bluuebunny/crossref_metadata_2025 huggingface dataset:
Human umbilical vein endothelial cells generate leukotriene C4 via microsomal glutathione S‐transferase type 2 and express the CysLT1 receptor
Authors: Sjöström Mattias , Jakobsson Per‐Johan , Heimburger Mikael , Palmblad Jan , Haeggström Jesper Z.
Published: March 2003

Certain immunocompetent myeloid cells, such as eosinophils, basophils and mast cells, have a large capacity to synthesize the potent proinflammatory and spasmogenic mediator leukotriene (LT) C4 via a specific microsomal glutathione S‐transferase (MGST) termed LTC4 synthase (LTC4S). Here, we report that MGST2, a distant homologue of LTC4S, is abundantly expressed in Human umbilical vein endothelial cells (HUVEC) and converts LTA4 into a single product, LTC4. Thus, using Northern blot, RT‐PCR, Western blot, and enzyme activity assays, we show that MGST2 is the main, if not the only, enzyme that converts LTA4 into LTC4 in membrane preparations of HUVEC. In fact, we failed to detect any expression of LTC4S, MGST1 or MGST3 in these cells, indicating that MGST2 is a critical enzyme for transcellular LTC4 biosynthesis in the vascular wall. Unlike LTC4S, MGST2 prefers the naturally occurring free acid of LTA4 over the methyl ester as substrate and is also susceptible to product inhibition with an IC50 of about 1 µm for LTC4. Moreover, HUVEC were found to express the CysLT1 receptor in line with a paracrine and autocrine role for cysteinyl‐leukotrienes in endothelial cell function.
Pfnek‐1, a NIMA‐related kinase from the human malaria parasite Plasmodium falciparum
Authors: Dorin Dominique , Le Roch Karine , Sallicandro Pina , Alano Pietro , Parzy Daniel , Poullet Patrick , Meijer Laurent , Doerig Christian
Published: March 2003

We have cloned Pfnek‐1, a gene encoding a novel protein kinase from the human malaria parasite Plasmodium falciparum. This enzyme displays maximal homology to the never‐in‐mitosis/Aspergillus (NIMA)/NIMA‐like kinase (Nek) family of protein kinases, whose members are involved in eukaryotic cell division processes. Similar to other P. falciparum protein kinases and many enzymes of the NIMA/Nek family, Pfnek‐1 possesses a large C‐terminal extension in addition to the catalytic domain. Bacterially expressed recombinant Pfnek‐1 protein is able to autophosphorylate and phosphorylate a panel of protein substrates with a specificity that is similar to that displayed by other members of the NIMA/Nek family. However, the FXXT motif usually found in NIMA/Nek protein kinases is substituted in Pfnek‐1 by a SMAHS motif, which is reminiscent of a MAP/ERK kinase (MEK) activation site. Mutational analysis indicates that only one of the serine residues in this motif is essential for Pfnek‐1 kinase activity in vitro. We show (a) that recombinant Pfnek‐1 is able to specifically phosphorylate Pfmap‐2, an atypical P. falciparum MAPK homologue, in vitro, and (b) that coincubation of Pfnek‐1 and Pfmap‐2 results in a synergistic increase in exogenous substrate labelling. This suggests that Pfnek‐1 may be involved in the modulation of MAPK pathway output in malaria parasites. Finally, we demonstrate that recombinant Pfnek‐1 can be used in inhibition assays to monitor the effect of kinase inhibitors, which opens the way to the screening of chemical libraries aimed at identifying potential new antimalarials.
Structure of the H subunit of the photosynthetic reaction center from the thermophilic purple sulfur bacterium, Thermochromatium tepidum
Authors: Fathir Insan , Mori Takayuki , Nogi Terukazu , Kobayashi Masayuki , Miki Kunio , Nozawa Tsunenori
Published: March 2003

The photosynthetic reaction center (RC) is a transmembrane protein complex that catalyzes light‐driven electron transport across the photosynthetic membrane. The complete amino‐acid sequence of the H subunit of the RC from a thermophilic purple sulfur bacterium, Thermochromatium tepidum, has been determined for the first time among purple sulfur bacteria. The H subunit consists of 259 amino acids and has a molecular mass of 28 187. The deduced amino‐acid sequences of this H subunit showed a significant (40%) degree of identity with those from mesophilic purple nonsulfur bacteria. The determined primary structure of the H subunit was compared with the structures of mesophilic B. viridis and R. sphaeroides based on the three‐dimensional structure of the H subunit from T. tepidum, which has been recently determined by X‐ray crystallography. One lipid molecule was found in the crystal structure of the T. tepidum RC, and the head group of the lipid appears to be stabilized by the electrostatic interactions with the conserved basic residues in the H subunit. The above comparison has suggested the existence of a lipid‐binding site on the molecular surface at which a lipid molecule can interact with the RC in a specific manner.
Identification and molecular structural prediction analysis of a toxicity determinant in the Bacillus sphaericus crystal larvicidal toxin
Authors: Yuan Zhiming , Rang Cécile , Maroun Rachid C. , Juárez‐Pérez Victor , Frutos Roger , Pasteur Nicole , Vendrely Charlotte , Charles Jean‐François , Nielsen‐LeRoux Christina
Published: March 2003

