An instance of Boiga dendrophila dendrophila (Boie, 1827) (Reptilia: Colubridae) being parasitized by Amblyomma helvolum Koch, 1844 (Acari: Ixodidae), with comments about the attachment sites of this tick species

Ectoparasites, such as ticks, may exhibit preferences for particular attachment sites on various hosts, since the choice of attachment sites may affect tick survival. Herein we report an instance of a mangrove snake, Boiga dendrophila dendrophila , being parasitized by the tick Amblyomma helvolum , with comments on this tick’s attachment sites. Our collection of A. helvolum appears to be the first record of this species from Sandakan, a city on the northeast coast of Borneo, in the Malaysian state of Sabah.


Introduction
For ectoparasites, such as ticks, survival not only entails locating a suitable host, but also attaching at sites that facilitate feeding, while at the same time providing protection against host defensive behaviors and environmental abrasion accompanying host movements. However, not all tick species that parasitize a particular host necessarily utilize the same attachment sites, i.e., spatial niche segregation may occur (Anderson et al., 2013). Even within a particular species the sexes and active developmental stages (larvae and nymphs) may make use of different attachment sites (Chilton et al., 1992;Mysterud et al., 2014). Additionally, for a particular tick species there can be variation in the attachment sites on different host species (Chilton et al., 1992). An understanding of the natural history of tick species thus requires knowing not only which hosts they infest, but also the range of likely attachment sites on hosts.
The mangrove snake, Boiga dendrophila (Boie, 1827), is a relatively large arboreal member of the family Colubridae that inhabits lowland rainforests and swamps in southern Thailand, western peninsular Malaysia, Singapore, parts of Indonesia, Cambodia, Myanmar, Vietnam, and the Philippine Islands (Cox et al., 1998;Mattison, 1999). The subspecies Boiga dendrophila dendrophila (Boie, 1827) is endemic to Borneo (Uetz and Hosek, 2018). Boiga dendrophila is a nocturnal species, and although it may occasionally be found on the ground, it is primarily arboreal (Groen, 2008). Herein we report on ticks that were collected from a B. d. dendrophila specimen, with comments on their attachment sites.

Observation
On September 6, 2015, an adult male B. d. dendrophila (measurements were not taken) was found on the side of a road within an African oil palm (Elaeis guineensis Jacq.) plantation in Sepilok (N5°52'03.02" E117°57'19.53"; elevation: 16 m), Sandakan, in the Malaysian state of Sabah on the northeast coast of Borneo. Upon inspection, it was found that the snake was being parasitized by three ticks, two of which were attached to the dorsal surface posterior to the head ( Figure 1) and the other on the left ventral side of the mid-body of the snake ( Figure  2). After the ticks were removed and placed in a plastic vial of 75% ethanol for further study, the snake was released back into the wild. Based on the keys in Anastos (1950), and Voltzit and Keirans (2002), the two ticks from the head of the B. d. dendrophila were determined to be females of Amblyomma helvolum Koch, 1844. The remaining specimen was an Amblyomma nymph, but since the immature stages in this genus are morphologically conservative with few diagnostic characters (Lampo et al., 1997), we can only state that our nymph does not represent A. helvolum. The ticks were deposited in the Zoological Collection of the Forestry and Natural Resource Department of National Ilan University, Taiwan, R.O.C. (voucher number NIUFNR-PA-000019-Bd for the two Amblyomma helvolum females, and NIUFNR-PA-000020-Bd for the Amblyomma sp. nymph).

Discussion
Amblyomma helvolum has a natural distribution that extends from the Nicobar Islands of India eastward through parts of Thailand, Laos, Malaysia, Singapore, Vietnam, Indonesia, the Philippines, and Taiwan (Auffenberg, 1988;Kolonin, 1995;Petney and Keirans, 1995;Chao et al., 2013). Although this tick species has been collected from parts of Borneo (Kohls, 1957), we could not find reports specifically pertaining to Sandakan, so our observation appears to be a new distribution record.
Previous reports from Anastos (1950) and Robinson (1926) of A. helvolum parasitizing B. dendrophila are based on specimens collected by A.C. Oudemans on Berhala Island, also within the Malaysian state of Sabah. The apparent few records of this snake as a host of this tick is likely because the snake is rarely found on the ground, therefore making it an infrequent host for ticks. We are aware of only one East Asian ixodid tick species that might be described as arboreal, the unrelated Haemaphysalis megalaimae Rajagopalan, 1963, which is apparently specific to barbets (Aves: Piciformes, Megalaimidae) and has never been collected from ground-dwelling hosts (Geevarghese and Mishra, 2011). In addition no descriptions of the attachment sites were provided by Oudemans (1928). It is worth noting that Auffenberg (1988) and Lazell et al. (1991) reported on A. helvolum attaching to sites associated with wounds and scars on Luzon giant forest skinks, Otosaurus cumingi Gray, 1845, and a Sulawesi black racer, Ptyas dipsas (Schlegel, 1837), respectively, which suggests that these ticks will exploit sites that would enable efficient feeding (i.e., sites without protective scales). However, the choice of attachment site is likely not only determined by accessibility. Auffenberg (1988) also noted that although A. helvolum attached to similar sites on Gray's monitors, Varanus olivaceus Hallowell, 1837 (reported as Varanus grayi), and common water monitors, Varanus salvator (Laurenti, 1768), there were differences. On V. olivaceus, A. helvolum females mostly attached to the foreparts of the lizards, and were absent from the chin, while the males primarily attached to the base of the claws (Auffenberg, 1988). On V. salvator, however, the attachment sites of A. helvolum females were restricted to the foreparts of the lizards, including the chin, while the males primarily attached to the ventral areas of the chin, throat, chest, belly, cloaca, and tail (Auffenberg, 1988). Attachment site preferences may vary in both lizards and snakes. Thus, Chao et al. (2013) reported an instance similar to ours, where three A. helvolum females were attached to the dorsal neck area (posterior to the head) of a king rat snake, Elaphe carinata (Günther, 1864), whereas Simmons et al. (2002) recorded 21 A. helvolum males that were attached along the dorsal and lateral surfaces of three king cobras, Ophiophagus hannah (Cantor, 1836).
Throughout its distribution range A. helvolum infests a variety of reptilian hosts, many of which are collected from the wild for the pet trade. Since potential pathogenic Hepatozoon and Rickettsia species have been detected in A. helvolum in part of its distribution range (Sumrandee et al., 2014;Sumrandee et al., 2015), proactive measures to minimize the introduction of this tick into areas outside of its natural distribution range are essential. Importation inspections can be greatly improved if the feeding behaviors (e.g., attachment site preference) of these ticks are better understood. The anecdotal observations reported herein are insufficient to definitively determine the attachment site preferences of A. helvolum, but they suggest that such preferences may vary with host species and sex, and possibly with tick life history stage. Additional empirical studies are needed to further examine this aspect of the natural history of A. helvolum.

Disclosures
This study was partly funded by a grant to Jean-Jay Mao from the Tropical Rain Forest Course of National Ilan University, Taiwan. The opinions expressed herein are those of the authors and are not to be construed as official or representing the views of the U.S. Departments of the Army or Defense.