Cambrian organisms

Specimens of inarticulate brachiopods (family Acrotrctidae) with boreholes were found in Upper Cambrian carbonates in the southern Great Basin of the United States. Some morphologic features and preferred orientation of the borings are similar to those made by predators and previously reported in the fossil and Holocene record. Such predatory activity on brachiopods is previously unknown in Cambrian rocks. Taxa associated with these specimens are not known to have been predators and identity of the predatory organism is unknown. Cambrian brachiopods, predation, paleoecology.     

Multiple scale patterns of shell and anatomy variability in land snails: the case of the Sicilian Marmorana (Gastropoda: Pulmonata, Helicidae)

Certain major aspects of phenotypic diversity are still largely unexplained. When phenotypic patterns do not relate to habitat variables, fine analysis of morphological patterns and their distribution sheds light on the origin of diversity. Among invertebrates, snails are an ideal model for studying the roles of the neutral processes and selection involved in creating diversity. To understand patterns and processes of variability on different scales (regional: areas; local: sites), morphological variability of two sets of characters (shell and genitalia) was quantified in a group of rock-dwelling land snails of the genus Marmorana (Pulmonata, Helicidae). To analyse shell variability, partitioning of the overall variation into size and shape components was analysed by a principal component-based approach. Shell shape and size variability is not significantly influenced by any environmental pressure. Variability at site scale is mainly attributed to shell size, which is a trait demonstrated to have a high degree of phenotypic plasticity. No sharp changes were observed for genitalia. Moreover, allometries between shell size and genitalia measurements involve a few populations. The observed multiple scale patterns are in line with the hypothesis that genital variance may be selectively controlled to maintain function.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 359–370.     

Post settlement behaviour of brachiopods on hard and soft substrates

Abstract

This paper describes the variation in shell and pedicle morphology of three species of brachiopods. Two are specialists that live on hard or soft surfaces, respectively, and the third is a generalist that can live on either. The interaction between behaviour and substrate explains (1) the morphology of the specialists, (2) variability in the lifestyle of the generalists, and (3) diversity in fossil brachiopods.     

Eccentricity in the clypeasteroid echinoid Dendraster: environmental significance and application in Pliocene paleoecology

Stanton, Robert J., Jr., Dodd, J. Robert & Alexander, Richard R. 1979 01 15: Eccentricity in the clypeasteroid echinoid Dendraster: environmental significance and application in Pliocene paleoecology. Lethaia . Vol. 12, pp. 75–87. Oslo. ISSN 0024–1164.
The echinoid Dendraster lives in the northwest Pacific in environments ranging from open exposed coast to protected embayment. Water energy and the abundance and quality of food along this environmental gradient are correlated with test size and eccentricity of the apical area, so that larger and more eccentric specimens occur on the open coast than in bays. Study of Dendraster in Pliocene strata of the Coalinga California region indicates that these morphologic characteristics provide valuable information for paleoenvironmental reconstruction. Lateral and temporal environmental gradients within a broad Pliocene embayment and the location and size of the bay entrance can be determined on the basis of Dendraster eccentricity and size. Several species and subspecies of Dendraster in the Pliocene of the Coalinga region, described largely by differences in eccentricity, are probably not valid taxa but are merely ecophenotypic expressions of the laterally and temporally variable environment.     

Is assemblage variability related to environmental variability? An answer for riverine fish

We examine the variability of riverine fish assemblages in terms of assemblage stability (i.e. variability of numbers of individuals within species over time and variability of assemblage total density), assemblage persistence, and assemblage species richness using data from a 9-yr survey of 27 sites within 18 coastal streams of North-western France. To do so, we test a hypothesized directional model for the expected relationships between environmental variability, assemblage variability, assemblage persistence, and assemblage species richness: 1) environmental variability within a given system is likely to generate variable local population size within this system, thus increasing local assemblages variability; 2) environmental variability should increase extinction rates (or, under constant colonization rates, decrease persistence), because the more population sizes vary within an assemblage, the more likely they are to become zero in some period of time; 3) assemblage variability should reduce assemblage species richness by increasing extinction rates within populations composing these assemblages. Results are compatible with our starting hypotheses and show that assemblage variability increased with environmental variability (i.e. discharge variability), that assemblage persistence decreased with environmental variability, and that species richness decreased with assemblage variability after environmental factors were controlled for. Thus, disturbance regimes, in our case, can alter the stability properties of assemblages and extrinsic determinants of assemblage variability may be an important determinant of assemblage species richness. These results have important conservation and management implications, due to the strong impact of river regulation on flow regimes.     

