Larger Adult Size Research Articles

Fish with slow life-history cope better with chronic manganese exposure than fish with fast life-history.

Animals with different life-history types vary in their stress-coping styles, which can affect their fitness and survival in changing environments. We studied how chronic exposure to manganese sulfate (MnSO4), a common aquatic pollutant, affects life-history traits, physiology, and behavior of zebrafish (Danio rerio) with two life-history types: fast (previously selected for fast juvenile growth, early maturation, and small adult body size) and slow life histories (selected for slow juvenile growth, late maturation, and large adult body size). We found that MnSO4 had negative effects on growth and condition factors, but the magnitude of these effects depended on the life-history type. Individuals with fast life histories were more susceptible to MnSO4 than fish with slow life histories as they had lower growth rate, condition factor and feeding probability in high MnSO4 concentrations. Our results demonstrate that MnSO4 can impair fish performance, and life-history variation can modulate the stress-coping ability of individuals.

Transcriptome analysis reveals polyploidy-related differential gene expression among diploid, triploid, and tetraploid Pacific oysters (Crassostrea gigas) based on growth-related phenotypes

Tetraploid oysters hold a significant position in the global oyster industry, particularly as core germplasm resources for the production of triploids. Triploids exhibit desirable characteristics such as reduced gonadal development, larger adult size, and superior flesh quality compared with diploids. However, tetraploids often face challenges of slow growth and chromosomal instability during the breeding process, and the mechanisms underlying the formation of these polyploid characteristics remain unclear. This study aimed to elucidate these mechanisms by constructing a polyploid oyster system and comparing the differences in growth-related phenotypes and gene expression among diploids, triploids, and tetraploids. We identified 1404 differentially expressed genes (DEGs) between diploids and triploids, 1814 DEGs between triploids and tetraploids, and 933 DEGs between diploids and tetraploids. Furthermore, we observed distinct gene expression patterns related to innate immunity response and biomineralization between different ploidy levels. Through trend analysis, we clustered genes with similar expression level changes across different ploidy levels and conducted gene ontology (GO) enrichment analysis on genes with different expression profiles. The results indicated that genes associated with the innate immunity response exhibited significantly upregulated expression with increasing ploidy, while genes related to biomineralization showed higher or lower expression levels in triploid oysters. As biomineralization is closely linked to oyster shell growth, this highlights the crucial role of genes associated with biomineralization in regulating the rapid shell growth observed in triploid oysters. Confronted with environmental challenges, tetraploid oysters may display a stronger innate immune response than diploids and triploids. Our study provides valuable resources for investigating the functional aspects of genes related to polyploid phenotype differences and offers new insights into the molecular mechanisms of existing issues in tetraploid oyster breeding.

Hemigrammopetersius barnardi (Teleostei: Characiformes: Alestidae): a study of skeletal ontogeny and identification of homology for phylogenetic analysis

Members of Alestidae, a family of characiforms found in sub–Saharan Africa, have a wide range ofadult body sizes. Because of this range of adult size, phylogenetic characters for the group may be difficult to distinguish from ontogenetic features, resulting in groups being united based on body size rather than evolutionary relatedness. Although previous studies have presented the morphology and osteology of some small and miniature taxa, these were pre–cladistic and did not attempt to distinguish between phylogenetic and ontogenetic features. Here we provide a study on the external morphology and osteology of a small alestid, Hemigrammopetersius barnardi which has reductions and losses of osteological features. We compared this species to juveniles of Alestes dentex, an alestid that attains much larger adult size, to identify characters in H. barnardi that potentially result from a decrease in body size rather than shared ancestry. We found that the loss of particular bones of the circumorbital series and postcranium, as well as a reduction of the sensory canal system, are likely the result of small body size, and therefore are not useful in establishing phylogenetic relationships among alestids.

