Life in the slow lane revisited: ontogenetic separation between chimpanzees and humans

This study investigates the evolution of human growth by analyzing differences in body mass growth trajectories among three populations: the Ache of eastern Paraguay, the US (NHANES, 1999-2000), and captive chimpanzees. The relative growth statistic "A" from the mammalian growth law is allowed to vary with age and proves useful for comparing growth across different ages, populations, and species. We demonstrate ontogenetic separation between chimpanzees and humans, and show that interspecific differences are robust to variable environmental conditions. The human pattern of slow growth during the lengthened period from weaning to the beginning of the adolescent growth spurt is found among the Ache (low energy availability and high disease load) and also in the US (high energy availability and low disease load). The human growth pattern contrasts with that of the chimpanzee, where absolute growth rates and relative "A" values are faster and less prolonged. We suggest that selection has acted to decrease human growth rates to allow more time for increased cognitive development with lower body-maintenance costs.     

The secrets of lemur teeth

New tools are available for teasing out aspects of life‐history variation among extinct species. Here we summarize research on the life histories of the extinct lemurs of Madagascar. There is a wide range of variation in dental developmental timing among these species, from among the most accelerated (Palaeopropithecus) to among the most prolonged (Hadropithecus) within the Order Primates. Rather than reflecting variation in body size, this diversity appears to relate to niche characteristics and encephalization.     

A java applet for exploring the new higher level classification of eukaryotes with emphasis on the taxonomy of protists

ABSTRACT. We have converted the hierarchically organized new higher level classification of eukaryotes with emphasis on the taxonomy of protists proposed by Adl et al. into an interactive and dynamic Java applet. The current version of the applet can be accessed via http://phylogenetics.bioapps.biozentrum.uni-wuerzburg.de/etv . We use the layout from a Degree-of-Interest tree (DOITree) that effectively displays all the taxonomic information as well as the phylogenetic relationships described in the original article by Adl et al. The tree was made using the Prefuse Toolkit for interactive information visualization. All browsers capable of using Java applets will be able to view the tree. The applet is freely available for scientists, teachers, and students.     

Application of Perturbation Simulations in Population Risk Assessment for Different Life History Strategies and Elasticity Patterns

Population structure and life history strategies are determinants of how populations respond to stressor-induced impairments in organism-level responses. Effects on population growth rate were modeled using seven theoretical constructs that represented the life history strategies and elasticity patterns of a broad range of species. Simulations of low to high ranges of simultaneous reductions in survival and reproduction were conducted and results indicated that stressor impacts on population growth rate were a function of population characteristics and the magnitude of the stress. Species that had high reproductive elasticity had greater population-level impacts than species with high survival elasticity for the same organism-level effects. Perturbation simulations were performed to assess the extinction risk in two species with similar elasticity patterns but different life history strategies: mysid shrimp, Americamysis bahia, and the gypsy moth, Lymantria dispar, which can be related to classical K- and r-strategists, respectively. Deterministic extinction risk was greater for the K-strategist, which indicated that population level risks were dependent on life history strategies, and toxicity values (e.g., LC50s) should be interpreted with caution. Ecological risk assessments should consider both population structure and life history strategy of an ecological receptor, in addition to the intrinsic sensitivity of the species to contaminant stressors.     

Maladaptive changes in multiple traits caused by fishing: impediments to population recovery

Some overharvested fish populations fail to recover even after considerable reductions in fishing pressure. The reasons are unclear but may involve genetic changes in life history traits that are detrimental to population growth when natural environmental factors prevail. We empirically modelled this process by subjecting populations of a harvested marine fish, the Atlantic silverside, to experimental size-biased fishing regimes over five generations and then measured correlated responses across multiple traits. Populations where large fish were selectively harvested (as in most fisheries) displayed substantial declines in fecundity, egg volume, larval size at hatch, larval viability, larval growth rates, food consumption rate and conversion efficiency, vertebral number, and willingness to forage. These genetically based changes in numerous traits generally reduce the capacity for population recovery.     

Bigger is better: age class-specific survival rates in long-lived turtles increase with size

Vital rates for small, non-breeding individuals are important components of population dynamics for many species, but often individuals of these sizes are difficult to locate, capture, and track. As such, biologists frequently lack reliable estimates of juvenile survival because sample sizes and recapture rates for this life stage are low. Long-lived animals often take many years to reach sexual maturity and spend much of this time in the smaller size classes, making them sensitive to changes in survival rates. We estimated the survival rates of all size classes for the northern map turtle (Graptemys geographica) using a mark-recapture dataset with >3,500 captures from 2019–2021 and 210 nests from 2018–2021. As turtle size increased, annual survival probability increased regardless of sex. Estimated annual survival probability for turtles >18 cm long (i.e., adult females >15 years) was about 0.95, over 4 times higher than turtles that were 3 cm long (i.e., hatchlings <1 year; 0.22 annual survival probability). Although we did not observe a difference in survival probability between sexes of any size class, adult females are nearly twice the size of adult males, leading to an increased annual survival probability for females of 0.95, compared to 0.80 for males. Changes in adult survival had the greatest influence on population estimates over time, with temporary decreases, such as those due to poaching or an environmental disaster, potentially leading to unrecoverable decreases in the overall population size. Our study provides detailed survival rates for all size classes in a long-lived turtle, which are necessary to assess population stability and can be used to determine the most effective conservation or management practices.     

THE LIVING CELL: A COMPLEX AUTODYNAMIC MULTI‐OSCILLATOR SYSTEM?

Life cannot be simply defined in biochemical terms but it is associated with autodynamic behaviour. This fact implies that all aspects of cell biology should be viewed in terms of the resultant temporal features. Theoretical arguments indicate that the dynamic state can be explained only by the existence of periodicity. In accordance with this view, experimental evidence indicates the existence of multiple oscillators and at least some are highly complex, implying that failure to understand aspects of cell biology can stem from inadequate concepts.     

A high standard metabolic rate constrains juvenile growth

The allocation of energy to various components of an individual's energy budget is often viewed as a competitive process. As such, a tradeoff may exist between production (growth) and maintenance metabolism. One view of a potential tradeoff, termed “the principle of allocation”, suggests that individuals with lower maintenance metabolic expenditures may have higher growth rates. To determine whether such a tradeoff exists, I analyzed the relationship between growth rate and maintenance metabolism of 225 juvenile snapping turtles housed in the laboratory. I measured growth from hatching to 6 months of age, and then measured oxygen consumption and calculated standard metabolic rate. Mean growth rate was 0.19 g d⁻ and mean standard metabolic rate (SMR) was 1.41 kJ d⁻. Maintenance metabolism and growth were negatively correlated after both were adjusted for body mass. The results support the “principle of allocation” theory: individuals with higher standard metabolic rates tended to have low growth rates.     

Experimental observations on maternal reproductive rate and offspring characteristics

Starting from a clone of Philodina roseola (Rotifera, Bdelloidea) six homogeneous animals have been reared. From them three different age cohorts have been studied in order to determine their life tables. Cohorts and parental life schedules are compared and discussed. A sort of correlation between offspring fecundity and life span and maternal rate of egg production could be established.