Michael H. Figler

Shelter competition in juvenile red swamp crayfish (Procambarus clarkii) : the influences of sex differences, relative size, and prior residence

Abstract Using a resident–intruder model, 24-h resident juvenile male and female red swamp crayfish, Procambarus clarkii, were intruded upon by same or opposite sex juvenile conspecifics that were the same size or larger than the residents. Relative size was significantly related to contest outcomes. Residents that were the same size as the intruders won a significantly higher proportion of their encounters than residents that were smaller than the intruders. Overall, neither sex nor prior residence was significantly related to contest outcome. There was clear shelter-related territorial defense in both male and female juveniles, and is very similar to that shown in adult conspecifics. The provision of shelter for juveniles in the aquaculture of P. clarkii is especially important because of the shelter competition advantage of adults. This indirectly increases juvenile vulnerability to heterospecific predation and cannibalism by conspecific adults and juveniles.

Maternal aggression in red swamp crayfish (Procambarus clarkii, Girard): the relation between reproductive status and outcome of aggressive encounters with male and female conspecifics

A series of experiments investigated intraspecific aggression by maternal (carrying eggs and/or hatched young) and non-maternal female red swamp crayfish (Procambarus clarkii) residents against intrusions by non-maternal female and Form I (reproductively active) male conspecifics. Each resident occupied an aquarium containing a shelter for 24 hours prior to the initial intrusion. The winner of each encounter was determined, as well as the pair member that initiated the aggressive interaction, and the relation between the initiation of aggression and contest outcome. The results showed that: (1) Maternal female residents were winners in 92% of the encounters with male intruders, and initiated aggression in a significantly higher proportion of encounters than the male intruders. (2) Maternal female residents were the winners in 75% of the encounters with non-maternal female intruders. The maternal residents also initiated aggression in a significantly higher proportion of the encounters than the non-maternal intruders. (3) Non-maternal female residents lost 77% of the encounters with non-maternal intruders. Also, the non-maternal intruders initiated aggression in a significantly higher proportion of the encounters than did the non-maternal residents. (4) Non-maternal female residents lost all of their encounters with male intruders. However, there was no significant difference in the proportion of the encounters in which aggression was initiated by residents or intruders. (5) For all experiments combined, maternal residents won a significantly higher proportion of their encounters than did non-maternal residents, regardless of whether the intruders were males or non-maternal females. (6) For the three experiments combined, the initiation of aggression reliably predicted contest outcome (i.e. the initiator of aggression ultimately won). The present results provide the first empirical demonstration, with appropriate non-maternal controls, of maternal aggression in decapod crustaceans. Also, the direct relation between reproductive status and contest outcome in both ovigerous and post-hatch P. clarkii are the first such data reported in crustaceans, in general. Finally, the findings of these experiments bear notable similarities to the results of maternal aggression research in other taxonomic groups.

INTERSPECIFIC SHELTER COMPETITION BETWEEN THE SYMPATRIC CRAYFISH SPECIES PROCAMBARUS CLARKII (GIRARD) AND PROCAMBARUS ZONANGULUS (HOBBS AND HOBBS)

ABSTRACT Aggressive interactions and shelter possession were used to examine interspecific competition between Form I males of the sympatric crayfish species Procambarus clarkii and Procambarus zonangulus. Paired encounters were staged between heterospecifics, using a type of shelter shown to be equally preferred by both species. On Day 1, each heterospecific intruder encountered a resident P. clarkii or P. zonangulus, which had been occupying the shelter for the previous 24 h. Each pair remained in the residents tank for 48 h after the initial encounter was settled, in order to determine subsequent shelter possession. Results indicated a significant prior residence advantage on Day 1 for resident P. clarkii, but not for resident P. zonangulus. Furthermore, on Days 2 and 3, resident and intruder P. clarkii were in possession of the shelters in a significantly higher proportion of cases than opponent P. zonangulus, reflecting an eventual species dominance advantage by P. clarkii. The influence of this competitive advantage on the differential prevalence of these species in the natural environment remains to be explored.

Shelter competition between resident male red swamp crayfish Procambarus clarkii (Girard) and conspecific intruders varying by sex and reproductive status

The shelter defense dynamics of reproductively active (Form I) male red swamp crayfish Procambarus clarkii (Girard) were investigated by staging serial intrusions by male, maternal or non-maternal female conspecifics after one day of residence. The male residents showed a direct contest advantage only against non-maternal females, and won a significantly higher proportion of the encounters against non-maternal females than against either male or maternal female intruders. However, there was no significant difference in success against male or maternal female intruders. Further experiments against male intruders showed that increasing male prior residence to either 2 or 4 days did not significantly improve the residents’ proportion of successful encounters. A final experiment revealed extremely low shelter fidelity in male P. clarkii, the most likely reason why male shelter defense against conspecific males and maternal females is not successful. These results, combined with those of past research, suggest that non-maternal females, juveniles and recently molted conspecifics are most vulnerable to predation and cannibalism, since males and maternal females easily out-compete non-maternal females for shelter, and adults out-compete juveniles. These findings may have implications for P. clarkii aquaculture and general management.

