Concentrations of substituted p-benzoquinones and 1-pentadecene in the flour beetles tribolium confusum J. Du Val and tribolium castaneum (herbst)

• 1.1. 2-Methyl-1,4-benzoquinone (MBQ), 2-ethyl-1,4-benzoquinone (EBQ) and 1-pentadecene (PD) concentrations in Tribolium confusum and T. castaneum were found to be extremely low in newly eclosed adults (<2.0 μg/insect). The levels of all three compounds increased with age until 20–30 days after eclosion, after which time the concentrations were maintained or declined slowly.
• 2.2. In 30-day and older adults, females of both species routinely contained higher levels of MBQ, EBQ and PD than males of the same age.
• 3.3. Each 30-day adult T. confusum or T. castaneum contained 35–46 μg substituted p-benzoquinone plus 14–24 μg PD.
• 4.4. The odoriferous secretion of 30-day adults had a p-benzoquinone composition of 44% MBQ and 56% EBQ for T. confusum and 50–51% MBQ and 49–50% EBQ for T. castaneum.

     

Density-related mortality of the flour beetle,Tribolium confusum duval

Life tables were constructed to assess the relative importance of some factors causing mortality of Tribolium confusum and to gauge their response to increasing population density. Observations focussed on three population densities (100, 400 and 800 individual/8 g medium) from the egg to the adult stage. The medium was not renewed in order to maximize predatory interactions. Generation mortality at densities 100, 400 and 800 was 42%, 50% and 74% respectively, i. e. density-dependent. Mortality in the first 10 days was also density-dependent reaching a maximum of 27% at density 800: predation by small larvae on eggs seemed the principal causative factor. The overall pattern of larval mortality was density-independent. Data on the mortality of pupae and callows were ultimately consistent with an inversely density-dependent pattern. Apparently, only mortality occurring within the first 10 days was capable of population regulation.     

Circadian oxygen consumption rhythm of the flour beetle, Tribolium confusum

Oxygen consumption is circadian (about 24 hr) rhythmic in sterilized Tribolium confusum adults kept on a 12 hr light-12 hr dark regimen. High values for oxygen consumption occur shortly after ‘light-on’ and low ones at the beginning of the dark span. When the light-dark cycle is advanced by 6 hr, the oxygen consumption rhythm is phase-shifted within about 6 days; with a delay of the light-dark schedule (a return to the initial regimen) the oxygen consumption rhythm re-adjusts in 3 days. This directedness or polarity of the phase-shift adjustment constitutes a quantitative circadian system characteristic shared by organisms studied thus far.     

Selection for high and low amylase activity in adult flour beetles (Tribolium confusum) (Coleoptera,Tenebrionidae)

As a result of selection for high amylase activity in two strains of the flour beetle Tribolium confusum, mean activity considerably increased. Selection for low activity was ineffective in one strain, and mean activity increased, contrary to expectation, in the downward-selection line of the other.Heritabilities of amylase activity were 0.52 and 0.18 for the two strains (estimated by offspring-midparent regression in generation 1). Environmental factors have considerable effects on activity.The outcome of selection and possible models for the genetic control of amylase activity in Tribolium are discussed.     

Hormonal responses to female conspecifics in hyperprolactinemic male rats and mice

Exposure to a female results in an acute release of LH and testosterone (T) in normal male rats and mice. This study was conducted to determine whether these hormonal responses are altered in hyperprolactinemic (hyperPRL) male rats in which copulatory behavior is known to be suppressed and in hyperPRL male mice in which it is not. Adult male CDF (F-344) rats were made hyperPRL either by grafting of three anterior pituitaries under the kidney capsule or by treatment with diethylstilbestrol (DES). Exposure of control males to receptive females for 10-15 min produced the expected two- to fourfold statistically significant elevations in plasma LH levels. In contrast, plasma LH levels in pituitary grafted or DES-treated males were not altered by female exposure. Male mice were pituitary grafted (two pituitaries per recipient) or sham-operated and housed individually with a female for 1 week. The resident females were then replaced with novel females in half of the cages and blood samples were taken from the males after 5 min exposure for determination of LH levels or after 45-60 min exposure for T levels. Female-induced LH and T elevations occurred in both hyperPRL and control groups. Failure of hyperPRL male rats to experience an increase in plasma LH levels in response to a female suggests abnormality of mechanisms controlling LHRH release. Suppression of LHRH release may be involved also in the induction of deficits of sexual behavior in these animals.     

