Chemosensory discrimination of male age by female Psammodromus algirus lizards based on femoral secretions and feces

Chemical communication plays an essential role in several social and reproductive behaviors of many animals. In lizards, the main sources of semiochemicals are femoral or pre‐anal gland secretions and feces. In male lizards Psammodromus algirus, there are age‐related differences in the chemical composition of femoral gland secretions and in the reproductive strategies, with older males defending territories and females, while younger males adopting sneak‐mating strategies. Females flee more often from mating advances of young males than from those of old males, which are more successful in obtaining matings. This suggests that age discrimination of males may be important for females. We tested here whether females showed differential chemosensory responses to chemical cues (femoral gland secretion and feces) of males of two age classes, and whether females use information from substrate scent marks of males of different ages to select where to stay. We found that females elicited more tongue‐flicks to the secretion and feces of old males than to control or secretion and feces of young males. Also, the time spent by females on a scented paper depended on the treatment, suggesting that females tended to spend more time on scent marks made with femoral secretions of old males. Adult females seemed capable to discriminate between young and old males based on chemical cues alone and showed more interest in scents of old males. However, substrate scent marks did not seem to entirely determine site selection by females, suggesting that females might need additional cues to perform the choice. These results can be explained by the different age‐dependent reproductive strategies of males, which can affect differentially to females.     

Age related differences in lipophilic compounds found in femoral gland secretions of male spiny-footed lizards, Acanthodactylus erythrurus

Although chemoreception plays an important role in social organization of many lizards, only a few studies have examined the chemicals found in secretions used for intraspecific communication. We report the composition of the secretion of the femoral glands of males of the spiny-footed lizard (Acanthodactylus erythrurus). On the basis of mass spectra, obtained by GC/MS, we identified 45 lipophilic compounds, including several alcohols ranging from 10 to 29 carbon atoms (mainly hexacosanol and tetracosanol), steroids (mainly cholesterol and dehydrocholesterol), n-C9 to n-C20 carboxylic acids, esters of carboxylic acids, and minor components such as lactones, ketones, squalene and a-tocopherol. Some of these compounds are reported for the first time in lizards. Adult and subadult males differed in the composition of secretions, with C9 to C15 carboxylic acids being more abundant in younger than in older lizards, whereas C16 to C20 carboxylic acids were more abundant in older lizards. Also, older lizards had significant lower proportions of cholesterol and campesterol but higher proportions of dehydrocholesterol.     

Chemical compounds from femoral gland secretions of male Iberian rock lizards, Lacerta monticola cyreni

In spite of the importance of chemoreception and chemical signals in the social organization of lizards, there are only a few studies examining the chemical composition of secretions of lizards used for scent marking. The secretion of the femoral glands of male Iberian rock lizards (Lacerta monticola cyreni) contains 44 lipophilic compounds, including several steroids (mainly cholesterol), and n-C6 to n-C22 carboxylic acids, and minor components such as esters of carboxylic acids, alcohols, squalene, and one lactone. These compounds were identified on the basis of mass spectra, obtained by GC-MS. Most lipids were detected in all individuals, although relative proportions of each chemical show a high interindividual variability. This variability might be related to the characteristics or physical and health condition of males and might be the basis of female choice based on chemical cues observed in this lizard species.     

Determinants of survival in juvenile Psammodromus algirus lizards

Theories posit that the relative mortality rate of adults and juveniles is a major determinant of population dynamics and life history evolution. Moreover, differential survival of pre-reproductive individuals may be an important source of variation in lifetime reproductive success, and characters that influence survival of juveniles are likely to be under strong selection. We examined survival from hatching to maturity in a natural population of Psammodromus algirus lizards using data from a capture-mark-recapture study. We found that mortality from hatching to maturity was high: only 8% of males and 14% of females that hatched in 1996 survived the entire study period until maturity in spring 1998. The probability of survival was 75% during both the first and second overwinter periods when lizards were inactive most of the time, and about 25% during their first spring to autumn activity season. Our analyses further revealed significant associations between survival and snout-vent length, body condition, sex and microhabitat use. However, the relationship between survival and morphological characters varied among time periods, presumably because the sources of mortality during the activity season were different from those during hibernation. The association between survival and body condition also varied within time periods, both between large and small individuals and between the two sexes. This suggests that the relative importance of different selective agents may change during the life of individuals and vary between males and females due to differences in body size and behaviour. Received: 24 March 1999 / Accepted: 14 February 2000     

