Food resources and foraging habits of the common shrew,Sorex araneus: does winter food shortage explain Dehnel's phenomenon?

It is widely assumed that winter is a critical time for homeotherms because of decreased ambient temperatures coupled with reduced food supply. Shrews are excellent models for investigating overwintering strategies, not only because of their particularly small size, high energy requirements relative to their size and short fasting endurance, but also the dramatic reduction in body size (Dehnel's phenomenon) exhibited by soricine shrews in northern temperate winters. The cause of Dehnel's phenomenon is poorly understood but food supply is implicated. To test the hypothesis that winter at higher latitudes is a period of food shortage for small homeotherms, we compared feeding habits of common shrews, Sorex araneus, and abundance and biomass of their prey in winters and summers in northeastern Poland using scat analysis combined with pitfall and ground core sampling for invertebrates. Ground‐surface activity and numbers of invertebrates in pitfall traps were greatly reduced in winter but, contrary to prediction, no significant differences between winter and summer were found in total numbers and biomass of prey invertebrates in ground core samples. However, certain prey types changed seasonally with respect to numbers, biomass and distribution in the soil profile, which was reflected in shrews’ food composition and foraging behaviour. Dehnel's phenomenon appears not to be caused by reduction in total prey numbers and biomass, at least in our study area. Smaller body mass coupled with lowering of absolute food requirements may have important survival value in winter with its reduced numbers of certain major prey coupled with increased difficulty of locating and extracting invertebrates within the soil profile resulting in higher energetic costs of foraging.     

Bacterial morphology: why have different shapes?

The fact that bacteria have different shapes is not surprising; after all, we teach the concept early and often and use it in identification and classification. However, why bacteria should have a particular shape is a question that receives much less attention. The answer is that morphology is just another way microorganisms cope with their environment, another tool for gaining a competitive advantage. Recent work has established that bacterial morphology has an evolutionary history and has highlighted the survival value of different shapes for accessing nutrients, moving from one place to another, and escaping predators. Shape may be so important in some of these endeavors that an organism may change its morphology to fit the circumstances. In short, if a bacterium needs to eat, divide or survive, or if it needs to attach, move or differentiate, then it can benefit from adopting an appropriate shape.     

Environmental correlates of phenotypic variation: do variable tidal regimes influence morphology in intertidal seaweeds?

Seaweed morphology is often shaped by the hydrodynamic environment. However, exposure to air at low tide represents an additional factor potentially affecting the morphology of intertidal species. Here, we examined the relationships between the morphology of Hormosira banksii, an important intertidal habitat‐forming seaweed in southern Australia, and environmental factors across multiple spatial scales around the island of Tasmania, Australia. Tasmania is surrounded by a diverse coastline with differences in wave exposure, tidal parameters, and temperature. We sampled Hormosira from four regions (100s km apart), three sites (10s km apart) within each region, and two zones (meters apart; eulittoral and sublittoral) at each site, and measured multiple morphological variables to test for differences in morphology at those different spatial scales. Thirteen environmental variables reflecting wave exposure, tidal conditions, and temperature for each site were generated to assess the relationship between Hormosira morphology and environmental variation. Morphology varied at all spatial scales examined. Most notably, north coast individuals had a distinct morphology, generally having smaller vesicles and shorter fronds, compared to other regions. Tidal conditions were the main environmental factors separating north coast sites from other sites and tidal regime was identified as the best predictor of morphological differences between regions. In contrast to other studies, we found little evidence that wave exposure was associated with morphological variation. Overall, our study emphasizes the role of tidal conditions, associated with emersion stress during low tide, in affecting the morphology of intertidal seaweeds.     

Courtship tactics in garter snakes: how do a male's morphology and behaviour influence his mating success?