Size, shape and the distribution of organic matter in the Recent Antarctic brachiopod Liothyrella uva

The living terebratulid articulate brachiopod Liothyrella uva (Jackson 1912) was sampled from a shallow water population at Signy Island, South Orkney Islands, Antarctica. Neither shell height nor shell breadth were directly proportional to length and as a result there was a change in shell shape with size (and hence age); this change was small but statistically significant. The proportion of the total organic matter found in the shell and internal (mantle) tissues also changed with size. In small (5–7 mm length) brachiopods 70–80% of the total organic matter was located within the shell; this fraction decreased with increasing size until above about 25 mm length the proportion of organic matter in the shell was constant at 30–45%. Variability in this measure was influenced by infection with endolithic red algae. Punctal density was independent of size with a mean value of 95.7 per mm² [SE (standard error) ± 2.2], which was greater than in populations sampled from higher latitudes. With increasing shell length there was a slight increase in the size of puncta close to the shell edge. In all morphometric measures the range of variation observed was similar to that described from populations of Liothyrella from other areas of the Southern Ocean.     

Recent brachiopods from the southern Brazilian shelf: palaeontological and biogeographical implications

Until recently, the rhynchonelliform (articulated) brachiopod fauna from the Brazilian continental shelf (western South Atlantic) was represented only by the endemic species Bouchardia rosea (Mawe), reported from coastal waters of the states of São Paulo and Rio de Janeiro. The present study, based on samples from coastal (<30 m), shelf, and continental slope waters (99–485 m), documents the South Atlantic brachiopod fauna and shows that this fauna is more widespread, diverse, and cosmopolitan than previously thought. Based on a total of 16,177 specimens, the following brachiopods have been identified: Bouchardia rosea (Family Bouchardiidae), Platidia anomioides (Family Platidiidae), Argyrotheca cf. cuneata (Family Megathyrididae), and Terebratulina sp. (Family Cancellothyrididae). In coastal settings, the fauna is overwhelmingly dominated by Bouchardia rosea . Rare juvenile (<2 mm) specimens of Argyrotheca cf. cuneata were also found at two shallow-water sites. In shelf settings (100–200 m), the fauna is more diverse and includes Bouchardia rosea , Terebratulina sp., Argyrotheca cf. cuneata , and Platidia anomioides . Notably, Bouchardia rosea was found in waters as deep as 485 m, extending the known bathymetric range of this genus. Also, the record of this brachiopod in waters of the state of Paraná is the southernmost known occurrence of this species. The genera Platidia and Terebratulina are documented here for the first time for the western South Atlantic. The Brazilian brachiopod fauna shares similarities with those from the Atlantic and Indian shelves of southern Africa, and from the Antarctic, Caribbean and Mediterranean waters. The present-day brachiopods of the western South Atlantic are much more cosmopolitan than previously thought and their Cenozoic palaeobiogeographic history has to be reconsidered from that perspective.     

Silurian reef-dwelling pentamerid brachiopods, Wisconsin and Illinois, USA

Eight species of pentamerid brachiopods, assigned toApopentamerus, Capelliniella, Kirkidium, Lissocoelina, Rhipidium, Supertrilobus andStenopentamerus, occur in stromatoporoid-coral reefs of the Silurian (Wenlockian) Racine Formation, Wisconsin and Illinois, USA. One new taxon,Rhipidium kuglitschi n.sp., is described. In contrast to level-bottom communities, where single pentamerid species occur in great numbers over large areas, pentamerids were generally rare members of the Racine reef fauna, and most species have localized distributions. An increase in diversity from one pentamerid species in the north to six species in the south correlates with a southward increase in reef size. Four morphologic groups of pentamerid species differed in the shape of the mantle cavity, which suggests different dynamics of suspension-feeding. Where two or more species are present in single reefs, co-occurrence of these groups represents a partitioning of the pentamerid niche. The relatively high diversity, local distributions, and morphologic distinctions among the Racine pentamerid fauna represent an evolutionary radiation and functional specialization of pentamerids in Wenlock reefs.     

