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Bibliographic Details
Main Author:	Kaur, Davinder
Format:	Recurso digital
Language:	En
Published:	Zenodo 2025
Online Access:	https://doi.org/10.5281/zenodo.18982570
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Table of Contents:

Crayfish   are   nocturnal freshwater  crustaceans  that  inhabit regions worldwide, except in  India,  continental Africa,  and   Antarctica. Due  to the low  visibility  in  their often-turbid environments, they   rely  heavily  on  olfactory signals for  communication rather than visual or  mechanical cues. These  chemical signals, primarily  transmitted through urine,  reflect the crayfish’s  physiological state and are controlled and directed using  currents generated by their fanning organs. Antennules then detect these cues, which  play a vital role  in guiding various behaviours, such  as social  interactions involving mating rituals, territorial disputes, and  brood care,  ensuring the crayfish’s  survival and  success in their environment. This thesis aimed to explore the mother-offspring interactions, predator-prey dynamics, navigation strategies and  the development and  enhancement of laboratory methods. These studies addressed the significant knowledge gaps, particularly in how the environment impacts these interactions and  how  chemical communication drives  critical  behavioural responses. Crayfish   females  can   modify   behaviour  and   physiological processes  to  ensure the development and   survival   of  their  brood  under  challenging circumstances.  Mothers can extend maternal care,  delay  moulting, and  inhibit  the development of juveniles in response to  extreme environmental conditions. They  use   chemosensory  modalities to detect the external conditions leading to a bidirectional reciprocal feedback mechanism. Activation of mechanoreceptors on the abdomen, the release of brood pheromone, cannibalism inhibition, delay  in  moulting and  control over  the juvenile  growth rate are  maternal care  strategies adopted by mothers to protect their offspring in unfavourable environments (Chapter 2). Juveniles  in normal conditions become independent at the third  developmental stage (in the family  Cambaridae and  Parastacidae) and  start  exploring the habitat as  independent individuals. During  foraging, they  encounter different chemicals including the cue  associated with  known and  unknown predators along  with  injured conspecifics. Crayfish  juveniles who have  already encountered the predator previously are more cautious or stressed, reduce their feeding and  become intolerant to any of the threatening cues. The combination of predator and  alarm  cues induces a threat  among individuals forcing  them to inhabit the shelter and avoid  the area with  the inlet of cues. The initial first hour  is enough to explore and  sense the prevailing risk, with the later few hours being constantly moving  towards the area with shelter. The first encounter with  life-threatening odours is not activated in crayfish  without visual or mechanical cues, while previous experience with predators can cause high caution in the new habitat (Chapter 3). Adults, during their lifetime, inhabit various types of ecosystems and adapt various strategies to explore that habitat. Individuals living in riverine  environments face major  alterations in the cue  due  to the varying  hydrodynamic features.  Animals  opt for  an  edge-tracking strategy to reach the source. The success rate is higher in beneficial odours such  as  food  and  high turbulence. The haemolymph potentially increases the walking  speed, distance covered and activity  in individuals to limit the time spent exploring the arena. These  eco-hydraulic studies can potentially help  in managing invasive  species (Chapter 4). For performing experiments in the laboratory, crayfish  are subjected to various protocols or techniques involving the introduction of foreign substances, which can impair their physiology and   behaviour. Among  the  most used administration procedures, the  Intracoelomic (IC) method dominates the Intrapericardial (IP) ones. IP administration involves  injection of the chemical directly into  the heart, which  leads to high  mortality due  to accidental rupture of the heart. Due to the open circulatory system, the IC procedure almost performed similarly or even  had  better results than IP injections, offering the least harmful but  effective approach for crayfish  injections (Chapter 5). In  conclusion, the  results  of  the  presented  study offer   valuable  ecological  insights, particularly in understanding how chemical communication shapes key behaviours in crayfish, such  as  maternal care  and  predator  avoidance. These  results have  significant implications for  managing invasive  species, conserving crayfish  populations, and  enhancing laboratory practices, ultimately contributing to the broader field  of  chemical ecology and  ecosystem management.   I appreciate the financial  support from  the following  projects that funded parts of the research discussed in this  dissertation: •   Grant  agency of USB (project No. 027/2022/Z, project No. 072/2023/Z and  project No. 028/2024/Z). •   Ministry of Education, Youth and  Sports of the Czech Republic  - project “CENAKVA” (No. LM2023038). •   South Bohemian Research Centre of  Aquaculture and   Biodiversity  of  Hydrocenoses (CENAKVA,  ID 90238) in accordance with  the objectives of  the European consortium DANUBIUS-RI.

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