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Natural History Notes. Varanus salvator macromaculatus (Southeast Asian Water Monitor). Leech parasitism
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Zdunek, P. 2023. Natural History Notes. Varanus salvator macromaculatus (Southeast Asian Water Monitor). Leech parasitism. Herpetological Review 54(3):476
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Leaving the water to bask (usually in the sun) is a common behavior for many freshwater turtles, with some species also engaging in “nocturnal basking.” Ectoparasite removal is an obvious hypothesis to explain nocturnal basking and has also been proposed as a key driver of diurnal basking. However, the efficacy of basking, day or night, to remove leeches has not been experimentally tested. Therefore, we examined the number of leeches that were removed from Krefft's river turtles (Emydura macquarii krefftii) after experimentally making turtles bask at a range of times of day, durations, and temperatures. Turtles had high initial leech loads, with a mean of 32.1 leeches per turtle. Diurnal basking under a heat lamp for 3 hr at ~28°C significantly reduced numbers of leeches relative to controls. In diurnal trials, 90.9% of turtles lost leeches (mean loss of 7.1 leeches per turtle), whereas basking for 30 min under the same conditions was not effective (no turtles lost leeches, and all turtles were still visibly wet). Similarly, “nocturnal basking” at ~23°C for 3 hr was not effective at removing leeches. Only 18% of turtles lost leeches (one turtle lost one leech and another lost four leeches). Diurnal basking outdoors under direct sunlight for 20 min (mean temp = 34.5°C) resulted in a small reduction in leeches, with 50% of turtles losing leeches and an average loss of 0.7 leeches per turtle. These results indicate basking can remove leeches if temperatures are high or basking durations are long. However, it was only effective at unusually long basking durations in this system. Our data showed even the 20-min period was longer than 70.1% of natural diurnal basking events, many of which took place at cooler temperatures. Therefore, leech removal does not appear to be the purpose of the majority of basking events.
Journal of the Arkansas Academy of Science
In total, 435 specimens of the Southeast Asian freshwater leech species within the Hirudinidae family were collected from 17 locations of various types of aquatic habitats in northeastern Thailand. They were all morphologically placed within the genus Hirudinaria Whitman, 1886 and there were three distinct species: the common Hirudinaria
manillensis, 78.2% of all collected specimens and at all 17 locations, Hirudinaria
javanica at 20.3% of collected samples and from five locations and a rarer unidentified morphospecies (Hirudinaria sp.) with six samples from only two locations. The karyotypes of these three species were examined across their range in this study area for 38, 11 and 6 adult specimens of Hirudinaria
manillensis, Hirudinaria
javanica and Hirudinaria sp., respectively. This revealed different chromosome numbers among all three species, with Hirudinaria
javanica having n = 13, 2n = 26, Hirudinaria
manillensis lacked one small chromosome pair with n = 12, 2n = 24, and the unknown Hirudinaria sp. differed from any known Hirudinaria karyotypes in exhibiting a higher chromosome number (n = 14, 2n = 28) and a gradual change in size from large to small chromosomes. This suggests that the unknown Hirudinaria sp. is a new biological species. However, phylogenetic analysis based upon a 658 bp fragment of the cytochrome oxidase subunit I gene placed this unknown morphospecies within the Hirudinaria
manillensis clade, perhaps then suggesting a recent sympatric speciation, although this requires further confirmation. Regardless, the chromosomes of all three species were asymmetric, most with telocentric elements. A distinct bi-armed chromosome marker was present on the first chromosome pair in Hirudinaria
javanica, whilst it was on pairs 1, 2, 3 and 5 in Hirudinaria
manillensis, and on pairs 3 and 5 for the unknown Hirudinaria sp.
Molecular identifi cation of water monitors (Varanus salvator complex) from confi scations and the pet trade, including phylogenetic placement of V. s. ziegleri-a molecular reference for species conservation enforcement and conservation breeding Genetische Identifi zierung von Bindenwaranen (Varanus salvator-Komplex) aus Beschlagnahmungen und dem Tierhandel, einschließlich der phylogenetischen Einordnung von V. s. ziegleri-eine molekulare Referenz für Artenschutzvollzug und Erhaltungszucht Abstract Monitor lizards of the Varanus salvator species complex recently were split up into 15 taxa, either at the species or subspecies level. Most of them, viz. eight species, are endemic to the Phi-lippines: V. bangonorum, V. cumingi, V. dalubhasa, V. marmoratus, V. nuchalis, V. palawanensis, V. rasmusseni and V. samarensis. However, almost none of these species from the Philippines, except for V. cumingi, have so far been held in zoological gardens. Considering that monitors of this complex are regularly confi scated from the illegal pet trade, mainly for private keeping purposes, and several taxa are diffi cult to diagnose morphologically, we aimed to contribute to a molecular reference data set to facilitate their quick and reliable identifi cation for setting up conservation breeding programs. We sequenced a fragment of the mitochondrial ND2 gene from 28 individuals confi scated at the airports of Leipzig/Halle, Germany in 2016 and 2018, and Vienna, *Corresp. author: E-Mail: ziegler@koelnerzoo.de (Thomas Ziegler) 32 Thomas Ziegler & Miguel Vences · Molecular identifi cation of water monitors Austria, September 2019, as well as several other individuals held in zoological institutions. This included individuals of V. salvator ziegleri from Obi Island (Moluccas, Indonesia) for which so far no DNA sequence information was available. The molecular data identifi ed the confi scated monitors from the Philippines as V. marmoratus, V. nuchalis and V. cumingi, building the basis for the fi rst breeding groups of V. marmoratus and V. nuchalis in Europe. Individuals from Obi Island, the type locality of V. s. ziegleri, clustered with other individuals purportedly originating from Hal-mahera, suggesting that this taxon may also occur on this latter island. We found V. s. ziegleri to be sister to V. togianus, from which it differed by 3.6% uncorrected pairwise sequence divergence in the ND2 gene. In contrast, the two purported species V. cumingi and V. samarensis, originally considered as subspecies, only differed by 2.4-2.6%. We conclude that the taxonomy within the V. salvator complex is in need of critical re-assessment, given that extremely young evolutionary ages inferred in other studies for some species-level taxa would rather suggest their classifi cation as subspecies. The phylogenetic tree with updated/renewed identifi cations and names presented herein can be used as a reference for allocating samples from the V. salvator complex lacking locality information or being diffi cult to identify, including living individuals as well as confi s-cated skins and manufactured products of Varanus skins, thus providing an important service to relevant conservation authorities and zoos.
