Species specificity between ectoparasites and rats Dao 1 Species s pecificity b etween e ctoparasites and r ats in Monteverde, Costa Rica Kathy Dao Department of Ecology and Evolutionary Biology University of California, Los Angeles EAP Tropical Biology and Conservation, Fall 2017 1 5 December 2017 ABSTRACT To determine if there is species specificity between ec toparasites and their host rats, I set up Sherman traps in various locations in Monteverde to capture rats Once I obtained the rats I removed any ectoparasites present and observed them under a dissecting microscope for morphological characteristics. Species specificity is defined for this study as the prevalence of a certain type of ectoparasite to a specifi c species of rat. From my results, I determined that there is species specificity between ectoparasites and their host rats. Lice were species specific to the Clo ud dwelling Spiny Pocket Mouse, f leas to the Mexican Deer Mouse, t icks t o the Fulvous Pygmy Ri ce Rats and Mexican Deer Mouse. Yellow mites were species specific to the Mexican Deer Mouse and Cloud dwelling Spiny Pocket Mouse Red mites were specific to the Fulvous Pygmy Rice Rat. Brown mites and octopus mites were specific to the Rat. The Hispid Cotton Rat that was caught contained no ectoparasites. The presence of pseudoscorpions in the Spiny Pocket Mouse further introduced a new variable that can potentially explain this species specificity at least parti ally, for its predation on some ectoparasites Hair morphologies of the rats were further examined in an attempt to explain the mechanism behind the species specificity. Especificidad entre ectopar sitos y ratones en Monteverde, Costa Rica RESUMEN Para evaluar la especificidad entre ectoparsitos y ratones, dispuse trampas Sherman en varios sitios de Monteverde, para capturar ratones y registrar sus ectoparsitos O bserv las caractersticas morfolgicas de los ectoparsitos bajo el estereoscopio y los i dentifiqu en morfo tipos. D de ratn. De mis resultados, determin que s hay especificidad entre ectoparsitos y grupos de ratones hospederos. Encontr piojos en ra tones de abazones ( Heteromys nubicolens ), pulgas en ratones de patas rosadas ( Peromyscus mexicanus ), garrapatas en ratones arroceros ( Oligoryzomys fulvescens ) as como tambin en ratones de patas rosadas Encontr caros amarillos en ratones de patas rosadas rata trepadora ( Tylomys watsoni ) y ratones de abazones. Los caros rojos fueron especficos de ratones arroceros. Los caros cafs y tipo pulpo fueron especficos del ratn cantante ( Scotinomys teguina ). El nico ratn algodonero hspido ( Sigmodon hispidus ) que atrap no tena ectoparsitos. La presencia de pseudoescorpiones en uno de los ratones de abazones introduce una nueva variable que podra explicar la especificidad que encontr, al menos parcialmente, por su depredacin sobre algunos ectopa rsitos. La morfologa del pelo de los ratones fue examinada ms a fondo pues podra explicar la especificidad en ciertos casos
Species specificity between ectoparasites and rats Dao 2 Coevolution is when species interact so closely they influence the evolutionary change in one another ( Coevolution, 2009 ). There are two types of coevolution: mutualistic and competitive. Amongst competitive coev olution, there are two additional types of interactions which are predation and parasitism. Para sitism is when one organism, a parasite, receives benefits by harming b ut not killing ano ther organism, the host In some parasitic relationships the host and parasite are so integrated that this results in a specialization between specific species of parasites and hosts (Futuyama & Slatkin, 1983). In domesticated animals a nd humans, the interactions between parasites and their hosts are well documented. Such is an example with microhabitat spec ialization. Microhabitat specialization is when an organism utilizes a small area that is unique from its l arger, surrounding habitat. Demodex folliculorum for example, is a louse that completes its entire life cycle specifically on the human eyelashes (Rather & Hassan, 2014). Other lice, such as the crab louse ( Pthirus pubis ) live on course hair, such as the pubic area of the human (Flinders & Schweinitz, 2004). These two lice are species specific to human s T hey also happen to be in capable of surviving on any other animal. Lice can also be found on rats, along with ticks, mites, and fleas For example, Mexic an Deer Mice are a known rodent species present in Monteverde that are abundant with fleas ( Thones, 2016 ). This study will attempt to discover if there is species specifi city between ectoparasites and their host rats. Species specificity in this study is defined as the prevalence of a certain type of ectoparasite to a specific species of rat. If there is species specificity, I will attempt to discover the mechanism explaining the interaction. I expect that though there will not be solely one species of ectoparasite to each species of rat the re will still be a clear majority of one species of ectoparasite present. MATERIALS AND METHODS From 14 November 2017 1 December 2017 I had set up eighteen Sherman traps at five different sites switching sites every 3 4 days The sites were: San Gerardo, Baj o del Tigre, La Calandria, Curi C ancha, and the Monteverde Institute. I place d each trap 3 5 meters apart from one an other. Preferred lo cations were near burrows where rats were expected to nest and flat ground where the trap s would be stable. I trigger ed each trap beforehand by gently pressing on the lever to ensure th e trap door would close properly. Afterwards, I placed a tablespoon of bait (a mixture of oats, vanilla, an d