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Ticks on emerged hatchlings of Komodo Dragon June 27, 2008

Posted by ekologi in Uncategorized.
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Ticks on emerged hatchlings of Komodo Dragon (Varanus komodoensis) on Komodo island, Indonesia

M. JERI IMANSYAH

Komodo Survival Program, Jl Pulau Moyo, Komplek Karantia Blok 2 no 4, Denpasar, Bali 80222, Indonesia

mjimansyah@yahoo.co.id

TIM S. JESSOP

Zoos Victoria, PO Box 74, Parkville, Melbourne, VIC 3052, Australia

tjessop@zoo.org.au

The ticks (Acarina) that parasitise varanid lizards (Sauridae) are mainly from two Genera; Amblyomma and Aponomma (King & Green, 1999). Ticks as ectoparasites consume host blood, cause disease and can function as important vectors for microparasites, which can negatively influence the fitness of reptiles (Main and Bull 2000). The Komodo dragon (Varanus komodoensis), a large monitor lizard, from South Eastern Indonesia has been documented to possess three species of tick including Amblyomma helvolum a generalist, and two host specific species- A. robinsoni and Aponomma komodoense (Auffenberg, 1981). In Zoos, Komodo also reported loaded by A. komodoense that were infested from wild specimens (Burridge et al., 2004). However as yet little is known about the ecology, or the fitness implications, of this host-parasite dynamic. One aspect of this host-parasite dynamic that remains unknown is the possibility that ticks have evolved strategies to parasitise hatchling dragons on emergence from their nests. From a parasites perspective, host environments of juvenile animals, are those that provide the east resistance with respect to immunological (i.e. lack of acquired immunity) or physical (eg skin thickness) barriers could provide greater benefit (reference). Herein we report on the capacity of ticks to parasitise recently emerged hatchling Komodo dragons from three nests on Komodo Island.

In January of each year (2003-2006) a sample of known active nests of V. Komodoensis were caged to enable capture of hatchlings as part of routine annual monitoring of the ecology and life-history of this species in Komodo National Park (Jessop et al., 2004). Prior to emergence in March/April (late wet season), nest cages were monitored twice daily (morning and afternoon coinciding with emergence of hatchlings from the ground) to enable measurement and marking of individual hatchlings prior to release. In 2004, we also examined for the presence of ectoparasites of hatchlings on Komodo Island, one of four extant populations within Komodo National Park.

From the three nests monitored on Komodo Island in 2004 (referred to as LSB1, LL64 and LSB3), 47 hatchling Komodo were captured in March (estimated within 4 hours post-emergence). Together these hatchlings has a mean- weight of 95.53 ± 2.20 gr and SVL 18.78 ± 0.14 cm. Hatchlings from two of the three nests, were found to be carrying nymphal ticks of one species, Aponomma komodoense. Two of the 18 hatchlings (11.11%) from nest LSB1 had ticks, one had 1 tick, the other had 3 (Table 1). Clutch LL64 had 16 individuals, of which 9 (8.333%) carried ticks. The number of ticks ranged from 1 to 20, with an average number of ticks per hatchling of 7.44 ± 2.46. Hatchlings (n =12) from nest LSB2 were not observed to carry ticks.

Table 1. Tick infestation of emerged hatchlings from two of three nests of Komodo dragon Varanus komodoensis on Komodo island.

Nest

Latitude

Longitude

Hatchlings

Number of Ticks

Frequency with ticks

1

2-5

>5

LSB1

8:32:11

119:31:44

18

1

1

0

11 %

LL64

8:33:14

119:30:38

12

2

2

6

83 %

LSB2

8:32:04

119:32:40

16

0

0

0

0 %

Our results indicate that alongside larger Komodo dragons, hatchlings can act as hosts for ticks. By parasitizing hatchlings on emergence, ticks could greatly increase their capacity to find new and potentially more importantly immunologically naïve hosts (i.e. no acquired resistance). Female dragons, which act as hosts for ticks, spend considerable periods of time around the nest both prior to and after oviposition and thus could enable ticks to deposit eggs (that remain quiescent) around the nest site until hatchlings emerge. Seasonal cues, including the conspicuous transition from an extended dry season through to the short summer wet season coinciding with the monsoon represent an important cue for many organisms breeding in the wet-dry tropics of Eastern Indonesia (Kerr and Bull, 2006; Monk et al., 1997). This seasonal cue could provide necessary environmental information enabling nymphal ticks to synchronise their own hatching and questing activity with the emergence of hatchling Komodo dragons (reference). At present we do not know of the specific fitness consequences that ticks impart on their hatchling hosts. While ticks can illicit fitness costs by reducing growth, condition and the locomotor capacity in other lizards, similar consequences for hatchling Komodo dragons remain to be determined (Hanson et al., 2007; Main and Bull, 2000).

Acknowledgement

We thank Ibrahim Payung, Heru Rudiharto, and Zamzam for their assistance during field work. Financial support was provided by a Millennium Post Doctoral Fellowship from the Zoological Society of San Diego (ZSSD) to TSJ. Approval for the research was granted under a MOU between ZSSD and The Nature Conservancy (Indonesia Program) and by the Indonesian Department of Forest Protection and Nature Conservation (PHKA).

References:

Auffenberg, W. 1981. The Behavioral ecology of the Komodo dragon. Gainesville, University Florida Press.

Burridge, M.J., Leight-Anne Simmons, T.Condie. 2004. Control of an exotic tick Aponoma komodoense) infestatation in a Komodo dragon (Varanus komodoensis) exhibit at a zoo in Florida. Journal of Wildlife Medicine. 35(2): 248-249.

Hanson, B.A., P.A.Frank, J.W.Mertins, J.L.Corn. 2007. Tick paralysis of a snake caused by Amblyoma rotundatum (Acari: Ixodidae). Journal of Medical Entomology. 44(1): 155-157.

Jessop, T.J., Sumner, J., Rudiharto, H. Purwandana, D., Imansyah, M.J. & Philips, J.A. 2004. Study on nest distribution, utilization, and selection by Komodo dragon, Varanus komodoensis: implication for conservation and management. Biological Conservation. 117: 463-470.

Kerr, G. D., C.M. Bull,. 2006. Interaction between climate, host refuge use, and tick population dynamics. Parasitology Research. 99: 214-222.

King, D.R. & Green, B. 1999. Goannas: the biology of Varanid lizards. Sydney, New South Wales Press Ltd.

Main, A.R., Bull, C.M. 2000. The impact of tick parasites on the behaviour of the lizard Tiliqua rugosa. Oecologia 122: 574-581.



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