Non-gravid Females Research Articles

Costs of reproduction in lizards: escape tactics and susceptibility to predation

Increased basking and reduced agility in gravid female southern water skinks (Eulamprus tympanum) suggest that they will be more vulnerable to predators. However, gravid females shift their anti-predator tactics towards crypsis, by allowing potential predators (such as a human observer) to approach more closely than do males and non-gravid females. Gravid females were taken no more frequently than were non-gravid females or males when exposed to two types of natural predators, birds (kookaburra, Dacelo gigas) or snakes (common blacksnakes, Pseudechis porphyriacus) in field enclosures. Both these results suggest that the vulnerability of potential prey in this system is determined by the predator's probability of detecting a potential prey item, not its probability of capturing the prey item after detection. Hence, laboratory-based measures of performance demonstrating reduced escape speed may sometimes have little relevance to actual fitness under field conditions, if the probability that an animal will be taken by a predator depends primarily on whether or not it is seen, rather than on how quickly it can escape.

Effect of the repellent deet on the antennal chemoreceptors for oviposition in Aedes aegypti (Diptera: Culicidae).

The insect repellent, N,N-diethyl-m-toluamide (deet), interferes with detection of the host attractant, lactic acid (LA), by LA-excited neurons on the antennae of female Aedes aegypti (L.) mosquitoes. In the current laboratory behavioral experiment, the attraction of gravid female mosquitoes to a source of ethyl propionate, an oviposition attractant, was reduced by a factor of two when deet was present. Similarly, when deet was presented together with ethyl propionate in electrophysiological experiments, sensitivity of the neural response to ethyl propionate was depressed in a transient, dose-dependent manner that could account for the reduction in behavioral attraction of gravid females to ethyl propionate. Electrophysiologically, the sensitivity of oviposition attractant receptors to ethyl propionate on gravid females was not different from that on nongravid host-seeking females. The similarity between the depression of sensitivity of the oviposition attractant-sensitive neurons induced by deet and that observed in the host attractant-sensitive neurons suggest a common mode of action of deet on peripheral chemoreceptor neurons that mediate these behaviors.

Tumor formation and sister chromatid exchange induction by ethyl carbamate: relationships among non-pregnant murine females, gravid dams, and transplacentally exposed offspring.

Sister-chromatid exchange (SCE) induction and cell cycle kinetics alterations by ethyl carbamate in bone marrow of non-gravid murine Swiss Webster, ICR/Jcl, and C57Bl/6J dams were evaluated, and data from non-gravid females were compared with those previously reported for pregnant dams of the same strains. In addition, lung adenoma induction by ethyl carbamate in gravid Swiss Webster dams, their offspring, and in non-pregnant Swiss Webster females was also determined. Relative cytogenetic and tumor responses in non-gravid and gravid Swiss Webster females and their offspring were compared. In contrast to the increased sensitivity reported for gravid Swiss Webster dams versus ICR/Jcl and C57Bl/6J dams, SCE responses to 1.1, 2.2, or 3.3 mmol/kg of ethyl carbamate in non-gravid females were approximately equivalent among strains. In Swiss Webster and C57Bl/6J (but not ICR/Jcl) strains, SCE responses in non-gravid females at 2.2 and 3.3 were significantly lower than those of their pregnant counterparts. Tumor induction by 3.3 mmol/kg ethyl carbamate paralleled relative SCE induction with Swiss Webster dams, demonstrating a 5-fold increase in the number of tumors relative to their offspring and a 4-fold enhancement of tumor induction relative to their non-pregnant counterparts.

Thermal biology of reproduction in viviparous skinks, Eulamprus tympanum: why do gravid females bask more?

