Mechanistic studies on the physiology of CO2 tolerance in cephalopods

• Main Author: Hu, Marian Yong-An
• Other Authors: Melzner, Frank, Bleich, Markus
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2011
• Subjects: ddc:570; thesis; Ocean acidification; Acid-base regulation; Cuttlefish; Squid; Ozeanversauerung; Säure-Baseregulation; Tintenfisch; Kalmar
• Online Access: https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-65186; https://macau.uni-kiel.de/receive/diss_mods_00006518; https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00003811/Dissertation_final1.pdf

Elevated environmental CO2 concentrations (hypercapnia) are a stressor that has lately received considerable attention: anthropogenic CO2 emissions are predicted to lead to a rise in surface ocean pCO2 from 0.04 kPa up to 0.08 - 0.14 kPa within this century. The increased hydration of CO2 changes seawater chemistry, causing a drop in ocean pH. This phenomenon has been termed “ocean acidification” (OA). Changes in aquatic CO2 partial pressure affect the physiology of all water breathing animals as the CO2 concentration in body fluids will increase as well in order to maintain a substantial outward directed diffusion gradient for CO2. Among the aquatic taxa some have been identified as rather sensitive species (e.g. less active calcifying species such as corals or echinoderms) whereas others (many active species such as adult fish and cephalopods) can tolerate high CO2 concentrations over long exposure times. It was shown that more tolerant organisms share the ability to compensate for a hypercapnia induced acidosis by actively accumulating bicarbonate and eliminating protons from their body fluids. This process requires the presence of an acid-base regulating machinery consisting of a variety of ion transporters and channels. Using in situ hybridization and immuno histochemical methods, the present work demonstrates that Na+/K+-ATPase (NKA), a V-type-H+-ATPase (V-HA), and Na+/HCO3- cotransporter (NBC) are co-localized in NKA-rich cells in the gills of cephalopods. Furthermore, mRNA expression patterns of these transporters and selected metabolic genes were examined in response to moderately elevated seawater pCO2 (0.16 and 0.35 kPa) over a time-course of six weeks in different ontogenetic stages. Our findings support the hypothesis that the energy budget of adult cephalopods is not significantly compromised during long-term exposure to moderate environmental hypercapnia. However, the down regulation of ion-regulatory and metabolic genes in late stage embryos, taken together with a significant reduction in somatic ...