Palliative Care Psychiatry: Building Synergy Across the Spectrum.

PURPOSE OF REVIEW: Palliative care (PC) psychiatry is a growing subspecialty focusing on improving the mental health of those with serious medical conditions and their caregivers. This review elucidates the current practice and ongoing evolution of PC psychiatry. RECENT FINDINGS: PC psychiatry leverages training and clinical practices from both PC and psychiatry, addressing a wide range of needs, including enhanced psychiatric care for patients with serious medical illness, PC access for patients with medical needs in psychiatric settings, and PC-informed psychiatric approaches for individuals with treatment-refractory serious mental illness. PC psychiatry is practiced by a diverse workforce comprising hospice and palliative medicine-trained psychiatrists, psycho-oncologists, geriatric psychiatrists, other mental health professionals, and non-psychiatrist PC clinicians. As a result, PC psychiatry faces challenges in defining its operational scope. The manuscript outlines the growth, current state, and prospects of PC psychiatry. It examines its roles across various healthcare settings, including medical, integrated care, and psychiatric environments, highlighting the unique challenges and opportunities in each. PC psychiatry is a vibrant and growing subspecialty of psychiatry that must be operationalized to continue its developmental trajectory. There is a need for a distinct professional identity for PC psychiatry, strategies to navigate administrative and regulatory hurdles, and greater support for novel clinical, educational, and research initiatives.

Phylogeny and temporal diversification of darters (Percidae: Etheostomatinae).

Discussions aimed at resolution of the Tree of Life are most often focused on the interrelationships of major organismal lineages. In this study, we focus on the resolution of some of the most apical branches in the Tree of Life through exploration of the phylogenetic relationships of darters, a species-rich clade of North American freshwater fishes. With a near-complete taxon sampling of close to 250 species, we aim to investigate strategies for efficient multilocus data sampling and the estimation of divergence times using relaxed-clock methods when a clade lacks a fossil record. Our phylogenetic data set comprises a single mitochondrial DNA (mtDNA) gene and two nuclear genes sampled from 245 of the 248 darter species. This dense sampling allows us to determine if a modest amount of nuclear DNA sequence data can resolve relationships among closely related animal species. Darters lack a fossil record to provide age calibration priors in relaxed-clock analyses. Therefore, we use a near-complete species-sampled phylogeny of the perciform clade Centrarchidae, which has a rich fossil record, to assess two distinct strategies of external calibration in relaxed-clock divergence time estimates of darters: using ages inferred from the fossil record and molecular evolutionary rate estimates. Comparison of Bayesian phylogenies inferred from mtDNA and nuclear genes reveals that heterospecific mtDNA is present in approximately 12.5% of all darter species. We identify three patterns of mtDNA introgression in darters: proximal mtDNA transfer, which involves the transfer of mtDNA among extant and sympatric darter species, indeterminate introgression, which involves the transfer of mtDNA from a lineage that cannot be confidently identified because the introgressed haplotypes are not clearly referable to mtDNA haplotypes in any recognized species, and deep introgression, which is characterized by species diversification within a recipient clade subsequent to the transfer of heterospecific mtDNA. The results of our analyses indicate that DNA sequences sampled from single-copy nuclear genes can provide appreciable phylogenetic resolution for closely related animal species. A well-resolved near-complete species-sampled phylogeny of darters was estimated with Bayesian methods using a concatenated mtDNA and nuclear gene data set with all identified heterospecific mtDNA haplotypes treated as missing data. The relaxed-clock analyses resulted in very similar posterior age estimates across the three sampled genes and methods of calibration and therefore offer a viable strategy for estimating divergence times for clades that lack a fossil record. In addition, an informative rank-free clade-based classification of darters that preserves the rich history of nomenclature in the group and provides formal taxonomic communication of darter clades was constructed using the mtDNA and nuclear gene phylogeny. On the whole, the appeal of mtDNA for phylogeny inference among closely related animal species is diminished by the observations of extensive mtDNA introgression and by finding appreciable phylogenetic signal in a modest sampling of nuclear genes in our phylogenetic analyses of darters.

Escaping the flow: boundary layer use by the darter Etheostoma tetrazonum (Percidae) during benthic station holding.

Aquatic habitats characterized by directional water flow (lotic environments) pose numerous challenges to their inhabitants, including the constant threat of dislodgement and downstream transport. As a result, many organisms exhibit morphological and/or behavioral adaptations that facilitate midwater or benthic station holding in these environments, such as the ventral sucker disc of armored catfishes. However, a few groups, including the species-rich group of small (7-8 cm long and 1-2 cm high) North American stream fishes called darters, exhibit no obvious morphological adaptations to life in lotic habitats. We therefore asked whether small size itself facilitates benthic station holding in these fish. We first used digital particle image velocimetry to quantify the fluid dynamics of flow over a variety of substrates. We then visualized the patterns of flow over the darter Etheostoma tetrazonum during benthic station holding. The thickness of the region of decreased water velocity (i.e. the boundary layer) associated with several types of rocky substrate was large enough (∼2 cm high in some cases) for E. tetrazonum and many other darter species to escape the oncoming flow. We also found that, despite the large size of its pectoral fins, E. tetrazonum is capable of producing only very weak negative lift forces with fins. These substrate-directed forces likely act in conjunction with upstream-directed frictional forces between the tail, anal and pelvic fins and the substrate to facilitate station holding. Thus, we hypothesize that, in darters, small size is an adaptation to life in the benthic boundary layer of lotic environments.