Stability of genetic structure and effective population size inferred from temporal changes of microsatellite DNA polymorphisms in the land snail Helix aspersa (Gastropoda: Helicidae)

Temporal evolution of genetic variability may have far-reaching consequences for a diverse array of evolutionary processes. Within the polders of the Bay of Mont-Saint-Michel (France), populations of the land snail Helix aspersa are characterized by a metapopulation structure with occasional extinction processes resulting from farming practices. A temporal survey of genetic structure in H . aspersa was carried out using variability at four microsatellite loci, in ten populations sampled two years apart. Levels of within-population genetic variation, as measured by allelic richness, H _e or F _is , did not change over time and similar levels of population differentiation were demonstrated for both sampling years. The extent of genetic differentiation between temporal samples of the same population established (i) a stable structure for six populations, and (ii) substantial genetic changes for four populations. Using classical F -statistics and a maximum likelihood method, estimates of the effective population size ( N _e) illustrated a mixture of stable populations with high N _e, and unstable populations characterized by very small N _e estimates (of 5–11 individuals). Owing to human disturbances, intermittent gene flow and genetic drift are likely to be the predominant evolutionary processes shaping the observed genetic structure. However, the practice of multiple matings and sperm storage is likely to provide a reservoir of variability, minimizing the eroding genetic effects of population size reduction and increasing the effective population size.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 89–102.     

Traces of predation/parasitism recorded in Eocene brachiopods from the Castle Hayne Limestone,North Carolina,USA

Schimmel, M., Kowalewski, M. & Coffey, BP. 2011: Traces of predation/parasitism recorded in Eocene brachiopods from the Castle Hayne Limestone, North Carolina, USA. Lethaia, Vol. 45, pp. 274–289. The Castle Hayne Limestone (Middle Eocene, North Carolina), noted for its diverse macro‐invertebrate fossils, was sampled to assess if Early Cenozoic brachiopods from eastern North America record any traces of biotic interactions. Systematic surveys of two North Carolina quarries yielded 494 brachiopods dominated by one species: Plicatoria wilmingtonensis (Lyell and Sowerby, 1845). Despite subtle variations in taphonomy, taxonomy and drilling patterns, the two sampled quarries are remarkably similar in terms of quantitative and qualitative palaeoecological and taphonomic patterns. In both quarries, brachiopods contain frequent drillholes (24.5% specimens drilled). The majority of drillholes were singular, perpendicular to shell surface and drilled from the outside. Ventral valves were drilled slightly more frequently than dorsal ones, but site‐selectivity in drilhole location was not evident. Larger brachiopods were drilled significantly more frequently than smaller ones. However, drillhole diameter did not correlate with brachiopod size. The drillholes are interpreted as records of ‘live‐live’ biotic interactions, representing either predatory attacks or parasitic infestations or a combination of those two types of interactions. A notable fraction of specimens bear multiple drillholes, which is consistent with either parasitic nature of interactions or frequent failed predatory events. The high drilling frequency reported here reinforces other reports (from other continents and other epochs of the Cenozoic), which suggest that brachiopods may be an important prey or host of drilling organisms in some settings. The number of case studies reporting high frequencies of drilling in brachiopods is still limited and thus insufficient to draw reliable generalizations regarding the causes and consequences of these occasionally intense ecological interactions. □Brachiopods, drilling parasitism, drilling predation, Eocene, North Carolina, taphonomy.     

THE ENIGMATIC EARLY CAMBRIAN SALANYGOLINA– A STEM GROUP OF RHYNCHONELLIFORM CHILEATE BRACHIOPODS?

Abstract:  New material of the enigmatic brachiopod Salanygolina obliqua Ushatinskaya from the Early Cambrian of Mongolia shows that it has a colleplax – a triangular plate – in the umbonal perforation, which is enlarged by resorption. This structure is otherwise only known from the equally enigmatic Palaeozoic orders Chileida and Dictyonellida (Rhynchonelliformea, Chileata). The colleplax in Salanygolina is here considered to be homologous with that of the chileates. Salanygolina is also provided with a ridge-like pseudodeltidium, which is another chileate feature. Other characters of Salanygolina , like the radial arrangement of adductor muscle scars and postero-medially placed internal oblique muscles are characteristic of chileates, but also found in the paterinates. In contrast, mixoperipheral dorsal valves with low rudimentary interareas are well known in paterinates, but not yet recorded from chileates. Thus, Salanygolina shows a mosaic combination of morphologic characters, known both from the paterinates and chileates, indicating that it may represent a stem group of the rhynchonelliform chileate brachiopods. The laminar phosphatic secondary shell of Salanygolina is composed of closely packed and nearly identical hexagonal prisms, oriented with their long axis normal to the laminae in a honeycomb pattern. The prism walls appear to have originally been composed of organic membranes and might represent precursors of the organic sheaths of calcite fibers that are typical of calcitic shells with a fibrous microstructure.     

