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Optimal diet theory predicts that predators optimize energy intake by balancing costs and benefits of foraging. One extreme strategy of snake foraging ecology is shown by specialist species that forage on low-energy prey, such as Thamnophis scaliger (Jan, 1863) which feeds almost exclusively on earthworms. Compared with other prey types such as small mammals, lizards, or arthropods, earthworms are low-energy prey because of their small size and high water content. Given the importance of energy acquisition for fueling snake reproduction, we expect that a low-energy dietary specialist such as T scaliger needs to forage frequently to store enough fat to reproduce. The high frequency of snakes containing prey, the presence of multiple earthworms in snakes, and the fact that females continue to feed when gravid suggest that T. scaliger is a voracious consumer of earthworms. Despite these foraging behaviours, females did not reproduce in sequential years, suggesting constraints in energy input to reproduce more frequently. A meta-analysis of the diet, body size, and reproductive frequency of some species of the genus Thamnophis Fitzinger, 1843 confirms that consumption of invertebrate prey is associated with small snake size, but not with biennial reproductive frequency within the genus. La theorie du regime alimentaire optimal predit que les predateurs optimisent leur ingestion d'energie en equilibrant les couts et les benefices de la recherche de nourriture. Une strategie extreme s'observe chez les especes specialisees qui se nourrissent de proies de faible valeur energetique, telles que Thamnophis scaliger (Jan, 1863) qui s'alimente presque exclusivement de vers de terre. Par comparaison avec d'autres types de proies, tels que les petits mammiferes, les lezards ou les arthropodes, les vers de terre sont des proies de basse valeur energetique a cause de leur petite taille et de leur fort contenu en eau. Etant donne l'importance de l'acquisition d'energie pour soutenir la reproduction des couleuvres, nous prevoyions que des specialistes alimentaires pour des proies de faible valeur energetique, tels que T scaliger, doivent s' alimenter frequemment afin d'accumuler suffisamment de graisse pour se reproduire. La frequence elevee de couleuvres qui contiennent des proies, la presence de plusieurs vers de terre dans les couleuvres et le fait que les femelles continuent de se nourrir pendant leur grossesse laissent croire que T. scaliger est un consommateur vorace de vers de terre. Malgre ces comportements alimentaires, les femelles ne se reproduisent pas deux annees d'affilee, ce qui indique que des contraintes dans l' apport d' energie empechent des reproductions plus frequentes. Une meta-analyse du regime alimentaire, de la taille corporelle et de la frequence des reproductions chez certaines especes de la genre Thamnophis Fitzinger, 1843, confirme que la consommation de proies invertebrees est associee a des couleuvres de petite taille, mais non a la frequence de reproduction a tous les deux ans dans ce genre. [Traduit par la Redaction], Introduction Because of their limbless condition and lack of powerful jaws, snakes can only swallow whole prey items. In spite of these morphological constraints, this group has evolved diverse foraging [...]

Background: Advance care planning (ACP) is the process of having conversations with patients to ensure preferences are known and support patient healthcare goals. ACP and the Age-Friendly Health Systems (AFHS) Initiative's, "What Matters," are synergistic approaches to patient-centered conversations. Implementation and measurement of ACP in primary care (PC) are variables in quality and consistency. We examined whether participation in an ACP learning collaborative (LC) would improve knowledge and ability to conduct ACP discussions and increase the frequency of documented ACP in participating practices., Methods: The WWAMI (Washington, Wyoming, Alaska, Montana, and Idaho) region Practice and Research Network (WPRN) and the Northwest Geriatrics Workforce Enhancement Center collaboratively organized a 9-month virtual LC. It consisted of 4 synchronous, 1.5-h sessions, technical support, and a panel of ACP experts. A Wilcoxon rank sum test assessed differences in knowledge from a pre-post survey. Documentation of ACP in the EHR was collected after at least one plan-do-study-act cycle., Results: We enrolled 17 participants from 6 PC practices (3 hospital-affiliated; 3 Federally Qualified Health Centers) from the WPRN. Two practices did not complete all LC activities. There was a trend toward increased ACP knowledge and skills overall especially in having discussions patients and families (pre-mean 2.9 [SD = 0.7]/post-mean 4.0[SD = 1.1], p < 0.05). 4/6 practices observed an increase in EHR documentation post-collaborative (median 16.3%, IQR 1.3%-36.9%)., Conclusions: The LC increased PC providers knowledge and skills of ACP and AFHS's What Matters, reported ACP EHR documentation, and contributed to practice change., (© 2024 The Author(s). Journal of the American Geriatrics Society published by Wiley Periodicals LLC on behalf of The American Geriatrics Society.)