The operon containing the genes encoding the subunits of the binary crystal toxin of Bacillus sphaericus strain LP1‐G, BinA and BinB (41.9 kDa and 51.4 kDa, respectively), was cloned and sequenced. Purified crystals were not toxic to Culex pipiens larvae. Comparison of the amino‐acid sequences of this strain (Bin4) with those of the three other known toxin types (Bin1, Bin2 and Bin3) revealed mutations at six positions, including a serine at position 93 of BinA4, whereas all other types of BinA toxin from B. sphaericus had a leucine at this position. Reciprocal site‐directed mutagenesis was performed to replace this serine in BinA4 from LP1‐G with a leucine and the leucine in the BinA2 protein from strain 1593 with a serine. Native and mutated genes were cloned and overexpressed. Inclusion bodies were tested on C. pipiens larvae. Unlike the native Bin4 toxin, the mutated protein was toxic, and the reciprocal mutation in Bin2 led to a significant loss of toxicity. In vitro receptor‐binding studies showed similar binding behaviour for native and mutated toxins. In the absence of any experimental data on the 3D structure of these proteins, sequence analysis and secondary‐structure predictions were performed. Amino acid 93 of the BinA polypeptide probably belongs to an α helix that is sensitive to amino‐acid modifications. Position 93 may be a key element in the formation of the BinA–BinB complex responsible for the toxicity and stability of B. sphaericus Bin toxins.
Expression of placental leucine aminopeptidase/oxytocinase in neuronal cells and its action on neuronal peptides
Authors: Matsumoto Hideko , Nagasaka Tetsuro , Hattori Akira , Rogi Tomohiro , Tsuruoka Nobuo , Mizutani Shigehiko , Tsujimoto Masafumi
Published: March 2003

The placental leucine aminopeptidase (P‐LAP)/oxytocinase whose serum level increases with gestation is thought to contribute to the maintenance of normal pregnancy. P‐LAP mRNAs are expressed in various tissues other than the placenta. In this study, we identified P‐LAP protein in the brain. In contrast with the placenta where a significant portion of P‐LAP is released, the enzyme was localized in the membrane fraction in brain and PC12 cells and no soluble form of the enzyme was detected. When PC12 cells were differentiated into neuronal cells by nerve growth factor (NGF), a significant increase in the expression level of P‐LAP in the cell was observed. As in the case of insulin treatment of 3T3‐L1 adipocytes, treatment of PC12 cells with forskolin caused the translocation of the enzyme from intracellular vesicle to the cell surface plasma membrane. In addition, P‐LAP was shown to degrade several bioactive neuropeptides such as Met‐enkephalin and dynorphin A (1–8). These results suggest that P‐LAP plays an important role in the regulation of neuronal cell function in the brain.
Photoactivatable α‐conotoxins reveal contacts with all subunits as well as antagonist‐induced rearrangements in the Torpedo californica acetylcholine receptor
Authors: Kasheverov Igor , Rozhkova Anna , Zhmak Maxim , Utkin Yuri , Ivanov Vadim , Tsetlin Victor I
Published: March 2003

Azidobenzoyl (AzBz) and benzoylbenzoyl (BzBz) derivatives of α‐conotoxin MI and l‐benzoylphenylalanine (Bpa) analogs of α‐conotoxin GI were synthesized. All these compounds, similarly to native α‐conotoxins, completely displaced the radioiodinated MI or GI from the membrane‐bound nicotinic acetylcholine receptor (AChR) of Torpedo californica. However, the GI(Bpa11) analog was considerably less potent than GI in competing with radioiodinated α‐bungarotoxin (αBgt). Irradiation of iodinated AzBz derivatives bound to AChR resulted in labeling of all AChR subunits. The BzBz and Bpa derivatives gave lower levels of specific cross‐linking but considerable labeling at additional sites that was enhanced, rather than suppressed, by an excess of native α‐conotoxins or αBgt. Both equilibrium binding of benzophenone‐derivatized α‐conotoxins and their cross‐linking could be totally abolished by physostigmine. The results obtained demonstrate that (a) specific binding sites for α‐conotoxins and αBgt are overlapping but not identical, (b) each of the AChR subunits can be labeled with photoactivatable α‐conotoxins and (c) enhancement of benzophenone‐derivatized α‐conotoxins cross‐linking at additional (physostigmine‐related) sites by αBgt or GI indicates that these antagonists induce structural alterations in the AChR outside their binding sites.
Concurrent maltodextrin and cellodextrin synthesis by Fibrobacter succinogenes S85 as identified by 2D NMR spectroscopy
Authors: Matulova Maria , Delort Anne‐Marie , Nouaille Régis , Gaudet Geneviève , Forano Evelyne
Published: March 2003