Planting exceptional tropical tree species to increase long‐term carbon storage in assisted secondary succession

Abstract With rising atmospheric CO2 concentrations, strategies for greater carbon sequestration and long‐term storage are urgently needed. Current reforestation schemes typically use fast‐growing tree species with low wood density, limiting the amount of carbon stored. In most tropical forests, there are native species with relatively fast growth rates, high wood density and low mortality rates that also achieve large adult size—‘exceptional species’. We present a simulated assessment of the carbon sequestration potential using these exceptional species in assisted secondary succession in the Neotropics. In our example, the selected exceptional species could add up to 16.2 Mg C/ha of sequestered carbon in secondary wet forests at maturity. Synthesis and applications. By increasing the representation of exceptional species in reforestation efforts, we could potentially boost long‐term carbon storage in reforestation projects focussed on carbon sequestration. However, our approach is not a substitute for protecting existing old primary forests and reforested lands plus reducing deforestation and emissions.

Allometric wing growth links parental care to pterosaur giantism.

Pterosaurs evolved a broad range of body sizes, from small-bodied early forms with wingspans of mostly 1-2 m to the last-surviving giants with sizes of small airplanes. Since all pterosaurs began life as small hatchlings, giant forms must have attained large adult sizes through new growth strategies, which remain largely unknown. Here we assess wing ontogeny and performance in the giant Pteranodon and the smaller-bodied anurognathids Rhamphorhynchus, Pterodactylus and Sinopterus. We show that most smaller-bodied pterosaurs shared negative allometry or isometry in the proximal elements of the fore- and hindlimbs, which were critical elements for powering both flight and terrestrial locomotion, whereas these show positive allometry in Pteranodon. Such divergent growth allometry typically signals different strategies in the precocial-altricial spectrum, suggesting more altricial development in Pteranodon. Using a biophysical model of powered and gliding flight, we test and reject the hypothesis that an aerodynamically superior wing planform could have enabled Pteranodon to attain its larger body size. We therefore propose that a shift from a plesiomorphic precocial state towards a derived state of enhanced parental care may have relaxed the constraints of small body sizes and allowed the evolution of derived flight anatomies critical for the flying giants.

High Investment in Reproduction Is Associated with Reduced Life Span in Dogs.

AbstractProminent differences in aging among and within species present an evolutionary puzzle. The theories proposed to explain evolutionary differences in aging are based on the axiom that selection maximizes fitness, not necessarily life span. This implies trade-offs between investment in self-maintenance and investment in reproduction, where high investments in growth and current reproduction are associated with short life spans. Fast growth and large adult size are related to shorter life spans in the domestic dog, a bourgeoning model in aging research; however, whether reproduction influences life span in this system remains unknown. Here we test the relationship between reproduction and differences in life span among dog breeds, simultaneously controlling for shared ancestry and recent gene flow. We found that shared ancestry explains a higher proportion of the among-breed variation in life history traits, in comparison with recent gene flow. Our results also show that reproductive investment negatively impacts life span, and more strongly so in large breeds, an effect that is not merely a correlated response of adult size. These results suggest that basic life history trade-offs are apparent in a domestic animal whose diversity is the result of artificial selection and that among-breed differences in life span are due to a combination of size and reproduction.

Patterns of biogeographic and regional life-history trait variation in four large-bodied tropical wrasses

Ectotherms display substantial demographic variation across latitudinal gradients of temperature. Higher temperatures are often associated with smaller size, rapid initial growth rates, and early maturation, generally described as the Temperature-Size Rule (TSR). The longevity of most ectotherms also declines at warmer, lower latitudes. However, these patterns may be modified by increases in food resources that can flow on to continuous growth and large adult size. The present study estimates age-based demographic parameters of large-bodied tropical wrasses (Hemigymnus melapterus, H. fasciatus, Cheilinus fasciatus, and Oxycheilinus digramma) collected from Philippine fish markets (9–11°N) and sampled from Palm (18.53–18.70°S) and Whitsunday (20.05–20.21°S) reefs on the Great Barrier Reef, Australia (GBR). Differences in longevity, initial growth rates, and the age at sexual maturation at a biogeographic scale, between the Philippines and GBR, conformed to predictions of the TSR. However, Philippine specimens exhibited greater relative body condition and sustained periods of growth beyond sexual maturity resulting in larger adult size than GBR samples. Size-structure data from Philippine marine reserves and fished sites indicated that these differences were not confounded by fishery-dependent sampling. Moreover, latitudinal length–weight relationships could not be explained by lower densities of the focal wrasses in the Philippines or by relative gonad size. Less pronounced patterns of demographic variation that differed across species were evident at a regional scale, among Palm and Whitsunday reefs. Patterns of demographic variation between the Philippines and GBR strongly suggest that differences in food resource levels will be important in explaining the observed geographic variation.

