Terrie M. Williams

Genome 10K: A Proposal to Obtain Whole-Genome Sequence for 10 000 Vertebrate Species

The human genome project has been recently complemented by whole-genome assessment sequence of 32 mammals and 24 nonmammalian vertebrate species suitable for comparative genomic analyses. Here we anticipate a precipitous drop in costs and increase in sequencing efficiency, with concomitant development of improved annotation technology and, therefore, propose to create a collection of tissue and DNA specimens for 10,000 vertebrate species specifically designated for whole-genome sequencing in the very near future. For this purpose, we, the Genome 10K Community of Scientists (G10KCOS), will assemble and allocate a biospecimen collection of some 16,203 representative vertebrate species spanning evolutionary diversity across living mammals, birds, nonavian reptiles, amphibians, and fishes (ca. 60,000 living species). In this proposal, we present precise counts for these 16,203 individual species with specimens presently tagged and stipulated for DNA sequencing by the G10KCOS. DNA sequencing has ushered in a new era of investigation in the biological sciences, allowing us to embark for the first time on a truly comprehensive study of vertebrate evolution, the results of which will touch nearly every aspect of vertebrate biological enquiry.

KILLER APPETITES: ASSESSING THE ROLE OF PREDATORS IN ECOLOGICAL COMMUNITIES

Large body size, carnivory, and endothermic costs lead to exceptionally high caloric demands in many mammalian predators. The potential impact on prey resources may be marked but is difficult to demonstrate because of the mobility, sparseness, and cryptic nature of these animals. In this study, we developed a method based on comparative bioenergetics and demographic modeling to evaluate predator effects and then used this approach to assess the potential impact of killer whales on sea otter and Steller sea lion populations in the Aleutian Islands. Daily caloric requirements of killer whales determined from allometric regressions for field metabolic rate show that an adult killer whale requires 51-59 kcal·kg 21 ·d 21 (2.5-2.9 W/kg). Caloric values of prey items determined by bomb calorimetry ranged from 41 630 kcal for an adult female sea otter to sequentially higher values for male otters, sea lion pups, and adult Steller sea lions. Integrating these results with demographic changes in marine mammal populations show that fewer than 40 killer whales could have caused the recent Steller sea lion decline in the Aleutian archipelago; a pod of five individuals could account for the decline in sea otters and the continued suppression of sea lions. The collapse of the historical prey base of killer whales due to human whaling may have contributed to a sequential dietary switch from high to low caloric value prey, thereby initiating these declines. This study demonstrates that a combined physiological-demographic approach increases our ability to critically evaluate the potential impact of a predator on community structure and enables us to define underlying mechanisms

The cost of foraging by a marine predator, the Weddell seal Leptonychotes weddellii: pricing by the stroke.

SUMMARY Foraging by mammals is a complex suite of behaviors that can entail high energetic costs associated with supporting basal metabolism, locomotion and the digestion of prey. To determine the contribution of these various costs in a free-ranging marine mammal, we measured the post-dive oxygen consumption of adult Weddell seals (N=9) performing foraging and non-foraging dives from an isolated ice hole in McMurdo Sound, Antarctica. Dives were classified according to behavior as monitored by an attached video-data logging system (recording activity, time, depth, velocity and stroking). We found that recovery oxygen consumption showed a biphasic relationship with dive duration that corresponded to the onset of plasma lactate accumulation at approximately 23 min. Locomotor costs for diving Weddell seals increased linearly with the number of strokes taken according to the relationship: locomotor cost =– 3.78+0.04 × stroke number (r2=0.74, N=90 dives), where locomotor cost is in ml O2 kg–1. Foraging dives in which seals ingested Pleuragramma antarcticum resulted in a 44.7% increase in recovery oxygen consumption compared to non-foraging dives, which we attributed to the digestion and warming of prey. The results show that the energy expended in digestion for a free-ranging marine mammal are additive to locomotor and basal costs. By accounting for each of these costs and monitoring stroking mechanics, it is possible to estimate the aerobic cost of diving in free-ranging seals where cryptic behavior and remote locations prevent direct energetic measurements.

