Abstract
This study describes the physiological performance of two populations of the razor clam Tagelus dombeii from two geographic areas with different histories of exposure to paralytic shellfish poisoning (PSP) linked to the toxic dinoflagellate Alexandrium catenella. Clams from Melinka-Aysén, which are frequently exposed to PSP, were not affected by the presence of toxins in the diet. However, clams from Corral-Valdivia, which have never been exposed to PSP, exhibited significantly reduced filtration activity and absorption, affecting the energy allocated to scope for growth (SFG). Ammonia excretion and oxygen uptake were not affected significantly by the presence of A. catenella in the diet. Measurements of energy acquisition and expenditure were performed during a 12-day intoxication period. According to three-way repeated measure ANOVAs, the origin of the clams had a highly significant effect on all physiological variables, and the interaction between diet and origin was significant for the clearance and absorption rates and for the scope for growth. The scope for growth index showed similar positive values for both the toxic and non-toxic individuals from the Melinka-Aysén population. However, it was significantly reduced in individuals from Corral-Valdivia when exposed to the diet containing A. catenella. The absence of differences between the physiological response of the toxic and non-toxic clams from Melinka-Aysén may be related to the frequent presence of A. catenella in the environment, indicating that this bivalve does not suffer negative consequences from PSP. By contrast, A. catenella has a negative effect on the physiological performance, primarily on the energy gained from the environment, on T. dombeii from Corral-Valdivia. This study supports the hypothesis that the history of PSP exposure plays an important role in the physiological performance and fitness of filter feeding bivalves.
Highlights
Harmful algae blooms (HABs) are cosmopolitan phenomena that cause serious public health problems
The present study looks at how historical exposure to a toxic dinoflagellate may affect physiological performance and fitness of specimens of Tagelus dombeii from two populations from different geographic areas
The Tagelus dombeii clams from Melinka-Aysen, which are frequently exposed to paralytic shellfish poisoning (PSP), were not affected by the presence of toxin in the diet, unlike the population from Corral-Valdivia, which is not exposed to PSP
Summary
Harmful algae blooms (HABs) are cosmopolitan phenomena that cause serious public health problems. Mya arenaria clams from areas frequently exposed to toxic dinoflagellate blooms are less affected by PSP than specimens from areas that have not been previously exposed to PSP [9] According these authors, the different responses of bivalves to toxins are related to nerve sensitivity, where resistance to the toxin is caused by a mutation of an amino acid that causes a decrease in the affinity of saxitoxin at the sodium channel pore of the cell membrane. The presence of PSP in the environment can act as an agent of natural selection, leading to increased resistance of the bivalves to the toxin, with a smaller impact on behavioral and physiological responses. A study that analyzed the digestive enzymatic activity and absorption efficiency in the razor clam Tagelus dombeii upon exposure to Alexandrium catenella [15] showed that a feeding history of exposure to A. catenella was reflected in the digestive responses of T. dombeii
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