In mammals the fila olfactoria, fascicles of axons coursing from sensory neurons in the olfactory epithelium to the glomeruli of the olfactory bulb, not only have a topographic projection pattern but also serve as routes for cerebrospinal fluid (CSF) drainage from around the brain. Les is known about the fila olfactoria in nonmammalian taxa. This work explores the fila olfactoria of the American alligator (Alligator mississippiensis) using a combination of gross dissection, histology, Diffusible Iodine-based contrast-enhanced computed tomography, latex corrosion casting, and India ink tracers. In Crocodylians, as in other nonmammalian vertebrates, the fila olfactoria courses through a foramen in the nasal capsule rather than an ethmoidal cribriform plate. In Alligator this foramen is filled by dense connective tissue; prominent perineural spaces extend through the connective tissue, effectively making it perforate like the cribriform plate. Latex or India ink introduced into the cranial CSF pass through the dense connective to reach the submucosa of the olfactory epithelium, suggesting that Crocodylians have the same cranial CSF drainage pattern as mammals. In Alligator, the fila olfactoria is asymmetric, with more fascicles entering the ventral and lateral surfaces of the olfactory bulb than the dorsal or medial surfaces. If individual fascicles of the fila olfactoria are traced in Alligator, a clear topographic projection emerges; with medial and lateral polarity maintained between olfactory epithelium and olfactory bulb, and a rostral-caudal polarity projecting as dorsal-ventral on the olfactory bulb.

Experimental amniotic fluid embolism in animals produces profound pulmonary hypertension and acute cor pulmonale without evidence of left ventricular compromise. Authors reporting hemodynamic alterations associated with clinical amniotic fluid embolism have traditionally attempted to explain their findings within this experimental framework. A reanalysis of the five published cases of amniotic fluid embolism, which include hemodynamic data derived from pulmonary artery catheterization as well as a report of a sixth case suggests a hemodynamic interpretation different from the traditional one based on the animal model. Left ventricular failure is the only hemodynamic abnormality consistently observed in humans, and the published data are most readily explained on this basis alone. A theoretical model of hemodynamic changes accompanying amniotic fluid embolism that incorporates both experimental and clinical observations is presented. Therapeutic implications are discussed.

Abstract Severe declines in the abundance of insects, including economically and ecologically important pollinators, are alarming conservationists and the public. Yet despite these increasingly well‐documented declines, relatively few pollinating insects other than butterflies, moths, and bumble bees have appeared as Species of Greatest Conservation Need (SGCN) in State Wildlife Action Plans, decadal‐scale blueprints for wildlife conservation efforts across the United States that require updating in 2025. Species absent from SGCN lists are ineligible for congressionally appropriated State Wildlife Grants that direct millions of dollars annually for their conservation. In the past, knowledge about the distribution and abundance of many insect pollinators was too poor to identify those meeting state guidelines for inclusion as SGCN. Using case studies from 4 northeastern states, we demonstrate that sufficient conservation status data now exist for many pollinators, including bees, butterflies, moths, beetles, and flower flies, to identify at‐risk species meriting inclusion on SGCN lists in many states. Doing so will increase funding for surveys, habitat protection and enhancement, and other conservation activities that will benefit this vitally important guild.

IntroductionIdentifying habitat of migratory species to effectively support conservation and management requires careful consideration of (1) the data used to inform habitat models, (2) the biology of the organism, (3) land tenure, and (4) the needs of the target audience.MethodsTo provide this information for western U.S. monarch butterflies, a population undergoing decline, we modeled habitat during the spring and fall migrations. Our approach controlled for biases in citizen science locality data, the principal source of monarch observation data, and incorporated needs for milkweed host plants in the spring and nectar plants in the fall.Results and DiscussionThe results showed the distribution of habitat for spring and fall migration, where the Coast Range and Central Valley in California and riparian areas throughout the range were particularly important. Just 29% of predicted habitat for spring and fall migrations, combined, overlapped between the two seasons. Although the U.S. federal government manages 53% of the land in the western U.S., government land makes up just 11.7% of the spring migration range and 23.5% of the fall migration range. State and local governments and non-governmental organizations (NGOs) manage an additional 4.2% of the spring and 4.0% of the fall migration habitat. Thus, like eastern monarchs, western monarchs rely heavily on land under private ownership for their migration and to be successful, monarch conservation efforts must embrace a public-private approach. Among federal agencies, the Bureau of Land Management (BLM; 5.9% of spring and 9.7% of fall habitat) and Forest Service (3.3% of spring and 9.2% of fall habitat) manage the greatest shares. Less than half of the government and NGO owned habitat for both migrations is managed for biodiversity conservation rather than multiple uses (spring, 46.0%; fall, 36.5%). We created custom model outputs for the BLM to highlight areas of both regional and local importance for migrating monarchs in each BLM administrative unit, enabling managers across the agency to contribute to recovery. The outcomes provide input at a relevant spatial scale to support actions such as habitat restoration, riparian zone protection, and pesticide use reduction to enhance conditions for migrating monarchs on both government and private lands.