The behavioural determinants of male mating success play a pivotal role in sexual selection, but remain poorly known for most kinds of organisms, including most reptiles. In Manitoba, Canada, large numbers of red-sided garter snakes, Thamnophis sirtalis parietalis, court and mate in early spring near communal overwintering dens. To understand how a male's morphology and behaviour might influence his mating success, we videotaped 21 groups of snakes each comprising four males of varying body sizes plus a female. All males engaged in courtship, and mating occurred in all groups. Males with better body condition courted more vigorously and successfully than their smaller rivals did. The males that obtained matings were those that maintained their own cloaca closest to that of the female, aligned most of their body with the female, showed high rates of caudocephalic waving, chin pressing and tail searching, and did not allow other males to insert their body beside the female's. These behavioural differences between ‘winners’ and ‘losers’ were apparent from the beginning of each trial. Thus, male mating success in this ‘scramble’ system is determined not by chaotic, stochastic struggle (as has often been inferred) but instead is strongly linked to male courtship tactics. Energy stores (as evidenced by good body condition) may be critical determinants of mating success in these vigorous courtship episodes.     

Defining “high quality” food resources of herbivores: the case for meadow voles (Microtus pennsylvanicus)

Summary Food availability, food utilization patterns and levels of some nutritional factors in plants were studied in 1984–85 in an old-field community supporting low to moderate densities of meadow voles (Microtus pennsylvanicus). Food choice and preference indices were positively related to levels of proteins, and negatively related to levels of total phenolics and ADL fibers in plants. High quality resources for voles were resources that had the highest amount of proteins, and the lowest level of total phenolics and ADL fibers among available plant species. There were only two plants species among the available ones that possessed these characteristics, Festuca rubra and Vicia cracca and they represented 25 to 50% of the available biomass during summer. Vole densities of up to 64 animals/ha were therefore not limited by the availability of high quality resources. Fecal analyses performed on 267 animals in 1984 and 269 voles in 1985 showed that all voles ate high quality resources. Meadow voles appear to choose foods with high protein content and low levels of digestion inhibitors, and not on the basis of caloric content or availability. These observations contradict predictions arising from current antiherbivore hypotheses and lead us to reconsider these models in light of this new evidence.     

Motivation and placebos: do different mechanisms occur in different contexts?

This paper challenges the common assumption that the mechanisms underlying short-term placebo paradigms (where there is no motivation for health improvement) and long-term placebo paradigms (where patients value improvement in their health) are the same. Three types of motivational theory are reviewed: (i) classical placebo motivation theory that the placebo response results from the desire for therapeutic improvement; (ii) goal activation model that expectancy-driven placebo responses are enhanced when the placebo response satisfies an activated goal; and (iii) motivational concordance model that the placebo response is the consequence of concordance between the placebo ritual and significant intrinsic motives. It is suggested that current data are consistent with the following theory: response expectancy, conditioning and goal activation are responsible for short-term placebo effects but long-term therapeutic change is achieved through the effects of goal satisfaction and affect on the inflammatory response system and hypothalamic-pituitary-adrenal axis. Empirical predictions of this new theory are outlined, including ways in which placebo effects can be combined with other psychologically mediated effects on short-term and long-term psychological and physiological state.     

What do children think happens to the food they eat?

In this study, the explanations of two classes of 10-year old children about what happens to the food that they eat were explored, particularly in the context of theories about the development of children's concepts of the human body. These ideas were investigated in a number of ways: obtaining children's own writing and drawings; semi-structured individual interviews; and examining choices made between alternative explanations. The results suggested that children applied their knowledge of everyday materials to understand the initial stages of what happens to food, but their ideas about later stages were more tentative and within the group there was a range of different kinds of explanation preferred. The limitations and achievements of the children's thinking are considered in the context of the school curriculum.     

Beneath the beard: do facial morphometrics influence the strength of judgments of men's beardedness?

