Modulation of digestive physiology and biochemistry inMytilus californianusin response to feeding level acclimation and microhabitat

Abstract

The intertidal mussel Mytilus californianus is a critical foundation species that is exposed to fluctuations in the environment along tidal- and wave-exposure gradients. We investigated feeding and digestion in mussels under laboratory conditions and across environmental gradients in the field. We assessed whether mussels adopt a rate-maximization (higher ingestion and lower assimilation) or a yield-maximization acquisition (lower ingestion and higher assimilation) strategy under laboratory conditions by measuring feeding physiology and digestive enzyme activities. We used digestive enzyme activity to define resource acquisition strategies in laboratory studies, then measured digestive enzyme activities in three microhabitats at the extreme ends of the tidal- and wave-exposure gradients within a stretch of shore (<20 m) projected sea-ward. Our laboratory results indicated that mussels benefit from a high assimilation efficiency when food concentration is low and have a low assimilation efficiency when food concentration is high. Additionally, enzyme activities of carbohydrases amylase, laminarinase and cellulase were elevated when food concentration was high. The protease trypsin, however, did not increase with increasing food concentration. In field conditions, low-shore mussels surprisingly did not have high enzyme activities. Rather, high-shore mussels exhibited higher cellulase activities than low-shore mussels. Similarly, trypsin activity in the high-shore-wave-sheltered microhabitat was higher than that in high-shore-wave-exposed. As expected, mussels experienced increasing thermal stress as a function of reduced submergence from low to high shore and shelter from wave-splash. Our findings suggest that mussels compensate for limited feeding opportunities and thermal stress by modulating digestive enzyme activities.

Application of a new targeted low density microarray and conventional biomarkers to evaluate the health status of marine mussels: A field study in Sardinian coast, Italy

“…These changes in mitochondria-and carbohydrate-associated genes are particularly relevant in terms of respiration processes through which energy is provided to the cells. Moreover, anaerobic ATP synthesis could be important in mollusks (Bayne,2009).In fact, this bivalve tends to lock its valves in the presence of polluted water, reducing the respiration rate (Connor et al, 2016), which could lead to a need for the organism to increase anaerobic ATP production.…”

Maintenance of Distal Intestinal Structure in the Face of Prolonged Fasting: A Comparative Examination of Species From Five Vertebrate Classes

“…Some animals [e.g., rate‐maximizing loricariid catfishes (German and Bittong, ); yield‐maximizing ruminants (Hofmann, )] can largely exist near extreme ends of the spectrum, whereas many animals likely switch back and forth depending on intake (Klumpp and Nichols, ; Connor et al, ) because the presence of new ingesta in the stomach is a promoter of gut motility (Olsson and Holmgren, ). Because the animals in this study were deprived of food, we forced them into a yield maximizing situation (i.e., no intake means no new ingesta promoting more rapid gut motility).…”

The observation of starch digestion in blue mussel Mytilus galloprovincialis exposed to microplastic particles under varied food conditions

“…Mussels were evenly distributed into two 25-gallon tanks and acclimated for 4 weeks in artificial 35 ppt seawater using Instant Ocean™ (Instant Ocean Spectrum Brands, Blacksburg, VA) at 17˚C. To simulate the two levels of energy balance that occurs from tidal variation or seasonal changes in food abundance, two food regimes were implemented using Shellfish Diet 1800™ (Reed Mariculture, Campbell CA) based upon previous reported protocols in Connor et al (2016) [27]. The low and high concentrations of food in the experimental tanks were~8 and~15 mg/L of particulate organic matter respectively.…”

“…Protocols were similar to those used in Connor et al (2016) [27]. The Somoygi-Nelson method was used to measure amylase activity in each mussel.…”

“…We chose the low plastic groups because the concentration is still beyond current real-world conditions. We used BLAST to align an EST sequence in M. californianus (GenBank: ES735872.1) previously shown to respond to temperature [27], with the M. galloprovincialis transcriptome (90% identity to transcript GenBank: GAEM01001309.1). Resulting primers were FWD: TACCTGG TCGTTGGCTATG and REV: CGACGATTGAGAGGGCAAG.…”