Should Animals Navigating Over Short Distances Switch to a Magnetic Compass Sense?

Magnetoreception can play a substantial role in long distance navigation by animals. I hypothesize that locomotion guided by a magnetic compass sense could also play a role in short distance navigation. Animals identify mates, prey, or other short distance navigational goals using different sensory modalities (olfaction, vision, audition, etc.) to detect sensory cues associated with those goals. In conditions where these cues become unreliable for navigation (due to flow changes, obstructions, noise interference, etc.), switching to a magnetic compass sense to guide locomotion toward the navigational goals could be beneficial. Using simulations based on known locomotory and flow parameters, I show this strategy has strong theoretical benefits for the nudibranch mollusk Tritonia diomedea navigating toward odor sources in variable flow. A number of other animals may garner similar benefits, particularly slow-moving species in environments with rapidly changing cues relevant for navigation. Faster animals might also benefit from switching to a magnetic compass sense, provided the initial cues used for navigation (acoustic signals, odors, etc.) are intermittent or change rapidly enough that the entire navigation behavior cannot be guided by a continuously detectable cue. Examination of the relative durations of navigational tasks, the persistence of navigational cues, and the stability of both navigators and navigational targets will identify candidates with the appropriate combination of unreliable initial cues and relatively immobile navigational goals for which this hypothetical behavior could be beneficial. Magnetic manipulations can then test whether a switch to a magnetic compass sense occurs. This hypothesis thus provides an alternative when considering the behavioral significance of a magnetic compass sense in animals

rAAV-compatible MiniPromoters for restricted expression in the brain and eye

Abstract Background Small promoters that recapitulate endogenous gene expression patterns are important for basic, preclinical, and now clinical research. Recently, there has been a promising revival of gene therapy for diseases with unmet therapeutic needs. To date, most gene therapies have used viral-based ubiquitous promoters–however, promoters that restrict expression to target cells will minimize off-target side effects, broaden the palette of deliverable therapeutics, and thereby improve safety and efficacy. Here, we take steps towards filling the need for such promoters by developing a high-throughput pipeline that goes from genome-based bioinformatic design to rapid testing in vivo. Methods For much of this work, therapeutically interesting Pleiades MiniPromoters (MiniPs; ~4 kb human DNA regulatory elements), previously tested in knock-in mice, were “cut down” to ~2.5 kb and tested in recombinant adeno-associated virus (rAAV), the virus of choice for gene therapy of the central nervous system. To evaluate our methods, we generated 29 experimental rAAV2/9 viruses carrying 19 different MiniPs, which were injected intravenously into neonatal mice to allow broad unbiased distribution, and characterized in neural tissues by X-gal immunohistochemistry for icre, or immunofluorescent detection of GFP. Results The data showed that 16 of the 19 (84 %) MiniPs recapitulated the expression pattern of their design source. This included expression of: Ple67 in brain raphe nuclei; Ple155 in Purkinje cells of the cerebellum, and retinal bipolar ON cells; Ple261 in endothelial cells of brain blood vessels; and Ple264 in retinal Müller glia. Conclusions Overall, the methodology and MiniPs presented here represent important advances for basic and preclinical research, and may enable a paradigm shift in gene therapy

Effect of Animal Stocking Density and Habitat Enrichment on Survival and Vitality of Wild Green Shore Crabs, Carcinus maenas, Maintained in the Laboratory

The wide geographic distribution, large size and ease of capture has led to decapod crustaceans being used extensively in laboratory experiments. Recently in the United Kingdom decapod crustaceans were listed as sentient beings, resulting in their inclusion in animal care protocols. Ironically, little is known about how captive conditions affect the survival and general condition of wild decapod crustaceans. We used the green shore crab, Carcinus maenas, to investigate the effects of stocking density and shelter on survival and vitality indices during a 6 month period in the laboratory. Neither stocking density nor the presence of shelter affected survival. Stocking density also had no effect on the vitality indices (limb loss, claw strength, BRIX, righting time, leg flare and retraction). The presence of shelter did affect the number of limbs lost and the leg retraction response, but had no effect on the other vitality indices. All vitality indices changed, and mortality increased over time, independent of treatment: this became most apparent after 8 to 11 weeks storage in the laboratory. This decline in condition may have been due to repeated handling of the crabs, rather than the stocking conditions. In support of this, untracked, non-handled (control) individuals sustained a 4% mortality rate compared with 67% mortality in experimental crabs during the 6 month period. Although simple experimental monitoring of crabs with biweekly vitality tests only produced transient short-term stress events, the repeated handling over time apparently led to a cumulative stress and a deterioration in animal health. Bringing wild crustaceans into the laboratory and holding them, even with modest experimental manipulation, may result in high mortality rates. Researchers and animal care committees need to be aware that wild captive invertebrates will respond very differently to laboratory-bred vertebrates, and plan experiments accordingly

Detection of substrate-associated odour cues versus prey-associated cues by the oral veil in <i>Tritonia diomedea</i>

<p>Our goal was to test two potential sensory roles for the oral veil in the nudibranch <i>Tritonia diomedea</i> (now synonymous with <i>T. tetraquetra</i>). First, we hypothesized this cephalic sensory organ could detect substrate-associated odours left behind by an odour plume flowing across sediment. In two experiments in a laboratory flow tank, however, <i>T. diomedea</i> did not show consistent crawling headings in response to either prey or predator odours associated with sediment substrate. In one of the experiments, the slugs did significantly decrease crawling speed in response to prey odours. Although slugs could thus detect at least some substrate-associated odours, these results suggest such cues are not used for navigation. We next considered the oral veil’s potential role in behaviours requiring responses to nearby cues. Our observations of animals before and after denervation of the oral veil suggest that, unsurprisingly, predatory bite-strikes do rely on sensory input from the oral veil. Overall, these data, combined with the results of earlier studies, are consistent with the oral veil detecting cues primarily from nearby stimuli (including both chemical and mechanical modalities), while having little or no role in detecting and responding to odour cues originating from distant sources used for navigation behaviour.</p

Assessing the viability of pre-industrial sediment prior to remediation using primary producer (Zostera marina and Spartina alterniflora) growth and survival

Boat Harbour (BH), Nova Scotia, has served as a polishing pond for treated pulp and paper effluent since 1967. In 2020, the effluent flow ceased, and the site will be remediated. The focus of the remediation is the removal of a layer of contaminated sediment, shown to contain high levels of metals and dioxins and furans. Our primary objective was to test whether the underlying pre-industrial sediment could support growth and survival of estuarine plants. A large-diameter (15 cm) corer was used to extract cores from underneath the contaminated layer. These cores were inserted into a reference estuary, along with cores of reference estuarine sediment. Four 3 X 3 subtidal plots were used to test transplants of the estuarine plant Z. marina, and five 1 X 9 marsh edge plots were used to test S. alterniflora. No significant differences in plant growth or survival were observed between BH and reference sediment after 2 months. Post-experiment analysis of contaminants (metals and PCDD/F’s) in both types of sediment and plant tissues showed similarly low levels of contaminants.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author