Converging evidence suggests men's beards, like many androgen-dependent masculine secondary sexual traits, communicate masculinity and dominance intra-sexually while effects of men's beardedness on attractiveness ratings are more equivocal. Beards may enhance perceived masculinity and dominance via amplifying aspects of underlying craniofacial masculinity, particularly the size of the lower face and jaw. Here we tested these predictions across two studies. In study 1, we tested how three facial metrics - objectively measured craniofacial masculinity, facial-width-to-height ratio (fWHR), and jaw size - calculated while clean-shaven impacted on ratings of attractiveness, masculinity and dominance of 37 men photographed when clean-shaven and with full beards. Results showed that beards exerted significant and positive effects on masculinity, dominance and to a lesser extent attractiveness. However, fWHR did not significantly interact with beardedness to influence the directions of any of the ratings, and while some linear and nonlinear interactions were significant between objective craniofacial masculinity and beardedness as well as between jaw size and beardedness, they tended to be subtle and dwarfed by the large main effect of beardedness on perceptual ratings. In study 2, we measured ratings of attractiveness, masculinity and dominance for composite clean-shaven and bearded stimuli experimentally manipulated in facial shape to represent ±50% the shape of a beard, essentially manipulating the size of the lower face and jaw of the stimuli. We found a strong main effect whereby bearded stimuli enhanced dominance and masculinity ratings over clean-shaven stimuli. Increasing the size of the lower face and jaw augmented ratings of masculinity and dominance in clean-shaven stimuli but did not exert strong effects within bearded stimuli. Attractiveness ratings were highest for bearded faces with smaller jaws followed by bearded and clean-shaven faces with larger jaws and lowest for clean-shaven faces with small jaws. Taken together, our findings suggest that beards exert main effects on masculinity and dominance possibly by amplifying male typical facial shape. Attractiveness ratings of facial hair may reflect a compromise between overly dominant looking faces with larger jaws and the additive effects beardedness has on these ratings.     

The Calicotyle conundrum: do molecules reveal more than morphology?

Partial large subunit 28S rDNA sequences were obtained for specimens of Calicotyle (Monogenea: Monocotylidae) from eight different host species distributed worldwide to test the validity of some species and to address the question of host-specificity in others. Sequences obtained for Calicotyle specimens identified as C. kroyeri based on morphological methods from the type-host Raja radiata (Rajidae) and an additional host R. clavata, both from the North Sea, were identical. However, `C. kroyeri' from the cloaca of R. naevus from Tunisia, Raja sp. A from Tasmania and R. radula from Tunisia differed from C. kroyeri from R. radiata by five (0.51%), 21 (2.13%) and 39 (3.96%) base pairs, respectively, over 984 sites. Therefore, it is likely that the specimens from Raja sp. A, R. radula and perhaps even from R. naevus are not C. kroyeri. Molecular results determined that the calicotylines from the cloaca of Urolophus cruciatus and U. paucimaculatus (Urolophidae) from southern Tasmania identified previously as C. urolophi are indeed identical. Large subunit 28S rDNA sequences of C. palombi and C. stossichi collected from the cloaca and rectal gland, respectively of Mustelus mustelus (Triakidae) from the coast of Tunisia differ sufficiently for these calicotylines to be considered separate and valid species. Our results indicate that some species of Calicotyle are not strictly host-specific, but that C. kroyeri may not be as widely distributed in rajids as was believed previously. Calicotyle specimens from rajids must be re-examined critically to determine whether there are morphological differences indicative of specific differences that may have been overlooked previously.     

Insect herbivory and ontogeny: How do growth and development influence feeding behaviour,morphology and host use?

Herbivorous insects exploit many different plants and plant parts and often adopt different feeding strategies throughout their life cycle. The conceptual framework for investigating insect–plant interactions relies heavily on explanations invoking plant chemistry, neglecting a suite of competing and interacting pressures that may also limit herbivory. In the present paper, the methods by which ontogeny, feeding strategies and morphological characters inhibit herbivory by mandibulate holometabolous insects are examined. The emphasis on mechanical disruption of plant cells in the insect digestive strategy changes the relative importance of plant ‘defences’, increasing the importance of leaf structure in inhibiting herbivory. Coupled with the implications of substantial morphological and behavioural changes in ontogeny, herbivores adopt a range of approaches to herbivory that are independent of plant chemistry alone. Many insect herbivores exhibit substantial ontogenetic character displacement in mandibular morphology. This is tightly correlated with changes in feeding strategy, with changes to the cutting edges of mandibles increasing the efficiency of feeding. The changes in feeding strategy are also characterized by changes in feeding behaviour, with many larvae feeding gregariously in early instars. Non‐nutritive hypotheses considering the importance of natural enemies, shelter‐building and thermoregulation may also be invoked to explain the ontogenetic consequences of changes to feeding behaviour. There is a need to integrate these factors into a framework considering the gamut of potential explanations of insect herbivory, recognizing that ontogenetic constraints are not only viable explanations but a logical starting point. The interrelations between ontogeny, size, morphology and behaviour highlight the complexity of insect–plant relationships. Given the many methods used by insect herbivores to overcome the challenges of consuming foliage, the need for species‐specific and stage‐ specific research investigating ontogeny and host use by insect herbivores is critical for developing general theories of insect–plant interactions.     