In some reptiles, gravid females bask more, and/or maintain higher body temperatures than do males or non-gravid females. This phenomenon is usually explained in terms of the female or her offspring benefitting from accelerated embryogenesis and early birth, but the effect of increased basking on gestation period has not been studied. In a laboratory experiment, gestation periods of gravid female skinks (Eulamprus tympanum) decreased with the duration of access to radiant heat. Embryonic development was more rapid in the laboratory than in the field, and there were no apparent adverse effects of this accelerated gestation on females or offspring. Number and mass of offspring, survival rates of embryos, relative clutch mass and female mass before and after parturition were not influenced by the decrease in gestation period caused by increased basking. Females selected similar temperatures in the laboratory and field (32° C), despite the availability of higher temperatures in the laboratory. Thus, gestation in the laboratory was accelerated by spending longer periods at usual basking temperatures, rather than by selecting higher temperatures. In the field, mean and modal body temperatures of active animals were similar in gravid females, males and non-gravid females, but gravid females appear to bask more of the time, even in cloudy weather when other members of the population do not bask. Hence, an apparent similarity in thermal regimes of gravid and non-gravid animals may mask significant underlying differences in thermoregulatory strategies.

Changes in swimming behavior of male Diaptomus leptopus (Copepoda: Calanoida) in response to gravid females

Swimming behavior of male Diaptomus leptopus was recorded before and after introduction of gravid females, nongravid females, or males into one compartment of a two-compartment vessel. The compartments were separated by 110-µm nylon mesh. Analysis of swimming behavior found that both swimming speed and turning behavior of male D. leptopus were altered significantly only after exposure to water from gravid females. Swimming behavior was unaltered in an apparatus where the holding compartment was separated from the other compartment by 5.0 cm, but some changes were observed when the separation between the two compartments was decreased to 2.5 cm, implying that the cue has a very short lifetime or that the pheromone diffuses slowly.

Mating and Multiple Clutches in Australian Boeckella and Calamoecia (Copepoda: Calanoida)

Experiments were performed with Australian centropagid calanoid copepods of Boeckella and Calamoecia to test the hypotheses that species in these genera are capable of producing multiple clutches with one insemination and that successful mating occurs at all stages of the female's ovigerous cycle. The second hypothesis was also tested by an examination of natural populations; spermatophore placement on gravid and nongravid females was scored. Both hypotheses were confirmed. Egg development times and patterns of resting egg hatching were examined under laboratory conditions for up to 100 d. These characteristics and patterns of egg development and resting egg production may result from selection for highly variable and unpredictable environments that existed in Australia before human intervention.

Thermal Biology of Two Populations of Red-Chinned Lizards (Sceloporus undulatus erythrocheilus) Living in Different Habitats in Southcentral Colorado

The thermal biology of two populations of red-chinned lizards (Sceloporus undulatus eryth- rocheilus) living in different habitats in southcentral Colorado was examined over two summers. One population lives on an isolated volcanic cone that rises 65 m above the surrounding short-grass prairie, while the other population occupies a nearby pinyon-juniper covered mesa. Mean body temperature for all populations sampled varied between 34.8 and 35.5 C. Females had a slightly but significantly higher mean body temperature than males (35.3 vs. 34.9 C, respectively), but variance in mean body temperature did not differ between sexes. Neither mean body temperature nor its variance differed significantly among populations, years, and months, nor in comparisons between gravid and non-gravid females or between juveniles and adults. Analysis of thermoregulatory performance revealed significant differences between populations and between sexes but not among any other groups tested. This study provides additional support to the view that temperate lizards are evolutionarily conservative in their thermal physiology and that they have mean body temperatures which are largely non-responsive to short-term environmental variation. An investigation of thermoregulatory performance and daily ac- tivity patterns of red-chinned lizards, on the other hand, suggests that these characteristics may be quite sensitive to physical and biological factors.

