Seasonality in basal metabolic rate and thermal conductance in a long-distance migrant shorebird,the knot (Calidris canutus)

Knots Calidris canutus live highly seasonal lives, breeding solitarily on high arctic tundra and spending the non-breeding season in large social flocks in temperate to tropical estuaries. Their reproductive activities and physiological preparations for long flights are reflected in pronounced plumage and body mass changes, even in long-term captives of the islandica subspecies (breeding in north Greenland and northeast Canada and wintering in western Europe) studied in outdoor aviaries. The three to four fattening episodes in April-July in connection with the flights to and from the high arctic breeding grounds by free-living birds, are represented by a single period of high body mass, peaking between late May and early July in a sample of ten captive islandica knots studied over four years. There are consistent and synchronized annual variations in basal metabolic rate and thermal conductance in three islandica knots. Basal metabolic rate was highest during the summer body mass peak. Within the examined individuals, basal metabolic rate scales on body mass with an exponent of about 1.4, probably reflecting a general hypertrophy of metabolically expensive muscles and organs. Any potential effect of moult on basal metabolic rate was obscured by the large seasonal mass-associated variations. In breeding plumage, insulation (the inverse of thermal conductance) was a factor of 1.35 lower than in winter plumage. This was paralleled by the dry mass of contour feathers being a factor of 1.17 lower. In this subspecies the breeding season is indeed the period during which the costs of thermoregulation are lowest. In captive knots seasonal changes in basal metabolic rate and thermal conductance likely reflect an anticipatory programme adaptive to the variable demands made by the environment at different times of the year.     

Diapause, quiescence, hatching requirements: what we can learn from large freshwater branchiopods (Crustacea: Branchiopoda: Anostraca, Notostraca, Conchostraca)

The extent to which dormancy in large freshwater branchiopods is controlled endogenously (diapause) or exogenously (quiescence) is not always clear. It is assumed that both processes occur even within the same brood. Based on the effectiveness of common diapause-deactivating processes such as desiccation, hibernation, and resting, it can be stated that diapause is not a general process controlling responsiveness of large freshwater branchiopod eggs. Only in limited cases unequivocal evidence for the positive influence of these treatments is found.With few exceptions, hatching of activated cysts is effected by specific conditions that may even differ among conspecific populations. Generally, each species (or even population) has a specific temperature range or regime for optimal hatching performance. In a suitable thermal environment with sufficient light and oxygen, hatching is invariably invoked by a low osmotic medium.The erratic hatching pattern in most species is thought to be an adaptation to the variable temporary habitat. Hatching is generally spread over several days or even weeks, but the highest peak usually occurs on the first or second day of hatching. Low hatching percentages were found only in subtropical/desert species and may be a reflection of the low chances for successful reproduction. Generation carry-over of propagules in the egg bank by dormancy, and hatching at low conductivity, are, together with obligate oviparity and absence of an asexual life cycle phase, thought to be highly adaptive to the temporary environment. This enabled large branchiopods to survive since the Upper Cambrian.     

Survival mechanisms of the central mudminnow (Umbra limi), fathead minnow (Pimephales promelas) and brook stickleback (Culaea inconstans) for low oxygen in winter

Synopsis Three species (central mudminnow, fathead minnow and brook stickleback) survive when a northern Wisconsin lake becomes anoxic in winter. Some gas bubbles beneath the ice contained as much as 11° oxygen when the lake water contained <0.30 mg 1^–1 dissolved oxygen. Experiments conducted in the field determined that gas bubbles prolonged survival of all species, especially the mudminnow and stickleback. In the laboratory, brook sticklebacks exhibited the lowest and fathead minnows the highest routine metabolic rate corrected for weight. Rate of gill ventilation of all three increased from 20 to 70 beats per minute as oxygen levels declined from 4.0 to 0.25 mg 1^–1. At low oxygen levels they moved to the upper one-third of the test tanks. Small size, low metabolic rate, tolerance of low oxygen conditions and reduced activity resulted in reduced demand for dissolved oxygen. Head shape, ventilation rate, vertical movement and utilization of high oxygen microzones also enhanced exploitation of low levels of dissolved oxygen. Central mudminnows used oxygen directly from gas bubbles found under the ice.     