1D and 2D NMR experiments were used to analyse the synthesis of various metabolites by resting cells of Fibrobacter succinogenes S85 when incubated with [1‐13C]glucose, in both extracellular and cellular media. Besides the expected glycogen, succinate, acetate, glucose‐1‐P and glucose‐6‐P, maltodextrins and cellodextrins were detected. Maltodextrins were excreted into the external medium. They were found to have linear structures with a maximum degree of polymerization (DP) of about 6 or 7 units. Cellodextrins were located in the cells (cytoplasm and/or periplasm), and their DP was ≤ 4. Both labelled (1‐13C and 6‐13C) and unlabelled maltodextrins and cellodextrins were detected, showing the contribution of carbohydrate cycling in F. succinogenes, including the reversal of glycolysis and the futile cycle of glycogen. The mechanisms of these oligosaccharide syntheses are discussed.
Mechanism of substrate inhibition in cellulose synergistic degradation
Authors: Väljamäe Priit , Pettersson Göran , Johansson Gunnar
Published: March 2003

A comprehensive experimental study of substrate inhibition in cellulose hydrolysis based on a well defined system is presented. The hydrolysis of bacterial cellulose by synergistically operating binary mixtures of cellobiohydrolase I from Trichoderma reesei and five different endoglucanases as well as their catalytic domains displays a characteristic substrate inhibition. This inhibition phenomenon is shown to require the two‐domain structure of an intact cellobiohydrolase. The experimental data were in accordance with a mechanism where cellobiohydrolases previously bound to the cellulose by means of their cellulose binding domains are able to find chain ends by lateral diffusion. An increased substrate concentration at a fixed enzyme load will also increase the average diffusion distance/time needed for cellobiohydrolases to reach new chain ends created by endoglucanases, resulting in an apparent substrate inhibition of the synergistic action. The connection between the binding properties and the substrate inhibition is encouraging with respect to molecular engineering of the binding domain for optimal performance in biotechnological processes.
Cytosolic chaperonin‐containing t‐complex polypeptide 1 changes the content of a particular subunit species concomitant with substrate binding and folding activities during the cell cycle
Authors: Yokota Shin‐ichi , Yanagi Hideki , Yura Takashi , Kubota Hiroshi
Published: March 2003

The chaperonin‐containing t‐complex polypeptide 1 (CCT) is a cytosolic molecular chaperone composed of eight subunits that assists in the folding of actin, tubulin and other cytosolic proteins. We show here that the content of particular subunits of CCT within mammalian cells decreases concomitantly with the reduction of chaperone activity during cell cycle arrest at M phase. CCT recovers chaperone activity upon resumption of these subunits after release from M phase arrest or during arrest at S phase. The levels of α, δ and ζ‐1 subunits decreased more rapidly than the other subunits during M phase arrest by colcemid treatment and recovered after release from the arrest. Gel filtration chromatography or native (nondenaturing) PAGE analysis followed by immunoblotting indicated that the α and δ subunit content in the 700‐ to 900‐kDa CCT complex was appreciably lower in the M phase cells than in asynchronous cells. In vivo, the CCT complex of M‐phase‐arrested cells was found to bind lower amounts of tubulin than that of asynchronous cells. In vitro, the CCT complex of M phase‐arrested cells was less active in binding and folding denatured actin than that of asynchronous cells. On the other hand, the CCT complex of asynchronous cells (a mixture of various phases of cell cycle) exhibited lower α and δ subunit content and lower chaperone activity than that of S‐phase‐arrested cells obtained by excess thymidine treatment. In addition, turnover (synthesis and degradation) rates of the α and δ subunits in vivo were more rapid than those of most other subunits. These results suggest that the content of α and δ subunits of CCT reduces from the complete active complex in S phase cells to incomplete inactive complex in M phase cells.
Structural basis for the inhibitory efficacy of efavirenz (DMP‐266), MSC194 and PNU142721 towards the HIV‐1 RT K103N mutant
Authors: Lindberg Jimmy , Sigurðsson Snævar , Löwgren Seved , O. Andersson Hans , Sahlberg Christer , Noréen Rolf , Fridborg Kerstin , Zhang Hong , Unge Torsten
Published: March 2003

The K103N substitution is a frequently observed HIV‐1 RT mutation in patients who do not respond to combination‐therapy. The drugs Efavirenz, MSC194 and PNU142721 belong to the recent generation of NNRTIs characterized by an improved resistance profile to the most common single point mutations within HIV‐1 RT, including the K103N mutation.