UNDERSTANDING AND PREDICTING ECOLOGICAL DYNAMICS: ARE MAJOR SURPRISES INEVITABLE

Ecological surprises, substantial and unanticipated changes in the abundance of one or more species that result from previously unsuspected processes, are a common outcome of both experiments and observations in community and population ecology. Here, we give examples of such surprises along with the results of a survey of well-established field ecologists, most of whom have encountered one or more surprises over the course of their careers. Truly surprising results are common enough to require their consideration in any reasonable effort to characterize nature and manage natural resources. We classify surprises as dynamic-, pattern-, or intervention-based, and we speculate on the common processes that cause ecological systems to so often surprise us. A long-standing and still growing concern in the ecological literature is how best to make predictions of future population and community dynamics. Although most work on this subject involves statistical aspects of data analysis and modeling, the frequency and nature of ecological surprises imply that uncertainty cannot be easily tamed through improved analytical procedures, and that prudent management of both exploited and conserved communities will require precautionary and adaptive management approaches.

Swimming Performance and Hydrodynamic Characteristics of Harbor Seals Phoca vitulina

Hydrodynamic characteristics, including fineness ratios, coefficients of drag, and the influence of body size, shape, and position on drag were examined for harbor seals (Phoca vitulina). Drag for towing animals increased curvilinearly with velocity over the range 0.7 to 3.5 m·s⁻¹ and was described by the equations: Drag(N) = 6.49 velocity (m·s−1)0.79 for a submerged adult seal, and Drag(N) = 1.29 e1.9 velocity (m·s⁻¹) for the seal towing at the water surface. The importance of streamlining was demonstrated by comparing these values with those of a towing human subject. At 2.0 m·s⁻¹ drag for a submerged human was 113 N, representing a 5.0-fold and a 1.9-fold increase in drag over submerged and surface towing seals, respectively. Coefficients of drag (Cd) followed this trend and were three times greater for the human subject. Alterations in body configuration of the seals, as occurs during stroking movements, resulted in an increase in body drag. From our calculations, body drag during gliding phases may more than double during active swimming by seals and influences the swimming performance of these animals.

Body size and skeletal muscle myoglobin of cetaceans: adaptations for maximizing dive duration

Cetaceans exhibit an exceptionally wide range of body mass that influence both the capacities for oxygen storage and utilization; the balance of these factors is important for defining dive limits. Furthermore, myoglobin content is a key oxygen store in the muscle as it is many times higher in marine mammals than terrestrial mammals. Yet little consideration has been given to the effects of myoglobin content or body mass on cetacean dive capacity. To determine the importance of myoglobin content and body mass on cetacean diving performance, we measured myoglobin content of the longissimus dorsi for ten odontocete (toothed whales) and one mysticete (baleen whales) species ranging in body mass from 70 to 80000 kg. The results showed that myoglobin content in cetaceans ranged from 1.81 to 5.78 g (100 g wet muscle)(-1). Myoglobin content and body mass were both positively and significantly correlated to maximum dive duration in odontocetes; this differed from the relationship for mysticetes. Overall, the combined effects of body mass and myoglobin content accounts for 50% of the variation in cetacean diving performance. While independent analysis of the odontocetes showed that body mass and myoglobin content accounts for 83% of the variation in odontocete dive capacity.

Swimming Metabolism of Yearling and Adult Harbor Seals Phoca vitulina

The swimming metabolism of yearling and adult harbor seals was measured by indirect calorimetry in a flow channel at speeds ranging from 0.5 to 1.4 m·s−1. Minimum resting metabolic rates in still water were 5.1 and 4.6 ml O2·min−1·kg−1 for the two yearling seals (body mass [Mb] = 33 kg) and one adult seal (Mb = 63 kg), respectively. Minimum resting metabolic rates were about 1.1 × the predicted standard metabolic rate for mammals of equivalent size. During steady-state swimming, metabolism increased curvilinearly with speed and was best described by the equation V̇o2 (ml O2·min−1·kg−1) = 5.1 + 6.25 velocity (m·s−1)1.42 for the yearling seals and V̇o2 = 4.6 + 3.1 velocity1.42 for the adult seal. Stroke frequency increased linearly as a function of swimming speed. Cost of transport decreased asymptotically with swim velocity, approaching a minimum at 1.0–1.4 m·s−1 of 3.6 J·m−1·kg−1 for yearling and 2.3 J·m−1·kg−1 for adult seals. The minimum cost of transport was less than for other semiaquatic birds and mammals but 3–4 × the predicted value for salmonid fish of equivalent size at 25 C.