Conservation and Survival Adaptations of Temminck’s Red Colobus <Emphasis Type="Italic">(Procolobus badius temmincki)</Emphasis>, in Senegal

In the Fathala Forest, Saloum Delta National Park, Senegal, in 1974–1976 and 1988–2002, we studied the northernmost populations of the endangered Temminck’s red colobus (Procolobus badius temmincki). Drastic habitat changes in the last 30 yr have reduced the forests by > 50% (75% in the gallery forests used by the red colobus). The woody species diversity decreased by > 30%. Despite these changes, the red colobus population only decreased from ca. 600 to ca. 500 individuals. We examined the ecological conditions and behavioral adaptations that may have influenced survival of the population. We found that 5 major adaptations have emerged in the last 30 yr that may have influenced the survival of red colobus at Fathala: (1) frugivory, (2) terrestriality, (3) tendency to form polyspecific associations with green monkeys, (4) tendency to frequent more open habitats, and (5) use of mangrove swamps for refuge and forage. By developing these adaptations, red colobus demonstrated their ability to persist in degraded habitats of the Fathala Forest. Preserving the forest should ensure the conservation of the red colobus population there.     

The Ethiopian water mouse Nilopegamys Osgood, with comments on semi-aquatic adaptations in African Muridae

A highly distinctive rodent from the highlands of Ethiopia is currently being confused with a very different mouse from the Zaire Basin. The Ethiopian water mouse, Nilopegamys Osgood 1928, can be distinguished from Colomys and all other African murids by external, cranial, post-cranial and dental characters. Adaptations of Mlopegamys for swimming are more extreme than those of any other African murid; as noted by Osgood, it is the only one with specializations reminiscent of Neotropical ichthyomyines or Australasian hydromyines. However, the African mice Colomys, Malacomys , and Deomys also exhibit varying degrees of semi-aquatic specializations. These genera constitute a previously unrecognized guild of 'waders'. Without swimming and while perched on elongate hind feet, all three consume insects and other small animals in shallow forest streams and pools. Both waders and swimmers show neurological adaptations to life in water, but Nilopegamys redefines certain extremes of cerebral development among African murids. Resurrected from synonymy with Colomys , this genus further accentuates the distinctiveness and imperilled status of the Ethiopian highland fauna.     

Of crazy-ants and Curetinae: are Curetis butterflies tended by ants?

The larvae of the lycaenid subfamily Curetinae have never been reported to be associated with ants. Observations on Curetis regula Evans from Brunei are presented which show that this species may be tended by ants both as larvae and adults. The observations are discussed in relation to a recent review on lycaenid/ant associations, u is suggested that the Curetinae will be found to be associated with ants when more species have been reared, on evidence of the larval tentacle organs and apparent ‘pore cupolas’, both of which are ant adaptations. More studies are needed on Curetis biology and larval morphology to resolve the relationships of this enigmatic genus within the Lycaenidae.     

Cranial morphology of Platypterygius longmani Wade, 1990 (Reptilia: Ichthyosauria) from the Lower Cretaceous of Australia

Exceptionally well-preserved remains belonging to the Australian Early Cretaceous (Albian) ichthyosaur Platypterygius longmani Wade, 1990 are described in detail. The material is used to reconstruct some of the cranial musculature and provide a brief functional analysis of the skull and mandible. Preparation of specimens using acetic acid and application of high-resolution X-ray computed tomographic analyses has revealed many previously unrecorded anatomical details, including the absence of a coronoid and squamosal, and the presence of well-developed epipterygoid facets on the pterygoid and parietal (possibly indicating retention of an unossified epipterygoid element). Reconstruction of the jaw musculature suggests a well-developed m. adductor mandibulae internus pterygoideus (serving to close the jaws against inertia and drag of the surrounding water), and possibly an m. intramandibularis (acting to accentuate static pressure along the elongate mandible when the jaws were closed). Despite its large size (maximum total body length of around 7 m), the long, narrow snout of P. longmani (together with preserved gut contents) indicates selective feeding on relatively small prey such as fish, small tetrapods and probably cephalopods. Large orbits are indicative of a visual hunter, but extensive external passages for nerves and blood vessels might suggest the presence of a dermal sensory system. The massive stapes appears to have lost all sound conductive function, serving primarily as structural support in the basicranial region.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 145 , 583–622.     

