Pheromonal markers as indicators of parasite load: parasite-mediated behavior in salamanders ( Plethodon angusticlavius )

Abstract

Assessment of parasite load of conspecifics may be important during social interactions such as courtship and aggressive encounters. We used a correlational study to test whether pheromonal markers can be used to assess parasite load of conspecifics, and whether the parasite load of the pheromone receivers affected their responses. We tested the responses of parasitized and nonparasitized Ozark zigzag salamanders, Plethodon angusticlavius, to territorial markers (fecal pellets) from conspecific males. Males and females were simultaneously exposed to fecal pellets placed in front of two artificial burrows located at the opposite ends of their chambers. The treatments were (1) fecal pellet of male with low parasite load versus fecal pellet of male with high parasite load, (2) fecal pellet of male with low parasite load versus control pellet (chemical blank), and (3) fecal pellet of male with high parasite load versus control pellet. Nonparasitized females spent significantly more time near fecal pellets of males with low parasite load in test condition 1, whereas the behavior of parasitized females was not significantly different from random in any test condition. Males responded differently to treatments only in condition 3; males with low parasite loads spent significantly more time near control pellets, whereas males with high parasite loads spent significantly more time near fecal pellets of males with high parasite loads. This study demonstrates that pheromonal markers may be used for assessment of parasite load of conspecifics and that responses by both males and females may be influenced by their own level of infection.

From molecules to mating: Rapid evolution and biochemical studies of reproductive proteins

“…In contrast, lungless salamanders of the family Plethodontidae are purely terrestrial, with females laying clutches of eggs on land and juveniles hatching already in their adult morph [47]. Plethodontid salamanders contain various skin glands that secrete pheromones which provide information on species [90, 91], body size [92], sex [90], female gravidity [92,93], diet [94,95], and parasite load [96]. The most well-characterized of these glands is a male-specific chin gland – the mental gland – that seasonally hypertrophies in response to elevated plasma androgens that coincide with the courtship season [97,98].…”

Rapid onset of mate quality assessment via chemical signals in a woodland salamander (Plethodon cinereus)

“…Plethodontid pheromones also convey a large amount of information about the sender, such as species (Jaeger and Gergits 1979;Dawley 1984Dawley , 1986, sex (Dawley 1984;Jaeger et al 1986;Dantzer and Jaeger 2007a), size (Mathis 1990a;Marco et al 1998), and individual identity (Madison 1975;Tristram 1977;McGavin 1978;Jaeger 1981;Simon and Madison 1984;Jaeger et al 1986). Other information transferred by chemical signals relates to conditiondependent aspects of the sender that can change over time, such as the reproductive status of females (gravid vs. nongravid, Marco et al 1998;Dantzer and Jaeger 2007b), parasite load (Maksimowich and Mathis 2001), tail autotomy (partial loss of tail) and injury (Sullivan et al 2003;Wise et al 2004), as well as the quality of an individual's diet (Walls et al 1989).…”

“…Females of many species prefer males of higher "quality," as assessed by signals conveying information about their diets (Walls et al 1989;Ferkin et al 1997;Fisher and Rosenthal 2006). Other condition-dependent information may also be utilized by females to assess potential mates, such as male health and parasite load (Penn and Potts 1998;Maksimowich and Mathis 2001;Doucet and Montgomerie 2003) or dominance status (Moore et al 1997;Kortet and Hedrick 2005). In general, condition-dependent signals serve to provide females with information regarding behavioral, physiological, and even potentially genetic information that indicates the sender as a potentially valuable reproductive partner (Andersson 1994).…”

Discrimination of chemical stimuli in conspecific fecal pellets by a visually adept iguanid lizard, Crotaphytus collaris

“…Fecal pellets appear to utilize multiple sensory modalities, where chemical cues may either enhance or supplement the effects of certain visual cues, as Madison (1977) previously predicted for iguanids. Males may utilize the visual component of the signal to assess territorial boundaries of rival males, while either sex may utilize the chemical component to assess various aspects of conspecifics, including individual identity (Alberts 1992;Léna and de Fraipont 1998), social status (Duvall 1979;Cooper and Pérez-Mellado 2002), determination of reproductive status or preferences (López et al 2003;Head et al 2005), and indication of internal parasite load, as evidenced in salamanders (Maksimowich and Mathis 2001). Future research is necessary to determine the type and usage of various potential signals that collared lizards (male and/or females) may utilize in conspecific fecal pellets.…”