Social costs and development of nuptial coloration in male Psammodromus algirus lizards: an experiment

In the lizard Psammodromus algirus, larger and older males show orangenuptial coloration on most of the head and are dominant oversmaller and younger, albeit sexually mature, males which donot show such extensive nuptial coloration. This raises thequestion of why young, small males delay the development ofnuptial coloration until a later breeding season. We tested thehypothesis of social costs by manipulating the color of thehead of small males. The results of agonistic interactions suggestedthat small males may pay a cost in terms of being punished bylarge males. Small males with heads painted orange were stillrecognized as small by other small males, suggesting that theywould not gain in social status relative to normal, dull, small males.We also manipulated the coloration of large males. Small malesshowed a similar response toward all large males, independentof coloration. This suggests that in short-distance communication,males used other cues, such as body size and behavior, whenjudging fighting ability. In staged experiments without malecompetition, female acceptance of matings was influenced bymale body size but not by coloration because large males weremore successful in obtaining matings than were small males,and within each age/size category there was no difference inmating success between experimental and control males.     

Lipids in femoral gland secretions of male lizards, Psammodromus hispanicus

Many lizards produce chemical secretions that may be used as pheromones in reproductive behavior, but only a few studies have identified chemical compounds in secretions. By using GC–MS, we found only 20 lipophilic compounds in femoral glands secretion of male lizards, Psammodromus hispanicus. Main compounds were six steroids (mainly cholesterol and campesterol) and seven n-C₉ to n-C₁₈ carboxylic acids (especially dodecanoic acid), and minor components were six alcohols between C₁₆ and C₂₉ and squalene. We compared these chemicals with those previously found in secretions of the closely related sister species Psammodromus algirus and other lizard species.     

Tail loss reduces home range size and access to females in male lizards, Psammodromus algirus

Numerous lizard species use caudal autotomy as an antipredatordevice even though there must be significant costs during theperiod of tail regeneration. Strategies used by tailless individualsto enhance survival in natural populations are still poorlyunderstood. We experimentally examine tail loss in large, dominantmales of Psammodromus algirus in the middle of the breedingseason in the field. We report data showing home range reductionof large dominant males after autotomy, reduction in the numberof females in the home ranges of manipulated males, and a potentialincrease in mating opportunities of small subordinate maleswith complete tails. We conclude that changes in home rangeuse because of desertion of areas with less cover can resultin decreased predation risk at the cost of decreased accessto females.     

Lipids in the femoral gland secretions of male Schreiber's green lizards, Lacerta schreiberi

In spite of the importance of chemoreception and chemical signals in social organization of lizards, only a few studies have examined the chemical composition of secretions that lizards use for intraspecific communication. The secretion of the femoral glands of male Schreiber's green lizards (Lacerta schreiberi) contains 51 lipophilic compounds, including several steroids, a-tocopherol, n-C9 to n-C22 carboxylic acids and their esteres, and minor components such as alcohols between C12 and C24, two lactones, two ketones, and squalene. These compounds were identified on the basis of mass spectra, obtained by GC-MS. We compared these chemicals with those found in other lizard species, and discussed how environmental conditions could explain the differential presence of chemicals in different lizards. Particularly, the high abundance of a-tocopherol in this lizard is suggested to contribute to avoid oxidation of other lipids in secretions, increasing chemical stability of scent marks in the humid conditions of its habitat.     

