Chemosensory cues play an important role in the daily lives of salamanders, mediating foraging, conspecific recognition, and territorial advertising. We investigated the behavioral effects of conspecific whole-body odorants in axolotls, Ambystoma mexicanum, a salamander species that is fully aquatic. We found that males increased general activity when exposed to female odorants, but that activity levels in females were not affected by conspecific odorants. Although males showed no difference in courtship displays across testing conditions, females performed courtship displays only in response to male odorants. We also found that electro-olfactogram responses from the olfactory and vomeronasal epithelia were larger in response to whole-body odorants from the opposite sex than from the same sex. In males, odorants from gravid and recently spawned females evoked different electro-olfactogram responses at some locations in the olfactory and vomeronasal epithelia; in general, however, few consistent differences between the olfactory and vomeronasal epithelia were observed. Finally, post hoc analyses indicate that experience with opposite-sex conspecifics affects some behavioral and electrophysiological responses. Overall, our data indicate that chemical cues from conspecifics affect general activity and courtship behavior in axolotls, and that both the olfactory and vomeronasal systems may be involved in discriminating the sex and reproductive condition of conspecifics.

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Although mate number is perceived to be the primary factor affecting male reproductive success in polygynous systems, differences in female reproductive qualities may also influence variation in male reproductive success. We combined 32 years of data on variation in reproductive qualities (clutch size and clutch frequency) of female Midland Painted Turtles ( Chrysemys picta marginata Agassiz, 1857) with genetic data on patterns of repeated paternity (i.e., stored sperm use) and multiple paternity to examine the potential influence on male reproductive success. Over 24 years (1983–2006), the number of reproductive females each year averaged 84 (minimum–maximum = 62–106) and, on average, 23% (minimum–maximum = 6%–40%) produced two clutches (intraseasonally). Among females with reproductive histories spanning 5–24 years (N = 167), 26% of individuals produced only one clutch annually, whereas 74% produced two clutches within a season. Among just intraseasonally iteroparous females, second-clutch production varied from 7% to 50%. Repeated paternity was observed in 97.5% of 40 paired clutches and 44% of 9 among-year comparisons of clutches from consecutive years. The frequent use of stored sperm to fertilize sequential clutches within and potentially among years can substantially increase a male’s reproductive success, particularly if males can base mating decisions on phenotypic characteristics correlated with female quality.

Male reproductive success (RS) in polygamous species with minimal social systems is often determined by the number of mates. However, because male RS is translated through females, the number of offspring sired can also be influenced by female qualities. Empirically sufficient data to document how tradeoffs between mate number and quality influence male RS are seldom available for long-lived, iteroparous species. We combined long-term life history data on the E. S. George Reserve (ESGR, MI, USA) with parentage data from 155 clutches of 59 female painted turtles (Chrysemys picta marginata) of varying reproductive frequencies (2003)(2004)(2005)(2006) to determine the relative contribution of female numbers and qualities on male RS. One previously documented trait of female painted turtles that can have substantial influences on male RS is repeat paternity through the use of stored sperm to fertilize over 95 % of within-year clutches. In addition, our study found that second-clutch producing female painted turtles on the ESGR have higher among-year reproductive frequencies than do first-clutch only females. Multiple paternity was detected in 14.1 % of clutches (min-max=6.1-30.0 % annually), and the number of mates of both sexes was low annually (males 1.0; females 1.2) and over 4 years (males 1.1; females 1.7). Among successful males, RS varied substantially (1-32 offspring) and was strongly influenced by the combination of female reproductive frequency and repeat paternity (>38 % among years), but not mate number. Low mate number for both sexes was unexpected in a species without complex mating behaviors or parental care.

Summary The effects of stream environmental conditions on inter individual variability were quantified for lake sturgeon, Acipenser fulvescens (Rafinesque, 1817) yolk sac larvae in the expression of behavioral and morphological traits. Simulated experimental treatments including food availability (brine shrimp), presence of chemosensory predator cues (adult crayfish and odonate larvae), and conspecific density (2 verses 1 larvae) were applied to determine the effects on the duration of time in substrates following hatch and growth from hatch until emergence. In spring 2010, larvae from two full‐sib families were individually placed into 240 mL perforated plastic containers (n = 263) with gravel substrate immediately following hatch. Containers were maintained in stream water at ambient temperatures and constant flow (~0.03 m/sec) in 4 m experimental flowing streams. Duration of time (days) each individual remained in the substrate was recorded. Morphological traits including total length (mm), body area (mm2), and yolk‐sac area (mm2) were measured at hatch and at the time of emergence from substrate to compare growth and amount of endogenous yolk reserves used in individuals among experimental treatments. Environmental conditions significantly affected emergence time. Individuals emerged earlier in treatments exposing larvae to chemosensory predator odorants and higher conspecific density. Use of endogenous reserves (yolk‐sac area) at the time of emergence did not differ among treatments. Growth was significantly greater when individuals were provided a food source compared to all other treatments. Quantifying the magnitude and direction of phenotypic responses to environmental conditions is important to understand potential factors affecting survival during early life stages and population viability under conditions of increasing environmental variability.