A cross-sectional study of pediatric hidradenitis suppurativa and the value of the International Hidradenitis Suppurativa Severity Score System (IHS4) as a pediatric clinical trial inclusion criteria.

Hidradenitis suppurativa (HS) often develops in pediatrics, but few interventional studies include pediatric patients. This dual analysis of a pediatric HS cohort and typical eligibility criteria in adult trials aims to identify potential patient characteristics and inclusion criteria for future pediatric HS studies. This cross-sectional and descriptive study is based on a prospectively collected data registry from an HS clinic. We also queried 125 HS studies from the Clinicaltrials.gov database and information from 61 interventional systemic HS drug trials was analyzed. The mean abscess and inflammatory nodule (AN) count in 81 pediatric subjects was 2.3 compared to 5.0 in adults with majority being Hurley stage I (39.5%, 32/81) or II (55.6%, 45/81). Most clinical trials required patients to be Hurley stage II/III with AN count of ≥3. When developing clinical trials for pediatric HS, it is imperative to consider how baseline characteristics impact recruitment and disease assessment. Frequently used eligibility criteria in adult trials may severely limit pediatric recruitment. Although our registry had a large adult sample size, the main limitation of this study was the relatively smaller pediatric sample size.

Growth variation in the endangered fish Zingel asper: Contribution of substrate quality, hydraulics, prey abundance, and water temperature

Abstract Intraspecific variation in life histories and its environmental correlates can indicate the degree of vulnerability to extinction of endangered taxa and guide conservation actions. Zingel asper (Percidae) is an endangered fish endemic to the Rhône catchment (France and Switzerland), where five populations subsist in separate river systems (Loue, Beaume, Durance, Verdon, and Doubs). Two populations of Z. asper differ in growth and longevity, but the existence of broader intraspecific differentiation in life histories and the environmental origins of this variation (if any) remain unknown. The age structure and growth profile of four populations of Z. asper (Loue, Beaume, Durance, and Verdon) and nine additional sub‐populations within the Durance system were determined by scale‐reading analysis, before evaluating the contribution of measured variation in substrate quality, hydraulics, prey availability, and water temperature to growth differentiation among and within populations. A trade‐off between early growth and longevity largely differentiated the populations of Z. asper along a slow (i.e. slower growth, smaller adult size, longevity of >5 years) to fast (i.e. faster growth, larger adult size, longevity of <4 years) continuum of life histories. This continuum differentiated populations from different river catchments along a south (Durance, Verdon) to north (Beaume, Loue) latitudinal gradient, and mapped onto an upstream–downstream gradient of sub‐populations within the Durance system. Differences in prey availability, hydraulics, and water temperature explained most of the growth variation among populations from different catchments, whereas local variation in prey availability, substrate quality, and water temperature mostly contributed to within‐river growth differentiation. These results indicate that short life cycles strongly expose all populations of Z. asper to extirpation and should motivate additional conservation actions. This study illustrates how quantifying intraspecific variation in life histories and its sensitivity to ecological context can reliably assess extinction risk and guide conservation actions by identifying endangered populations requiring priority management.

Aboveground biomass accumulation and tree size distribution in seasonal Atlantic Forest restoration sites

Tropical forests undergoing restoration can present high biomass accumulation rates, especially in the first 20 years. However, native species reforestations often present a bias toward fast growth, low wood density, and small maximum adult size species, contrasting with most mature forest species. Since tree species adult size and wood density are key traits that influence biomass accumulation, these induce uncertainty regarding carbon uptake capabilities of restoration projects in the long term. We compared the density of individuals (DI), basal area (BA), aboveground biomass (AGB), and weighted average wood density (WDW) in 13–14‐year‐old restoration sites and in mature seasonal Atlantic Forest fragments. We also assessed the contribution of pioneer and non‐pioneer and planted and non‐planted species on these variables at restoration sites. Furthermore, we investigated the DI and WDW for saplings and seedlings, in order to foresee changes in forest structure that may result from natural recruitment of dense‐wood mature species. The BA and WDW at restoration sites were similar to forest fragments, except for large trees (DBH ≥50 cm). Restoration sites recovered AGB to the level of forest fragments only for the smaller size class (DBH 5–19.9 cm). Planted pioneer and non‐pioneer species accumulated the greatest AGB (93%), BA (94%), and DI (90%) at restoration sites. The DI of non‐planted non‐pioneer species with higher WDW increased among saplings and seedlings at restoration sites. The presence of species with a larger adult size and higher WD may indicate long‐term increase in biomass accumulation at restoration sites.

