Dual Color Neural Activation and Behavior Control with Chrimson and CoChR in Caenorhabditis elegans

By enabling a tight control of cell excitation, optogenetics is a powerful approach to study the function of neurons and neural circuits. With its transparent body, a fully mapped nervous system, easily quantifiable behaviors and many available genetic tools, Caenorhabditis elegans is an extremely well-suited model to decipher the functioning logic of the nervous system with optogenetics. Our goal was to establish an efficient dual color optogenetic system for the independent excitation of different neurons in C. elegans. We combined two recently discovered channelrhodopsins: the red-light sensitive Chrimson from Chlamydomonas noctigama and the blue-light sensitive CoChR from Chloromonas oogama. Codon-optimized versions of Chrimson and CoChR were designed for C. elegans and expressed in different mechanosensory neurons. Freely moving animals produced robust behavioral responses to light stimuli of specific wavelengths. Since CoChR was five times more sensitive to blue light than the commonly used ChR2, we were able to use low blue light intensities producing no cross-activation of Chrimson. Thanks to these optogenetics tools, we revealed asymmetric cross-habituation effects between the gentle and harsh touch sensory motor pathways. Collectively, our results establish the Chrimson/CoChR pair as a potent tool for bimodal neural excitation in C. elegans and equip this genetic model organism for the next generation of in vivo optogenetic analyses.     

Aim‐then‐shoot anemotaxis involved in the hopping approach of potato tuberworm moth Phthorimaea operculella toward a sex pheromone source

Male moths locate conspecific females by pheromone‐induced upwind flight maintained by detecting a visual flow, termed optomotor anemotaxis. Their behavioural pattern is characterized by an upwind surge in response to a pheromone stimulus and crosswind casting after odour loss, which is considered to be reset and restarted on receipt of another pheromone pulse. However, pheromone‐stimulated males of the potato tuberworm moth Phthorimaea operculella exhibit a series of short and straight intermittent flights, or hops, when moving upwind. It is unclear whether they navigate by employing the same behavioural pattern and wind detection mechanism as that used by flying moths. To analyze odour‐modulated anemotaxis in male potato tuberworm moths, a flat wind tunnel is constructed to give regular odour stimuli to an insect regardless of its location. Moths are subjected to pheromone pulses of different frequencies to test whether they show a behavioural pattern that is reset and restarted by a pheromone pulse. Moths on the ground are also subjected to crosswind shear to examine their detection of wind direction. Path analyses reveal that males surge upwind when they receive a pheromone pulse and exhibit casting by successive hops when they lose odour. This behavioural pattern appears to be similar to that of flying moths. When the direction of the airflow is switched orthogonally, males adjust their course angle accordingly when they are on the ground. It is suggested that, instead of optomotor anemotaxis, this ‘aim‐then‐shoot’ system aids the detection of wind direction, possibly by mechanosensory means.     

Tubes and foraging behavior in larval Chironomidae: implications for predator avoidance

Summary In laboratory experiments, I studied differential susceptibility of four co-occurring species of chironomids to a predatory damselfly. The chironomids differed in foraging behavior and could be ranked according to the amount of time they spent outside of their tubes. In choice experiments, the predator consistently selected the prey which spent more time out of the tube, and time out of tube was a significant predictor of the predation rate coefficient. Electivity indices, calculated from field samples and diet analyses of the predator, supported the laboratory results. The data suggest that exposure to predators in a heterogeneous prey community is largely determined by tubedwelling behavior.     

Urine-marking during agonistic encounters in the bush dog (Speothos venaticus)

During staged encounters, bush dogs of the same sex showed a high level of aggressive-defensive behaviors and a higher than normal frequency of urine-marking. Where dominance was established during encounters, dominant individuals marked more than subordinates. Where dominance was not clearly established, both participants remained aggressive and showed higher than normal levels of marking. Urine-marking appears to communicate aggressiveness and may be used to compensate for the otherwise relatively inconspicuous aggressive and dominance displays of this species.     

Behavioral and physiological effects of chronic 2,450-MHz microwave irradiation of the rat at 0.5 mW/cm2

Adult male Long-Evans rats were intermittently exposed to 2450 MHz CW microwaves at an average power density of 0.5 mW/cm2 for 90 days. The resulting SAR was 0.14 W/kg (range 0.11 to 0.18 W/kg). The animals were exposed 7 h/day, 7 days/wk, for a total of 630 h in a monopole-above-ground radiation chamber while housed in Plexiglas holding cages. Daily measures of body mass and food and water intake indicated no statistically significant effects of microwave exposure. Monthly assessment of reactivity to electric footshock, levels of cholinesterase and sulfhydryl groups in blood, and 17-ketosteroids in urine revealed no reliable differences between 14 sham-exposed and 14 microwave-exposed rats. After the 90 days of exposure, seven rats, randomly chosen from each group, were assessed for open-field behavior, shuttlebox performance, and schedule-controlled (IRT schedule) lever pressing for food pellets. Statistically significant differences between microwave-exposed and sham-exposed rats were observed in shuttlebox performances and lever pressing. Post mortem measures of mass of several organs and microscopic examination of adrenal tissue revealed no differences between the two groups of animals.     

Cellulose-microfibril-orienting mechanisms in plant cells walls

A brief review is given of the changing views over the years, as knowledge of wall structure has developed, concerning the mechanism whereby cellulose chains may be oriented. This leads to an examination of current concepts, particularly those concerning microtubules. It is shown that none of the mechanisms suggested whereby microtubules might cause orientation of cellulose microfibrils is consistent with the known range of molecular architectures found in plant cell walls. It is further concluded that any mechanism which necessitates an indissoluble link between the plasmalemma and the cellulose-synthesising complex at the tip of a microfibril is unacceptable. A new proposal is presented in which it is speculated that both microtubules and microfibrils are oriented by a mechanism separate from both. It is shown that if two vectors are contemplated, one parallel to cell length and one at right angles, and a sensor exists on the plasmalemma surface which responds to changes in the vectors, then all known wall structures may be explained. The possible nature of the vectors and the sensor are considered.     

The biological roots of morality

The question whether ethical behavior is biologically determined may refer either to thecapacity for ethics (e.i., the proclivity to judge human actions as either right or wrong), or to the moralnorms accepted by human beings for guiding their actions. My theses are: (1) that the capacity for ethics is a necessary attribute of human nature; and (2) that moral norms are products of cultural evolution, not of biological evolution.Humans exhibits ethical behavior by nature because their biological makeup determines the presence of the three necessary, and jointly sufficient, conditions for ethical behavior: (i) the ability to anticipate the consequences of one's own actions; (ii) the ability to make value judgements; and (iii) the ability to choose between alternative courses of action. Ethical behavior came about in evolution not because it is adaptive in itself, but as a necessary consequece of man's eminent intellectual abilities, which are an attribute directly promoted by natural selection.Since Darwin's time there have been evolutionists proposing that the norms of morality are derived from biological evolution. Sociobiologists represent the most recent and most subtle version of that proposal. The sociobiologists' argument is that human ethical norms are sociocultural correlates of behaviors fostered by biological evolution. I argue that such proposals are misguided and do not escape the naturalistic fallacy. The isomorphism between the behaviors promoted by natural selection and those sanctioned by moral norms exist only with respect to the consequences of the behaviors; the underlying causations are completely disparate.This article is based on a paper presented at the International Symposium onBiological Models of Human Action, Palma de Mallorca, Spain, 16–18 December 1985.