Do Flies Have A Red Receptor?

(1) The compound eye of Musca exhibits characteristics which have heretofore frequently been considered evidence for color receptors: (a) The spectral sensitivity curve has several peaks whose relative heights can be altered by selective adaptation to colored lights, and (b) the shape of the retinal action potential varies with wave length. (2) The action spectrum for the red enhancement of on and off responses is compared with the "red receptor" calculated by Mazokhin-Porshnyakov from colorimetric data obtained in rapid color substitutions. Both have maxima at 615 to 620 mµ and appear to be different expressions of the same phenomenon. (3) A red receptor is absent. The evidence which suggests different types of receptors in the region 500 to 700 mµ can be accounted for by variations in the numbers of receptors stimulated. In red light there is a recruitment of additional ommatidia caused by leakage of long wave lengths through the pigment screen, and this spatial summation potentiates the on and off responses. The principal evidence is: (a) a white eye mutant which has no accessory screening pigments also lacks the peak of sensitivity in the red, even when adapted to violet light; (b) white-eyed flies give identical responses with large on and off effects at all wave lengths from 500 to 700 mµ; and (c) reducing the number of excited ommatidia by decreasing the size of the test spot makes the on and off transients smaller relative to the receptor component.     

Do Horses Have a Concept of Person?

Background

Animals'' ability for cross-modal recognition has recently received much interest. Captive or domestic animals seem able to perceive cues of human attention and appear to have a multisensory perception of humans.

Methodology/Principal Findings

Here, we used a task where horses have to remain immobile under a vocal order to test whether they are sensitive to the attentional state of the experimenter, but also whether they behave and respond differently to the familiar order when tested by a familiar or an unknown person. Horses'' response varied according to the person''s attentional state when the order was given by an unknown person: obedience levels were higher when the person giving the order was looking at the horse than when he was not attentive. More interesting is the finding that whatever the condition, horses monitored much more and for longer times the unknown person, as if they were surprised to hear the familiar order given by an unknown voice.

Conclusion/Significance

These results suggest that recognition of humans may lie in a global, integrated, multisensory representation of specific individuals, that includes visual and vocal identity, but also expectations on the individual''s behaviour in a familiar situation.     

Animal Communication: Do Dolphins Have Names?

A new study of contact calls in dolphins shows that individuals can recognize one another using information encoded in the frequency modulation pattern of these calls, in the absence of general voice characteristics.     

Do Older Professional Musicians Have Cognitive Advantages?

The current study investigates whether long-term music training and practice are associated with enhancement of general cognitive abilities in late middle-aged to older adults. Professional musicians and non-musicians who were matched on age, education, vocabulary, and general health were compared on a near-transfer task involving auditory processing and on far-transfer tasks that measured spatial span and aspects of cognitive control. Musicians outperformed non-musicians on the near-transfer task, on most but not all of the far-transfer tasks, and on a composite measure of cognitive control. The results suggest that sustained music training or involvement is associated with improved aspects of cognitive functioning in older adults.     

Do Spermatogonial Stem Cells Have A Circadian Rhythm?

Abstract. Mitotic index was determined in whole mounts of segments of seminiferous tubules of (101 × C3Hf)F₁ male mice at 3 hr intervals from 18.00 to 06.00 hours, and at hourly intervals from 08.00 to 16.00 hours. the highest frequency of metaphase-anaphase figures occurred at 10.00 and 11.00 hours, but was not significantly higher than for other times. Injection of 25 μCi ₃H-TdR per mouse, followed 24 hr later by exposure to 300 rad X-rays and killing 207 hr after labelling was used to test for circadian rhythm in DNA synthetic activity of the long-cycling A, spermatogonia. No significant effect of time of day was observed. Likewise, the number of undifferentiated spermatogonia scored 183 hr after 300 rad showed no effect of time of day. the testis therefore appears to have no circadian rhythm in mitotic activity. Stage of the cycle of the seminiferous epithelium, however, showed a significant effect on mitotic index of A_s spermatogonia and on DNA synthetic activity of undifferentiated spermatogonia. These data are compared with those for other organisms and tissues in respect to which properties of stem cells are general for all organisms and tissues and which are specific for spermatogonia.     

Language Evolution: What Do Chimpanzees Have to Say?

Although unique in important ways, language shares some properties with other animal communication systems. Comparative analyses of nonhuman primate vocalizations can shed light on the evolution of language's special features.     

Do Confocal Microscopy and Tardigrades Have a Future Together?

Confocal microscopy was used with acridine orange as a fluorescent probe to optically section Echiniscus testudo (Doyère, 1840) (Echiniscidae). The advantages of the confocal technique and possible developments are discussed.     

Granite Rock Outcrops: An Extreme Environment for Soil Nematodes?