Physiological bases of genetic differences in cannibalism behavior of the confused flour beetle Tribolium confusum

Physiological causes of genetic differences in cannibalism were examined to gain a better understanding of constraints on behavior evolution. Cannibalism has complex population level consequences in Tribolium confusum, including dramatic effects on population size. Laboratory strains with low and high cannibalism rates, obtained through inbreeding, have maintained distinct levels of cannibalism for over two decades even in the absence of artificial selection to maintain the differences. Why strains differ in their cannibalism rates was examined by measuring: (1) the nutritional benefit from cannibalism in both nutritionally good and poor environments, and (2) the possibility that eggs are an important source of water. How strains achieve differences in cannibalism was examined by testing for differences between strains in their ability to find eggs and in their tendency to eat eggs. Beetles from both strains survive equally well in a nutritionally good environment, but they accomplish this in different ways. The low cannibalism strain has high survivorship with and without cannibalism. The high cannibalism strain has low survivorship when not fed eggs and survivorship equivalent to the low cannibalism strain when fed eggs, suggesting it compensates for poor nutritional adaptation by eating eggs. The strains also differ in feeding behavior; beetles from the high cannibalism strain have a higher appetite for eggs. Beetles from the two strains did not differ in locomotor activity, search efficiency, or need for water. The observed behavioral and nutritional differences may contribute to the maintenance of different levels of cannibalism.     

Social facilitation of male song by male and female conspecifics in the zebra finch, Taeniopygia guttata

Zebra finches are a ubiquitous model system for the study of vocal learning in animal communication. Their song has been well described, but its possible function(s) in social communication are only partly understood. The so-called ‘directed song’ is a high-intensity, high-performance song given during courtship in close proximity to the female, which is known to mediate mate choice and mating. However, this singing mode constitutes only a fraction of zebra finch males’ prolific song output. Potential communicative functions of their second, ‘undirected’ singing mode remain unresolved in the face of contradicting reports of both facilitating and inhibiting effects of social company on singing. We addressed this issue by experimentally manipulating social contexts in a within-subject design, comparing a solo versus male or female only company condition, each lasting for 24 h. Males’ total song output was significantly higher when a conspecific was in audible and visible distance than when they were alone. Male and female company had an equally facilitating effect on song output. Our findings thus indicate that singing motivation is facilitated rather than inhibited by social company, suggesting that singing in zebra finches might function both in inter- and intrasexual communication.     

Attraction and transport of male gametes for fertilization

 Two capabilities are critical in attracting and transporting male gametes for fertilization: (1) the pollen tube must locate, enter and discharge its contents at the correct site within the female gametophyte, and (2) once inside the embryo sac, the non-motile male gametes must be transported to the egg and the central cells for double fertilization. This review summarizes current information about evidence for communication between embryo sac and pollen tube and the means by which the non-motile male gametes are transported from the aperture of the pollen tube to the site of gamete fusion. Received: 6 June 1996 / Revision accepted: 9 July 1996     

Discrimination by male ring-tailed Lemurs (Lemur catta) between the scent marks of male and those of female conspecifics

Olfaction plays an important role in the social communication of all prosimians. (The experiment reported in this paper forms part of an intensive chemobehavioral study of olfaction in Lemur catta (ring-tailed lemur) being carried out in this laboratory.) Five male Lemur cattawere tested on their behavioral responses to paired scent stimuli. Responses measured were (1) total investigation time, (2) arm-marking, (3) ABO/BO rubbing, and (4) flehmen. Males showed a strong discrimination between the scent stimuli,giving higher levels of response to female scent on measures 1, 3, and 4. This response suggests an olfactory-related preference by males for female scent under controlled conditions. This preference may be a consequence of the females’ dominance over males and the brevity of estrus in L. catta,both of which would favor such choice behavior.     

Persistent conditioned place preference to aggression experience in adult male sexually‐experienced CD‐1 mice