Crocodylians evolved a unique gular valve that is capable of creating a water-tight seal between the oral and pharyngeal cavities, allowing the animal to safely submerge with an open mouth. The gular valve has traditionally been described as consisting of two separate parts: an active mobile ventral portion (consisting of the tongue and portions of the hyolingual apparatus) and a dorsal portion, which is a static fold on the hard palate (often termed the palatal velum). The results of the present study argue that the two portions of the gular valve are functionally integrated, not separate, and that the dorsal portion (herein the dorsal gular fold) is a dynamic element the shape and tension of which are influenced by active and passive forces. Using gross dissection, histology, and DiceCT, the present study documents a previously underscribed component of the gular valve, the velar chord, which links the hyolingual apparatus to the dorsal gular fold, functionally integrating the two halves of the gular valve. Through endoscopic videography and a variety of manipulations on living crocodylians, this study demonstrates that changes in the tension on the velar chord directly alter the shape and tension of the dorsal gular fold. The shape changes observed in the dorsal gular fold could be accommodated by a shallow depression in the ventral surface of the palatine bones, herein termed the velar fossa. The velar fossa is a prominent feature of Alligator mississippiensis and was observed in other crocodilians; however, a survey of living and fossil crocodylians demonstrated that the velar fossa is not a universal feature in this clade. Understanding the functional linkage between the dorsal and ventral portions of the gular valve has implications beyond the dive reflex of crocodylians, since active manipulation of the dorsal gular fold likely plays a role in a variety of behavioral and physiological processes such as deglutition and vocalization.

State Wildlife Action Plans (SWAPs), including lists of Species of Greatest Conservation Need (SGCN), outline state strategies for protecting species and habitats in the United States. In developing the current, second revision SWAPs, states are increasingly pursuing coordinated landscape conservation approaches. Analyzing SGCN lists in the first revision SWAPs, we found evidence that they already support multistate conservation. Most states address a common set of vertebrate and invertebrate groups, include most of the imperiled species from these groups, do not prioritize endemics over non-endemics, and often include most imperiled species that are shared with neighboring states. Also, a regional SGCN coordination effort was successful. Although 65% of animals on each SGCN list were assessed as at elevated risk of extirpation by state authorities, only 43% of the combined national list were at elevated risk of global extinction. Over 40% of the combined animal SGCNs are considered globally apparently secure. Plants, snails, freshwater shrimps, and freshwater insects were poorly represented in SGCN lists. For the current SWAP revisions, we recommend improving foundational data on taxonomy, range-wide distribution, and conservation status; expanded taxonomic coverage in SGCN lists; supporting existing and establishing new interstate initiatives; and diversifying funding mechanisms that target regional cooperation.

In tetrapedal locomotion, whether horizontal or during climbing, interactions between the foot and the contact surface or substrate influence the locomotor performance. Multiple previous studies of tetrapedal squamates (lizards) have reported that the animals used the same locomotor velocity, regardless of the angle of ascension. The present study was performed to determine if the American alligator (Alligator mississippiensis) would exhibit a stable climbing velocity and to determine to what degree, if any, this climbing velocity could be modified by substrate differences. Sub -adult Alligator mississippiensis, with body lengths around 170 cm, used the same stride velocity when moving at angles of 0 degrees, 30 degrees, and 55 degrees. During these trials, both the sub -adult and juvenile alligators used a "low walk" gait, rather than a distinctive climbing gait. When the alligators traversed an open grate, their stride duration increased (and stride velocity decreased) presumably due to the insertion (and retraction) of their claws and digits into the grate. When climbing at 55 degrees the juvenile and sub -adult alligators used the same stride duration; the sub -adults used a stride length that was significantly larger in absolute terms, but significantly shorter in relative terms. Despite their large size, and their more caudal center of mass, the climbing performance of Alligator mississippiensis is similar to what has been described in the previously -studied tetrapedal squamates.