In the present study we present structural observations from Efavirenz in complex with wild‐type protein and the K103N mutant and PNU142721 and MSC194 in complex with the K103N mutant. The structures unanimously indicate that the K103N substitution induces only minor positional adjustments of the three inhibitors and the residues lining the binding pocket. Thus, compared to the corresponding wild‐type structures, these inhibitors bind to the mutant in a conservative mode rather than through major rearrangements. The structures implicate that the reduced inhibitory efficacy should be attributed to the changes in the chemical environment in the vicinity of the substituted N103 residue. This is supported by changes in hydrophobic and electrostatic interactions to the inhibitors between wild‐type and K103N mutant complexes. These potent inhibitors accommodate to the K103N mutation by forming new interactions to the N103 side chain. Our results are consistent with the proposal by Hsiou et al. [Hsiou, Y., Ding, J., Das, K., Clark, A.D. Jr, Boyer, P.L., Lewi, P., Janssen, P.A., Kleim, J.P., Rosner, M., Hughes, S.H. & Arnold, E. (2001) J. Mol. Biol.309, 437–445] that inhibitors with good activity against the K103N mutant would be expected to have favorable interactions with the mutant asparagines side chain, thereby compensating for resistance caused by stabilization of the mutant enzyme due to a hydrogen‐bond network involving the N103 and Y188 side chains.
An Observational Study of Coyote (Canis latrans) Scent‐marking and Territoriality in Yellowstone National Park
Authors: Allen Joseph J. , Bekoff Marc , Crabtree Robert L.
Published: March 2003

Free‐ranging coyotes (Canis latrans) living in neighboring packs were observed in the Lamar Valley of Yellowstone National Park, Wyoming, from Jan. to May 1997. Through direct observation, we recorded the location of coyote scent marks and information regarding the identity of the marking animal. Patterns of scent‐marking were then analyzed spatially and demographically. All of the evidence from the present study supports a strong relationship between scent‐marking and territoriality in these coyotes, and all predictions were met. A preponderance of scent marks was found in the periphery of territories. Most of those marks were raised‐leg urinations (RLUs) and forward‐lean urinations (FLUs), postures associated very strongly with males, particularly dominant individuals. Ground‐scratching was also closely associated with these types of marks and was performed more on the periphery of territories than in the interior. A complete lack of overlap of adjacent territories and very limited overlap of movements into territories fits classic definitions of territory and home range. Scent‐marking seems to be strongly associated with the establishment and maintenance of these boundaries between packs of coyotes competing for the same resources in a limited space.
Nuptial Coloration and Mate Guarding Affect Escape Decisions of Male Lizards Psammodromus algirus
Authors: Martín José , López Pilar
Published: March 2003

Males of many species show conspicuous breeding colours that are important for status signalling, but that may decrease crypsis and increase predation risk. However, prey may adjust their escape response, such that the optimal distance at which an animal starts to flee (approach distance) would be the point where the costs of staying exceed the cost of fleeing. We examined in the field the escape response of Psammodromus algirus lizards, to test the hypothesis that more conspicuous old males, showing orange nuptial coloration on most of the head, which presumably have a higher probability of being detected (i.e. increased costs of staying), have longer approach distances, independent of other environmental variables. As predicted, old brightly coloured males had significantly longer approach and flight distances than young dull males, and young males had longer ones than females. In contrast, neither the distance to the nearest refuge nor the air temperature when the lizards escaped were significantly different. In addition, although male and female lizards differed in their use of microhabitats, old and young males did not differ. We also found that old males guarding a female (i.e. increased costs of fleeing) had shorter approach distances than old males that were found alone.
The Problem of Adult Play Fighting: A Comparative Analysis of Play and Courtship in Primates
Authors: Pellis Sergio M. , Iwaniuk Andrew N.
Published: March 2003

Although play fighting, like play generally, is predominantly a feature of the juvenile phase, such behavior persists in the adults of many species. There are two major contexts in which adults engage in play fighting – with juveniles and with other adults. The least attention has been given to adult–adult play. However, one pattern that has been noted by several authors is that the most commonly occurring context of adult–adult play fighting is during courtship, and that this is more likely to occur in solitary species. Supposedly, such play could function to overcome the aggressiveness of potential pairmates unfamiliar with one another, or as a means of evaluating mate quality by one or both partners. By contrasting the presence and degree of play fighting during courtship with the degree of male–female familiarity, the hypothesis that the former is influenced by the latter is tested. Data on 35 species of primates, from 15 families, were compiled from the literature and compared using a method of independent contrasts that incorporates information on phylogenetic relationships. A significant regression was found, with the degree of male–female familiarity accounting for 40% of the variance in courtship play. Therefore, our data support the hypothesis that play fighting in courtship is influenced by male–female patterns of association. However, the data also indicate that other factors must influence the occurrence of play fighting amongst adults, not only during courtship, but also in nonsexual contexts. The broader context of adult–adult play in mammals is discussed.
The Mechanism of Replacement of Red Squirrels by Grey Squirrels: A Test of the Interference Competition Hypothesis
Authors: Wauters Luc A. , Gurnell John
Published: March 2003

Introduced American grey squirrels have replaced native red squirrels in most of the range currently occupied in Britain and northern Italy. The mechanisms of the replacement are not yet fully understood. We restated the commonly cited Interference Competition Hypothesis (ICH) that grey squirrels interfere with the behaviour of red squirrels in three possible ways: 1. by direct aggressive interactions; 2. by interrupting red squirrel mating‐chases; or 3. by forcing red squirrels to actively avoid areas intensively used by grey squirrels. We compared the activity pattern, behaviour and reproductive performance of red squirrels in two study areas in northern Italy, one with only red squirrels (control area C1), the other with both species (experimental area E1). The following predictions were tested: 1. the total time spent in both intraspecific and interspecific interactions by red squirrels increases in the experimental area; 2. most interspecific interactions are aggressive, with grey squirrels being the dominant species; 3. the proportion of breeding female red squirrels that are unsuccessful at weaning offspring increases in area E1; 4. grey squirrels take part and interfere with red squirrel mating‐chases, and thereby decrease the reproductive output of red squirrel females; 5. the activity pattern of red squirrels in the mixed‐species area is shifted with respect to that in the control area to the hours of the day during which grey squirrels show little activity; and 6. red squirrels will shift their home range (or at least their core‐area) when grey squirrel densities increase to avoid interspecific core‐area overlap.