Recognizing the enemy: do predator cues influence hatching in Neotropical annual killifish?

Annual fish species have evolved complex adaptations to survive in temporary wetlands. The main adaptation of these fish is the ability to produce embryos that survive dry periods. Embryo development of this fish can show variation at multiple levels influenced by many environmental factors, such as photoperiod and temperature. Predator cues are another factor that can influence the embryonic stage. One way in which annual fish could adapt to predators is by using risk-spreading strategies (through bet-hedging). Nonetheless, this strategy depends on the coevolutionary history between predators and preys and on the degree of environmental unpredictability, resulting in different responses across different species. This study investigated the influence of predator cues on the embryonic development and hatching of two Austrolebias species that inhabit ponds that present differences in hydroperiod and the risk of predator presence. The results confirmed a differentiated response between the two annual fish species tested, corroborating the modulation of hatching against the risk of predation by native predatory fish. The authors further showed that development times varied between the two annual fish species, regardless of the presence of predators. They highlight that the variation in embryonic development is strongly affected by different levels of hydroperiod unpredictability faced by the two species. To unravel finer-scale local adaptations in the annual fish embryo development, future studies should focus on a region with greater spatial gradient.     

Treating obesity: does antagonism of NPY fit the bill?

In this issue of Cell Metabolism, Erondu et al., (2006) identify a selective neuropeptide Y5 receptor antagonist that, as predicted from rodent studies, results in weight loss when administered to overweight and obese human subjects. In a one-year randomized placebo-controlled clinical trial, the weight loss was modest; the results support the emerging concept that NPY acts via overlapping and redundant energy homeostasis pathways.     

Scaling food chains in aquatic mesocosms: do the effects of depth override the effects of planktivory?

To assess the effects of physical dimension and planktivorous fish on phytoplankton standing crop, we repeated an experiment at different scales in plastic enclosures during summer 1995 in Lake Créteil, France. Enclosures were scaled for a constant surface (1.5 × 1.5 m) as depth was increased from 2.5 to 4.5 m. Even-link (zooplankton and phytoplankton) and odd-link (planktivorous fish, zooplankton and phytoplankton) food webs were established in both shallow and deep enclosures. Fish densities in the deep enclosures were scaled to allow comparisons with shallow ones for both in individuals m⁻² or individuals m⁻³. We explicitly designed this experiment to examine the scale-dependent behavior of the top-down mechanism of algal biomass control in lakes, and in particular to test the hypothesis of stronger cascading effects of fish on lower trophic levels at reduced depth. Both fish and enclosure size had highly significant effects on phytoplankton biomass over the duration of the experiment. No depth × fish interaction effects were observed. The presence of planktivorous fish enhanced phytoplankton biomass in both shallow and deep enclosures, although the reduction in depth generally produced a stronger effect. The mean concentration of chlorophyll a in the deep odd-link systems (ca 5 mg m⁻³) was lower than in the shallow even-link systems (ca 17 mg m⁻³). Statistical interpretation did not change when data were expressed as phytoplankton biomass per unit of surface area. Light limitation and zooplankton grazing are the most probable mechanisms explaining our results in these nutrient-enriched systems. Moreover, we found that the strength of the cascading effect of fish on plankton was not a function of depth. We believe that further studies on scaling effects should be conducted in order to improve our understanding of ecological patterns and to extrapolate results from micro/mesocosms to natural ecosystems. Received: 18 January 1999 / Accepted: 7 June 1999     

Are monophyly and synapomorphy the same or different? Revisiting the role of morphology in phylogenetics