Ontogenetic shifts in habitat use and activity in a stream‐dwelling isopod

We examined ontogenetic changes in diel patterns of habitat use and activity of the lotic isopod Lirceus fontinalis in relation to differences in predation risk from green sunfish, Lepomis cyanellus. Juveniles are ≤5 mm total length (TL), individuals 6‐9 mm TL are mature females (c. 90%) and immature males, and mature males are ≥10 mm TL. Isopods of all sizes were far more dense in Cladophora, a filamentous green algae, than in open silt/sand substrates in fish pools. Densities of each size did not increase in open areas at night in fish pools when risk of predation presumably decreases. Few individuals of any size class occurred in open silt/sand areas in fish pools. However, habitat use did not depend on fish presence. Densities and relative abundances of all sizes were similar between algal and open habitats in fishless pools both day and night, except for mature males which were more abundant in open areas during daylight. All sizes of isopods were significantly more dense in fishless versus fish pools, and density of a size class was influenced by fish presence. Densities of size classes were typically juveniles > individuals 6‐9 mm TL > mature males. Green sunfish are size selective feeders on isopods, thus demography of isopods within pools may be partially influenced by the size structure of the fish population.Isopods reduced their activity, as measured by captures in benthic traps, in the presence of caged green sunfish only at night. This behavior coupled with relatively high activity levels during daylight regardless of fish presence suggests other predators or factors may influence diel activity. Mature males were overrepresented in traps relative to their occurrence in fish runs, indicating high activity levels. Mature males were also more active than gravid and nongravid females and juveniles in the presence of fish in laboratory aquaria. Number of male encounters with nongravid females depended on activity level.

Toxicity of Several Insecticide Formulations Against Adult German Cockroaches (Dictyoptera: Blattellidae)

Toxicity of bendiocarb, chlorpyrifos, cyfluthrin, cypermethrin, fenvalerate, hydramethylnon, malathion, propetamphos, propoxur, and pyrethrins against the adult German cockroaches, Blattella germanica (L.), was investigated. At LD50, cyfluthrin was the most toxic insecticide to adult males (0.53 microgram/g), adult females (1.2 micrograms/g), and gravid females (0.85 microgram/g). Malathion was the least toxic insecticide to adult males (464.83 micrograms/g), adult females (335.83 micrograms/g), and gravid females (275.90 micrograms/g). Males and gravid females were generally more sensitive than nongravid females to the insecticides that we tested. In tests with malathion, however, males were more tolerant. The order of toxicity of the insecticide classes varied among the stages of adult German cockroaches. The order of toxicity for males and nongravid females was pyrethroids greater than pyrethrins = organophosphates (except malathion) greater than carbamates = amidinohydrazone. The order of toxicity for gravid females was pyrethroids greater than pyrethrins = organophosphates (except malathion) greater than carbamates greater than amidinohydrazone. These differences in toxicity suggest that sex differences should be considered when determining insecticide toxicity for German cockroaches.

Further characterization of a dispersion-inducing contact pheromone in the saliva of the German cockroach, Blattella germanica L. (Blattodea: Blattellidae)

The dispersion-inducing substance in the saliva of the German cockroach was characterized by different chemical extraction and precipitation procedures. The repellency factors of probe solutions were estimated by a computer-aided device analysing the pheromone-induced motility behaviour. The dispersion pheromone was perceived by contact only and remained active for at least 15 days. Saliva of males, nymphs, gravid and non-gravid females showed significant repellency, but in a quantitatively varying manner. Overcrowding procedures increased the dispersal activity of the saliva and the content of the 77, 80 and 82 kDalton (kDa) proteins in the saliva. Antagonism between the dispersal pheromone in the saliva and the aggregation pheromone in the faeces could be demonstrated herewith. Salivary proteins were detected to be the only source of the repellent activity. After characterization and fractionation of the salivary proteins by gel electrophoretic and HPLC-techniques it was shown that the dispersion-inducing behaviour was caused by the 77–82 kDa proteins. A strong linear correlation ( r = 0.914) between the applicated quantity of the 77–82 kDa proteins and the resulting repellency was calculated. Male German cockroaches perceiving a threshold quantity of 250 ng of the 77–82 kDa proteins/cm 2 displayed typical dispersion behaviour. It is suggested that the dispersion-inducing proteins take effect in two different ways: 1. (1) as a defence pheromone of early nymphal stages deterring adult cockroaches from cannibalism; 2. (2) as a dispersion pheromone mainly emitted by females under stress-inducing conditions, thus acting as a regulator of space. In both cases, males presenting the strongest reaction are presumed to be the main target group for the pheromone.