Our results supported only the first prediction of the ICH: they failed to support all the other predictions. Moreover, the increase in the percentage of active time red squirrels spent interacting with other squirrels in the experimental study area was very small (only 1–2 min/day). Red squirrels did not avoid the woodland patches most intensively used by grey squirrels and the interspecific core‐area overlap was similar to red squirrel intraspecific core‐area overlap. This suggested that red squirrels avoided spatial overlap with grey squirrels in a similar manner as with conspecifics and that an increase in grey squirrel numbers will augment the intensity of resource competition. We therefore conclude that our results do not lend support to the Interference Competition Hypothesis and that interference competition by grey squirrels cannot explain the large‐scale replacement of red by grey squirrels that has occurred in Britain and in Piedmont.
Hiding Behaviour of Long‐tailed Macaques (Macaca fascicularis): II. Use of Hiding Places during Aggressive Interactions
Authors: Gygax Lorenz
Published: March 2003

In an observational study on captive long‐tailed macaques (Macaca fascicularis), the ability to hide was investigated in the social context of aggression. The use of five different types of hiding place during highly aggressive interactions was recorded and the choices of six different rank‐sex classes were compared using an index of attractiveness of the different types of hiding place during highly aggressive interactions. There was no significant difference between the rank‐sex classes in selection of the hiding places that could be connected with visibility: no specific location or type was preferred, either by the group as a whole or by any specific rank‐sex class. Thus long‐tailed macaques do not seem to hide shortly after aggressive interactions.
Sexual Competition, Coercive Mating and Mate Assessment in the One‐Sided Livebearer, Jenynsia multidentata: Are They Predictive of Sexual Dimorphism?
Authors: Bisazza Angelo , Manfredi Silvia , Pilastro Andrea
Published: March 2003

We investigated the mechanisms of sexual selection operating on body size in the one‐sided livebearer (Jenynsia multidentata), a small fish characterized by male dwarfism. Mating in the one‐sided livebearer is coercive: males approach females from behind and try to thrust their copulatory organ at the female genital pore. Females counter males' mating attempts by either swimming away or attacking them. We tested the hypothesis that the components of sexual selection favouring small size in males (sexual coercion) were more effective than those favouring a large size (male competition and mate choice). When alone, small males had a significantly higher success in their mating attempts than large males. The proportion of successful attempts was also positively correlated with female size. When two males competed for the same female, the large male had a significant mating advantage over the small one. With a 1 : 1 sex ratio, the large‐male mating advantage vanished because each male tended to follow a different female. Large males, however, preferentially defended large females, thus compelling small males to engage with smaller, less fecund females. Males did not discriminate between gravid and non‐gravid females, but preferred mating with larger females. This preference disappeared when males were much smaller than the female, probably in relation to the risk for the male of being eaten or injured by the female. In a choice chamber, male‐deprived females that had their sperm storage depleted remained close to males and showed a preference for large individuals, a behaviour not observed in non‐deprived females. Nonetheless, when placed with males in the same aquarium, all females showed avoidance and aggression. Struggling may represent a way by which the female assesses the skill and endurance of males.
Detection and Avoidance of Predators in White‐Tailed Deer (Odocoileus virginianus) and Mule Deer (O. hemionus)
Authors: Lingle Susan , Wilson W. Finbarr
Published: March 2003

In this paper, we investigate the relationship between early detection of predators and predator avoidance in white‐tailed deer (Odocoileus virginianus) and mule deer (O. hemionus), two closely related species that differ in their habitat preferences and in their anti‐predator behavior. We used observations of coyotes (Canis latrans) hunting deer to test whether the distance at which white‐tails and mule deer alerted to coyotes was related to their vulnerability to predation. Coyote encounters with both species were more likely to escalate when deer alerted at shorter distances. However, coyote encounters with mule deer progressed further than encounters with white‐tails that alerted at the same distance, and this was not due to species differences in group size or habitat. We then conducted an experiment in which a person approached groups of deer to compare the detection abilities and the form of alert response for white‐tails and mule deer, and for age groups within each species. Mule deer alerted to the approacher at longer distances than white‐tails, even after controlling for variables that were potentially confounding. Adult females of both species alerted sooner than conspecific juveniles. Mule deer almost always looked directly at the approacher as their initial response, whereas white‐tails were more likely to flee or to look in another direction with no indication that they pinpointed the approacher during the trial. Mule deer may have evolved the ability to detect predators earlier than white‐tails as an adaptation to their more open habitats, or because they need more time to coordinate subsequent anti‐predator defenses.
Offspring Grazing and Suckling Rates in a Sexually Dimorphic Ungulate with Biased Maternal Investment (Ammotragus lervia)
Authors: Cassinello Jorge
Published: March 2003