The IUCN Red List of Threatened Species underpins much decision-making in conservation and plays a key role in monitoring the status and trends of biodiversity. However, the shortage of funds and assessor capacity slows the uptake of novel data and techniques, hampering its currency, applicability, consistency and long-term viability. To help address this, we developed sRedList, a user-friendly online platform that assists Red List assessors through a step-by-step process to estimate key parameters in a standardised and reproducible fashion. Through the platform, assessors can swiftly generate outputs including species' range maps, lists of countries of occurrence, lower and upper bounds of area of occupancy, habitat preferences, trends in area of habitat, and levels of fragmentation. sRedList is compliant with the IUCN Red List guidelines and outputs are interoperable with the Species Information Service (SIS; the IUCN Red List database) in support of global, regional and national assessments and reassessments. sRedList can also help assessors prioritise species for reassessment. sRedList was released in October 2023, with a complete documentation package (including text documentation, ‘cheatsheets’, and 15 video tutorials), and will soon be highlighted in the official Red List online training course. sRedList will help to bridge the gap between extinction risk research and Red List assessment practice, increase the taxonomic coverage and consistency of assessments, and ensure the IUCN Red List is up-to-date to best support conservation policy and practice across the world.

The proatlas, a bone located between the skull and the neural spines of the cervical vertebrae, is best known from reptiles. Most previous studies of the proatlas have centered on its developmental, debating the relationship between the proatlas and the cervical neural arches. The present study was intended as a description of the proatlas in the American alligator (Alligator mississippiensis) and an experimental test of its hypothesized role in venous blood and cerebrospinal fluid (CSF) distribution. In Alligator, the proatlas is chevron-shaped; ventrally it has a loose connection to the dorsal surface of the first cervical vertebrae, dorsally it has a robust elastic tissue tether on the otoccipital and supraoccipital bones. The ventral surface of the proatlas parallels the dorsal margin of the foramen magnum and rests on the dorsal surface of the spinal venous sinus. Experimental manipulation of the proatlas demonstrated that displacement of the proatlas causes pressure changes in both the spinal venous sinus and the enclosed spinal CSF. The results of this study represent the first demonstration of an explicit functional role for the proatlas, the circulation of fluids between the cranial and spinal compartments of the central nervous system. In Crocodylians the proatlas is positioned between the caudal surface of the skull and the cervical neural spines; the ventral surface of this bone rests on the surface of the spinal venous sinus. The proatlas is not fixed in place, only loosely anchored to C1 ventrally and the supraoccipital dorsally. This study demonstrates that in Alligator mississippiensis, physical displacement of the proatlas alters the fluid pressure of the spinal sinus venous blood as well as the spinal cerebrospinal fluid. image

The epidural space of the American alligator (Alligator mississippiensis) is largely filled by a continuous venous sinus. This venous sinus extends throughout the trunk and tail of the alligator, and is continuous with the dural sinuses surrounding the brain. Segmental spinal veins (sl) link the spinal venous sinus (vs) to the somatic and visceral venous drainage. Some of these sl, like the caudal head vein along the occipital plate of the skull, are enlarged, suggesting more functional linkage. No evidence of venous valves or external venous sphincters was found associated with the vs; the relative scarcity of smooth muscle in the venous wall of the sinus suggests limited physiological regulation. The proatlas (pr), which develops between the occipital plate and C1 in crocodylians, is shaped like a neural arch and is fused to the dorsal surface of the vs. The present study suggests that the pr may function to propel venous blood around the brain and spinal cord. The vs effectively encloses the spinal dura, creating a tube-within-a-tube system with the (smaller volume) spinal cerebrospinal fluid (CSF). Changes in venous blood pressure, as are likely during locomotion, would impact dural compliance and CSF pressure waves propagating along the spinal cord.