Testosterone supplementation in juvenile Psammodromus algirus lizards: consequences for aggressiveness and body growth

In some species, more aggressive individuals are more successful in resource competition. High testosterone level is associated with increased activity and aggressive behavior, and this may have a direct effect on metabolic rate and cause an increase in energy expenditure. Here, I examined the influence of exogenously administered testosterone on aggressiveness and body growth in juvenile Psammodromus algirus male lizards. Juvenile males were given testosterone-filled (experimental) or empty (control) implants. Testosterone produced an increase in aggressiveness and activity in the experimental males. However, despite being more aggressive, experimental males did not acquire larger home ranges than control males. Experimental males also experienced a significant reduction in growth rate over the 2-month period following implantation. Experimental males also were in poorer condition at the completion of the experiment, compared to control males. These results suggest that although an elevated testosterone level may have positive effects on aggressiveness and activity, it also may have negative effects manifested as reduced growth rate and body condition. Received in revised form: 15 June 2001 Electronic Publication     

Lipophilic compounds in femoral secretions of male collared lizards,Crotaphytus bicinctores (Iguania,Crotaphytidae)

In many lizards, chemical compounds from the femoral gland secretions are used in intraspecific communication, but most studies describing these chemicals are for lizard species included in the Scleroglossa clade, whereas lizards within the Iguanian clade have been much less studied, probably because these lizards were considered to rely more on visual cues. However, many iguanian lizards have abundant femoral secretions and are able of chemosensory conspecific recognition, which might be based on compounds secreted by femoral glands. By using GC–MS analyses, we found 58 lipophilic compounds in femoral gland secretions of male Great Basin collared lizard, Crotaphytus bicinctores (Iguania, Crotaphytidae). Main compounds were steroids (mainly two triunsaturated steroids and cholesterol), carboxylic acids (mainly hexadecanoic acid), waxy esters of long chain fatty acids, alcohols (mainly hexadecanol), aldehydes and other minor compounds. We compared these compounds with those found in other lizard species and discussed the potential signaling function of some compounds and how the xeric habitat of this lizard could have conditioned the composition of secretions.     

Chemical constituents of the femoral gland secretions of male tegu lizards (Tupinambis merianae) (Family teiidae)

In spite of the importance of chemical signals (pheromones) in the reproductive behaviour of lizards, the chemical compounds secreted by their femoral glands, which may be used as sexual signals, are only known for a few lizard species. Based on mass spectra, obtained by GC-MS, we found 49 lipophilic compounds in femoral gland secretions of male tegu lizards (Tupinambis merianae) (fam. Teiidae), including a very high proportion of carboxylic acids and their esters ranging between n-C8 and n-C20 (mainly octadecanoic and 9,12-octadecadienoic acids), with much less proportions of steroids, tocopherol, aldehydes, and squalene. We discuss the potential function of these compounds in secretions, and compare the compounds found here with those documented for other lizard species.     

Electron microscopy of the medial cortex in the lizard Psammodromus algirus

The medial cortex of Psammodromus presents a three-layer organization. Most of the cell bodies are localized in a compact lamina, the cellular layer. Two plexiform layers, superficial and deep, enclose the cellular layer. The most external portion of the superficial plexiform layer is formed by a limiting glial sheet consisting of tanycytic processes that reach the surface of the cortex. Astrocytes are localized close to the glial sheet. There are two types of axon terminals within the superficial plexiform layer: type S with spheric vesicles and type F with pleomorphic vesicles. Large solitary neurons are present at middle levels of the layer. In the cellular layer there are three neuronal types: large neurons with dispersed chromatin, neurons of medium size with chromatin clumps, and electron-dense neurons. Protoplasmic astrocytes are found superficially in this layer. In the deep plexiform layer numerous neuronal cell bodies are visible, and three types can be distinguished: horizontal fusiform cells, globous neurons with indented nuclei, and electron-dense neurons. Protoplasmic astrocytes are present throughout this layer. Oligodendrocytes are more frequent in the inner third of the layer, often related to fibers of a thick fascicle running in contact with the ependyma, the alveus. The ependyma is formed by a single row of prismatic cells bordering the lateral ventricle.     