An analysis of resource gain is provided for Ammotragus calves during their first year of age. Both grazing and suckling rates are analysed and potential effects caused by age, sex, mother’s rank and weaning period studied. During their first day of life, calves devote their time mainly to suckling, grazing starting at the second week of age and exceeding suckling rate from the fourth week onwards. When suckling rate reaches a significant decrease (at 2 mo), male calves show a significantly higher grazing rate than female calves, suggesting a higher energetic demand for males at this age. When calves are 1 mo old, sons of high‐ranking mothers devote less time grazing than those of low‐ranking ones, which is in accordance with the higher maternal investment they receive. Grazing rate shows distinctive values for the different weaning periods distinguished in this species, but the resumption of mothers’ sexual activity, when a mother–offspring conflict occurs, does not affect grazing behaviour. These results are consistent with the biased maternal investment recently found in the same study population but focusing on another aspect, i.e. grazing behaviour, which is determined by calves’ own decisions.
Microgeographic Variation, Habitat Effects and Individual Signature Cues in Calls of ChiffchaffsPhylloscopus collybita canarensis
Authors: Naguib Marc , Hammerschmidt Kurt , Wirth Jutta
Published: March 2003

Variation of signals is a widespread feature in animal communication. Signals usually vary among signallers and in some cases vary across geographic areas. Individual variation provides the basis for individual recognition and thus has important implications for social interactions. Microgeographic variation can reveal insights into patterns of dispersal and into timing and mechanism of acquisition or development of behavioral traits. In addition, it may reflect adaptations of signals to the transmission characteristics of local habitat types. In song birds these kinds of variation have been documented in particular for male song. Here, we examined individual signature cues, site‐specific variation, and variation among habitat types in tonal contact calls of 26 chiffchaffs,Phylloscopus collybita canarensis, recorded on two Canary islands. Multiparametric analyses of calls and subsequent discriminant function analyses revealed clear individual differences as well as microgeographic variation in call structure. Call structures differed not only between islands but also among the different locations on Tenerife, indicating that individuals on the same island do not share the same call, as suggested earlier. Calls recorded in different types of habitat, however, did not differ in structure as predicted by the ‘acoustic adaptation hypothesis’. The findings indicate that individual recognition may be possible on the basis of calls and they contribute to the understanding of development of behavioural trails in relation to life history patterns such as the timing and pattern of dispersal.
State‐Dependent Mate‐Assessment and Mate‐Selection Behavior in Female Threespine Sticklebacks (Gasterosteus aculeatus, Gasterosteiformes: Gasterosteidae)
Authors: Luttbeg Barney , Towner Mary C , Wandesforde‐Smith Alix , Mangel Marc , Foster Susan A.
Published: March 2003

Most investigations of mate‐choice have focused on the outcomes of mate‐choice (i.e. which mates are chosen), and thus we generally know very little about how mates are chosen (i.e. how mates are found, assessed, and selected). Mate‐choice by females has been shown to be dependent on the state of the female, with females being less selective when limited by time or energy. This result could be caused by changes in female mate‐assessment or mate‐selection behavior. We examined whether manipulations of time and energy affected the mate‐choice behavior of female threespine stickleback (Gasterosteus aculeatus). We found that female mate‐choice behavior, when not divided into stages, was affected by both of the manipulations. This matches previous findings. When we divided female courtship behavior into six stages, we found that the two manipulations affected different portions of the mate‐choice process. The holding‐time manipulation changed female behavior at the beginning and end of the mate‐choice process and the swimming manipulation changed female behavior only at the end of the mate‐choice process. Neither of the manipulations significantly affected female behavior in the middle portion of the mate‐choice process. Thus, the mate‐choice process appears to be composed of multiple state‐dependent decisions. We discuss how a better mechanistic understanding of how female state affects female mate‐choice behavior can produce testable predictions and provide a basis for investigating the evolution of mating systems.
Yellow‐Footed Rock‐Wallaby Group Size Effects Reflect A Trade‐Off
Authors: Blumstein Daniel T. , Daniel Janice C. , Evans Christopher S.
Published: March 2003