We studied soil nematode communities from the surface of granite flatrock outcrops in the eastern Piedmont region of the United States. The thin soils that develop here experience high light intensity and extreme fluctuations in temperature and moisture and host unique plant communities. We collected soils from outcrop microsites in Virginia (VA) and North Carolina (NC) in various stages of succession (Primitive, Minimal, and Mature) and compared soil properties and nematode communities to those of adjacent forest soils. Nematodes were present in most outcrop soils, with densities comparable to forest soils (P > 0.05). Nematode communities in Mature and Minimal soils had lower species richness than forest soils (P < 0.05) and contained more bacterial-feeders and fewer fungal-feeders (P < 0.05). Primitive soils contained either no nematodes (NC) or only a single species (Mesodorylaimus sp., VA). Nematode communities were similar between Mature and Minimal soils, according to trophic group representation, MI, PPI, EI, SI, and CI (P > 0.05). Forest soils had a higher PPI value (P < 0.05), but otherwise community indices were similar to outcrop soils (P > 0.05). Outcrop nematode communities failed to group together in a Bray-Curtis cluster analysis, indicating higher variability in community structure than the Forest soils, which did cluster together. A high proportion of the nematodes were extracted from outcrop soils in coiled form (33-89%), indicating that they used anhydrobiosis to persist in this unique environment.     

Pain without Nociceptors? Nav1.7-Independent Pain Mechanisms

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Do Tropical Frugivores Compete for Food?

In this paper I ask two questions: Is fruit ever limiting tovertebrate frugivores and, if so, do frugivores presently competefor food, either with closely- or distantly-related species?A brief review of the fruiting strategies of tropical plantsindicates that fruit can occasionally be superabundant, butit is often produced at low rates and in low quantities. Variationin fruit abundance results from several biotic selective pressures,including variation in the density, diversity, and reliabilityof potential dispersal agents. To judge from the size structure,dietary similarities, habitat preferences and foraging behaviorsof taxonomically-restricted guilds of frugivorous birds andmammals, members of these guilds have competed for food in thepast and must occasionally do so today. Unusual climatic conditionscan occasionally "upset" phenological patterns and can createfood shortages that promote competition among closely-relatedspecies of frugivores. Avian and mammalian frugivores, however,probably seldom compete with each other for food in present-daytropical ecosystems. A major reason for this is that many tropicalplants have evolved fruits that are attractive to only a limitedsubset of frugivores (e.g., only birds or only bats). Plantsapparently "perceive" qualitative differences in the dispersalservices of birds and mammals and attempt to attract membersof one group but not the other.     

Do Triplets Have Enough Information to Construct the Multi-Labeled Phylogenetic Tree?

The evolutionary history of certain species such as polyploids are modeled by a generalization of phylogenetic trees called multi-labeled phylogenetic trees, or MUL trees for short. One problem that relates to inferring a MUL tree is how to construct the smallest possible MUL tree that is consistent with a given set of rooted triplets, or SMRT problem for short. This problem is NP-hard. There is one algorithm for the SMRT problem which is exact and runs in time, where is the number of taxa. In this paper, we show that the SMRT does not seem to be an appropriate solution from the biological point of view. Indeed, we present a heuristic algorithm named MTRT for this problem and execute it on some real and simulated datasets. The results of MTRT show that triplets alone cannot provide enough information to infer the true MUL tree. So, it is inappropriate to infer a MUL tree using triplet information alone and considering the minimum number of duplications. Finally, we introduce some new problems which are more suitable from the biological point of view.     

Which electrodic solutions for immobilized pH gradients?

Carrier ampholytes covering a pH range corresponding to, or narrower than, the span of the immobilized pH gradient (IPG) are a most suitable electrodic solution for IPGs. They are able to collect, and completely remove from the gel, much higher amounts of non-buffering ions than are solutions of acidic and basic amino acids. This makes it possible to directly run IPGs just after their polymerization, without the need of a washing step to remove catalysts and unreacted Immobiline monomers. The same applies most advantageously when the gel formulation includes urea and/or detergents. Ions contributed by the sample solution are also prevented from casting high-conductivity ridges around the electrodes, without any need either of a dialysis step or of an increased slab size with pH plateaus. The migration of the sample proteins toward their equilibrium position is faster in the presence of carrier ampholytes. The effective concentrations of the latter are in the range 0.3-1%.     

Do aphids actively search for ant partners?

The aphid–ant mutualistic relationships are not necessarily obligate for neither partners but evidence is that such interactions provide them strong advantages in terms of global fitness. While it is largely assumed that ants actively search for their mutualistic partners namely using volatile cues; whether winged aphids (i.e., aphids’ most mobile form) are able to select ant‐frequented areas had not been investigated so far. Ant‐frequented sites would indeed offer several advantages for these aphids including a lower predation pressure through ant presence and enhanced chances of establishing mutuaslistic interactions with neighbor ant colonies. In the field, aphid colonies are often observed in higher densities around ant nests, which is probably linked to a better survival ensured by ants’ services. Nevertheless, this could also result from a preferential establishment of winged aphids in ant‐frequented areas. We tested this last hypothesis through different ethological assays and show that the facultative myrmecophilous black bean aphid, Aphis fabae L., does not orientate its search for a host plant preferentially toward ant‐frequented plants. However, our results suggest that ants reduce the number of winged aphids leaving the newly colonized plant. Thus, ants involved in facultative myrmecophilous interactions with aphids appear to contribute to structure aphid populations in the field by ensuring a better establishment and survival of newly established colonies rather than by inducing a deliberate plant selection by aphid partners based on the proximity of ant colonies.