Lipid reserves of the brown water snake Nerodia taxispilota

1. 1. Lipid stores of the brown water snake ( Nerodia taxispilota) varied seasonally with reserves increasing before ovulation in females and prior to hibernation in both sexes. 2. 2. Gravid females had greater lipid reserves than either males or nongravid females of equal size. 3. 3. Relative lipid content of fat bodies increased with weight of fat bodies; small fat bodies had low lipid content while large fat bodies were more than 98% lipid. 4. 4. Mass of fat bodies was an accurate predictor of energy content of fat bodies; however, small masses provided inaccurate estimates since little of the fat body actually was lipid.

Effect of Relative Clutch Mass on Sprint Speed in the Lizard Lacerta vivipara

Relative clutch mass (RCM; the ratio of clutch to female body mass), a measure of the physical burden imposed on gravid females, is considered an important life history trait in reptiles. Several authors (Vitt and Congdon, 1978; Vitt, 1981; Vitt and Price, 1982; Seigel and Fitch, 1984) have hypothesized that RCM has evolved through differential mortality resulting from decreased locomotor ability and increased energetic costs of locomotion associated with transporting the added mass of the clutch. Three lines of evidence support this hypothesis or its assumptions. First, comparative studies (Vitt and Congdon, 1978; Vitt and Price, 1982; Seigel and Fitch, 1984) have shown that high RCM values are found in lizards that do not rely on fast movement for foraging and escaping (sit-and-wait foraging, cryptic escape behavior), and in oviparous snakes; low RCM is associated with active foraging and fleeing escape behavior in lizards, and with viviparity in snakes. Secondly, intraspecific studies have shown a reduction of sprint speed (Shine, 1980; Bauwens and Thoen, 1981; Garland, 1985; Seigel et al., 1987) or endurance (Seigel et al., 1987) in gravid lizards and snakes. Thirdly, differences among individuals in sprint speed and RCM have been identified in four scincid lizards (Shine, 1980) and one snake (Seigel et al., 1987). The latter studies strongly suggest that the added clutch mass exerts a direct negative effect on the locomotor performance of gravid females. In this note we document the relation between sprint velocity and RCM in gravid females of the lizard Lacerta vivipara. Lacerta vivipara is a small (adult body length: 45-65 mm) viviparous lizard that reproduces once a year. It is an agile lizard that forages actively on insects and other invertebrates (Avery, 1966; Itamies and Koskela, 1971; Koponen and Hietakangas, 1972; Pilorge, 1982), behaves like a typical heliotherm (Avery, 1976; Van Damme et al., 1987), and uses crypsis, flight and tail autotomy to escape from predators (Bauwens and Thoen, 1981). At parturition, this species has a remarkably high RCM (=clutch mass/female body mass after parturition). Mean values observed in different populations/years are: 0.81 (Bauwens and Thoen, 1981), 0.41-1.02 (Pilorge et al., 1983), 0.45-0.56 (Pilorge 1987) and 0.63 (this study). These values are among the highest reported for lizards in general (x = 0.29; range 0.05-0.68) as well as in live-bearing species (x = 0.31; range 0.13-0.48; recalculated from table 1 in Vitt and Price, 1982). During April 1984, we captured adult female lizards in the Belgian national nature reserve de Kalmthoutse heide (51?25'N, 4?25'E, Province of Antwerp, Belgium). They were mated in the laboratory and maintained individually in outdoor enclosures until parturition. About two weeks (x = 14.9 days, range: 8-25) before parturition, we determined sprint speeds of 17 gravid and 6 nongravid adult females by chasing them by hand down a 2 m racetrack (Huey et al., 1981). The t ack was constructed of plywood with walls 30 cm high positioned 15 cm apart; its floor was covered with carpet that provided excellent traction. Nine pairs of photocells measured the time the lizards needed to cover 8 consecutive intervals of 25 cm. Before test-

Leishmaniasis in the Jordan Valley: Differential Attraction of Dispersing and Breeding Site Populations of Phlebotomus papatasi (Diptera: Psychodidae) to Manure and Water

