Orchids,bilateral symmetry and insect perception

The basic characteristics of orchids, possessing the greatest number of complex floral images of any Angiosperm family, are reviewed. Bilateral symmetry (zygomorphy) is shown by use of information theory techniques to give much greater possibilities for the transmission of visually mediated information than radial symmetry. The difference in information content is further enhanced by motion. The analysis is offered as evidence that the evolution of diversity in complex images, if effected by the unique behavioral specificity of pollinators known as “flower constancy”, is most economically explained by hypothesizing recognition and storage of the total image (“gestalt”) in the agents of natural selection.     

Ploidy of endothelium in high-grade astrocytomas

To determine the ploidy and proliferative activity of the endothelium in high-grade astrocytomas, the nuclear DNA content of 11 high-grade astrocytomas, including two gliosarcomas, was measured by cytophotometry. This technique allowed comparison of the endothelial population with the astrocytic population. In all cases, the endothelium was diploid, with an average of 24.6% of cells in the S + G2M phases of the cell cycle. In contrast, the astrocytic population displayed marked DNA abnormalities. The two gliosarcomas had a marked difference in proliferative activity of the endothelium with 4% and 40% of cells, respectively, in the S + G2M phases. These data indicate that the vast majority of endothelial cells compromising the vascular hypercellularity observed in high-grade astrocytomas are in the normal cell cycle whereas in many cases the malignant astrocytes are not. The nuclear DNA content of gliosarcomas appears to be similar to other high-grade astrocytomas.     

Responses of the mussel L. to simulated subarctic tide pool conditions

Mussels in subarctic Norway commonly occur in shallow intertidal pools. By living in pools (a habitat rarely inhabited in lower latitudes) they are insulated against low air temperatures but exposed to high salinities (<70°/oo) beneath overlying ice. Mussels avoid exposing their tissues to such high salinities because a shell valve closure response to low temperature operates at about −1.5°C before ice sheets form and bottom water salinities rise. Shell valve closure coincides with very low cardiac and ciliary activity.     

Increased oxygen consumption in blennies (Blennim pholis L.) exposed to their mirror images

The sight of its mirrored image increases the oxygen consumption of Blennius pholis. This is due to an increased metabolic rate and an increased activity. For schooling species, the opposite effect has been reported in the literature and has been termed the 'group effect'. The B. Pholis response is discussed in relation to species specific preferences of the social environment. The hypothesis is put forward that deviations form the preferred social environment cause an activation of the individual.     

Genetic structure and admixture in sheep from terminal breeds in the United States

Selection for performance in diverse production settings has resulted in variation across sheep breeds worldwide. Although sheep are an important species to the United States, the current genetic relationship among many terminal sire breeds is not well characterized. Suffolk, Hampshire, Shropshire and Oxford (terminal) and Rambouillet (dual purpose) sheep (n = 248) sampled from different flocks were genotyped using the Applied Biosystems Axiom Ovine Genotyping Array (50K), and additional Shropshire sheep (n = 26) using the Illumina Ovine SNP50 BeadChip. Relationships were investigated by calculating observed heterozygosity, inbreeding coefficients, eigenvalues, pairwise Wright’s F_ST estimates and an identity by state matrix. The mean observed heterozygosity for each breed ranged from 0.30 to 0.35 and was consistent with data reported in other US and Australian sheep. Suffolk from two different regions of the United States (Midwest and West) clustered separately in eigenvalue plots and the rectangular cladogram. Further, divergence was detected between Suffolk from different regions with Wright’s F_ST estimate. Shropshire animals showed the greatest divergence from other terminal breeds in this study. Admixture between breeds was examined using admixture , and based on cross-validation estimates, the best fit number of populations (clusters) was K = 6. The greatest admixture was observed within Hampshire, Suffolk, and Shropshire breeds. When plotting eigenvalues, US terminal breeds clustered separately in comparison with sheep from other locations of the world. Understanding the genetic relationships between terminal sire breeds in sheep will inform us about the potential applicability of markers derived in one breed to other breeds based on relatedness.     

Mobile piscivores and the nature of top-down forcing in Upper Amazonian floodplain lakes

Shallow lakes can change states in response to manipulations of top predators. In most reported experiments, the top piscivore has been a fish. However, low-latitude lakes typically support non-piscine piscivores, including mammals, birds, and reptiles. The roles of these groups have been little investigated, and whether they are more important as piscivores than fish remains unknown. We report both a longitudinal (2001–2018) and a cross-sectional (2012) study of the bird, caiman, and giant otter populations of floodplain lakes in Perú’s Manu National Park. We compare the three groups, after removing the effects of taxonomic status and body mass, using allometric equations to estimate the field metabolic rate (FMR) for each group in each lake. Giant otters emerge as the dominant piscivore in lakes that support a resident family, with an energy requirement more than twice that of piscivorous birds and more than seven times that of caiman. However, giant otters were resident in only eight of 27 surveyed lakes. Indirect evidence suggests that these eight lakes are more productive than lakes not occupied by otters. The fact that lakes occupied by otters are dominated by phytoplankton suggests an underlying five-tiered trophic structure in keeping with the prominence of alternating levels in the structure of food webs.