1951, p. 94). Ritualization is useful to the species, since it retains 

 the most reproductively valuable males. There is another means for 

 elimination of the contradiction: inter- and intra-species aggressiveness 

 helps to scatter individuals over the maximum number of microbiotopes within 

 the limits of their area of distribution. Ritualization is highly differ- 

 entiated in decapods and, in a number of ways, is comparable to that of 

 birds (Hazlett, 1972b). The hierarchy within a population arises in the 

 process of aggressive collisions between animals, but after it is established, 

 battles, as in the vertebrates, are replaced by ritualized behavior. The 

 previous group contacts among decapods are important for the results of 

 encounters between males: If in a previous battle a male won, it is probable 

 that he will win again in a later battle with an opponent of equal size. 

 Superior size, initiative in beginning the conflict and the experience of 

 previous victories increase the chances of success in encounters (Mainardi, 

 Rossi, 197?; Rubenstein, Hazlett, 1974). The position of the legs and claws 

 during agonistic reactions in the crabs Microphrys bicornutus are more 

 strictly fixed than during walking and feeding, allowing the crab to recognize 

 the intentions of the enemy, by comparing its behavior with the stereotype 

 (Hazlett, 1972a). The strategy of the victor in a battle between hermit 

 crabs consists in the best possible adaptation of his own behavior to the 

 behavior of the enemy, while the behavior of the loser always contains 

 greater elements of chance (Hazlett, Estabrook, 1974). 



However, true battles arise (for example, among C allinectes s apidus ) 

 only when ritualized attempts to stop a crab approaching food or a female 

 are unsuccessful (Jachowski, 1974). Ritualized aggressive behavior for 

 the protection of individual territory is clearly expressed even in 

 certain individual species with no hierarchy, such as Muni da sarsi 

 (Berrill, 1970). The degree of correlation between ritualized behavior 

 and the defense of the territory, may change as a function of local 

 conditions. For example, D ardanus a rrosor , after losing its sea anemone, 

 is more frequently attacked by other members of the same species. When 

 there is a shortage of food or an increase in the number of crabs, they 

 more frequently place an anemone on their shell. After many months in 

 an aquarium, hermit crabs lost their anemone-seeking activity, but when 

 an octopus was placed in the aquarium, this behavior was reactivated 

 (Balasch, Mengual , 1974). Aggressiveness is differentiated with respect 

 to mature and young animals, a behavioral adaptation to protection from 

 cannibalism. For example, in the hermit crab C libanarius vittatus , if 

 there are great differences in the sizes of two individuals, the larger 

 crab often simply ignores the smaller one (Hazlett, 1968). 



Relationships in a group are not always aggressive in nature. The 

 decrease in aggressiveness observed following long-term cohabitation of 

 Pagurus bernhardus , with an outbreak of aggressive behavior toward a new 

 individual, are apparently explained by the capacity for individual rec- 

 ognition (Hazlett, 1969). The shrimps Hymenocera pi eta live in pairs, 

 generally of different sexes. A male and female usually sit side by side, 

 side, undertaking no sexual activity and not feeding. The partners have a 

 quieting effect on each other. Isolated males seek out only their own 

 partner (Seibt, Wackier, 1972). The shrimp S tenopus hispidus fight to the 



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