The response of Phlebotomus papatasi Scopoli to traps baited with manure or water was used to compare the behavior of flies near rodent burrows (breeding sites) and dispersing flies in fallow fields. The degree of response in each biotype was defined for each bait by the difference between catches in baited and unbaited traps. Manure bait attracted twice as many flies near the burrows and 2.7 times more flies in the field compared with unbaited traps. In both locations, the manure bait increased the capture of males and nongravid females, whereas gravid females were attracted only near burrows and not in the fields. The catch in the fields with water bait was similar to the unbaited control. However, near burrows, water bait captured more males and gravid females, but not nongravid females. These results demonstrate specific behavioral patterns of the dispersing P. papatasi population.

Flight Activity of the Threecornered Alfalfa Hopper (Homoptera: Membracidae) in Soybean

Threecornered alfalfa hopper, Spissistilus festinus (Say), flight studies conducted with yellow sticky traps (3 m tall) in soybean, Glycine max (L.) Merr., showed that movement is primarily within 33 cm above the substrate. Two peaks in flight activity were detected in 1986 and one in 1987; significantly more males than females were trapped. Lateseason population peaks were detected by sweep net samples but not by sticky traps. Prevailing wind, sunny and shady exposures on sticky traps, and adjacent crops appeared to have no effect on trap catches. The proportion of nongravid females increased near the end of the growing season.

Selection component analysis of the Mpi locus in the amphipod Platorchestia platensis

Genotype frequencies of gravid females and their offspring, of non-gravid females, and of adult males were measured for the Mpi locus in a natural population of the amphipod Platorchestia platensis. These gave tests of gametic, sexual, fecundity and zygotic selection. The genotype distribution of adult males was significantly different from that of adult females. There were more heterozygous males than expected, suggesting that zygotic selection and not immigration produced the difference between the sexes.

Stress-induced changes in serum testosterone, estradiol-17β and progesterone in the turtle, Chelydra serpentina

1. 1. Adult male and female common snapping turtles, Chelydra serpentina were obtained during June, July and August and, starting immediately after capture, blood samples were drawn at timed intervals of 0, 6, 24, 48, 72 and 168 hr. 2. 2. Captivity induced significant changes in serum concentrations of testosterone (T) in males and estradiol-17β (E 2) and progesterone (P) in females. 3. 3. Males exhibited an initial rise in plasma T which was followed 24–48 hr later by a decline to levels significantly below the initial values. The month of capture influenced both the degree and pattern of the response. 4. 4. Females showed an initial rapid and significant rise in serum E 2 and P concentrations which returned to initial levels within 7 days. The level and pattern of response varied between gravid and non-gravid females.

Timber Rattlesnakes (Crotalus horridus) of the Pine Barrens: Their Movement Patterns and Habitat Preference

Radiotelemetry was used to monitor the movements and habitat use of timber rattlesnakes (Crotalus horridus) in the Pine Barrens of southern New Jersey. Reproductive condition strongly influenced both aspects of behavior. Males generally exhibited the largest activity ranges, and the sizes of their ranges were positively correlated with the number of days the snakes were monitored. This was not true for gravid or non-gravid females. Time series analyses indicated that movement patterns of males and non-gravid females consisted of constantly shifting, non-overlapping activity areas. In most cases these snakes moved in a looping pattern during the active season that returned them to the same hibernation site from which they departed. Gravid females exhibited more static, overlapping activity areas and shorter dispersal distances from hibernacula. Males and non-gravid females utilized forested habitat with greater than 50% canopy closure, thick surface vegetation (approx. 75%), and few fallen logs. This habitat occurred with high frequency throughout the study area. Gravid snakes utilized less densely forested sites with approx. 25% canopy closure, an equal mixture of vegetation and leaf litter covering the surface, frequent fallen logs, and warmer climatic conditions. This habitat occurred in low frequency on the study area and was largely restricted to the edge of sand roads.