Beads, Bifaces, and Boats: An Early Maritime Adaptation on the South Coast of San Miguel Island, California

Terminal Pleistocene and Early Holocene sites on California's Channel Islands provide evidence for early maritime activity, including the use of seaworthy boats. Numerous early shell middens have been identified, but specific information on the maritime peoples who occupied them is limited. Our research at CA-SMI-608, a roughly 9,500-year-old shell midden on San Miguel Island, produced a relatively large assemblage of bifaces and other chipped stone artifacts, shell beads, worked bone, and well-preserved faunal remains. Food remains are dominated by mussels, abalones, and other shellfish from the rocky intertidal, but fish, sea mammal, and sea bird remains were also recovered. These data provide a detailed view of early maritime activities along an arid coastline previously considered marginal to human settlement.     

Liver metabolism in cold hypoxia: a comparison of energy metabolism and glycolysis in cold-sensitive and cold-resistant mammals

The effects of cold hypoxia were examined during a time-course at 2 °C on levels of glycolytic metabolites: glycogen, glucose, glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate, phosphoenolpyruvate, pyruvate, lactate and energetics (ATP, ADP, AMP) of livers from rats and columbian ground squirrels. Responses of adenylate pools reflected the energy imbalance created during cold hypoxia in both rat and ground squirrel liver within minutes of organ isolation. In rat, ATP levels and energy charge values for freshly isolated livers were 2.54 mol·g^-1 and 0.70, respectively. Within 5 min of cold hypoxia, ATP levels had dropped well below control values and by 8 h storage, ATP, AMP, and energy charge values were 0.21 mol·g^-1, 2.01 mol·g^-1, and 0.17, respectively. In columbian ground squirrels the patterns of rapid ATP depletion and AMP accumulation were similar to those found in rat. In rat liver, enzymatic regulatory control of glycolysis appeared to be extremely sensitive to the decline in cellular energy levels. After 8 h cold hypoxia levels of fructose-6-phosphate decreased and fructose-1,6-bisphosphate increased, thus reflecting an activation of glycolysis at the regulatory step catalysed by phospho-fructokinase fructose-1,6-bisphosphatase. Despite an initial increase in flux through glycolysis over the first 2 min (lactate levels increased 3.7 mol·g^-1), further flux through the pathway was not permitted even though glycolysis was activated at the phosphofructokinase/fructose-1,6-bisphosphatase locus at 8 h, since supplies of phosphorylated substrate glucose-1-phosphate or glucose-6-phosphate remained low throughout the duration of the 24-h period. Conversely, livers of Columbian ground squirrels exhibited no activation or inactivation of two key glycolytic regulatory loci, phosphofructokinase/fructose-1,6-bisphosphatase and pyruvate kinase/phosphoenolpyruvate carboxykinase and pyruvate carboxylase. Although previous studies have shown similar allosteric sensitivities to adenylates to rat liver phospho-fructokinase, there was no evidence of an activation of the pathway as a result of decreasing high energy adenylate, ATP or increasing AMP levels. The lack of any apparent regulatory control of glycosis during cold hypoxia may be related to hibernator-specific metabolic adaptations that are key to the survival of hypothermia during natural bouts of hibernation.Abbreviations DHAP dihydroxyacetonephosphate - EC energy charge - F1,6P₂ fructose-1,6-bisphosphate - F2,6P₂ fructose-2,6-bisphosphate - F6P fructose-6-phosphate - FBP fructose-1,6-bisphosphatase - G1P glucose-1-phosphate - G6P glucose-6-phosphate - GAP glyceraldehyde-3-phosphate - GAPDH glyceraldehyde-3-phosphate dehydrogenase - L/R lactobionate/raffinose-based solution - MR metabolic rate - PDH pyruvate dehydrogenase - PEP phosphoenolpyruvate - PEPCK & PC phosphoenolpyruvate carboxykinase and pyruvate carboxylase - PFK phosphofructokinase; PK, pyruvate kinase - Q ₁₀ the effect of a 10 °C drop in temperature on reaction rates (generally, Q ₁₀=2–3) - TA total adenylates - UW solution University of Wisconsin solution (L/R-based)     

Ecology and evolutionary biology of fishing bats

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