rice) gently on the lever entry, keeping the front door open. I tied flagging tape to a nea rby sturdy object with a number corresponding to the trap to mark its location. I inspected each trap early the following mor ning. Traps without rats had the bait replaced while rats that are caught had the following measurements taken. First, I noted the location and date of when and where the rat was collected Next, I identified the s pecies of rat with the assista nce of Federico. If we were not able to identify the species in the field, a photo of the rat was taken and marked as UNKNOWN #__ to be searched for later. During this stage, I also noted the sex of the rat observing for the presence of a scrotum to ident ify the difference between male s and female s If the rat was young it would also be noted as a juvenile. I took the w eight of the rat using a 300 gr Pesola with the rat in the bag. The bag was later weighed by itself and deducted from the total weight to d Next, I measure d in millimeters I also took additional notes about the rat at this point, such as if it had a partial tail or was recaptured. I
Species specificity between ectoparasites and rats Dao 3 inspect ed the rat for ectopa rasites and a ny fleas, ticks, and mites I obtain ed were removed with tweezers and placed into a vial containing 70% ethanol. I snip ped the fur of rats that were captured as an indicator of it being processed. I collected the r at fur to be observed later I released the rats back at the location where they were originally captured I rinsed a ll cages that held rats to remove any traces of feces and food before being rebaited. If I was switching sites, I would rinse and clean all eighteen c ages thoroughly beforehand When I observed the ectoparasites, I place d them in a petri dish with 70% ethanol. I then place d the dish under a dissecting microscope to observe for morpho logical differences Rat hairs I collected were also observed under a dissecting microscope in an a ttempt to understand a possible mechanism for host parasite specificity. The idea that hair morphology played a part in ectoparasite abundances stemmed from the knowledge that lice inhabited certain areas of the human body depending on hair characteristics (Flinders & Schweinitz, 2004). I noted h air density, thickness, texture, and other traits The abundance between certain species of ectoparasites and certain species of rats were then calculated RESULTS Using the combined data from Noelle Pruett, Emily Parker, and myself, we caught a total of 48 rats across six rat species ( Table 1). The SPM and HCR had less than 50% of the captured rats with ectoparasites (Figure 1). On the other hand, the WCR, PRR, MDM, and ASM had over 50% of the rats captured with s ome type of ectoparasite present. Table 1: Table of six rat species caught across all sites. Common name and the corresponding scientific name s of each species are listed. The amount of each species captured is also listed, totaling 48 rats The future ref erence is how each species will be referred to for the rest of this study. Common Name Scientific Name # caught Future reference Mexican Deer Mouse Peromyscus mexicanus 8 MDM Cloud dwelling Spiny Pocket Mouse Heteromys nubicolens 33 SPM Mouse Scotinomys teguina 1 ASM Tylomys watsoni 1 WCR Hispid Cotton Rat Sigmodon hispidus 1 HCR Fulvous Pygmy Rice Rat Oligoryzomys fulvescens 4 PRR
Species specificity between ectoparasites and rats Dao 4 Figure 1 : The x axis represents each species of rat (refer to T able 1). The number in the light grey bar indicates the number of rats caught without ectoparasites, while the dark grey number indicates the number of rats with ectoparasites. From the rats with ectoparasites, mites were t he most abundant ectoparasite present in each sp e cies (Figure 2 ). Ectoparasites on the WCR and ASM were solely mites. MDM showed the largest variation of ectoparasites. Ticks were present on both the PRR and MDM. Fleas were found only on the MDM. One louse was found on one SPM Figure 2 : This graph includes only rats with ectoparasites present. A rat individual may be counted more than once if it has more than one type of ectoparasite present The x axis represents each species of rat (refer to T able 1). The lightest grey bar indicates the number of rats with fleas. The medium grey bar indicates the number of rats with ticks. The dark grey bar indicates the number of rats with mites The darkest grey bar indicates the number of rats with lice. 13 1 3 5 1 20 1 3 1 0 5 10 15 20 25 30 35 SPM WCR PRR MDM ASM HCR Number of Rats Captured Without Ectoparasites With Ectoparasites 0 0 0 2 0 0 0 2 1 0 13 1 3 4 1 1 0 0 0 0 0 2 4 6 8 10 12 14 SPM WCR PRR MDM ASM Rats with ectoparasites Fleas Ticks Mites Lice
Species specificity between ectoparasites and rats Dao 5 Mites that were collected were further separated into four morphologies: brown mites (Figure 3), r ed mites (Figure 4) yellow mites (Figure 5) and octopus mites (Figure 6 ) SPM and WCR had mites which were solely of the yellow morphology (Figure 7). Though MDM had both yellow and red mites pre sent, yellow mites were more prevalent. Red mites were the only mites on the PRR. ASM had mostly brown mites present, with one octopus mite on the ear. Brown mites and octopus mites were found only on the ASM. Figure 3: Brown mites viewed from under a dissecting microscope. Mites were < 0.5 mm in size. Collected from the base of the tail at Curi Cancha Figure 4: Red mite viewed from under a dissecting microscope. Red mites were about 0. 5 mm in size. Collected from the body of the Pygmy Rice Rat at Bajo del Tigre
Species specificity between ectoparasites and rats Dao 6 Figure 5 : