Maintenance of nongregarious burrowing animals, Homarus americanus , 

 in a group for some time subsequently decreased the aggressiveness of 

 these individuals when they were placed individually into aquariums with 

 one H omarus and one place of refuge (Dunham, 1972). "Swarming pheromones" 

 similar to those of many insects have been found in crustaceans: They are 

 present in S aron m armoratus and many hermit crabs (Hazlett, 1966). Thus, 

 the group effect and mass effect are manifestations of the initial phases 

 of formation of nontrophic group communication. 



Chemical protective substances, temporarily blocking the mobility 

 of an enemy, are known in plankters. For example, the medusa Aequorea 

 a equorea excretes a substance which inhibits the movement of the medusa 

 Stomotoca atra (Lenhoff, 1964), which frequently eat coelenterates. One 

 variety of protective pheromone is the alarm substance, which is also quite 

 widespread among aquatic invertebrates. If viscera of the sea urchin 

 D iadema antillarum contact the water, a substance is liberated which 

 causes other sea urchins to flee the area of danger. 



One special type of intraspecies signaling, intended to aid in 

 nocturnal visual reception, is bioluminescence. In females of the euphausiid 

 Meganyctiphanes norveqica , the periods of maximum response to the luminescent 

 flashes of the males correspond with the periods of attachment of the 

 spermatophores; thus, luminescence can be looked upon in this case as an 

 attribute of sexual behavior (preparedness signal). Imitative (response) 

 luminescence has been detected in the same animals (Kay, 1965; Tett, 1972). 

 In the ctenophorans B eroe and B ol inopsis and the hydromedusa Aeginopsis 

 l aurentiae , a flash can cause a defensive motor reaction (Labas, 1973). 



3.3 Interspecific Collective (Group) Reactions 



Group reactions which tend to support coexistence of species due to 

 negative contacts can be considered aggressive relationships. These 

 relationships are possible when the ability to recognize objects in the 

 surrounding world is developed. The most primitive form of collective 

 behavior is direct destruction of the neighboring species not for the 

 purpose of eating it. Recognition of the object in this case apparently is 

 chemoreceptor mediated. By this method, the madrepore corals, secondary 

 in terms of abundance, which construct relatively small and slowly growing 

 corallites, protect themselves from the dominant, more rapidly growing 

 forms: the more aggressive, slowly growing species destroys the polyps of 

 the other species, dissolving their tissues with mesenterial threads (Lang, 

 1973). This is a simple case of group behavior with a direct topic (to use 

 the terminology of V. N. Beklemishev, 1951) connection. However, the coral 

 reef biotope is also the site of indirect connections. A complex form of 

 group interspecies behavior with indirect topic and phoric connections is 

 seen in the relationship between fish and sea anemones and between hermit 

 crabs and sea anemones. The symbiotic relationship between the fish 

 P omacentridae and the sea anemones of the family S toichactidae is well known 

 iDhont, 1971; Mariscal , 1970). Frequently, one corallite, one sea anemone, 

 the mantle cavity of one tridacna or one sponge osculum is occupied by a 

 single pair of fish, shrimp or crabs, monopolizing the tiny microbiotope. 



27 



