Oxygen as a Driver of Early Arthropod Micro-Benthos Evolution

BACKGROUND: We examine the physiological and lifestyle adaptations which facilitated the emergence of ostracods as the numerically dominant Phanerozoic bivalve arthropod micro-benthos. METHODOLOGY/PRINCIPAL FINDINGS: The PO(2) of modern normoxic seawater is 21 kPa (air-equilibrated water), a level that would cause cellular damage if found in the tissues of ostracods and much other marine fauna. The PO(2) of most aquatic breathers at the cellular level is much lower, between 1 and 3 kPa. Ostracods avoid oxygen toxicity by migrating to waters which are hypoxic, or by developing metabolisms which generate high consumption of O(2). Interrogation of the Cambrian record of bivalve arthropod micro-benthos suggests a strong control on ecosystem evolution exerted by changing seawater O(2) levels. The PO(2) of air-equilibrated Cambrian-seawater is predicted to have varied between 10 and 30 kPa. Three groups of marine shelf-dwelling bivalve arthropods adopted different responses to Cambrian seawater O(2). Bradoriida evolved cardiovascular systems that favoured colonization of oxygenated marine waters. Their biodiversity declined during intervals associated with black shale deposition and marine shelf anoxia and their diversity may also have been curtailed by elevated late Cambrian (Furongian) oxygen-levels that increased the PO(2) gradient between seawater and bradoriid tissues. Phosphatocopida responded to Cambrian anoxia differently, reaching their peak during widespread seabed dysoxia of the SPICE event. They lacked a cardiovascular system and appear to have been adapted to seawater hypoxia. As latest Cambrian marine shelf waters became well oxygenated, phosphatocopids went extinct. Changing seawater oxygen-levels and the demise of much of the seabed bradoriid micro-benthos favoured a third group of arthropod micro-benthos, the ostracods. These animals adopted lifestyles that made them tolerant of changes in seawater O(2). Ostracods became the numerically dominant arthropod micro-benthos of the Phanerozoic. CONCLUSIONS/SIGNIFICANCE: Our work has implications from an evolutionary context for understanding how oxygen-level in marine ecosystems drives behaviour

Teaching Neurobiology in Psychiatry

The relationship between psychiatry and neuroscience has been constantly evolving since the conception of our field. The past two decades have witnessed a steep rise in research related to neurobiology in psychiatry. Advances in neuroscience have led psychiatry residency programs to steer towards a neuroscience-based approach instead of the traditional focus. Despite increased advances and interest in neuroscience and psychiatry, residency programs are not required to integrate neurobiology in psychiatry. There are several difficulties residency programs face when attempting to teach this subject area, including having availability of knowledgeable faculty, knowing what to teach, and how to deliver the information. Psychiatrists across all levels of training are enthusiastic about learning neuroscience. With the current advances in biological psychiatry, neurobiology needs to be integrated in the training and teaching of psychiatry residents. The approach of integration has to be transdiagnostic, clinically relevant, and applicable to both trainees and psychiatry educators. We will discuss the importance of teaching neurobiology in psychiatry residency programs, outline specific areas we recommend teaching, and propose teaching strategies that may enhance learning by psychiatry residents. The neurobiology topics we recommend psychiatry programs to teach their residents include neuroscience literacy, neuroanatomy, neuroimaging, neuropathology, neural circuits and neurotransmitters, neuroendocrinology, psychoneuroimmunology, neurophysiology, genetics and epigenetics, and neuropsychological testing. There are different strategies to teach residents that enhance adult learning, which include formal discussions, clinical case presentations, journal clubs, specialized neuroscience rotations, neuroanatomy modules, grand rounds, and classes discussing topics at the interface of neuroscience and psychiatry in the media