A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral‐like morphology

Tomteluva perturbata gen. et sp. nov. and Nasakia thulensis gen. et sp. nov., two new rhynchonelliformean brachiopod taxa, are described from carbonate beds from the lower middle Cambrian (Series 3, Stage 5) basinal Stephen Formation, Canada, and the upper lower Cambrian (Series 2, Stage 4) Henson Gletscher Formation, North Greenland, respectively. The two taxa are characterized by an unusual coral‐like morphology typified by a high conical ventral valve with an anteriorly curved umbo and a tube‐like structure inside the ventral valve, interpreted as pedicle tube. Both resemble the problematic late middle Cambrian (Drumian) species Anomalocalyx cawoodi Brock from Australia, whose systematic affiliation is controversial. Together, the three genera are interpreted as representatives of a new family of rhynchonelliformean brachiopods, the Tomteluvidae fam. nov., which is interpreted as an aberrant or derived taxon within the Order Naukatida. Convergence between the Tomteluvidae and the coralla of small solitary Cambrian coralimorphs, as well as the late Palaeozoic reef‐building richthofenioid brachiopods, might indicate adaptation to a similar life habits and environments. However, their small size (length 4 mm), well‐developed pedicle and perfect morphological symmetry make it more likely that tomteluvids lived attached to frondose algae or sponges, above the seafloor, in a similar fashion to the acrotretoid brachiopods with which they show a high degree of morphological convergence. Morphological features of the pedicle tube of N. thulensis suggest that the tomteluvid pedicle is homologous to that in modern rhynchonelliformean brachiopods. This is the first evidence of the pedicle type within the Naukatida and represents the oldest confirmation of a rhynchonellate pedicle.     

The Mediterranean bryozoan Myriapora truncata (Pallas, 1766): a potential indicator of (palaeo‐) environmental conditions

Fossil and Recent specimens of the Mediterranean bryozoan Myriapora truncata show considerable intra‐ and intercolonial differences in branch diameter and zooid size. Statistically significant variability occurs within colonies, between colonies within sites, and between sampled sites, while the presence of intracolonial variability clearly shows that branch diameter is largely controlled by environmental parameters. The three structural traits measured (branch diameter, zooid size and zooid depth) do not correlate, thus indicating a disconnection between the controls on overall zooid size and branch diameter. Possible environmental parameters that may have an influence on morphology are temperature, food supply or current energy. Whereas current energy has an effect on the colony branching pattern (branch spacing), there are indications that temperature may be the main, but not the only, parameter controlling zooid size, and it is suggested that food supply largely determines the branch diameter in M. truncata. However, the identification of the decisive factors and quantification of the relationships between environmental and morphological change is beyond the scope of this study. The results nevertheless show that, if the control factors of morphological variability can be ascertained in Recent M. truncata, this species may prove to be an indicator of environmental conditions and their change at different spatial and temporal scales in Cenozoic to Recent Mediterranean habitats.     

The relationship between major lamellae and epithelial regressions in some articulate brachiopods

Brunton, C. Howard C. & Alvarez, Fernando 1989 07 15: The relationship between major lamellae and epithelial regressions in some articulate brachiopods. Lethaia , Vol. 22, pp. 247–250. Oslo. ISSN 0024–1164.
Hiller (1988, Lethaia , Vol. 212) proposed three relationships between the secretory epithelium of articulate brachiopods and the shell surface ornamentations of growth lines, lamellae and spines. None of his models satisfy the growth of strongly lamellose athyrid shells and we propose a fourth involving strong regressions effecting both primary and secondary shell layers. In Recent Tegulorhynchia we suggest a growth function for the 'frayed' shell of Hiller occurring immediately in front of the spines.     