The development of diving in marine endotherms: preparing the skeletal muscles of dolphins, penguins, and seals for activity during submergence

Abstract. Myoglobin is an important oxygen store for supporting aerobic diving in endotherms, yet little is known about its role during postnatal development. Therefore, we compared the postnatal development of myoglobin in marine endotherms that develop at sea (cetaceans) to those that develop on land (penguins and pinnipeds). We measured myoglobin concentrations in the major locomotor muscles of mature and immature bottlenose dolphins (Tursiops truncatus) and king penguins (Aptenodytes patagonicus) and compared the data to previously reported values for northern elephant seals (Mirounga angustirostris). Neonatal dolphins, penguins, and seals lack the myoglobin concentrations required for prolonged dive durations, having 10%, 9%, and 31% of adult values, respectively. Myoglobin contents increased significantly during subsequent development. The increases in myoglobin content with age may correspond to increases in activity levels, thermal demands, and time spent in apnea during swimming and diving. Across these phylogenetically diverse taxa (cetaceans, penguins, and pinnipeds), the final stage of postnatal development of myoglobin occurs during the initiation of independent foraging, regardless of whether development takes place at sea or on land.

Swimming by sea otters: adaptations for low energetic cost locomotion

SummaryThe energetics and hydrodynamics of surface and submerged swimming were compared in the sea otter (Enhydra lutris).1.Sea otters used two distinct speed ranges that varied with swimming mode. Sustained surface swimming was limited to speeds less than 0.80 m/s, while sustained submerged swimming occurred over the range of 0.60 to 1.39 m/s.2.Rates of oxygen consumption (VO2) at the transition speed (0.80 m/s) were 41% lower for submerged swimming by sea otters in comparison to surface swimming.3.Total cost of transport for surface swimming sea otters, 12.56 joules/kg·sm, was more than 12 times the predicted value for a similarly-sized salmonid fish. Transport costs for submerged swimming at the same speed was only 7.33 times the predicted value.4.The allometric relationship for minimum cost of transport in surface swimming birds and mammals wasy=23.87x−0.15 wherey=cost of transport in joules/kg·m andx=body mass in kg. This regression loosely parallels the relationship for salmonid fish.5.Correlations between aquatic behavior, morphological specialization, and swimming energetics indicate that the development of swimming in mustelids involved transitions from fore-paw to hindpaw propulsion, and from surface to submerged swimming.

A killer appetite: metabolic consequences of carnivory in marine mammals ☆

Among terrestrial mammals, the morphology of the gastrointestinal tract reflects the metabolic demands of the animal and individual requirements for processing, distributing, and absorbing nutrients. To determine if gastrointestinal tract morphology is similarly correlated with metabolic requirements in marine mammals, we examined the relationship between basal metabolic rate (BMR) and small intestinal length in pinnipeds and cetaceans. Oxygen consumption was measured for resting bottlenose dolphins and Weddell seals, and the results combined with data for four additional species of carnivorous marine mammal. Data for small intestinal length were obtained from previously published reports. Similar analyses were conducted for five species of carnivorous terrestrial mammal, for which BMR and intestinal length were known. The results indicate that the BMRs of Weddell seals and dolphins resting on the water surface are 1.6 and 2.3 times the predicted levels for similarly sized domestic terrestrial mammals, respectively. Small intestinal lengths for carnivorous marine mammals depend on body size and are comparatively longer than those of terrestrial carnivores. The relationship between basal metabolic rate (kcal day(-1)) and small intestinal length (m) for both marine and terrestrial carnivores was, BMR=142.5 intestinal length(1.20) (r(2)=0.83). We suggest that elevated metabolic rates among marine mammal carnivores are associated with comparatively large alimentary tracts that are presumably required for supporting the energetic demands of an aquatic lifestyle and for feeding on vertebrate and invertebrate prey.