Sex ratio in flea infrapopulations: number of fleas, host gender and host age do not have an effect

Abstract

This study set out to determine whether the sex ratio of fleas collected from host bodies is a reliable indicator of sex ratio in the entire flea population. To answer this question, previously published data on 18 flea species was used and it was tested to see whether a correlation exists between the sex ratio of fleas collected from host bodies and the sex ratio of fleas collected from host burrows. Across species, the female:male ratio of fleas on hosts correlated strongly with the female:male ratio of fleas in their burrows, with the slope of the regression overlapping 1. Controlling for flea phylogeny by independent contrasts produced similar results. It was also ascertained whether a host individual is a proportional random sampler of male and female fleas and whether the sex ratio in flea infrapopulations depends on the size of infrapopulations and on the gender and age of a host. Using field data, the sex ratio in infrapopulations of 7 flea species parasitic on 4 rodent species was analysed. Populations of 3 species (Nosopsyllus iranus, Parapulex chephrenis and Xenopsylla conformis) were significantly female-biased, whereas male bias was found in 1 species (Synosternus cleopatrae). In general, the sex ratio of fleas collected from an individual rodent did not differ significantly from the sex ratio in the entire flea population. Neither host gender, and age nor number of fleas co-occurring on a host affected (a) the sex ratio in flea infrapopulations and (b) the probability of an infrapopulation to be either female- or male-biased.

Bartonella Genotypes in Fleas (Insecta: Siphonaptera) Collected from Rodents in the Negev Desert, Israel

“…However, as no characterization of Bartonella in the hosting rodent was carried out and no information on whether the fleas were hosting more than one host was available due to the characteristics of this survey, this enigma will remain unsolved. Previous studies have shown that the absolute amount of a blood meal taken by a male flea is smaller than that of a female flea meal (15,17). Our results suggest that the difference in the amount of a blood meal between male and female fleas is not a critical factor for acquiring Bartonella bacteria.…”

Subtle short-term physiological costs of an experimental augmentation of fleas in wild Columbian ground squirrels

“…If parasites have co-evolved to specific hosts, they are more likely to deliver less irritable bites and introduce saliva that does not elicit an immune or behavioral response from the host (Dick and Patterson, 2007). Unfortunately, our observations do not account for a sexbiased effect whereupon fleas of a particular sex differentially induce stress (Hawlena et al, 2005;Krasnov et al, 2008). As fleas were collected and assigned randomly to treated individuals, we can assume that any sex bias in the parasites averaged out when the treated and control groups were compared.…”

“…These hostparasite links are illustrated by eastern grey kangaroos selectively foraging away from better quality, but fecally contaminated grass patches (Garnick et al, 2010) or male grey squirrels suffering from higher flea parasitization when upregulating testosterone levels (Scantlebury et al, 2010). As a result, parasites, when numerous, have the potential to generate a high resource toll on their hosts (Khokhlova et al, 2002;Krasnov et al, 2008). For example, when feral rock doves had lice levels experimentally increased, they steadily lost feather and body mass, resulting in compromised integument insulation (increased thermal conductance) and increased metabolic rate (Booth et al, 1993).…”

Fleas as Useful Tools for Science

“…Given the vectorial capacity of fleas, prevalence has the potential to measure the dissemination of pathogens. When abundance and/or prevalence are related to the certain factors, especially in studies with fleas and mites parasitizing the same hosts species, some practical results can be observed, such as (i) flea species richness increases with latitude of the center of host geographical range [85]; (ii) the abundance of the host's body occupied by fleas can be reliably used as an indicator of the entire flea population size, because indices of fleas on host bodies and of fleas in host burrows are positively correlated [86]; (iii) the relationship between the number of flea species and the number of flea genera per host tends to decrease with an increasing local mean annual temperature [87]; (iv) both in fleas and mites, the mean abundance predicts prevalence, and the prevalence of a flea species increases with an increase in its mean abundance within and across host species [88,89]; (v) the sex ratio of fleas collected from an individual host does not differ significantly from the sex ratio of the entire flea population [90]; and (vi) the flea niche breadth, measured in terms of both their spatial (geographic range size) and biological (host specificity) components, increases at higher latitudes in accordance with hypotheses about latitudinal gradients [91]. Still in relation to environmental factors, a study involving three hosts-Monodelphis domestica, Necromys lasiurus, and Oligoryzomys eliurus-and different localities across Brazil found that the mean flea abundance significantly increased with increasing mean annual air temperatures and proximity to the equator.…”