Exercise and emersion in air and recovery in seawater in the green crab (Carcinus maenas): Effects on nitrogenous wastes and branchial chamber fluid chemistry

Abstract

At low tide, the green crab, which is capable of breathing air, may leave the water and walk on the foreshore, carrying branchial chamber fluid (BCF). N‐waste metabolism was examined in crabs at rest in seawater (32 ppt, 13°C), and during 18‐h recovery in seawater after 1 h of exhaustive exercise (0.25 BL s−1) on a treadmill in air (20°C–23°C), or 1 h of quiet emersion in air. Measurements were made in parallel to O2 consumption (ṀO2), acid‐base, cardio‐respiratory, and ion data reported previously. At rest, the ammonia‐N excretion rate (ṀAmm = 44 µmol‐N kg−1 h−1) and ammonia quotient (AQ; ṀAmm/ṀO2 = 0.088) were low for a carnivore. Immediately after exercise and return to seawater, ṀAmm increased by 65‐fold above control rates. After emersion alone and return to seawater, ṀAmm increased by 17‐fold. These ammonia‐N bursts were greater, but transient relative to longer‐lasting elevations in ṀO2, resulting in temporal disturbances of AQ. Intermittent excretion of urea‐N and urate‐N at rest and during recovery indicated the metabolic importance of these N‐wastes. Hemolymph glutamate, glutamine, and PNH3 did not change. Hemolymph ammonia‐N, urea‐N, and urate‐N concentrations increased after exercise and more moderately after emersion, with urate‐N exhibiting the largest absolute increments, and urea‐N the longest‐lasting elevations. All three N‐wastes were present in the BCF, with ammonia‐N and PNH3 far above hemolymph levels even at rest. BCF volume declined by 34% postemersion and 77% postexercise, with little change in osmolality but large increases in ammonia‐N concentrations. Neither rapid flushing of stored BCF nor clearance of hemolymph ammonia‐N could explain the surges in ṀAmm after return to seawater.

Emersion and recovery alter oxygen consumption, ammonia and urea excretion, and oxidative stress parameters, but not diffusive water exchange or transepithelial potential in the green crab (Carcinus maenas)

“…2A,B). These findings agree well with those Durand and Regnault (1998) and Wood (2023) on C. maenas, and of Regnault (1994) on Cancer pagurus. In these studies, the excretion of ammonia was negligible, and it built up in the hemolymph during emersion, but ammonia excretion was massively increased early in recovery.…”

“…In accord with the low control rate of O 2 consumption in our submersed crabs, rates of ammonia (−66 µmol-N kg −1 h −1 ) and urea-N excretion (−10 µmol-N kg −1 h −1 ) were similarly low (25-80%) relative to resting rates reported in most other studies on C. maenas (Spaargaren, 1982;Simonik and Henry, 2014;Durand and Regnault, 1998;Quijada-Rodriguez et al, 2022). However, they were comparable to rates reported for well-rested green crabs by Wood (2023) andDal Pont et al (2022). Supporting our original hypothesis, both ammonia and urea-N excretion rates declined to very low levels during the emersion period, and then rebounded to levels more than 2-fold greater than the control rates during post-emersion recovery (Fig.…”

“…The gills are potentially impaired by the water availability, which is limited in such environments. There have been many studies comparing the O 2 consumption rate (M ̇O2 ) of C. maenas in air versus water (reviewed by Simonik andHenry, 2014 andWood and. Most have reported that M ̇O2 falls by up to 50% in air (e.g.…”

“…Wallace, 1972;Newell et al, 1972;Simonik and Henry, 2014;Nancollas and McGaw, 2021), though others have reported no change (Taylor and Butler, 1978) or increases during emersion (Wood and Po, 2022). This species is known to excrete waste nitrogen largely as ammonia, together with lesser amounts of urea (Dal Pont et al, 2022;Durand and Regnault, 1998;Weihrauch et al, 2004;Wood, 2023), but there is limited and conflicting information on N-waste excretion during emersion. Ammonia-N excretion has been reported to either increase greatly upon reimmersion, suggesting that it is inhibited during the period of air exposure (Durand and Regnault, 1998;Wood, 2023), or not change during emersion and re-immersion (Simonik and Henry, 2014).…”

“…This species is known to excrete waste nitrogen largely as ammonia, together with lesser amounts of urea (Dal Pont et al, 2022;Durand and Regnault, 1998;Weihrauch et al, 2004;Wood, 2023), but there is limited and conflicting information on N-waste excretion during emersion. Ammonia-N excretion has been reported to either increase greatly upon reimmersion, suggesting that it is inhibited during the period of air exposure (Durand and Regnault, 1998;Wood, 2023), or not change during emersion and re-immersion (Simonik and Henry, 2014). Clearly, there is discord in the literature on these issues, some of which may have resulted from differences in methods, especially the degree of handling disturbance of the animals (Taylor and Butler, 1978;Houlihan et al, 1984;Wilson et al, 2021) and differences in air temperature versus seawater temperature during the treatments.…”