N-acetylglucosamino-1,5-lactone (NAGL) is a molting biomarker in the blue crab Callinectes sapidus The concentration of this compound in urine is highest at the premolt stage. Since sexually mature premolt females release sex pheromone in their urine, NAGL is a candidate sex pheromone molecule in C. sapidus This compound has not been reported in other species. In the present study, we quantified the concentration of NAGL in the urine of the helmet crab Telmessus cheiragonus, using nuclear magnetic resonance spectroscopy, and found that the concentration increases toward the day of molting and decreases after molting. However, the total amount of NAGL collected from individual animals was greatest two to five days after molting, because the amount of urine collected was the lowest at the premolt stage, and it increased after molting. The highest median concentration of NAGL in T. cheiragonas was 29 μmol l(-1), which is 75% of the highest concentration reported in C. sapidus This is the first report of NAGL as a molting biomarker in a species other than C. sapidus We assume that NAGL is part of a pheromone bouquet in these two species.
Intraspecific communication is essential for agonistic and mating behaviours. Agonistic strategy of males must change according to the sex of opponents and that of females is also dependent on their physiological state as to whether they are brooding or not. We have analysed here the agonistic encounters between pairs of male and female crayfish in various combinations to reveal the interaction between agonistic and mating behaviours. After male crayfish became dominant, they aggressively chased subordinate males with attacks, while they did not attack female opponents. Furthermore, the agonistic behaviour of males changed depending on whether females were ovigerous or not. On the other hand, two females showed intense combats despite being ovigerous or not. Crayfish discriminated the sex of opponents via chemical signals in the urine. However, the dominant and subordinate social order of crayfish had no effect on selecting mating partners.
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