The giant clam Tridacna crocea, native to Indo-Pacific coral reefs, is noted for its unique ability to bore fully into coral rock and is a major agent of reef bioerosion. However, T. crocea’s mechanism of boring has remained a mystery despite decades of research. By exploiting a new, two-dimensional pH-sensing technology and manipulating clams to press their presumptive boring tissue (the pedal mantle) against pH-sensing foils, we show that this tissue lowers the pH of surfaces it contacts by greater than or equal to 2 pH units below seawater pH day and night. Acid secretion is likely mediated by vacuolar-type Hþ-ATPase, which we demonstrate (by immunofluorescence) is abundant in the pedal mantle outer epi- thelium. Our discovery of acid secretion solves this decades-old mystery and reveals that, during bioerosion, T. crocea can liberate reef constituents directly to the soluble phase, rather than producing sediment alone as earlier assumed.
It’s 2017 and we are are off to a good start! Our most recent publication investigates the localization of acid-base sensor sAC in various leopard shark tissues, and found it highly abundant in the cytoplasm of gill acid- and base-secreting cells. sAC was also found present in or around the necleus of gill, cornea, and rectal gland cells, suggesting sAC’s possible role in regulating gene expression. To the best of our knowledge, this is the first description of nuclear sAC in an aquatic organism.
Check out this open access publication below.
Roa, J.N., Tresguerres, M. 2017. Bicarbonate-sensing soluble adenylyl cyclase is present in the cell cytoplasm and nucleus of multiple shark tissues. Physiological Reports
We have been busy researching and publishing our findings! One of our papers resulted from a collaboration with German researchers from Christian Albrechts University Kiel and Helmholtz Centre for Polar and Marine Research on ammonia excretion in mussels (Mytilus edulis). Our second paper is a commentary on the vacuolar-type H+ -ATPase (VHA). Lastly, our final paper is led by Jinae Roa and examines round stingray (Urolophus halleri) gill cells and its mechanisms for acid-base sensing.
Abstract: Aggression and responsiveness to noxious stimuli are adaptable traits that are ubiquitous throughout the animal kingdom. Like vertebrate animals, some invertebrates have been shown to exhibit anxiety- like behaviour and altered levels of aggression that are modulated by the neurotransmitter serotonin. To investigate whether this influence of serotonin is conserved in crabs and whether these behaviours are sensitive to human antidepressant drugs; the striped shore crab, Pachygrapsus crassipes, was studied using anxiety (light/dark test) and aggression (mirror test) paradigms. Crabs were individually exposed to acute doses of the selective serotonin reuptake inhibitor, fluoxetine (5 or 25 mg/L), commonly known as Prozac®, followed by behavioural testing. The high dose of fluoxetine significantly decreased anxiety-like behaviour but had no impact on mobility or aggression. These results suggest that anxiety-like behaviour is more sensitive to modulation of serotonin than is aggressiveness in the shore crab.
Congratulations to Jinae Roa for being awarded the Porter Fellowship from the American Physiological Society!