ABSTRACT
Four choice experiments were conducted with both sexes of the cichlid Pelvicachromis taeniatus using computer-manipulated stimuli of digital images differing in movement, body shape or colouration. The results show that computer animations can be useful and flexible tools in studying preferences of a cichlid with complex and variable preferences for different visual cues.
Subject(s)
Cichlids/physiology , Computers , Mating Preference, Animal/physiology , Zoology/methods , Animals , Color , Female , Male , Random Allocation , Video Recording , Zoology/instrumentationABSTRACT
The hut(P) region (i.e., the region responsible for regulation of hutUH expression) of the Klebsiella aerogenes histidine utilization (hut) operons contains a bidirectional promoter. One transcript from this promoter encodes the hutUH operon; the role of the oppositely directed transcript is unknown, although it appears to be involved in regulating hutUH expression (A.J. Nieuwkoop, S.A. Boylan, and R.A. Bender, J. Bacteriol. 159:934-939, 1984). A 247-base-pair (bp) fragment containing hut(P) carries two RNA-polymerase-binding sites agree with the start sites of the two transcripts produced from hut(P) DNA in vitro and in vivo. The binding sites share a 4-bp region, suggesting that occupancy of the regulatory site precludes occupancy of the hutUH promoter, and vice versa. In the absence of positive effectors, the binding to the site responsible for hutUH transcription is weaker than the binding to the site responsible for regulation. The nucleotide sequence of the 250-bp fragment containing hut(P) contains two possible matches to the consensus sequence for Escherichia coli promoters, a better and worse match, corresponding in position to the stronger and weaker RNA-polymerase-binding sites, respectively. The sequence also contains a region similar to the consensus sequence for binding of the catabolite gene activator protein of E. coli. A sequence similar to the consensus for Ntr-dependent promoters was also found, overlapping both RNA-polymerase-binding sites, but it is not a functional promoter. Finally, an initiation codon preceded by a Shine-Dalgarno consensus sequence and followed by an open reading frame identifies a probable start of the hutU gene coding sequences.