Adaptive differentiation of growth, energetics and behaviour between piscivore and insectivore juvenile rainbow trout along the Pace-of-Life continuum.

Adaptive trade-offs are fundamental mechanisms underlying phenotypic diversity, but the presence of generalizable patterns in multivariate adaptation and their mapping onto environmental gradients remain unclear. To understand how life history affects multivariate trait associations, we examined relationships among growth, metabolism, anatomy and behaviour in rainbow trout juveniles from piscivore versus insectivore ecotypes along an experimental gradient of food availability. We hypothesized that (a) selection for larger size in piscivorous adults would select for higher juvenile growth at the cost of lower active metabolism; (b) elevated growth of piscivores would be supported by a greater productivity of their natal stream and more proactive foraging behaviours and (c) general patterns of multivariate trait associations would match the predictions of the Pace-Of-Life Syndrome. Relative to insectivores, piscivorous fry showed a pattern of higher growth (+63%), maximum food intake (+33%), growth efficiency (+41%) and standard metabolic rate (SMR; +47%), but lower active metabolic capacity (maximum metabolic rate [MMR; -17%], aerobic scope [AS; -48%]), suggesting that faster piscivore growth is supported by greater food intake and digestive capacity but is traded-off against lower scope for active metabolism. A similar trade-off appeared among organ systems, with piscivorous fry exhibiting an 83% greater investment in average mass of organs associated with food consumption and processing (i.e. stomach and intestine), but an apparently smaller relative investment in organs involved in cardiovascular or cognitive activities (heart and brain, respectively). Higher invertebrate drift in their natal rearing habitat, quicker behavioural transition to a novel food source and lower anxiety after a frightening event in piscivorous fry suggest that faster growth requires both proactive foraging behaviours and higher prey availability in the environment. Finally, the sampling of replicate insectivore populations confirmed their lower juvenile growth (-73% on average) and reduced environmental productivity of their natal streams (-45% lower drift abundance) relative to the piscivore ecotype. Our results suggest that selection for large adult body size influences selection on high juvenile growth, high basal metabolism and proactive behaviours, and that the intense phenotypic divergence between piscivorous and insectivorous rainbow trout may be constrained by environmental productivity.

Gregariousness affects performance and defensive reactions in swallowtail caterpillars

1. Group living in caterpillars may enhance individual performance due to sharing of costs associated with individual tasks when dealing with biotic or abiotic ecological factors.2. In the gregarious caterpillar Battus polydamas archidamas (Papilionidae) egg clusters and caterpillar groups vary in size. We hypothesized that individual survival would be higher in larger groups and that group living would enhance individual performance: shorter development time and/or reduced frequency of (presumably costly) defensive reactions in larvae and larger adult size. We also tested whether the group size conferring the highest survival to laboratory‐reared caterpillars matched the most frequent egg clutch size in the field.3. We collected egg clutches in the field and reared caterpillars in groups of 1, 6, 10, and 14 individuals. We quantified larval survival and stage duration as well as adult mass under laboratory conditions, excluding natural enemies. We also recorded the frequency of larval defensive reactions (thrashing and osmeterium display) against a tactile stimulus of first‐instar larvae.4. Group living enhanced caterpillar survival, particularly during the first instars, when caterpillars are 100% gregarious. Groups of intermediate size reduced larval development time but group living did not affect adult mass. Individual caterpillars in groups showed defensive reactions less frequently than solitary individuals, revealing a cost‐saving feature of gregariousness for this swallowtail species. The most frequent clutch size in the field (9–10 eggs) did not match the larval group with highest survival (14 individuals), but did match the group with shortest development time.