Maternal aggression and post‐hatch care in red swamp crayfish, Procambarus clarkii (Girard): The influences of presence of offspring, fostering, and maternal molting

A series of experiments investigated aspects of maternal aggression and care in brooding (tending hatched juveniles) red swamp crayfish (Procambarus clarkii),using a resident‐intruder paradigm. In Experiment 1, maternal female residents won a significantly higher proportion of aggressive encounters than did intruding Form I males. When separated from ones brood for 24 hr, this maternal status effect disappeared, but both maternal care and a significant reproductive status effect reappeared upon reunion. Experiment 2 revealed that maternal care is provided for a brood other than ones own (i.e., fostering) and even after a maternal phase molt. Experiments 3 and 4 demonstrated a significant maternal resident contest outcome advantage against non‐maternal female intruders, and post‐molt maternal care and aggression. Also, there was a continuation of heightened aggression even briefly after other aspects of maternal care had ceased. These effects of presence of brood on contest outcome, fostering, and post‐m...

The Relationship Between Sex and Aggression in Convict Cichlids (Cichlasoma Nigrofasciatum Günther)

C. nigrofasciatum have been widely used as a preparation in the investigation of aggressive (threat/attack) behavior because of their reputation as a highly aggressive species. They have also frequently been used in studies of learning processes, especially habituation. The reproductive and aggressive behaviors of the family Cichlidae have been described extensively, however, the sexual behavior of C. nigrofasciatum has been treated only cursorily. Several investigators have postulated a mutually inhibitory relationship between sex and aggression such that any decrease in the level of one of these motivational states results in an increase in the level of the other. In order to test this hypothesized relationship between sex and aggression, male and female C. nigrofasciatum were exposed to either male or female stimulus fish for 24 consecutive hours. In the present investigation, performance of sexual behavior was found to inhibit performance of aggressive behavior and vice versa. A principle components statistical analysis was performed in order to reduce the number of dependent variables to a smaller number of underlying clusters of variables referred to as factors. The principle components analysis indicated that the data were characterized by two orthogonal factors, the first of which reflected qualitative differences between the sex and aggression variables, suggesting that a mutually inhibitory relationship exists between sex and aggression. Discriminant analyses indicated that females initiate courtship and perform more aggressive behaviors than males, males elicit more aggression than females, opposite sex dyads perform more sexual behaviors than same sex dyads, and same sex dyads perform more aggressive behaviors than opposite sex dyads. Habituation of aggression was demonstrated in all dyads. Significant decrements in sexual behaviors were not observed.

Modulation of Aggressive Behavior in Fish by Alcohol and Congeners

Studies of alcohol and congener effects on the aggressive behavior of fish have been reviewed. It is clear that alcohol has both depressing effects at very low and very high doses and a facilitating effect at moderate doses. Congener effects as they are present in bourbon and in rum appear to have aggression-inhibiting effects. A study of the most prevalent congener in rum and some bourbons, acetaldehyde, demonstrated that it is psychoactive and has a depressing effect on aggressive behavior at doses that do not cause locomotor decrements.

Chlordiazepoxide (librium)-induced changes in intraspecific attack and selected non-agonistic behaviors in male siamese fighting fish

Two experiments were undertaken to determine the effects of chlordiazepoxide on intraspecific attack behavior and selected non-aggressive behaviors in male Siamese fighting fish. In Exp. 1, pairs of fish fought while immersed in either 15 Μg/ml or 30 Μg/ml of chlordiazepoxide, or plain water. The drug groups showed significantly less attack (e.g., biting, jawlocking) than the control group, without noticeable behavioral toxicity. Also, in the drug groups alone, some variants of the copulatory clasp, seen in normal mating, occurred in many pairs. In Exp. 2, individual fish were isolated in one of the same doses or plain water for a period equivalent to that of Exp. 1. These doses produced no changes in measures of arousal, locomotion, and feeding behavior, as compared to the control condition. The drugrelated appearance of the intermale mating-like behavior is discussed in terms of a theoretical formulation postulating a mutually inhibitory relationship between sex and aggression in fish.

Pleasure travel (tourist) motivation: A factor analytic approach

The major motives underlying pleasure travel were investigated by factor-analyzing Figler’s Travel Motivation Survey, which is based on a variety of motives for pleasure travel suggested in the tourism literature. This questionnaire was administered to 325 subjects. The data analysis uncovered five orthogonal factors, which together accounted for 46.6% of the total response variance. The five factors, as well as the percentage of variance accounted for by each one, were as follows: anomie/authenticity-seeking (20.1%), culture/education (9.6%), escape/regression (7.4%), wanderlust/exploring the unknown (5.1%), and jetsetting/prestige-seeking (4.4%). The test-retest reliability of each factor was also established. These data empirically support some of the notions proposed in previous travel literature, although past studies have usually focused on only a few motives, have been nonquantified, and/or have not provided data on the relative importance of each motive. The present data quantitatively revealed a hierarchy of independent motives underlying pleasure travel.

Experimentally produced prior residence effect in male convict cichlids: The role of initial proximity to territorial markers

Investigating the effects of initial proximity to territorial markers on experimentally produced prior residence effects, 16 pairs of male convict cichlids were randomly assigned to two treatment conditions: a nonreversal condition where the natural resident was closest to the territorial markers at the onset of the encounter, or a reversal condition where the intruder had initially closer proximity to these cues. Results showed that the proximity variable did not change the relative frequency of dominance by the natural resident. The relative frequency of natural residents biting first was also not affected by the proximity variable. As in past studies, the natural residents significantly dominated over intruders, and bit first more frequently, with biting first being a reliable predictor of eventual dominance.