Living on the bottom: kinematics of benthic station-holding in darter fishes (Percidae: Etheostomatinae).

Darters represent a substantial radiation of freshwater fishes that live in close association with the substrate in North American streams and rivers. A key feature of any darter species is therefore its ability to stay in place or to "hold station" in flowing water. Here, we quantify the station-holding performance of two morphologically divergent darter species, the fantail darter Etheostoma flabellare and the Missouri saddled darter Etheostoma tetrazonum. We also characterize the primary kinematic responses of the two species when holding station in flow speeds ranging from 4 to 56 cm s(-1) in a flow tank on either plexiglas or small rock substrate. We then present a series of hypotheses about the potential hydrodynamic and functional consequences of the observed postural changes and the links among morphology, posture, and station-holding performance. On both substrates, E. tetrazonum was able to hold station at higher flow speeds than E. flabellare. On rocks, E. tetrazonum slipped at an average speed of 55.7 cm s(-1) whereas E. flabellare slipped at 40.2 cm s(-1). On plexiglas, E. tetrazonum slipped at an average speed of 24.7 cm s(-1) whereas E. flabellare slipped at 23.1 cm s(-1). We measured body and fin positions of the two species from individual frames of high-speed video while holding station on rocks and plexiglas. We found that on both substrates, the two species generally exhibited similar kinematic responses to increasing flow: the head was lowered and angled downward, the back became more arched, and the median and caudal fin rays contracted as water flow speed increased. The ventral halves of the pectoral fins were also expanded and the dorsal halves contracted. These changes in posture and fin position likely increase negative lift forces thereby increasing substrate contact forces and reducing the probability of downstream slip.

Relationship between species co-occurrence and rate of morphological change in Percina darters (Percidae: Etheostomatinae).

When the morphological diversity of a clade of species is quantified as the among-species variance in morphology, that diversity is a joint consequence of the phylogenetic structure of the clade (i.e., temporal pattern of speciation events) and the rates of change in the morphological traits of interest. Extrinsic factors have previously been linked to variation in the rate of morphological change among clades. Here, we ask whether species co-occurrence is positively correlated with the rate of change in several ecologically relevant morphological characters using the North American freshwater fish clade Percina (Teleostei: Etheostomatinae). We constructed a time-calibrated phylogenetic tree of Percina from mtDNA sequence data, gathered data on eight morphological characters from 37 species, used a principal components analysis to identify the primary axes of morphological variation, and analyzed 16,094 collection records to estimate species co-occurrence. We then calculated standardized independent contrasts (SIC) of the morphological traits (rate of change) at each node, estimated ancestral species co-occurrence, and quantified the correlation between species co-occurrence and rate of morphological change. We find that morphology changes more quickly when co-occurrence is greater in Percina. Our results provide strong evidence that co-occurrence among close relatives is linked to the morphological diversification of this clade.

Twenty ways to lose your bladder: common natural mutants in zebrafish and widespread convergence of swim bladder loss among teleost fishes.

Convergence is an important evolutionary phenomenon often attributed solely to natural selection acting in similar environments. The frequency of mutation and number of ways a phenotypic trait can be generated genetically, however, may also affect the probability of convergence. Here we report both a high frequency of loss of gas bladder (swim bladder) mutations in zebrafish and widespread convergent loss of gas bladders among teleost fishes. The phenotypes of 22 of 27 recessive lethal mutations, carried by a sample of 26 wild-caught zebrafish, involve loss or noninflation of the gas bladder. Nine of these bladderless mutations showed no other obvious phenotypic abnormalities other than the lack of an inflated gas bladder. At least 19 of the 22 bladderless mutations are genetically distinct, as shown by unique morphology or complementation. Although we were not able to obtain eggs for all 21 required crosses to demonstrate definitively that the remaining three mutations are different from all other bladderless mutations, all available evidence suggests that these mutants are also distinct. At least 79 of 425 families of extant teleosts include one or more species lacking a gas bladder as adults. Analysis of the trait's phylogenetic distribution shows that the gas bladder has been lost at least 30-32 times independently. Although adaptive explanations for gas bladder loss are convincing, a developmental bias toward bladderless phenotypes may also have contributed to the widespread convergence of this trait among teleosts. If gas bladder development in teleosts is as vulnerable to genetic perturbation as it is in zebrafish, then perhaps a supply of bladderless phenotypes has been readily available to natural selection under conditions for which it is advantageous not to have a gas bladder. In this way, developmental bias and selection can work together to produce widespread convergence.