Effects of larval exposure to sublethal doses of Bacillus thuringiensis var. israelensis on body size, oviposition and survival of adult Anopheles coluzzii mosquitoes

BackgroundApplication of the larvicide Bacillus thuringiensis var. israelensis (Bti) is a viable complementary strategy for malaria control. Efficacy of Bti is dose-dependent. There is a knowledge gap on the effects of larval exposure to sublethal Bti doses on emerging adult mosquitoes. The present study examined the effect of larval exposure to sublethal doses of Bti on the survival, body size and oviposition rate in adult Anopheles coluzzii.MethodsThird-instar An. coluzzii larvae were exposed to control and sublethal Bti concentrations at LC20, LC50 and LC70 for 48 h. Surviving larvae were reared to adults under standard colony conditions. Thirty randomly selected females from each treatment were placed in separate cages and allowed to blood feed. Twenty-five gravid females from the blood-feeding cages were randomly selected and transferred into new cages where they were provided with oviposition cups. Numbers of eggs laid in each cage and mortality of all adult mosquitoes were recorded daily. Wing lengths were measured of 570 mosquitoes as a proxy for body size.ResultsExposure to LC70Bti doses for 48 h as third-instar larvae reduced longevity of adult An. coluzzii mosquitoes. Time to death was 2.58 times shorter in females exposed to LC70Bti when compared to the control females. Estimated mortality hazard rates were also higher in females exposed to the LC50 and LC20 treatments, but these differences were not statistically significant. The females exposed to LC70 concentrations had 12% longer wings than the control group (P < 0.01). No differences in oviposition rate of the gravid females were observed between the treatments.ConclusionsExposure of An. coluzzii larvae to sublethal Bti doses reduces longevity of resultant adults and is associated with larger adult size and unclear effect on oviposition. These findings suggest that anopheline larval exposure to sublethal Bti doses, though not recommended, could reduce vectorial capacity for malaria vector populations by increasing mortality of resultant adults.

A subadult individual of Styracosaurus albertensis (Ornithischia: Ceratopsidae) with comments on ontogeny and intraspecific variation in Styracosaurus and Centrosaurus.

Styracosaurus albertensis is an iconic centrosaurine horned dinosaur from the Campanian of Alberta, Canada, known for its large spike-like parietal processes. Although described over 100 years ago, subsequent discoveries were rare the last few decades, during which time several new skulls, skeletons, and bonebeds were found. Here we described an immature individual, the smallest known for the species, represented by a complete skull and fragmentary skeleton. Although ~80% maximum size, it possesses a suite of characters associated with immaturity, and is regarded as a subadult. The ornamentation is characterized by a small, recurved, but fused nasal horncore; low, rounded postorbital horncores; and short, triangular, and flat parietal processes. Using this specimen, and additional skulls and bonebed material, the cranial ontogeny of Styracosaurus is described, and compared to Centrosaurus. Styracosaurus shows a similar early ontogeny of the nasal horncore, starting thin, recurved, and unfused, but retains the recurved morphology into large adult size, and never develops the procurved morphology common in Centrosaurus. The postorbital horncores of Styracosaurus are lower and more rounded than those of Centrosaurus throughout ontogeny, and show greater resorption later in ontogeney. The length and thickness of the parietal processes increase drastically through ontogeny, but their position and orientation are static across the size series. Several diagnostic Styracosaurus albertensis specimens now preserve medially orientated P3 spikes, causing issues for the diagnosis of S. ovatus. Variability in parietal ornamentation, either expression of P1 and P2 parietal processes, or other cranial ornamentations, does not appear to correlate with stratigraphy.

A case study of the coconut crab Birgus latro on Zanzibar highlights global threats and conservation solutions

Abstract The coconut crab Birgus latro, the largest terrestrial decapod, is under threat in most parts of its geographical range. Its life cycle involves two biomes (restricted terrestrial habitats near the coast, and salt water currents of the tropical Indian and Pacific Oceans). Its dependence on coastal habitat means it is highly vulnerable to the habitat destruction that typically accompanies human population expansion along coastlines. Additionally, it has a slow reproductive rate and can reach large adult body sizes that, together with its slow movement when on land, make it highly susceptible to overharvesting. We studied the distribution and population changes of coconut crabs at 15 island sites in coastal Tanzania on the western edge of the species' geographical range. Our aim was to provide the data required for reassessment of the extinction risk status of this species, which, despite indications of sharp declines in many places, is currently categorized on the IUCN Red List as Data Deficient. Pemba Island, Zanzibar, in Tanzania, is an important refuge for B. latro but subpopulations are fragmented and exploited by children and fishers. We discovered that larger subpopulations are found in the presence of crops and farther away from people, whereas the largest adult coconut crabs are found on more remote island reserves and where crabs are not exploited. Remoteness and protection still offer hope for this species but there are also opportunities for protection through local communities capitalizing on tourist revenue, a conservation solution that could be applied more generally across the species' range.