This study was undertaken to explore the forces acting on the pes during pedal anchoring and to discern if pedal anchoring required the activation of the intrinsic pedal musculature. Replica feet equipped with strain gauges were moved over mud substrate, mimicking locomotion and pedal anchoring. Quantification of the substrate tracks demonstrated that they were similar to those made by freely moving Alligator, that the locomotor and pedal anchoring tracks were significantly different, and that the composition of the artificial feet significantly altered the tracks. Strain gauges revealed significantly different forces at different locations (e.g., digit vs. heel) on the pes and between locomotor and pedal anchoring motions. Collectively, the results of the present study demonstrate that the forces acting on the pes during pedal anchoring are different from those during locomotion. Furthermore, varying the composition of the feet used in this study demonstrated the importance of flexion at the metatarsal/phalangeal joints. Resistance to this flexion in living crocodylians requires active muscle contraction, meaning that pedal anchoring is an active, not passive, behavior. These results offer the first insights into the mechanics of pedal anchoring and demonstrate how technologies like 3D printing can be applied to established problems like fossil trackways.

A variety of anatomical techniques, imaging modalities, dyes and contrast agents, were used to document the mechanisms/routes whereby spinal cerebrospinal fluid (CSF) would move beyond the confines of the spinal dura in the American alligator, Alligator mississippiensis. Three pathways for CSF loss were identified: spinal arachnoid granulations, perineural flow along the spinal nerves, and lymphatic drainage (both along the surface of the dura and at the venous plexus surrounding the spinal ganglion). These same three pathways for spinal CSF loss have been documented in mammals, suggesting that they may be a common feature of (at least) amniotes. Crocodilians, including A. mississippiensis, have the largest epidural venous sinus system of any vertebrate, the present study suggests that, as in mammals, the venous complex of the alligator plays a direct role in regulating the absorption of CSF from the spinal compartment.

In humans and most mammals, there is a notch-like portal, the foramen of Luschka (or lateral foramen), which connects the lumen of the fourth ventricle with the subdural space. Gross dissection, light and scanning electron microscopy, and μCT analysis revealed the presence of a foramen of Luschka in the American alligator (Alligator mississippiensis). In this species, the foramen of Luschka is a notch in the dorsolateral wall of the pons immediately caudal to the peduncular base of the cerebellum, near the rostral end of the telovelar membrane over the fourth ventricle. At the foramen of Luschka there was a transition from a superficial pia mater lining to a deep ependymal lining. There was continuity between the lumen of the fourth ventricle and the subdural space, via the foramen of Luschka. This anatomical continuity was further demonstrated by injecting Evans blue into the lateral ventricle which led to extravasation through the foramen of Luschka and pooling of the dye on the lateral surface of the brain. Simultaneous subdural and intraventricular recordings of cerebrospinal fluid (CSF) pressures revealed a stable agreement between the two pressures at rest. Perturbation of the system allowed for static and dynamic differences to develop, which could indicate varying flow patterns of CSF through the foramen of Luschka.

The IUCN recently coordinated the first assessment of extinction risk of the world's reptile species. This monu-mental undertaking allows, for the first time, an examination of threats and prioritization of conservation effort, not just for reptiles, but for land vertebrates as a whole. Reptiles are now the largest class of land vertebrates in terms of species numbers. The dynamic nature of reptile taxonomy, the 18 years it took for the Global Reptile Assessment to be completed, the poor state of knowledge for many species - especially of squamates - and the evolving nature of threats, however, all highlight the need for continued monitoring of reptile species and threats. Here we review the status of reptile conservation assessments, and identify the challenges facing the next reptile assessments. We then recommend potential avenues that could facilitate efficient, accurate and timely future assessments.

