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Reflections on crab research in North America since 1758
Published in Frank Truesdale, History of Carcinology, 2020
Larvae In the real world, however, live and develop in dynamic systems influenced by climate, season, weather, currents, and tides, that offer circumstances far different from those in controlled laboratory compartments. Enlightening as were results from initial laboratory experiments, attempts were made to assess the more complex interrelationships of nature in the larval culturing systems. Much of this work was impelled by the attempt to explain linkages between dispersal, distribution, and survival of species and the dynamics of estuarine and coastal systems in which they live. Breeding, Incubation, and hatching are linked to season; larvae released in systems with net seaward transport seemingly are able to capitalize on the dispersal abilities of those systems, either to remain within them, or return to the natal grounds after displacement to complete the cycle. Investigations were designed to study factors such as the time of appearance of phototaxis (Forward & Costlow 1974), effect of salinity and cyclic temperature on development (Christiansen & Costlow 1975), larval shadow response, depth regulation, and behavioral responses to rates of salinity change (Forward 1977). Aside from natural variables, none of the coastal aquatic waters where these studies were conducted are free from human Influences, especially near urban centers. Possible effects of pollutants and contaminants on larvae could be assayed by manipulations analogous to those employed for testing their reactions to natural environmental processes (reviewed by Epifanio 1979; Williams & Duke 1979).
Microfluidic Systems to Study the Biology of Human Diseases and Identify Potential Therapeutic Targets in Caenorhabditis elegans
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Pouya Rezai, Sangeena Salam, P. Ravi Selvaganapathy, Bhagwati P. Gupta
Light: The response of C. elegans to light, known as phototaxis, has been studied in some detail [120,121]. It was found that although C. elegans does not possess eyes, it senses light stimulus via ciliated amphid neurons and demonstrates repulsive reactions to it in a dose- dependent manner. Although ultraviolet-A, violet, and blue lights appeared to be most sensitive and induced reversals within few seconds, prolonged exposures (15 min) were detrimental, causing paralysis and death. In comparison, the repulsive response to green light was mild, low penetrant, and no paralysis was observed in 20 min exposure. Thus, while the phototactic response is rapid, because of its lethal effect (in the case of UV-A, violet, and blue lights) and low response (in the case of green light) it does not appear to be suitable to manipulate worm movement in a micro-fludic setup.
Parasite Versus Host: Pathology and Disease
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
In other cases, although neurotransmitter profiles may be altered in infected hosts, little progress has been made identifying the molecules released by parasites responsible for such alterations. For instance, in Chapter 3 (p. 102) we discussed behavioral changes in the aquatic amphipod Gammarus pulex, when serving as the intermediate host for the acanthocephalan Pomphorhynchus laevis. The positive phototaxis displayed by the amphipod increases the likelihood that the amphipod will be consumed by freshwater fish serving as definitive hosts for the parasite. Infected amphipods express unusually high levels of serotonin in their central nervous system. The role of serotonin in photophilia has been demonstrated experimentally by injecting uninfected amphipods with exogenous serotonin. Amphipods treated in this manner also become attracted to light. Other hosts for which altered neurotransmitter profiles in the central nervous system have been correlated with behavioral changes include small mammals infected with the apicomplexan Toxoplasma gondii (Box 5.2) and killifish (Fundulus parvipinnis) infected with the trematode Euhaplorchis californiensis. In the later example, killifish serve as the second intermediate host for the trematode. Seabirds, which consume the fish, are the definitive hosts. Infected fish, with encysted metacercariae in their brains, are especially likely to be eaten by birds, as they tend to remain near the surface, and they repeatedly roll over, exposing their white bellies. It is known that dopamine and serotonin levels are higher in infected fish. Furthermore, the distribution of metacercariae in the brains of infected killifish is not random; they tend to localize in the part of the brain responsible for locomotion. Yet precisely what the parasite does to affect the behavior of its host remains unresolved.
Influence of coating type, colour, and deployment timing on biofouling by native and non-native species in a marine renewable energy context
Published in Biofouling, 2022
Christopher R. Nall, Marie-Lise Schläppy, Elizabeth J. Cottier-Cook, Andrew J. Guerin
After a relatively short immersion time of 3 months, assemblages on the painted panels appeared to form two groups – the “darker” colours (red and black) and the “lighter” colours (white and yellow). When affected by colour, animal fouling taxa (exemplified by Ascidiella sp., and the NNS S. japonica and C. eumyota) were more abundant on darker surfaces, whilst algae (Chloropyhta spp.) were more abundant on the lighter surfaces. The tendency towards greater animal fouling on darker surfaces (Hurlbut 1993; Swain et al. 2006; Satheesh and Wesley 2010; Dobretsov et al. 2013) is likely to be at least partly mediated by negative phototaxis of many larvae during settlement (McDougall 1943; WHOI (Woods Hole Oceanographic Institute) 1952; Svane and Young 1989). This in contrast to active selection of lighter areas by some algal zoospores (Christie and Shaw 1968; Baynes 1999; Glasby 1999) and superior growth and adhesion strength of algae in lighter conditions (Hodson et al. 2000; Finlay et al. 2008). Lighter surfaces reflect more light over a wider range of wavelengths (Finlay et al. 2008); differences in surface reflectance may be more important than the colours as perceived by the human eye (Ells et al. 2016).
The light-activated TRP channel: the founding member of the TRP channel superfamily
Published in Journal of Neurogenetics, 2022
The no receptor potential complementation group A (norpA) was one of the first groups of ERG-defective X-chromosome mutants to be isolated (Pak, Grossfield, & Arnold, 1970). Two other groups (Heisenberg, 1971; Hotta & Benzer, 1970) also reported on the isolation of the same mutants, all based on phototaxis but each using its own protocol. The norpA phenotype is quite striking: it eliminates the photoreceptor response to light in an allele-dependent manner. In strong mutant alleles, the electrical response to light is completely abolished even though the eye morphology of young flies looks normal. The above investigators knew then that norpA encodes a gene product involved in phototransduction, although it would take 18 years by the Pak lab to identify the gene product.
From leptin to lasers: the past and present of mouse models of obesity
Published in Expert Opinion on Drug Discovery, 2021
Joshua R. Barton, Adam E. Snook, Scott A. Waldman
DBS, like ablation studies, lacks the specificity to target specific neuronal subtypes. To simulate particular neuronal populations, the Cre-lox system had to be adapted to express modulatory receptors controlled by cell-type-specific Cre drivers. Ideally, these modulatory receptors would be responsive only to external stimuli applied by the experimenter, to eliminate confounding endogenous signaling from the mice. Studies on the phototaxis responses of the green algae Chlamydomanas reinhardtii revealed a unique class of opsin-related proteins called channelrhodopsins that produced light-gated ion conductance in the eye spot of these organisms [128]. When packaged into a lentiviral vector, Channelrhodopsin-2 (ChR2) evoked blue-light-dependent spike chains in rat hippocampal neurons in vitro, establishing channelrhodopsins as a tool for selectively stimulating rodent neurons [129].168