As group size increases, individuals of many species modify the time allocated to anti‐predator vigilance and foraging. Group size effects can result from a reduction in predation risk or from an increase in competition as a function of aggregation. Anti‐predator models of vigilance and foraging group size effects both predict a non‐linear relationship between group size and time allocation. Linear relationships between group size and time allocation may reflect the modification of such relationships by intraspecific interference competition for limited resources, which would reveal a fundamental cost of sociality. We studied the degree to which group size effects in the yellow‐footed rock‐wallaby (Petrogale xanthopus, a macropodid marsupial) were non‐linear. Like several other macropods, yellow‐footed rock‐wallabies foraged more and looked less as group size increased. Variation in vigilance was best explained by the number of conspecifics within 10 m–a distance substantially less than the 30–50 m often used to quantify group size in macropodids. Linear regressions explained more variation than non‐linear ones, suggesting that wallabies traded‐off the benefits of aggregation with the costs of competition. Moreover, dominant yellow‐foots looked less and tended to forage more than subordinate animals. We hypothesize that competition may be relatively more important in the life‐histories of yellow‐footed rock‐wallabies than those of other macropodid marsupials.
Effects of Resource Allocation on Behavioural Strategies: A Comparison of Red Junglefowl (Gallus gallus) and Two Domesticated Breeds of Poultry
Authors: Schütz Karin E. , Jensen Per
Published: March 2003

Three different breeds of poultry, representing different degrees of domestication, were observed in semi‐natural conditions in order to study differences in foraging behaviour, activity levels and social behaviours which could be caused by correlated responses to selection for increased production. The breeds used were: (i) red junglefowl (Gallus gallus); (ii) Swedish bantam, which is a domestic breed that has not undergone selection for production traits; and (iii) Hy‐Line, a White leghorn laying hybrid, selected mainly for food conversion efficiency. The birds were offered ad libitum food simultaneously from sites where the food was freely available and from sites where the birds had to search and scratch for food which was mixed with wood‐shavings. The behaviour was observed three times per day (48 min/d), 3 d per week in eight groups (four birds per group) of each breed between 7 and 18 wks of age. Junglefowl and bantam obtained a significantly higher proportion of their food from the site that required effort. The opposite case was true for the Hy‐Line. Overall, bantams performed significantly more foraging behaviour than Hy‐Lines. The Hy‐Line breed was more inactive and less involved in social interactions than the junglefowl and the bantam. The results support the idea that selection for high production results in modified behavioural strategies. Behaviours that are of high energetic cost, such as extensive foraging and social interactions, were of lower in frequency in the laying hens compared to junglefowl and bantam, allowing the laying hens to save energy that can be reallocated to production traits.
Defining Vertical Bars in Relation to Female Preference in the Swordtail Fish Xiphophorus cortezi (Cyprinodontiformes, Poeciliidae)
Authors: Morris Molly R. , Elias Jason A. , Moretz Jason A.
Published: March 2003

Defining a male trait in relation to female preference is an important step towards determining the role that female preference has played in the evolution of a male trait. The pigment pattern ‘vertical bars’ is a complex male trait that functions as a sexual signal in swordtail fishes. A previous study suggested that X. cortezi females had a preference for males with more vertical bars. In that study, however, bar number had been reduced on the stimulus males by removing the most posterior bars, which changed the distance over which the bars spanned, in addition to changing bar number. To determine whether X. cortezi females have a preference for greater bar span and/or number of bars, we tested for female preference in two experiments. First, we gave females a choice between males with a greater bar span or a smaller bar span, holding bar number and total pigmented area constant. Females spent significantly more time with the males with the smaller bar span. This result, together with results from the previous study, suggest that females do not assess bar span alone, but possibly a composite component of the bars, such as bar frequency (number of bars/bar span). Secondly, we gave females a choice between six thinner bars or one wider bar of equal pigmented area. The six‐bar treatment had a greater bar span in addition to more bars. We detected no preference for either treatment. These results suggest that the previously detected preference for more bars may actually reflect a preference for greater pigmented area. Finally, we present data on natural variation in the bars for X. cortezi and use principal components analysis to provide a composite definition of this trait.
Multiple Paternity and Similar Variance in Reproductive Success of Male and Female Wood Mice (Apodemus sylvaticus) Housed in an Enclosure
Authors: Bartmann Susan , Gerlach Gabriele
Published: March 2003

The mating system and variance in individual reproductive success in wood mice (Apodemus sylvaticus) were analysed genetically and using observational studies within a large cage system in an outdoor enclosure. Four experimental groups contained four males and four females, each individually marked with a transponder (small computer chips injected under the skin) allowing individual detection of animals underground or within nest boxes without disturbance. The probability of paternity was analysed by comparing frequencies of cohabitation of males and females. In addition, DNA microsatellite analysis revealed reproductive success of each individual. Multiple paternity was found in 85% of all litters, which were sired by up to all four males. Males with a greater body mass, possibly indicative of a higher rank, sired more offspring than those with lower body mass. Interestingly, variance in the reproductive success of males and females did not differ. There was no indication that paternity could be assessed by the time males resided with a female shortly before she became pregnant. Our results indicate wood mice probably have a promiscuous mating system.
Chemical Alarm Signals Enhance Survival of Brook Charr (Salvelinus fontinalis) During Encounters with Predatory Chain Pickerel (Esox niger)
Authors: Mirza Reehan S. , Chivers Douglas P.
Published: March 2003

