Elucidating the Life History and Ecological Aspects ofAllodero hylae(Annelida: Clitellata: Naididae), A Parasitic Oligochaete of Invasive Cuban Tree Frogs in Florida

Abstract

Given their ubiquitous nature, it is surprising that more oligochaete annelid worms (Annelida: Clitellata) have not adopted an endoparasitic lifestyle. Exceptions, however, are the understudied members of the genus Dero (Allodero) that parasitize the ureters of tree frogs and toads. This study experimentally explores the life cycle and host specificity of Allodero hylae, the worm's use of chemical cues in host searching, and its seasonal prevalence and abundance over a year-long collection period on the Florida Southern College campus. A total of 2,005 A. hylae was collected from the ureter, urinary bladder, or expressed urine of wild Osteopilus septentrionalis ; a significant positive correlation was found between host snout-vent length and parasite intensity for female but not male hosts. Monthly prevalence of A. hylae reached a peak of 58% in April, but never dropped below 20% in any month; mean abundance peaked March-May, whereas few worms were recovered in December and January. Confirming a parasitic lifestyle, wild-collected hosts with intense infections, typically >40 worms, showed obvious dilatation of the ureter wall, and some young-of-the-year O. septentrionalis exposed to A. hylae in the laboratory were killed by the apparent rupture of the host's ureter. The worm has a direct life cycle: worms expelled in the host's urine are capable of locating and re-infecting other hosts within aquatic microhabitats such as bromeliad tanks, and worms can survive for weeks in a free-living environment, even undergoing a morphological change. Further, chemotaxis assays found a positive response to a tree frog attractant for worms recently removed from hosts. Overall, this study provides the first multifaceted investigation on the life history and ecology of any Allodero spp., which offers new insights into an understudied endoparasitic oligochaete.

Exploring Differential Gene Expression Profiles OfDero (Allodero) HylaeIn Their Parasitic And Free-Living Forms

“…However, it has recently been experimentally demonstrated that infections cause physical damage to the ureter that can kill young frogs (Andrews et al, 2015). Andrews et al (2015) also demonstrated that parasitic worms could be expelled from their host during urination. During intense infections, worms effectively spill over from the ureter into the urinary bladder and are susceptible to being voided with the urine.…”

“…This major morphological transformation provides the previously parasitic worms with the necessary anatomical structures of their free-living environment. The worms are capable of surviving in a free-living environment for an extended time period, although it is unclear under what circumstances free-living D. hylae seek anuran hosts (Andrews et al, 2015).…”

“…Facultative parasites can transition between free-living and parasitic lifestyles under specific environmental conditions, providing an opportunity to understand the genetic mechanisms that facilitate a transition to a parasitic lifestyle. The phenotypically plastic annelids in the genus Dero and their anuran hosts may serve as a model system to study the evolutionary transition to parasitism (Gelder, 1980; Andrews et al, 2015). While few studies have been conducted on these rare endoparasitic annelids, it is well-established that Dero worms facultatively parasitize or phoretically travel on anuran hosts (Lopez et al, 1999; Andrews et al, 2015).…”

“…The phenotypically plastic annelids in the genus Dero and their anuran hosts may serve as a model system to study the evolutionary transition to parasitism (Gelder, 1980; Andrews et al, 2015). While few studies have been conducted on these rare endoparasitic annelids, it is well-established that Dero worms facultatively parasitize or phoretically travel on anuran hosts (Lopez et al, 1999; Andrews et al, 2015). It is unknown what genetic mechanisms facilitated the presumed progression from phoresy to facultative parasitism in some species of Dero .…”

“…Dero hylae is capable of locating and infecting new hosts via the hosts’ urine, as it travels into the ureter by passage of the cloaca, where the worm adopts an endoparasitic lifestyle (Harman and Lawler, 1975; Andrews et al, 2015). Within 72 hours of a free-living worm infecting a host, they begin to lose their hair setae, some of their dorsal setae, and gills in the fossa are minimized (Fig.1).…”