We recently developed a conditioned place preference (CPP) procedure, commonly used to study rewarding drug effects, to demonstrate that dominant sexually‐experienced CD‐1 male mice form CPP to contexts previously associated with defeating subordinate male C57BL/6J mice. Here we further characterized conditioned and unconditioned aggression behavior in CD‐1 mice. In Exp. 1 we used CD‐1 mice that displayed a variable spectrum of unconditioned aggressive behavior toward younger subordinate C57BL/6J intruder mice. We then trained the CD‐1 mice in the CPP procedure where one context was intruder‐paired, while a different context was not. We then tested for aggression CPP 1 day after training. In Exp. 2, we tested CD‐1 mice for aggression CPP 1 day and 18 days after training. In Exp. 3–4, we trained the CD‐1 mice to lever‐press for palatable food and tested them for footshock punishment‐induced suppression of food‐reinforced responding. In Exp. 5, we characterized unconditioned aggression in hybrid CD‐1 × C57BL/6J D1‐Cre or D2‐Cre F1 generation crosses. Persistent aggression CPP was observed in CD‐1 mice that either immediately attacked C57BL/6J mice during all screening sessions or mice that gradually developed aggressive behavior during the screening phase. In contrast, CD‐1 mice that did not attack the C57BL/6J mice during screening did not develop CPP to contexts previously paired with C57BL/6J mice. The aggressive phenotype did not predict resistance to punishment‐induced suppression of food‐reinforced responding. CD‐1 × D1‐Cre or D2‐Cre F1 transgenic mice showed strong unconditioned aggression. Our study demonstrates that aggression experience causes persistent CPP and introduces transgenic mice for circuit studies of aggression.     

Within-group cannibalism by adult male chimpanzees

In the Mahale Mountains National Park, Tanzania, a young adult male chimpanzee was observed to feed on a 3-month-old male infant of the same unit-group. Four other adult males and an adult female shared the carcass. The mother of the victim had immigrated from a neighboring unit-group four years previously. Circumstantial evidence strongly suggests that the first-observed cannibal male also killed the infant. The adult male and the mother of the victim had been familiar socially and sexually with each other since the female immigrated. Since the mother of the victim had usually been ranging in the peripheral part of the unit-group's range, i.e., the overlapping area of the two unit-group's ranges during pregnancy and soon after birth, the infanticidal male might have had reason to suspect the paternity of her infant. Four such cases of within-group cannibalism by adult males suggest that the female range and association pattern before and after parturition are key factors allowing an infant to survive. The possibility of male-biased infanticide is also discussed.     

Molecular evidence for single Wolbachia infections among geographic strains of the flour beetle Tribolium confusum.

Infections with the rickettsial microorganism Wolbachia are cytoplasmically inherited and occur in a wide range of insect species and several other arthropods. Wolbachia infection often results in unidirectional cytoplasmic incompatibility (CI): crosses between infected males and uninfected females are incompatible and show a reduction of progeny or complete inviability. Unidirectional CI can also occur when males harbouring two incompatible Wolbachia strains are crossed with females infected with only one of the two strains. In the flour beetle Tribolium confusum, Wolbachia infections are of particular interest because of the severity of incompatibility. Typically, no progeny results from the incompatible cross, whereas only partial incompatibility is observed in most other hosts. Werren et al. (1995a) reported that Wolbachia infections in T. confusum consist of two bacterial strains belonging to distinct phylogenic groups, based on PCR amplification and sequence analysis of the bacterial cell division gene ftsZ. However, Fialho & Stevens (1996) showed that eight strains of T. confusum were infected with a single and common incompatibility type. Here we report analysis of the ftsZ gene by specific PCR amplification. Diagnostic restriction enzyme assays revealed no evidence of double infections in 11 geographic strains of T. confusum, including the strain examined by Werren et al. (1995a). Further, sequence analysis of the Wolbachia ftsZ gene and an internal transcribed spacer (ITS) region in two of these strains displayed no nucleotide variation or evidence of polymorphisms. Results suggest that T. confusum is infected with B-group Wolbachia only.     

Attraction of male winterform pear psylla to female-produced volatiles and to female extracts and evidence of male–male repellency

Pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae), is a major pest of commercial pears in North America and Europe. Olfactometer trials have shown that males of both the summer and winter morphotype are attracted to female-infested host material. Additional work with the summer morphotype has shown that males are attracted to females even in the absence of the host plant, which is evidence that female C. pyricola produce a volatile sex attractant. Here, we describe similar results with the winterform, confirming for this morphotype that the female psylla rather than the infested host material is the source of the attractant. Male winterforms displayed attraction to odors from live females in the absence of the host plant, freshly killed females, and female whole body extracts. The female whole body extracts were at least as attractive as a comparable number of live females, suggesting that we were successful at extracting the components of the attractant with this procedure. All previous olfactometer trials with C. pyricola used the insect as the attractant source; the current study is the first to demonstrate that volatile chemicals isolated from the female insect were attractive to male conspecifics. Winterform males were also assayed to odors produced by conspecific males. We found that male psylla avoided volatile odors from live males, freshly killed males, or whole body extracts of males. To our knowledge, these results are the first indication that males of any member of the Psyllidae avoid odors associated with conspecific males.