Species are groups of organisms, marked out by reproductive (replicative) properties. Monophyletic taxa are groups of species, marked out by synapomorphies. In Nelson’s analysis, monophyly and synapomorphy are identical relations. Monophyly and synapomorphy, however, are not equivalent relations. Monophyly is epistemically not accessible, whereas synapomorphy is epistemically accessible through character analysis. Monophyly originates with speciation, the two sister‐species that come into being through the splitting of the ancestral species lineage forming a monophyletic taxon at the lowest level of inclusiveness. Synapomorphy provides the empirical evidence for monophyly, inferred from character analysis in the context of a three‐taxon statement. If synapomorphy and monophyly were equivalent, phylogenetic systematists should find a single tree, instead of multiple equally parsimonious trees. Understanding synapomorphy as the relevant evidence for phylogenetic inference reveals a category mistake in contemporary phylogenetics: the treatment of morphological characters mapped onto molecular trees as synapomorphies and homoplasies. The mapping of morphological characters onto nodes of a molecular tree results in an empirically empty procedure for synapomorphy discovery. Morphological synapomorphies and homoplasies can only be discovered by morphological and combined analyses. The use of morphology in phylogenetic inference in general is defended by examples from Laurales and Squamata in particular. To make empirical evidence scientifically relevant in order to search for concordance, or dis‐concordance, of phylogenetic signal, is certainly more fruitful for phylogenetics than the uncritical mapping of morphological traits on a molecular scaffold. © The Willi Hennig Society 2010.     

Does the morphology of animal foraging pits influence secondary seed dispersal by ants?

Secondary seed dispersal by ants (myrmecochory) is an important process in semi‐arid environments where seeds are transported from the soil surface to an ant nest. Microsites from which ants often remove seeds are the small pits and depressions made by native and exotic animals that forage in the soil. Previous studies have demonstrated greater seed retention in the pits of native than exotic animals, but little is known about how biotic factors such as secondary seed dispersal by ants affect seed removal and therefore retention in these foraging pits. We used an experimental approach to examine how the morphology of burrowing bettong (Bettongia lesueur), greater bilby (Macrotis lagotis), short‐beaked echidna (Tachyglossus aculeatus) and European rabbit (Oryctolagus cuniculus) foraging pits and ant body size influenced ant locomotion and seed removal from pits along an aridity gradient. Ants took 3.7‐times longer to emerge from echidna pits (19.6 s) and six‐times longer to emerge from bettong pits (30.5 s) than from rabbit pits (5.2 s), resulting in lower seed removal from bettong pits than other pit types. Fewer seeds were removed from pits when cages were used to exclude large body‐sized (>2 mm) ants. Few seeds were removed from the pits or surface up to aridity values of 0.5 (humid and dry sub‐humid), but removal increased rapidly in semi‐arid and arid zones. Our study demonstrates that mammal foraging pit morphology significantly affects ant locomotion, the ability of ants to retrieve seeds, and therefore the likelihood that seeds will be retained within foraging pits.     

POPP the question: what do LEA proteins do?

Late embryogenesis abundant (LEA) proteins are produced in maturing seeds and anhydrobiotic plants, animals and microorganisms, in which their expression correlates with desiccation tolerance. However, their function has remained obscure for 20 years. We argue that novel computational tools devised for non-globular proteins might now overcome this problem. Predictions arising from bioinformatics fit well with recent data on Group 3 proteins, which potentially form cytoskeletal filaments, and suggest experimentally testable functions for these and other LEA protein groups.     

Digit morphogenesis: Is the tip different?

Digit formation is the last step in the skeletal patterning of developing limbs. This process involves important aspects such as determination of chondrogenic versus interdigital areas; growth of digital rays with periodic segmentation to form joints and thus phalanges, and finally tip formation. Traditionally it was believed that the properties of digital rays were fixed at earlier stages, but recently a surprising plasticity of digit primordia at the time of condensation has been demonstrated. This implies the presence of local interactions that are able to modulate the particular programs that make a given digit, but we don't fully understand how they operate. An involvement of signaling from the interdigital spaces and from the apical ectodermal ridge has been proposed. Another interesting question is the formation of the last limb structure, digit tips, which may involve a specific molecular and cellular program. Indeed, the expression of several developmentally important genes is restricted to digit tips at late stages of limb development. Understanding the molecular and cellular interactions that lead to digit morphogenesis has important implications not only in the context of embryonic development (for example, how early cues received by cells are translated into anatomy or what are the mechanisms that control the cease of activity of signaling regions) but also in terms of limb diversification during evolution.