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Background. Alcohol and drug use is associated with significant morbidity and mortality and is highly prevalent among homeless youth. Ecological Momentary Assessments (EMA) have been used to examine the effect of urges on drug use, though not among homeless youth. Objectives. We assessed the patterns of drug use and the correlation between real-time contextual factors and drug use using EMA collected daily. We identified predictors of drug use among a sample of homeless youth 18-25 years old in Houston, Texas. Methods. Homeless youth (n = 66, 62% male) were recruited from a drop-in center between September 2015 and May 2016. We used generalized linear mixed models and cross-validation methods to determine the best predictive model of drug use. Results. The overall drug use was high: 61% and 32% of participants reported using drugs or alcohol at least one day, respectively. Marijuana and synthetic marijuana use (i.e., Kush, K2, incense packs) were reported most frequently; 86% and 13% of the total drug use EMAs, respectfully. Drug use urge was reported on 26% of days and was the highest on drug use days. Drug use was predicted by discrimination, pornography use, alcohol use, and urges for drugs, alcohol, and to steal. Conclusions. EMA can be used to predict drug use among homeless youth. Drug use treatment among homeless youth should address the role of experiencing discrimination, pornography and alcohol use, and urge management strategies on drug use. Research is needed to determine if EMA informed just-in-time interventions targeting these predictors can reduce use.

The widespread ability to alter timing of hatching in response to environmental cues can serve as a defense against threats to eggs. Arboreal embryos of red-eyed treefrogs, Agalychnis callidryas, can hatch up to 30% prematurely to escape predation. This escapehatching response is cued by physical disturbance of eggs during attacks, including vibrations or motion, and thus depends critically on mechanosensory ability. Predator-induced hatching appears later in development than flooding-induced, hypoxia-cued hatching; thus, its onset is not constrained by the development of hatching ability. It may, instead, reflect the development of mechanosensor function. We hypothesize that vestibular mechanoreception mediates escapehatching in snake attacks, and that the developmental period when hatching-competent embryos fail to flee from snakes reflects a sensory constraint. We assessed the ontogenetic congruence of escapehatching responses and an indicator of vestibular function, the vestibulo-ocular reflex (VOR), in three ways. First, we measured VOR in two developmental series of embryos 3-7 days old to compare with the published ontogeny of escape success in attacks. Second, during the period of greatest variation in VOR and escape success, we compared hatching responses and VOR across sibships. Finally, in developmental series, we compared the response of individual embryos to a simulated attack cue with their VOR. The onset of VOR and hatching responses were largely concurrent at all three scales. Moreover, latency to hatch in simulated attacks decreased with increasing VOR. These results are consistent with a key role of the vestibular system in the escape-hatching response of A. callidryas embryos to attacks.

Mechanosensory-cued hatching (MCH) is widespread, diverse, and improves survival in many animals. From flatworms and insects to frogs and turtles, embryos use mechanosensory cues and signals to inform hatching timing, yet mechanisms mediating mechanosensing in ovo are largely unknown. The arboreal embryos of red-eyed treefrogs, Agalychnis callidryas, hatch prematurely to escape predation, cued by physical disturbance in snake attacks. When otoconial organs in the developing vestibular system become functional, this response strengthens, but its earlier occurrence indicates another sensor must contribute. Post-hatching, tadpoles use lateral line neuromasts to detect water motion. We ablated neuromast function with gentamicin to assess their role in A. callidryas’ hatching response to disturbance. Prior to vestibular function, this nearly eliminated the hatching response to a complex simulated attack cue, egg-jiggling, revealing that neuromasts mediate early MCH. Vestibular function onset increased hatching, independent of neuromast function, indicating young embryos use multiple mechanosensory systems. MCH increased developmentally. All older embryos hatched in response to egg-jiggling, but neuromast function reduced response latency. In contrast, neuromast ablation had no effect on timing or level of hatching in motion-only vibration playbacks. It appears only a subset of egg-disturbance cues stimulate neuromasts; thus embryos in attacked clutches may receive uni- or multimodal stimuli. A. callidryas embryos have more neuromasts than described for any other species at hatching, suggesting precocious sensory development may facilitate MCH. Our findings provide insight into the behavioral roles of two mechanosensory systems in ovo and open possibilities for exploring sensory perception across taxa in early life stages.