Loss of Habitat Leads to Bigger Toads and Bigger Eggs: Natural Area Management Predictions for the Eastern American Toad, Anaxyrus americanus americanus (Holbrook, 1836)

Reproductive characteristics of the Eastern American Toad (Anaxyrus americanus americanus) vary geographically across its broad eastern North American range. Northern populations are known to breed for a shorter period that begins later in the season (April and/or May) than southern populations that can begin in winter and last until April. Delayed maturity and larger minimum body size are also associated with northern populations. Specimens collected during two years of systematic trapping during 1982–1983 at the Powdermill Nature Reserve (PNR), Westmoreland County, Pennsylvania, were examined to test predictions of geographic patterns associated with reproduction and growth of a southwestern Pennsylvania population. The results indicate a short egg laying season in May, large adult body size, and delayed maturity. An apparent response to northern Allegheny climate, the reproductive-related patterns of this population were similar to those of other northern regions rather than populations at similar latitudes within Pennsylvania. Eastern American Toads collected from a breeding site at PNR in 2014 were larger in body size, clutch size, and egg size than those of the 1982–1983 study. Most notably, loss of open breeding habitat in the 30+ years between sampling periods resulted in fewer larger toads producing on average larger eggs and twice the clutch size than counterparts studied during earlier successional series of this study site. These differences quantify geographic and temporal variability in life history traits of an ecologically versatile and geographically widespread species and provide landscape-wide predictions of life history responses by the Eastern American Toad to natural or human-mediated changes to natural areas.

Embryonic Development of the Egyptian Fruit Bat Rousettus aegyptiacus (Mammalia: Chiroptera: Pteropodidae)

Bats have evolved several unique morphological traits related to powered flight, such as wings, patagia, minute hindlimbs, large pinna, and a larynx specialised for echolocation. Studies of embryonic development in bats provide important insights into the mechanisms underlying the evolution of flight-related structures in vertebrates. Although embryonic development has been described in some bats species, only one species of Old World fruit bats (family Pteropodidae) has previously had its embryonic development examined. In this paper, we describe the embryonic development of the Egyptian fruit bat, Rousettus aegyptiacus, ranging from middle pharyngula to just before birth. We compared the growth patterns during embryogenesis among nine bat species for which data on embryonic development have been obtained. We discovered that i) the crown-rump length (CRL) is almost equivalent among the bat species until stage 22, and ii) compared to other bat species examined, the growth rate rapidly and substantially increases in two pteropodid species (R. aegyptiacus and R. amplexicaudatus) after stage 22. In placental mammals, larger body size at birth is advantageous for postnatal survival. To obtain large adult body size, some pteropodid bats may accelerate their postnatal growth and take advantage of larger body size at birth.

Comparative skeletal anatomy of neonatal ursids and the extreme altriciality of the giant panda.

Mammalian neonates are born at a wide range of maturity levels. Altricial newborns are born with limited sensory agency and require extensive parental care. In contrast, precocial neonates are relatively mature physically and often capable of independent function shortly after birth. In extant mammals, placental newborns vary from altricial to precocial, while marsupials and monotremes are all extremely altricial at birth. Bears (family Ursidae) have one of the lowest neonatal-maternal mass ratios in placental mammals, and are thought to also have the most altricial placental newborns. In particular, giant pandas (Ailuropoda melanoleuca) are thought to be exceptionally altricial at birth, and possibly marsupial-like. Here we used micro-computer (micro-computed) tomography scanning to visualize the skeletal anatomy of ursid neonates and compare their skeletal maturity with the neonates of other caniform outgroups. Specifically, we asked whether ursid neonates have exceptionally altricial skeletons at birth compared with other caniform neonates. We found that most bear neonates are similar to outgroup neonates in levels of skeletal ossification, with little variation in degree of ossification between ursine bears neonates (i.e. bears of the subfamily Ursinae). Perinatal giant pandas, however, have skeletal maturity levels most similar to a 42-45-day-old beagle fetus (~70% of total beagle gestation period). No bear exhibits the skeletal heterochronies seen in marsupial development. With regards to skeletal development, ursine bears are not exceptionally altricial relative to other caniform outgroups, but characterized largely by the drastic difference between newborn and adult body sizes. A review on the existing hypotheses for ursids' unique reproductive strategy suggests that the extremely small neonatal-maternal mass ratio of ursids may be related to the recent evolution of large adult body size, while life history characteristics retained an ancestral condition. A relatively short post-implantation gestation time may be the proximal mechanism behind the giant panda neonates' small size relative to maternal size and altricial skeletal development at birth.