As trophic adaptations, rattlesnake venoms can vary in composition depending on several intrinsic and extrinsic factors. Ontogenetic changes in venom composition have been documented for numerous species, but little is known of the potential age-related changes in many rattlesnake species found in M&eacute;xico. In the current study, venom samples collected from adult and neonate Crotalus polystictus from Estado de M&eacute;xico were subjected to enzymatic and electrophoretic analyses, toxicity assays (LD 50 ), and MALDI-TOF mass spectrometry, and a pooled sample of adult venom was analyzed by shotgun proteomics. Electrophoretic profiles of adult males and females were quite similar, and only minor sex-based variation was noted. However, distinct differences were observed between venoms from adult females and their neonate offspring. Several prominent bands, including P-I and P-III snake venom metalloproteinases (SVMPs) and disintegrins (confirmed by MS/MS) were present in adult venoms and absent/greatly reduced in neonate venoms. Age-dependent differences in SVMP, kallikrein-like, phospholipase A₂ (PLA₂), and L-amino acid oxidase (LAAO) activity levels were confirmed by enzymatic activity assays, and like many other rattlesnake species, venoms from adult snakes have higher SVMP activity than neonate venoms. Conversely, PLA₂ activity was approximately 2.5 &times; greater in venoms from neonates, likely contributing to the increased toxicity (neonate venom LD 50 = 4.5 &mu;g/g) towards non-Swiss albino mice when compared to adult venoms (LD 50 = 5.5 &mu;g/g). Thrombin-like (TLE) and phosphodiesterase activities did not vary significantly with age. A significant effect of sex (between adult male and adult female venoms) was also observed for SVMP, TLE, and LAAO activities. Analysis of pooled adult venom by LC-MS/MS identified 14 toxin protein families, dominated by bradykinin-inhibitory peptides, SVMPs (P-I, P-II and P-III), disintegrins, PLA₂s, C-type-lectins, CRiSPs, serine proteinases, and LAAOs (96% of total venom proteins). Neonate and adult C. polystictus in this population consume almost exclusively mammals, suggesting that age-based differences in composition are related to physical differences in prey (e.g., surface-to-volume ratio differences) rather than taxonomic differences between prey. Venoms from adult C. polystictus fit a Type I pattern (high SVMP activity, lower toxicity), which is characteristic of many larger-bodied rattlesnakes of North America.

We compare morphological characteristics of male and female Barisia imbricata, Mexican alligator lizards, and find that mass, head length, coloration, incidence of scars from conspecifics, tail loss, and frequency of bearing the color/pattern of the opposite sex are all sexually dimorphic traits. Overall size (measured as snout-vent length), on the other hand, is not different between the two sexes. We use data on bite scar frequency and fecundity to evaluate competing hypotheses regarding the selective forces driving these patterns. We contend that sexual selection, acting through male-male competition, may favor larger mass and head size in males, whereas large females are likely favored by natural selection for greater fecundity. In addition, the frequency of opposite-sex patterning in males versus females may indicate that the costs of agonistic interactions among males are severe enough to allow for an alternative mating strategy. Finally, we discuss how sexual and natural selective forces may interact to drive or mask the evolution of sexually dimorphic traits.