Phosphorylated Carboxy Terminal Serine Residues Stabilize the Mouse Gap Junction Protein Connexin45 Against Degradation

Phosphoamino acid analysis of mouse connexin45 (Cx45) expressed in human HeLa cells revealed that phosphorylation occurred mainly at serine residues, but also on tyrosine and threonine residues. To characterize the role of Cx45 phosphorylation, different serine residues of the serine-rich carboxy terminal region were deleted or exchanged for other amino acids residues. Human HeLa cells deficient in gap junctional intercellular communication were stably transfected with appropriate constructs and analyzed for expression, localization, phosphorylation, formation of functional gap junction channels and degradation of mutant Cx45. After exchange or deletion of nine carboxy terminal serine residues, phosphorylation was decreased by 90%, indicating that these serine residues represented main phosphorylation sites of mouse Cx45. The various serine residues of this region contributed differently to the phosphorylation of Cx45 suggesting a cooperative mechanism for phosphorylation. Substitution of different serine residues for other amino acids did not interfere with correct intracellular trafficking and assembly of functional gap junction channels, as shown by localization of mutant Cx45 at the plasma membrane and by dye transfer to neighboring cells. Truncated Cx45 was also weakly phosphorylated but was trapped in perinuclear locations. Dye transfer of these transfectants was similar as in nontransfected HeLa cells. The half-life of mouse Cx45 protein in HeLa cells was determined as 4.2 hr. Pulse-chase experiments with the different transfectants revealed an increased turnover of Cx45, when one or both of the serine residues at positions 381 and 382 or 384 and 385 were exchanged for other amino acids. The half-life of these mutants was diminished by 50% compared to wild type Cx45. Received: 26 September 1997/Revised: 5 January 1997     

INTERSPECIFIC RECOGNITION AND DISCRIMINATION BASED UPON OLFACTORY CUES IN NORTHERN SWORDTAILS

Female Xiphophorus montezumae were attracted to olfactory cues from conspecific and heterospecific (X. cortezi and X. nigrensis) males when given a choice between the stimulus and water. When given a choice between conspecific and heterospecific cues, females only demonstrated a strong preference for the conspecific stimulus when it was matched against X. nigrensis. Female X. nigrensis were attracted to olfactory cues from their close relative, X. cortezi, but did not respond to cues from the more distantly related X. montezumae. They preferred the scent of their own males to the olfactory cues of both heterospecific species. Our results indicate that X. cortezi and X. nigrensis share an apomorphic change in some aspect of their olfactory cue-receiver system that is not shared with X. montezumae. We also uncovered an asymmetry in response based on olfactory stimuli in these fishes: X. montezumae is moderately attracted to the cue from X. nigrensis, whereas X. nigrensis does not respond to the cue from X. montezumae at all.     

The Landscape Game: A learning tool demonstrating landscape design principles

Summary A board game was developed for use in workshops to demonstrate some theoretical principles underpinning conservation planning at the landscape scale. The game is based on neutral landscape models and demonstrates the effects of habitat removal and arrangement on landscape connectivity for organisms with different mobility characteristics. This paper briefly describes the ecological principles underpinning the game, the equipment required to run a game session, and the rules of the game. The game was piloted in three workshops where it was played by a total of 75 people, primarily extension personnel. It proved to be an effective learning tool that was adopted by a number of the participants for their own communication activities.     

Inhibition of development of anti-predator morphology in the small cladoceran Bosmina by an insecticide: impact of an anthropogenic chemical on prey–predator interactions

1. The combined effect of the insecticide carbaryl and the predator (Leptodora kindtii) kairomone was assessed on the development of protuberant morphology in the small cladoceran Bosmina fatalis, a feature which evolved originally as a response to the kairomone. The experiment showed that Bosmina changed its morphology in response to the kairomone, but development was inhibited by carbaryl at a sub‐lethal concentration even in the presence of the kairomone. At the same time, reduction of fecundity was observed in animals exposed to carbaryl. 2. A short‐term feeding experiment (B. fatalis versus Leptodora) indicated that such low concentrations of the insecticide had no impact on predation by Leptodora. Thus, it is suggested that the inhibition of development of anti‐predatory defences in Bosmina can increase its vulnerability to predation. 3. Such disturbance of chemical communication by the insecticide reduces the individual survival rate of prey Bosmina in the environment with high predator density. On the other hand, reduction of fecundity may result in decreased population growth rate of animals. 4. The impact of the insecticide on the anti‐predator morphology in Bosmina (inhibition) was opposite to that in Daphnia (enhancement). This suggests that biochemical induction processes in the development of anti‐predatory morphology are evolutionally different between Daphnia and Bosmina.     

