Sensing electric fields is an ability that certain animal species utilize for communication, hunting, and spatial orientation. Freshwater planarians move toward the cathode in a static electric field (cathodic electrotaxis). First described by Raymond Pearl more than a century ago, planarian electrotaxis has received little attention and the underlying mechanisms and evolutionary significance remain unknown. We developed an apparatus and scoring metrics for automated quantitative and mechanistic studies of planarian behavior upon exposure to a static electric field. Using this automated setup, we characterized electrotaxis in the planarian Dugesia japonica and found that this species responds to voltage instead of to current, in contrast to results from previous studies using other species. Because longer planarians exhibited more robust electrotaxis than shorter planarians, we hypothesized that signals from the head impede cathodic electrotaxis. To test this hypothesis, we took advantage of the regenerative abilities of planarians and compared electrotaxis in head and tail fragments of various lengths. We found that tail and trunk fragments electrotaxed while head fragments did not, regardless of size. However, we could restore cathodic electrotaxis in head fragments via decapitation, demonstrating that the presence of the head impaired cathodic electrotaxis. This result is in stark contrast to other stimulated behaviors such as phototaxis, thermotaxis or chemotaxis, which are weaker or absent in headless fragments. Thus, electrotaxis may be an important ability of headless planarian fragments to support survival prior to head regeneration.
In complex biochemical systems, an enzyme, protein, or RNA, symbolized as E, has hundreds or thousands of substrates or interacting partners. The relative specificity hypothesis proposes that such an E would differentially interact with and influence its many distinct, downstream substrates, thereby regulating the underlying biological process (es). The importance of relative specificity has been underappreciated, and evidence of its physiological consequences particularly lacking. Previously we showed that human Drosha and Dicer ribonucleases (RNases) both discriminate their respective microRNA (miRNA) substrates, and that differential cleavage by Drosha contributes to global differential miRNA expression. If relative specificity is an important biological mechanism, it should be evolutionarily conserved. To test this hypothesis, we hereby examined the cleavage of hundreds of zebrafish and fruitfly miRNA intermediates by Drosha and Dicer and the impact on miRNA biogenesis in these organisms. We showed that Drosha action regulates differential miRNA expression in zebrafish and fruitflies and identified the conserved secondary structure features and sequences in miRNA transcripts that control Drosha activity and miRNA expression. Our results established the conservation of miRNA processing mechanisms and regulatory functions by Drosha and Dicer, greatly strengthened the evidence for the physiological consequences of relative specificity as well as demonstrated its evolutionary significance.
Wild sheep (Ovis spp.) are of conservation concern throughout the Middle East. Little is known, however, about the natural history or ecology of this taxon. To better understand size relationships among wild sheep occupying Iran, we analyzed results from 120 females collected from widely separated ecosystems. Morphometrics and body weights for all age categories of females occupying the Khosh-Yeilagh Wildlife Refuge in northeastern Iran were larger than those for the same age classes of females occupying Bamou National Park in southwestern Iran. Females from Bamou National Park, however, obtained adult body weight (x‾ = 25.8 ± 2.47 [SD] kg) at an earlier age than those from the Khosh-Yeilagh Wildlife Refuge (x‾ = 36.6 ± 3.21 kg). Ecological differences between these two areas suggest that net primary productivity, which is a function of numerous climatic and geographical factors, has been a primary force contributing to these results. Weights and measurements reported here provide the basic information for additional, more detailed research necessary to fully understand the evolutionary significance and management implications of these differences in body size and emphasize the conservation value of even the most basic natural history information.