Controls on body size during the Late Permian mass extinction event

This study examines the morphological responses of Late Permian brachiopods to environmental changes. Quantitative analysis of body size data from Permian–Triassic brachiopods has demonstrated significant, directional changes in body size before, during and after the Late Permian mass extinction event. Brachiopod size significantly reduced before and during the extinction interval, increased for a short time in more extinction‐resistant taxa in the latter stages of extinction and then dramatically reduced again across the Permian/Triassic boundary. Relative abundances of trace elements and acritarchs demonstrate that the body size reductions which happened before, during and after extinction were driven by primary productivity collapse, whereas declining oxygen levels had less effect. An episode of size increase in two of the more extinction‐resistant brachiopod species is unrelated to environmental change and possibly was the result of reduced interspecific competition for resources following the extinction of competitors. Based on the results of this study, predictions can be made for the possible responses of modern benthos to present‐day environmental changes.     

Reproduction in an endemic bird of a semiarid island: a food-mediated process

We analyse the effects of rainfall, temperature, food availability and nest predation on the between-year variation in reproduction of the Canary Islands stonechat Saxicola dacotiae , a bird species endemic of the semiarid island of Fuerteventura (Canary Islands, Spain). We monitored the reproductive performance and output of the species across its whole distribution area during three consecutive breeding periods, also measuring rainfall, temperature and food (arthropod) availability on the ground monthly. Rainfall varied from 27.3 mm in 2000–2001 (dry year) to 124.5 mm and 125.1 mm (average years), respectively, in the 2001–2002 and 2002–2003 breeding seasons. The onset of breeding closely matched variation in the onset of the autumn-winter rains among years. Arthropod availability was strongly and positively related to rainfall one month before. Reproductive investment (number of clutches and clutch size) was correlated to arthropod availability both among years and among sites within years. Stonechat pairs bred once or did not breed at all in the dry year whereas they bred twice in the other two years. Clutch size was smaller in the dry year and larger in the second as compared with the first in the other two years. Reproductive investment largely determined reproductive output (number of fledglings) as there were no significant spatial or temporal variation in hatching success (90% on average) or nest predation (29% on average, mostly due to feral cats Felis catus ). Within- and among years variability in temperature or predation did not match variability in the onset, length or reproductive investment and output recorded throughout the study years. These results suggest that variability in annual fecundity in the Canary Islands Stonechat was mainly driven by rainfall through a food-mediated process.     

Climate, size and flowering history determine flowering pattern of an orchid

The flowering pattern of plant species, including orchid species, may fluctuate irregularly. Several explanations are given in the literature to explain that pattern, including: costs associated with reproduction, herbivory effects, intrinsically triggered unpredictable variation of the system, and external conditions (i.e. weather). The influence of age is discussed, but is difficult to determine because relevant long-term field observations are generally absent in the literature. The influence of age, size, reproductive effort and climatic conditions on flowering variability of Himantoglossum hircinum are examined using data collected in a long-term project (1976–2001) in Germany. PCA and multiple regression analysis were used to analyse variability in flowering pattern over the years as a function of size and weather variability. We studied future size after flowering to quantify costs of reproduction. Flowering probability was strongly determined by plant size, while there was no significant influence of age class on flowering probability of the population. Costs associated with reproduction resulted in a decrease in plant size, causing reduced flowering probability of the plants in the following year. The weather explained about 50% of the yearly variation in the proportion of large plants and thus had an indirect, strong influence on the flowering percentage. We conclude that variability in flowering is caused mainly by the variability of weather conditions in the previous and current year, whereby reproductive effort causes further variability in flowering at the individual and, consequently, the population levels.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 511–526.     

SUBCELLULAR DISTRIBUTION AND TRANSPORT OF ACETYLCHOLINE IN CAT VENTRAL ROOTS AND SCIATIC NERVE

Abstract— The axonal transport of radioactive ACh, which was labelled by injecting radioactive choline into the ventral horn of the cat, was studied. Radioactivity analysed as ACh was transported in the nerves at a rate of 20–25 cm/24 h from the place of injection. Morphological and biochemical analysis after density gradient centrifugation revealed that endogenous ACh was principally distributed in three fractions-(a) a soluble fraction (provided homogenization was carried out in the presence of eserine), (b) a vesicular fraction (diameter 600–1600 A) in the 0.4M-sucrose layer of the density gradient, and (c) a fraction containing very small structures (size 90–100 A) in the 0.8–1.0 M-sucrose interphase. The radioactive ACh, however, was exclusively found in the soluble fraction (supernatant) after density gradient centrifugation. Analysis of ACh metabolites showed that radioactive ACh may have been formed locally in the nerves after transport of its precursor. Thus the morphologic and metabolic results do not support the hypothesis that ACh is transported in vesicles.