Despite being central to the implementation of conservation policies, the usefulness of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species is hampered by the 14% of species classified as data-deficient (DD) because information to evaluate these species' extinction risk was lacking when they were last assessed or because assessors did not appropriately account for uncertainty. Robust methods are needed to identify which DD species are more likely to be reclassified in one of the data-sufficient IUCN Red List categories. We devised a reproducible method to help red-list assessors prioritize reassessment of DD species and tested it with 6887 DD species of mammals, reptiles, amphibians, fishes, and Odonata (dragonflies and damselflies). For each DD species in these groups, we calculated its probability of being classified in a data-sufficient category if reassessed today from covariates measuring available knowledge (e.g., number of occurrence records or published articles available), knowledge proxies (e.g., remoteness of the range), and species characteristics (e.g., nocturnality); calculated change in such probability since last assessment from the increase in available knowledge (e.g., new occurrence records); and determined whether the species might qualify as threatened based on recent rate of habitat loss determined from global land-cover maps. We identified 1907 species with a probability of being reassessed in a data-sufficient category of >0.5; 624 species for which this probability increased by >0.25 since last assessment; and 77 species that could be reassessed as near threatened or threatened based on habitat loss. Combining these 3 elements, our results provided a list of species likely to be data-sufficient such that the comprehensiveness and representativeness of the IUCN Red List can be improved.

Background: Dural compliance influences the shape and magnitude of the cerebrospinal fluid (CSF) pulsations. In humans, cranial compliance is approximately 2× greater than spinal compliance; the differential has been attributed to the associated vasculature. In alligators, the spinal cord is surrounded by a large venous sinus, which suggests that the spinal compartment may have higher compliance than is found in mammals. Methods: Pressure catheters were surgically implanted into the cranial and spinal subdural spaces of eight subadult American alligators (Alligator mississippiensis). The CSF was propelled through the subdural space by orthostatic gradients and rapid changes in linear acceleration. Results: CSF pressure recordings taken from the cranial compartment were consistently, and significantly, larger than those taken from the spinal compartment. After the myodural bridge of Alligator was surgically released, the asymmetry in CSF pressure was decreased. Conclusion: Unlike the situation in humans, the spinal compartment of Alligator has greater compliance than the cranial compartment, presumably due to the presence of the large spinal venous sinus surrounding the dura. The change in CSF pressures after myodural surgical release supports the hypothesis that the myodural bridge functions, at least in part, to modulate dural compliance and the exchange of CSF between the cranial and spinal compartments.

In Alligator mississippiensis the spinal dura is surrounded by a venous sinus; pressure waves can propagate in the spinal venous blood, and these spinal venous pressures can be transmitted to the spinal cerebrospinal fluid (CSF). This study was designed to explore pressure transfer between the spinal venous blood and the spinal CSF. At rest the cardiac-related CSF pulsations are attenuated and delayed, while the ventilatory-related pulsations are amplified as they move from the spinal venous blood to the spinal CSF. Orthostatic gradients resulted in significant alterations of both cardiac- and ventilatory-related CSF pulsations. Manual lateral oscillations of the alligator's tail created pressure waves in the spinal CSF that propagated, with slight attenuation but no delay, to the cranial CSF. Oscillatory pressure pulsations in the spinal CSF and venous blood had little influence on the underlying ventilatory pulsations, though the same oscillatory pulsations reduced the ventilatory- and increased the cardiac-related pulsations in the cranial CSF. In Alligator the spinal venous anatomy creates a more complex pressure relationship between the venous and CSF systems than has been described in humans.

To resist forward displacement of their body during non-locomotor behaviors such as feeding, American alligators ( Alligator mississippiensis ) hold their hindfeet vertical, then push the foot into the substrate so that the dorsum of the foot forms a contact area with the substrate. Herein this form of bracing is termed pedal anchoring. The purpose of the present study was to describe pedal anchoring and to demonstrate whether it entailed interaction between the hindfoot (pes) of Alligator and the substrate that differed from the interactions seen during locomotion. Alligator tracks were studied in the wild, during controlled field trials, and on a mud trackway in the laboratory; in each setting locomotor and pedal anchoring tracks were photographed, cast in Plaster of Paris, then features of the casts quantified. Statistical analysis demonstrated greater variation in the wild tracks, presumably reflecting the larger size and velocity ranges of the alligators involved, and suggested that the mud trackway used during the locomotor trials did not create significant artifact. Tracks produced during locomotion and pedal anchoring by the same alligators, on the same substrate, yielded significantly different quantitative features, different matrices of Pearson correlation coefficients, and different patterns of character distribution following Principal Component Analysis. These results all support the conclusion that pedal anchoring involves fundamentally different interaction between the pes and the substrate than occurs during locomotion.