Meeting Abstract
The European green crab, Carcinus maenas, is variable in ventral sternite coloration, green after molting and often dark red after prolonged intermolt. Previous studies reported that red morphs are less stress tolerant than green morphs. In this study we test for stress tolerance changes throughout the molt cycle. Juvenile animals were collected 4-7 days after molting and assessed for various stress markers through the course of a full molt cycle. Animals were greenest 1-2 weeks after molting, before slowly turning yellow. No animals reached the dark orange and red stages typical of a prolonged intermolt, with the intermolt lasting from 40 to 83 days. Molting caused a carapace width increase of 14.7% to 33.7%. Animals were assessed for stress tolerance by righting response in normoxic conditions, and after 45 minutes of hypoxia exposure. Righting response remained constant through the molt cycle in both normoxic (1.5±0.2s), and hypoxic conditions (5.7±0.4s). Hemolymph lactate concentrations rose steadily through the molt cycle from 0.25±0.15mM directly after the first molt, to 2.83±0.34mM directly before the second molt, and dropped off sharply after the second molt (1.03±0.51mM). Oxygen consumption decreased from 0.17±0.06 µmol O2 min-1g-1 in the first week to 0.11±0.03 µmol O2 min-1g-1 in the tenth week. Overall we observed a gradual decrease in hypoxia tolerance during the molt cycle, which might be associated with an increasingly thicker cuticle on the gills, leading to decreased O2 uptake and a subsequently decreased scope for aerobic activity. This gradual transition towards reduced stress tolerance through the molt cycle can affect the overall tolerance of a population of green crabs during severe environmental events.