The Asian water monitor ( Varanus salvator ) is a large generalist predator and scavenger lizard. This species has a widespread distribution throughout South and Southeast Asia and is frequently encountered around the edges of urban settlements. Here, we present information on diet diversity and habitat utilisation of a population of Asian water monitors inhabiting the University of Malaysia Terengganu campus located on the east coast of mainland Malaysia. The stomach contents of 30 Asian water monitors were examined by stomach flushing, and 47.6% of stomach contents was mangrove crab, 26.2% was human waste and 26.2% was other natural foods consisting of fruits, fishes, leeches, snails, birds and insects. We then recorded the locations and habitats utilised by patrolling the campus area and found Asian water monitors preferred to use water and mangrove forest habitats that fringed and crisscrossed the campus. The broad diversity of stomach contents reflected food available at this location and indicates the opportunistic feeding habit of this species. Given that this species widely distributed in Southeast Asia, its broad diet diversity and habitat variations may promote the adaptation of Asian water monitor to different environments.
Leeches are one of the most commonly observed parasites of freshwater turtles. We used baited hoop traps to
capture 433 turtles belonging to five species (Apalone spinifera, Chelydra serpentina, Chrysemys picta, Sternotherus odoratus, and Trachemys scripta) to determine the host (species, microclimate use, sex, reproductive stage, and body size) and environmental characteristics (month of capture, turtle abundance, vegetation, turbidity, pond size, and availability of basking structures) that affected leech parasitism in Illinois ponds. Leech prevalence on turtles varied significantly among turtle species, was highest on bottom-walkers and adults, and varied throughout the year. Leech intensity was highest on larger turtles and in turbid ponds. The results from this study display the importance of utilizing turtle assemblages for examining overall trends in host–parasite dynamics, demonstrate the influence of environmental characteristics on leech parasitism, and provide baseline data for future studies examining leech parasitism on turtles.
The common tick of monitor lizards (Varanus) in Pakistan, India, and Sri Lanka is Aponomma gervaisi. In nature it occurs on only one of three native varanid species (V. bengalensis), in spite of the fact that both remaining varanid species in the main area investigated (V. griseus and V. flavescens) are ecologically and geographically syntopic with Varanus bengalensis at the two extreme ecological conditions in which the latter is found. Individuals of Aponomma gervaisi do not use their major host (Varanus bengalensis) at random. The level of infestation varies between different localities, between different seasons of the year, and between hosts of different sizes. Attachment sites of adult male and female Aponomma gervaisi are very specific. Males occur mainly on the lateral surfaces of the tail and/or in a shallow, medioventral depression immediately behind the cloaca; adult females are usually attached in the axillary or a nearby region. Larval and nymphal site preferences are less distinct than those of the adults, and attachment is probably partly determined by competitive factors. Breeding takes place at the adult female attachment sites. It is suggested that there is an advantage in adult male ticks aggregating in specific small areas due to the proportionally greater effect of several closely packed individuals on the hosts immune response system, particularly in reference to lymphoid cell density. These cells and body fluids seem to comprise the main food of the males. Male attachment sites are often located in areas of high potential abrasion. Females tend to attach in protected sites. Since females are mainly blood-sucking, there is probably an advantage in dispersed attachment patterns. Haemaphysalis sindensis Bilques and Masood is placed in the synonomy of Aponomma gervaisi.
- D Bennett
Bennett, D. (1998) Monitor Lizards: Natural History, Biology,Husbandry. Frankfurt am Main,
Germany, Edition Chimaira. 352 pp.
Biodiversity Record: Buffalo leech at Jurong Lake
- S.-Y Chan
- W L Lau
Chan, S.-Y, Lau, W.L. (2022) Biodiversity Record: Buffalo leech at Jurong Lake. Nature in
Singapore 15: e2022060.