The chemical composition of uropygial gland secretions from ralliformes

The uropygial gland wax from rails contains ester waxes, triester waxes and triglycerides. The ester waxes are composed of mainly methyl-substituted fatty acids with predominantly n-alkanols. Methyl-branched alcohols are only found in minor amounts. The occurrence of 2,6,10- and 4,8,12-trimethyl-substituted acids can be used as chemotaxonomie markers. The triester waxes contain n-fatty acids, n-alkanols and alkyl-hydroxymalonic acids.     

Chemical composition of femoral secretions of oviparous and viviparous types of male common lizards Lacerta vivipara

In spite of the importance of chemoreception in intraspecific communication of lizards, only a few studies have examined chemical composition of secretions of lizards. The secretion of the femoral glands of adult male lizards Lacerta vivipara contains a relatively low number (18) of lipophilic compounds in comparison with other related lacertid lizards. These compounds were identified on the basis of mass spectra, obtained by GC-MS. Chemicals included ten steroids (mainly cholesterol) and four carboxylic acids between n-C₁₂ and n-C₁₈, and minor components such as squalene, α-tocopherol, and two waxy esters, which may contribute to avoid oxidation of other lipophilic components in the fairly humid environments occupied by this lizard. Secretions of adult males from oviparous and viviparous populations did not differ in the numbers and quality of chemical compounds, but there were some differences in the relative proportion of some compounds. Males from oviparous populations had lower proportions of hexadecanoic acid and cholestan-3-one, and higher proportions of squalene than viviparous males. These differences might be explained by either small genetic differences between types or due to different microclimatic conditions in the original populations.     

Variation in the effect of profitability on prey size selection by the lacertid lizard Psammodromus algirus

Maximizing the average rate of energy intake (profitability) may not always be the optimal foraging strategy for ectotherms with relatively low energy requirements. To test this hypothesis, we studied the feeding behaviour of captive insectivorous lizards Psammodromus algirus, and we obtained experimental estimates of prey mass, handling time, profitability, and attack distance for several types of prey. Handling time increased linearly with prey mass and differed significantly among prey types when prey size differences were controlled for, and mean profitabilities differed among prey taxa, but profitability was independent of prey size. The attack distance increased with prey length and with the mobility of prey, but it was unrelated to profitability. Thus, lizards did not seem to take account of the rate of energy intake per second as a proximate cue eliciting predatory behavior. This information was combined with pitfall-trap censuses of prey (in late April, mid-June and late July) that allowed us to compare the mass of the prey captured in the environment with that of the arthropods found in the stomachs of sacrificed free-living lizards. In April, when food abundance was low and lizards were reproducing, profitability had a pronounced effect on size selection and lizards selected prey larger than average from all taxa except the least profitable ones. As the active season progressed, and with a higher availability of food, the number of prey per stomach decreased and their mean ize increased. The effect of profitability on size selection decreased (June) and eventually vanished (July–August). This variation is probably related to seasonal changes in the ecology of lizards, e.g. time minimization in the breeding season as a means of saving time for nonforaging activities versus movement minimization by selecting fewer (but larger) prey in the postbreeding season. Thus, the hypothesis that maximizing profitability could be just an optional strategy for a terrestrial ectothermic vertebrate was supported by our data.     

