Characteristics of The Bleached Microbiome of The Generalist Coral Pocillopora damicornis from Two Distinct Reef Habitats.

Generalist coral species may play an important role in predicting, managing, and responding to the growing coral reef crisis as sea surface temperatures are rising and reef wide bleaching events are becoming more common. Pocilloporids are amongst the most widely distributed and studied of generalist corals, characterized by a broad geographic distribution, phenotypic plasticity, and tolerance of sub-optimal conditions for coral recruitment and survival. Emerging research indicates that microbial communities associated with Pocilloporid corals may be contributing to their persistence on coral reefs impacted by thermal stress; however, we lack detailed information on shifts in the coral-bacterial symbiosis during bleaching events across many of the reef habitats these corals are found. Here, we characterized the bacterial communities of healthy and bleached Pocillopora damicornis corals during the bleaching events that occurred during the austral summer of 2020 on Heron Island, on the southern Great Barrier Reef, and the austral summer of 2019 on Lord Howe Island, the most southerly coral reef in Australia. Regardless of reef location, significant differences in α and ß diversities, core bacterial community, and inferred functional profile of the bleached microbiome of P. damicornis were not detected. Consistent with previous reports, patterns in the Pocilloporid coral microbiome, including no increase in pathogenic taxa or evidence of dysbiosis, are conserved during bleaching responses. We hypothesize that the resilience of holobiont interactions may aid the Pocilloporids to survive Symbiodiniaceae loss and contribute to the success of Pocilloporids.

Control of hemodynamic adjustments during acute volume expansion in the rabbit.

The influence of reflexes mediated by the carotid sinus, aortic, and vagus nerves on control of blood pressure were investigated in the pentobarbital-anesthetized rabbit during an acute intravascular volume expansion. Blood, kept at 37 degrees C, was gradually infused at 2.5-min intervals until the blood volume of each animal was expanded to 10, 20, 30, and 40% above normal. Responses in sinoaortic-vagally denervated rabbits were compared to intact rabbits. Both intact and denervated animals showed a significant increase in central venous pressure with each 10% addition of blood. Heart rate did fall significantly in the intact group but not in the denervated group. No significant changes were identified in mean arterial pressure (MAP) in either group. In both groups changes in cardiac output were significantly greater than control for 20, 30, and 40% expansion and calculated total peripheral resistance fell in both groups at all levels of expansion when compared to control. The absence of significant changes in MAP within the intact and denervated groups suggests that sinoaortic-vagal reflexes are not affecting control of MAP in response to slow, acute volume expansion in the intact rabbit. On the other hand, since total peripheral resistance fell in both groups, a non-sinoaortic-vagal mechanism appears to be functional. This mechanism may assist in increasing vascular capacitance in order to prevent significant increases in blood pressure.

Species differences in circulatory responses to nasopharyngeal perfusion with smoke.

Cardiovascular changes were observed in five species of laboratory mammals during upper airway perfusion with cigarette smoke. Apnoea occurred, both before and after vagotomy, in all species. Blood pressure always went up in rabbits, rats and hamsters but was not much affected in cats and guinea-pigs. Before vagotomy heart rate fell in rabbits and rats, rose in hamsters but did not change in cats and guinea-pigs. Vagotomy affected heart rate changes only in rabbits and rats. Results demonstrate markedly different autonomic responses in different species.