The Lupemban is an industry of the Middle Stone Age (MSA) that is found across the Congo Basin and on its plateau margins in central Africa. It takes its name from the site of Lupemba that was discovered in 1944 in the Democratic Republic of Congo (DRC, then the Belgian Congo). The Lupemban’s distinctive toolkit of elongated lanceolate bifaces, core-axes, points, blades, and other small tools coincides with the equatorial forest belt and is suitable for constructing hafted implements, which has led to speculation it was a special and specific prehistoric adaptation to rainforest foraging. Although poorly dated across most of its geographic range, radiometric dates for the Lupemban at Twin Rivers (Zambia) show it is at least ~265 ka years old, placing it among the oldest known expressions of the regional MSA. As such, the Lupemban bears on 21st-century debates about the evolution of complex cognitive abilities and behaviors that characterize the emergence of Homo sapiens at or before 300 ka bp. In spite of the Lupemban’s potential importance for understanding the evolution of technology, human–environment interactions, and cognition in early Homo sapiens, the industry remains enigmatic and poorly understood. Logistical, ecological, and political challenges continue to impede fieldwork in central Africa. Moreover, at sites including Gombe Point (DRC), severe soil bioturbation by tree roots has caused the vertical displacement of buried artifacts, which corrupts the basic integrity of stratigraphic sequences. This problem is known to be widespread and means that after 100 years of research, central Africa still lacks a refined Stone Age cultural sequence. Consequently, very little is known about spatiotemporal variability within the Lupemban, or its specific environmental or cultural adaptations. At the site of Kalambo Falls (Zambia), the industry is found in secondary but stratified context, which, as of the early 21st century, offers the best glimpse into Lupemban technology and its potential evolutionary significance.
Previous toxicokinetic studies have shown that mussels (Mytilus spp.) can readily absorb the three main mammalian sex steroids, estradiol (E2), testosterone (T) and progesterone (P) from water. They also have a strong ability to store E2 and the 5α-reduced metabolites of T and P in the form of fatty acid esters. These esters were shown to have half-lives that were measured in weeks (i.e. they were not subject to fast depuration). The present study looked at the toxicokinetic profile of two other common steroids that are found in water, the potent synthetic oestrogen, (ethinyl-estradiol) (EE2; one of the two components of ‘the pill’), and cortisol, a natural stress steroid in vertebrates. In the first three hours of uptake, tritiated EE2 was found to be taken up at a similar rate to tritiated E2. However, the levels in the water plateaued sooner than E2. The ability of the animals to both esterify and sulphate EE2 was found to be much lower than E2, but nevertheless did still take place. After 24 h of exposure, the majority of radiolabelled EE2 in the animals was present in the form of free steroid, contrary to E2, which was esterified. This metabolism was reflected in a much lower half-life (of only 15 h for EE2 in the mussels as opposed to 8 days for E2 and >10 days for T and P). Intriguingly, hardly any cortisol (in fact none at all in one of the experiments) was absorbed by the mussels. The implications of this finding in both toxicokinetic profiling and evolutionary significance (why cortisol might have evolved as a stress steroid in bony fishes) are discussed.
Facial symmetry, averageness, and the level of sex-typical development of dimorphic traits are traditionally associated with various biological quality indicators and should be, therefore, preferred in mate choice. The aim of this study is to propose a concept of morphological uniqueness and uncover its possible associations to putative phenotypic cues of biological quality. In contrast to typicality expressed by averageness, morphological uniqueness quantifies the degree of possessing characteristics unique to particular groups. I employed a combination of geometric morphometric and Bayesian multiple regression to analyze 300 Cameroonian faces, while an additional 1153 faces from eight distinct populations from across four continents were used as a reference sample of the global population to calculate the morphological uniqueness of Cameroonians. I found that morphological uniqueness is positively associated with a feminine facial shape in women and negatively with morphological masculinity in men. Facial symmetry was positively associated with female faces with greater levels of uniqueness; the result for male faces was inconclusive. The faces of both sexes perceived as more attractive had lower levels of morphological uniqueness. Facial distinctiveness showed no relationship to morphological uniqueness in either sex, which indicates that morphological uniqueness and distinctiveness are two complementary approaches to studying facial typicality. In the conclusion, the evolutionary significance of the proposed concept and its potential applicability is discussed.