Phenotypic characterization and performance evaluation of Burmese black pig: A unique indigenous germplasm of north east region of India

Burmese black pig is one of the unique and well adapted indigenous pig reared under low input backyard production system in the eastern Himalayan hill ecosystem. The present study was conducted in four states of north eastern India viz. Mizoram, Manipur, Nagaland and Meghalaya to identify the geographical distribution, breeding habitat, phenotypic and productive characteristics of the pig. Information on production system was collected from 251 Burmese pig farmers across 78 villages in 14 districts by providing structured pre tested questionnaire. The study revealed that the population of Burmese black pig was about twelve thousands and mostly distributed in Phek, Kiphire, Tuensang and Mon district of Nagaland (38%); Champhai, Kolasib and Siaha districts of Mizoram (28%); Ukhrul, Chandel, Churachandpur and Tamenglong districts of Manipur (27%); and East Khasi hills, West Khasi hills and Ribhoi districts of Meghalaya (7%) which covered approximately 33700 square km areas of distribution. The average herd size of Burmese black pigs was 3.26±0.34 which ranges from 1 to 12. Backyard earthen floor housing system (55.38%)was the most common, followed by backyard deep litter housing (19.52%),slatted floor housing (14.34%), concrete floor housing (7.17%) and girth tethering system (3.59%). These pigs are predominantly black in colour. Medium sized concave dish shaped head, short slightly upward curve snout, well build long body structure with short legs, prominent neck in both male and female are the unique feature of Burmese black pigs. The average body weight of adult (10 months) was 79.76 ± 1.97 kg. The average body length, height at withers, heart girth and neck girth at adult age were 84.86 ±1.76, 61.94 ±1.52, 87.06 ±2.41 and 78.27 ±1.98 cm in male and 81.66 ±1.70, 60.15 ±1.60, 83.05 ±2.10, 75.02 ±1.81 cm in female, respectively. The average age at first heat and age at first farrowing were 220.32 ± 23.61 days and 365.00 ± 20.75 days, respectively; while average litter size at birth and litter size at weaning was 10.76 ± 0.87 and 8.86 ± 0.61, respectively. These pigs are having faster growth rate, larger adult body size and higher liter size as compared to the other indigenous pig breeds in India. The Burmese black pig possesses unique physical and high productive as well as reproductive traits that distinguished them from other indigenous pig breeds in the region.

Broodmate aggression and life history variation in accipitrid birds of prey.

Aggressive sibling competition for parental food resources is relatively infrequent in animals but highly prevalent and extreme among certain bird families, particularly accipitrid raptors (Accipitriformes). Intense broodmate aggression within this group is associated with a suite of traits including a large adult size, small broods, low provisioning rates, and slow development. In this study, we apply phylogenetic comparative analyses to assess the relative importance of several behavioral, morphological, life history, and ecological variables as predictors of the intensity of broodmate aggression in 65 species of accipitrid raptors. We show that intensity of aggression increases in species with lower parental effort (small clutch size and low provisioning rates), while size effects (adult body mass and length of nestling period) are unimportant. Intense aggression is more closely related to a slow life history pace (high adult survival coupled with a restrained parental effort), rather than a by‐product of allometry or food limitation. Consideration of several ecological variables affecting prey abundance and availability reveals that certain lifestyles (e.g., breeding in aseasonal habitats or hunting for more agile prey) may slow a species’ life history pace and favor the evolution of intense broodmate aggression.