The Molting Biomarker Metabolite N-acetylglucosamino-1,5-lactone in Female Urine of the Helmet Crab Telmessus cheiragonus

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

Spiny lobsters detect conspecific blood-borne alarm cues exclusively through olfactory sensilla

When attacked by predators, diverse animals actively or passively release molecules that evoke alarm and related anti-predatory behavior by nearby conspecifics. The actively released molecules are alarm pheromones, whereas the passively released molecules are alarm cues. For example, many insects have alarm-signaling systems that involve active release of alarm pheromones from specialized glands and detection of these signals using specific sensors. Many crustaceans passively release alarm cues, but the nature of the cues,sensors and responses is poorly characterized. Here we show in laboratory and field experiments that injured Caribbean spiny lobsters, Panulirus argus, passively release alarm cues via blood (hemolymph) that induce alarm responses in the form of avoidance and suppression of feeding. These cues are detected exclusively through specific olfactory chemosensors,the aesthetasc sensilla. The alarm cues for Caribbean spiny lobsters are not unique to the species but do show some phylogenetic specificity: P. argus responds primarily with alarm behavior to conspecific blood, but with mixed alarm and appetitive behaviors to blood from the congener Panulirus interruptus, or with appetitive behaviors to blood from the blue crab Callinectes sapidus. This study lays the foundation for future neuroethological studies of alarm cue systems in this and other decapod crustaceans

Spiny lobsters use urine-borne olfactory signaling and physical aggressive behaviors to influence social status of conspecifics

Decapod crustaceans, like many other animals, engage in agonistic behaviors that enhance their ability to compete for resources with conspecifics. These agonistic behaviors include the release of chemical signals as well as physical aggressive and submissive behaviors. In this study, we report that Caribbean spiny lobsters, Panulirus argus, use both urine-borne chemical signaling and physical aggressive behaviors during interactions with conspecifics, and that these agonistic behaviors can influence the behavior and eventual social status of the interactants. Spiny lobsters that engaged primarily in physical aggressive behaviors became dominant, whereas spiny lobsters that received these physical aggressive behaviors responded with avoidance behaviors and became subordinates. Dominant animals frequently released urine during social interactions, more than when they were not in contact with subordinates and more than when they were not paired with another animal. Subordinates released urine significantly less often than dominants,and no more than when not paired. Preventing release of urine by catheterizing the animals resulted in an increase in the number and duration of physical interactions, and this increase was primarily driven by dominants initiating interactions through physical aggressive behaviors. Introducing urine from one of the catheterized animals into an aquarium reduced physical aggressive behavior by dominant animals to normal levels. Urine-borne signals alone were capable of inducing avoidance behaviors from solitary spiny lobsters in both laboratory and field conditions. We conclude that urine serves as a chemical signal that communicates social status to the interactants. Ablation experiments showed that that these urine signals are detected primarily by aesthetasc sensilla of the olfactory pathway

Chemical cues for intraspecific chemical communication and interspecific interactions in aquatic environments: applications for fisheries and aquaculture

Aquatic organisms detect chemical cues to sense the local environment, for example, to find a mate, locate food, and identify danger. Knowledge of chemical cues can be used in aquaculture, in practical applications such as controlling mating behavior to increase fertility, enhance feeding, and decrease stress; in fisheries, by catching selected species with low-cost artificial attractants; and to address maritime issues, by decreasing biofouling. Aquatic organisms also detect chemical cues related to global environmental changes, ocean acidification, and increases in ocean plastics, all of which can affect their chemosensory behaviors. Here we discuss the nature of chemical cues and chemosensory biology and ecology of aquatic organisms, and potential applications with an emphasis on sex pheromones in commercially important and well-studied animals, namely, decapod crustaceans and fish

Phyllosomas of smooth fan lobsters (Ibacus novemdentatus) encase jellyfish cnidae in peritrophic membranes in their feces

Jellyfish possess venomous cnidae on their tentacles to capture and consume marine zooplankton. Nevertheless, the planktonic larvae of the smooth fan lobster (Ibacus novemdentatus), known as phyllosoma, prey on jellyfish and successfully ingest both tentacle tissue as well as constituent cnidae, despite the presence of the venom-filled explosively penetrant cnidae or nematocysts. In the present study, we hypothesized that phyllosomas have mechanical and/or physiological resistance to internal envenomation by ingested nematocysts. To test this hypothesis, we examined the feces of phyllosomas (n=5) that were fed with Japanese sea nettle (Chrysaora pacifica) and found both undischarged as well as discharged cnidae surrounded by peritrophic membrane. We surmise that this membrane may mechanically insulate the lining of the midgut from stinging nematocysts to avoid injection of jellyfish venom into the phyllosomas’ body by nematocyst tubule penetration. We then tested physiological sensitivity of the phyllosomas (n=10) to crude extract of tentacle cnidae injected into their bodies. For this experiment, we used a crude venom extract prepared from nematocysts isolated from tentacles of a rhizostome jellyfish (Nemopilema nomurai) after exposure to high salt which disrupted tentacle integrity, and phosphate-buffered saline as a control. Nine out of 10 animals died after the injection of crude venom extract, while none of the animals died in the control group. These results indicate that the defense of phyllosoma larvae against the toxin of jellyfish is a combination of mechanical inactivation of the ingested nematocysts and chemical digestion of the toxin in the midgut rather than physiological resistance against the toxin