Olfactory responses to steroids in an African mouth-brooding cichlid, Haplochromis burtoni(Günther)

Underwater electro‐olfactogram (EOG) recordings involving 150 steroids and eight prostaglandins were used to determine which of these potential odorants are detected by the olfactory organ of an African cichlid, Haplochromis burtoni. In initial EOG tests at 10^?9 M, H. burtoni did not respond to unconjugated steroids or prostaglandins, but did respond to 17 conjugated steroids, 11 of which (17β‐oestradiol‐17β‐glucuronide; 17β‐oestradiol‐3‐sulphate; 17β‐oestradiol‐3,17β‐disulphate; epiandrosteron‐3β‐sulphate; etiocholanolone‐3α‐glucuronide; testosterone‐17β‐sulphate; dehydroepiandrosterone‐3β‐sulphate; 5α‐pregnan‐3β‐ol‐20‐one‐3β‐sulphate; 5β‐pregnan‐3α,17‐diol‐20‐one‐3α‐glucuronide; 5β‐pregnan‐3α,17,21‐triol‐11,20‐dione‐3α‐glucuronide; pregnenolone‐3β‐sulphate) were selected for EOG concentration‐response, cross‐adaptation and binary mixture tests. The EOG detection thresholds ranged from 10^?11 to 10^?9 M in all but one instance (female threshold to pregnenolone‐3β‐sulphate; 10^?8 M), and males and females exhibited only minor differences in EOG threshold or response magnitude. Results of EOG cross‐adaptation tests, which were supported by results of binary mixture tests, indicated that the response to the 11 steroid conjugates is mediated by five putative olfactory receptor mechanisms characterized by specificity for conjugate position and type: 3‐sulphate, 17‐sulphate, 3,17‐disulphate, 3‐glucuronide, 17‐glucuronide. Although there is no evidence that H. burtoni releases, or exhibits biological response to, the steroids shown to be detected in this study, the present results are suggestive of a complex pheromone system utilizing steroid conjugates.     

The development of butterfly settling posture: the role of predators, climate, hostplant-habitat and phylogeny

A model is described that explains the evolution of adult butterfly settling posture. The role of climate and the activity of butterflies is fundamental in determining the effectiveness of primary and secondary visual defence systems based on wing colour and pattern. Both dorsal (open winged) and lateral (closed wing) postures can be regarded as evolutionarily conservative; common postures are found within almost all sub-families. Lateral postures tend to be associated with cool temperate and arctic climates. Conditions that are marginal for activity place an emphasis on the development of underside primary defence, uncompromised by secondary visual defences. In turn, any primary defensive function of the upper surface is reduced but secondary defence may be emphasized. There is interaction between segregation of functions on different wing surfaces and the development of lateral posture. The use of predictable hostplant-habitat structures reduces the role of visual communication in mate-location and facilitates the adoption of a lateral resting posture and a cryptic underside wing pattern. When hostplant-habitat structures are unpredictable but a lateral posture is adopted, primary defence is more important than visual communication for the resting insect. Adjustments of wing morphology facilitate postural conservatism, allowing species to retain particular postures in new hostplant-habitats and climatic zones.     

THE ROLE OF COURTSHIP SONGS IN REPRODUCTIVE ISOLATION AMONG POPULATIONS OF GREEN LACEWINGS OF THE GENUS CHRYSOPERLA (NEUROPTERA: CHRYSOPIDAE)

Male and female lacewings tremulate during courtship, establishing duets that always precede copulation. Three distinct courtship songs are found in populations of the green lacewing Chrysoperla plorabunda (P1, P2 and P3 song morphs). Analysis of five features of the songs for individuals collected from Connecticut, Idaho, Oregon and California showed few differences within song morphs, but sympatric song morphs differed significantly in temporal features of the songs and their mode of presentation. Playback experiments using recorded songs were performed on females with all possible sympatric and allopatric combinations of females and recorded songs. The results showed that females strongly prefer to duet with recordings of males of their own song type and usually showed no responses to songs of other types. Thus, song differences are effective barriers to reproduction between the sympatric morphs. Our results support the hypothesis that the three song morphs are true biological species.     

Olfactory Associative Learning of the Pupal Parasitoid Pimpla luctuosa Smith (Hymenoptera: Ichneumonidae)

Laboratory experiments were conducted to determine the role of learning in olfactory host searching by the ichneumonid pupal parasitoid, Pimpla luctuosa Smith. Females learned to associate novel odors such as vanilla and strawberry with hosts when they oviposited in at least several hosts with the odors. Repeated experiences of hosts with an odor increased the response of the experienced odor, and females that had experienced host odor seven times responded to the experienced odors 90% of the time. Although the response by females to a learned odor gradually decreased with increasing host-deprivation time, 60% of the females that had experienced host odor 7 days earlier still responded to the experienced odor. Females also learned two separate odors associated with hosts at a time and responded to both odors without a preference for one odor over the other. When trained two separate odors with hosts, females learned the second odor more quickly than the first odor. After females experienced several stings in simulated hosts with the previously learned odor, they ceased to respond to the learned odor, suggesting that repeated unrewarding experiences cause females to cease to respond to the learned odors.     

The Significance of Odor Cues and Dance Language Information for the Food Search Behavior of Honeybees (Hymenoptera: Apidae)

Although several independent lines of evidence show that bees can make use of information provided by their dance language, there is an ongoing controversy about the significance of the dance information versus odor cues in the search behavior of recruited bees. A series of experiments was performed to assess the relative significance of dance information and odors for the site-specific search of recruit bees. In these experiments recruit bees were trapped automatically at arrays of artificial flowers at various distances from the hive. The distribution of directions in which the recruits searched for food was compared between recruitment by dancers performing well-oriented dances on the vertical side of the comb and dancers performing disoriented dances on a horizontal comb. The results show quantitatively that bees use both odor cues and the dance information. The greater the distance to the feeding site, the greater is the relative significance of the dance information.