A diversity of aquatic organisms release chemical alarm signals when attacked or captured by a predator. These alarm signals are thought to warn other conspecifics of danger and, consequently, may benefit receivers by increasing their survival. Here we experimentally investigated the differences in behaviour and survival of hatchery‐reared juvenile brook charr Salvelinus fontinalis that had been exposed to either brook charr skin extract (experimental treatment) or a control of swordtail skin extract (control treatment). Charr exposed to conspecific skin extract exhibited a significant reduction in movement and/or altered their foraging behaviour in the laboratory when compared with charr exposed to swordtail skin extract. We also exposed charr to either water conditioned by a single brook charr disturbed by a predatory bird model or water conditioned by a single undisturbed brook charr. Charr exposed to disturbance signals reduced activity significantly more than charr exposed to chemical stimuli from undisturbed charr. These results demonstrate the existence of both damage‐released alarm signals and disturbance signals in brook charr. Wild brook charr also responded to damage‐released alarm cues under natural conditions. Charr avoided areas of a stream with minnow traps labelled with conspecific alarm cues vs. control cues. During staged encounters with chain pickerel Esox niger in the laboratory, predator‐naive charr fry were better able to evade the predator if they were previously warned by an alarm signal, thus suggesting a survival benefit to receivers. Collectively, these results demonstrate that the presence of alarm signals in brook charr has important implications for understanding predator–prey interactions.
Scent Marking in Voles: A Reassessment of Over Marking, Counter Marking, and Self‐Advertisement
Authors: Thomas Shawn A. , Wolff Jerry O.
Published: March 2003

We conducted a series of experiments to discern among the counter‐marking, over‐marking, and self‐advertisement hypotheses for secondary marking in male prairie voles, Microtus ochrogaster, and meadow voles, M. pennsylvanicus. Secondary scent marks (those placed in an area that has already been marked by a conspecific) were not significantly greater than initial marks placed on clean substrate (a substrate without any previous scent marks) for either species and thus did not support a counter‐marking hypothesis. Similarly, overlapping of initial scent marks with secondary marks occurred less often than expected by chance and did not support an over‐marking hypothesis. Secondary marks tended to avoid overlap with scent marks previously deposited by a potential competitor. Our results suggest that secondary scent marking functions to self‐advertise by maximizing individual identity and avoiding masking or blending with previous donors. Future studies on secondary marking should be designed to quantify the observed and expected frequency and placement of original and secondary marks to discern among alternative hypotheses for the adaptive significance of secondary marking.
Opening the Social Gateway: Early Vocal and Social Sensitivities in Brown‐Headed Cowbirds (Molothrus ater)
Authors: White David J. , King Andrew P. , Cole Amanda , West Meredith J.
Published: March 2003

The organization of cowbird (Molothrus ater) social groups affords individuals living in the groups different opportunities for learning and also structures trajectories of social development. Here, we studied the influence of adults on social organization of very young cowbirds. In three experiments, we housed juvenile birds in large, seminatural environments that either contained or did not contain adult conspecifics. We then observed the social associations and vocalizations of juveniles in each environment. The presence of adults in the social environment influenced the assortment and singing patterns of juveniles, although throughout the three experiments adults rarely interacted physically with juveniles. Juveniles housed with adults interacted with other juveniles more often and sang significantly less often than juveniles housed without adults. Effects of adult presence or absence on social organization and singing patterns emerged extremely rapidly and could be reversed quickly. Taken as a whole, the experiments revealed that very young cowbirds, in the first days of independence from their hosts, were sensitive to, and reacted rapidly to, the composition of their social environment. Specifically, presence of other age classes of individuals within the group increased juvenile associations and delayed production of vocalizations by juvenile males. Self‐organization within the social group produced different social environments, which could in turn create different gateways for social learning and vocal development.
Geographic Variation in the Behaviour of the Cleaner Fish Labroides dimidiatus (Labridae)
Authors: Bansemer Carley , Grutter Alexandra S. , Poulin Robert
Published: March 2003

Geographical variation in the outcome of interspecific interactions has a range of proximate ecological causes. For instance, cleaning interactions between coral reef fishes can result in benefits for both the cleaner and its clients. However, because both parties can cheat and because the rewards of cheating may depend on the local abundance of ectoparasites on clients, the interaction might range from exploitative to mutualistic. In a comparative analysis of behavioural measures of the association between the cleaner fish Labroides dimidiatus and all its client species, we compared cleaning interactions between two sites on the Great Barrier Reef that differ with respect to mean ectoparasite abundance. At Heron Island, where client fish consistently harbour fewer ectoparasites, client species that tended to pose for cleaners were more likely to receive feeding bites by cleaners than client species that did not pose for cleaners. This was not the case at Lizard Island, where ectoparasites are significantly more abundant. Client fish generally spent more time posing for cleaners at Lizard Island than their conspecifics at Heron Island. However, fish at Heron Island were inspected longer on average by cleaners than conspecifics at Lizard Island, and they incurred more bites and swipes at their sides per unit time from cleaners. These and other differences between the two sites suggest that the local availability of ectoparasites as a food source for cleaners may determine whether clients will seek cleaning, and whether cleaners will feed on parasites or attempt to feed on client mucus. The results suggest that cleaning symbiosis is a mosaic of different outcomes driven by geographical differences in the benefits for both participants.