Physiological changes during torpor favor association with endosymbionts in the urochordate .

Environmental perturbations evoke down-regulation of metabolism in some multicellular organisms, leading to dormancy, or torpor. Colonies of the urochordate enter torpor in response to changes in seawater temperature and may survive for months as small vasculature remnants that lack feeding and reproductive organs but possess torpor-specific microbiota. Upon returning to milder conditions, the colonies rapidly restore their original morphology, cytology and functionality while harboring re-occurring microbiota, a phenomenon that has not been described in detail to date.

Transcriptome landscapes that signify Botrylloides leachi (Ascidiacea) torpor states.

Harsh environments enforce the expression of behavioural, morphological, physiological, and reproductive rejoinders, including torpor. Here we study the morphological, cellular, and molecular alterations in torpor architype in the colonial urochordate Botrylloides aff. leachii by employing whole organism Transmission electron (TEM) and light microscope observations, RNA sequencing, real-time polymerase chain reaction (qPCR) quantification of selected genes, and immunolocalization of WNT, SMAD and SOX2 gene expressions.

Insights into the unique torpor of Botrylloides leachi, a colonial urochordate.

Rough environmental conditions make the survival of many multi-cellular organisms almost impossible, enforcing behavioral, morphological, physiological and reproductive rejoinders that can cope with harsh times and hostile environments, frequently through down-regulation of metabolism into basal states of dormancy, or torpor. This study examines one of the most unique torpor strategies seen within the phylum Chordata, exhibited by the colonial urochordate Botrylloides leachi, which enters a state of hibernation or aestivation in response to thermal stress, during which all of its functional colonial units (zooids) are entirely absorbed and the colony survives as small remnants of the vasculature, lacking both feeding and reproduction organs. Tissue vestiges then regenerate fully functional colony when re-exposed to milder environmental conditions.