The most primitive metazoan animals, the placozoans, show high sensitivity to increasing ocean temperatures and acidities

Abstract

The increase in atmospheric carbon dioxide (CO2) leads to rising temperatures and acidification in the oceans, which directly or indirectly affects all marine organisms, from bacteria to animals. We here ask whether the simplest—and possibly also the oldest—metazoan animals, the placozoans, are particularly sensitive to ocean warming and acidification. Placozoans are found in all warm and temperate oceans and are soft‐bodied, microscopic invertebrates lacking any calcified structures, organs, or symmetry. We here show that placozoans respond highly sensitive to temperature and acidity stress. The data reveal differential responses in different placozoan lineages and encourage efforts to develop placozoans as a potential biomarker system.

Alternative NAD(P)H dehydrogenase and alternative oxidase: Proposed physiological roles in animals

“…Trichoplax adhaerens was shown to be sensitive to fluctuations in water salinity (Pearse and Voigt, 2007), temperature, and acidity (Schleicherová et al, 2017), however, this animal has developed molecular machinery to resist hypoxia (Loenarz et al, 2011).…”

Multiple surveys employing a new sample‐processing protocol reveal the genetic diversity of placozoans in Japan

“…A recent study revealed that population growth rates of placozoans are negatively affected by acidity stress (Schleicherová et al., ). In Mikama Bay, on Shikine‐jima Island, where sites J‐a and J‐b are located (Figure ), shallow CO 2 seeps result in reduced pH zones (Agostini et al., ).…”

“…Moreover, slides placed at J‐b were constantly exposed to a reduced pH, probably resulting in the failure of collection. The effect of low pH has been reported only in laboratory‐cultured placozoans (Schleicherová et al., ). Further studies at multiple sites exhibiting various pH levels within Mikama Bay would illustrate the effects of long‐term exposure to a reduced pH on wild placozoans and the ecological differences among the 16S haplotypes.…”

“…Moreover, slides placed at J-b were constantly exposed to a reduced pH, probably resulting in the failure of collection. The effect of low pH has been reported only in laboratory-cultured placozoans (Schleicherová et al, 2016).…”

“…Because of the lack of distinguishable morphological traits at the light microscopic level, Trichoplax adhaerens is still the only nominal species in the phylum Placozoa (Eitel, Osigus, DeSalle, & Schierwater, 2013). However, observations using electron microscopy revealed morphological differences among five groups cultured in the laboratory (Guidi, Eitel, Cesarini, Schierwater, & Balsamo, 2011), and differences in sensitivity to temperature and acidity within and between groups have also been recently reported (Schleicherová et al, 2016). Furthermore, molecular studies have elucidated considerable genetic diversity within the phylum (Pearse & Voigt, 2007;Signorovitch, Dellaporta, & Buss, 2006;Voigt et al, 2004).…”