Efficacy of Insecticides for German Cockroach Control, 1986 and 1987

Abstract Laboratory tests were initiated to determine the relative efficacy and residual life against the German cockroach for the organophosphates azamethiophos (50% wettable powder), TD2222 (24.4% chlorpyrifos, microencapsulated), Dursban ME (11.7% chlorpyrifos, microencapsulated), and Dursban LO (41.5% chlorpyrifos). Test sprays of various concentrations were applied to 1-sq-ft (929 cm2) tempered masonite panels at the rate of 1 gal/1000 sq ft (3.78 ml/929 cm2) using a mechanized spray tower apparatus equipped with a stainless steel nozzle tip, Spraying Systems Tee-Jet 8001E, at a constant pressure of 25 psi. After treatment, panels were placed into vertical storage compartments (dark conditions) for residual aging. Residual agings evaluated varied from 3 to 12 mo for any one of the test insecticides. At the appropriate aging period, test insects were confined (continuous exposure) to the treated panel using 12.7-cm-diam plastic rings, lightly greased with a petrolatum-mineral oil mixture. Three or 4 exposure times were evaluated at each aging period for any insecticide. Initial exposure times ranged from 10 s to 5 h, but as the spray deposits aged these exposure times were increased to as long as 24 h for some treatments. The particular range of exposure times evaluated was selected to deliniate the critical periods necessary to produce acceptable mortalities. After exposure, insects were removed from the treated panel and placed in unteated holding jars, with food and water provided, for 48 h. Mortality counts were recorded at the end of the exposure time and at 24 and 48 h after the start of the exposure; the final mortality 48 h after the exposure is reported here. Six replicates were conducted for each exposure time, at each aging period, for each insecticide treatment. Each replication consisted of 10 cockroaches—5 adult males and 5 adult nongravid females.

Efficacy of Orthene and Super Hydro-Sol for German Cockroach Control, 1987

Abstract Comparative laboratory tests were initiated to determine the relative efficacy and residual life of Orthene PCO Formula II (96% acephate) and Orthene PCO Formula II plus Super Hydro- Sol (Grillocin®, an odor neutralizer) against the German cockroach. Identical Orthene solutions were prepared at 1% AI; to one of these the deoderant Super Hydro-Sol was added at the rate of 1.5 oz/gal. Spray dilutions were applied to 1-sq-ft (929 cm2) tempered masonite panels at the rate of 1 gal/1000 sq ft (3.78 ml/929 cm2) using a mechanized spray tower apparatus equipped with a stainless steel nozzle tip, Spraying Systems Tee-Jet 8001E, at a constant pressure of 25 psi. After treatment, panels were placed into vertical storage compartments (dark conditions) for residual aging. Residual agings evaluated were 1, 14, 30, and 60 days. At the appropriate aging period, test insects were confined (continuous exposure) to the treated panel using 12.7-cm-diam plastic rings, lightly greased with a petrolatum-mineral oil mixture. Exposure times evaluated were 30 min and 1, 2, and 4 h. After exposure, insects were removed from the treated panel and placed in untreated holding jars, with food and water provided, for 48 h. Morbidity counts were recorded at the end of the exposure period and at 24 and 48 h after the start of the exposure; the final morbidity 48 h after the exposure is reported here. Six replicates were conducted for each exposure time, at each aging period, for each insecticide treatment. Each replication consisted of 10 cockroaches—5 adult males and 5 adult nongravid females.

Reduction in locomotor ability as a cost of reproduction in gravid snakes.

Recent studies suggest that lower survival among gravid squamate reptiles may be partially the result of decreased locomotor ability during gestation. In this study, we compared the speed and endurance of female garter snakes (Thamnophis marcianus), before, during, and after pregnancy. Gravid snakes had significantly lower locomotor performance than did non-gravid females, and performance varied among stages of gestation, reaching a minimum 0-6 weeks prior to parturition. Both number of offspring and relative clutch mass were inversely correlated with locomotor performance; as females increased these traits, locomotor ability decreased. If reduced locomotor performance results in greater risk of predation and/or lowered foraging ability, then natural selection (operating via differential mortality or feeding rates of gravid females) may result in important constraints on both clutch size and relative clutch mass in squamates.