Volatile compounds in shoulder gland secretions of male flying foxes, genus Pteropus (Pteropodidae, Chiroptera)

The shoulder gland secretions of captive males of the Indian flying fox (Pteropus giganteus), the little golden-mantled flying fox (P. pumilus), the island flying fox (P. hypomelanus), and the large flying fox (P. vampyrus) were examined by gas chromatography-mass spectrometry. Sixty-five compounds, including hydrocarbons, carboxylic acids, alcohols, aldehydes, ketones, esters, and amides, were identified among the four species. Many of these compounds, such as squalene, cholesterol, and C5-C16 straight- and branched-chain carboxylic acids, are typical of tetrapod epidermal products. Aldehydes, which were detected in all four Pteropus species, and some straight- and branched-chain ketones, which were detected in P. hypomelanus and P. pumilus, are known from other mammalian skin glands. Acetophenone, 4-acetoxyacetophenone, and 4-hydroxyacetophenone were observed in P. pumilus; the last compound comprised 37.1% of the total ion current. 2,3-Butanediol, a prominent component (5.2-19.3%) in the secretions of P. giganteus, P. hypomelanus, and P. pumilus, and C10 and C12 isopropyl esters and C10-C14 1-methylbutyl esters, observed in P. hypomelanus and P. vampyrus, have not previously been reported from vertebrates. alpha-Methyl-4-methoxybenzyl alcohol and dihydro-5-phenyl-2(3H)-furanone, from P. giganteus and P. pumilus, are new natural products. 1-Chloro-3-methyl-2-butene, another new natural product, and five C5 compounds exhibiting a similar isoprenoid structure were observed in P. giganteus. Striking contrasts were observed in the chemical profiles of the species we examined, with even general chemical classes differentially represented among them.     

棕尾别麻蝇雄性附腺分泌物的生理功能

棕尾别麻蝇Boettcherisca peregrina Robinean-Desvoidy雄性附腺的分泌物中包含许多生物活性分子,将成熟的雄性附腺分泌物注射到未交配的雌虫体内,发现其能影响雌虫生殖活性的很多方面:如降低雌虫的再次交配率;增加卵巢内的含卵量;缩短交配后雌虫的寿命。另外,还证明附腺分泌物中存在有可抑制革兰氏阳性菌的物质的存在。     

Age-related responses of hepatic ATPases to starvation and cold stress in male garden lizards

Hepatic Na⁺-K⁺-ATPase and Mg²⁺-ATPase activities of male green lizards declined during the maturation phase (juvenile to 1-year-old) and stabilized thereafter. On the other hand, the Ca²⁺-ATPase activity of the liver declined during the later half of the life span (1-year-old to 2–4-year-old). Starvation stress induced a decline in hepatic Na⁺-K⁺-ATPase and Mg²⁺-ATPase activities of juvenile lizards and caused an increase in 1-year-old and 2–4-year-old counterparts. The Ca²⁺-ATPase activity declined only in starved 1-year-old lizards. Following cold stress, the hepatic Na⁺-K⁺-ATPase activity of juvenile lizards showed a higher degree of decline than 2–4-year-old counterparts. The Mg²⁺-ATPase activity declined in cold-stressed juvenile lizards, but the parameter was elevated in similarly treated 1-year-old lizards. On the other hand, the increase in Ca²⁺-ATPase activity in response to cold stress was confined only to 2–4-year-old lizards.     

Diversity in chemical compositions of preen gland secretions of tropical birds

The chemical composition of preen gland secretions of antbirds (Thamnophilidae and Formicaridae) and phylogenetically closely related Dendrocolaptidae, Tyrannidae and Pipridae were investigated to understand the role of environment in secretion components. The secretions of Thamnophilidae consisted of long chain acids, alcohols, esters, unsaturated hydrocarbons, and isoprenoids. Formicaridae secretions contained exclusively squalene and its derivatives. In Pipridae, secretions were made up of complex long chain esters. In Dendrocolaptidae, the secretions consisted of long chain esters of both saturated and monounsaturated acids combined with mono-alcohols and those of Tyrannidae consisted of long chain esters of saturated, mono- and tri-unsaturated acids with mono- and di-ols that were less complex. Higher molecular weight saturated and unsaturated components in tropical species suggest that the volatility of the secretion components is correlated to environmental temperatures experienced by the birds. Squalene is a precursor in steroid biosynthesis, but higher amounts in Formicaridae secretions suggest that it may have some additional functions.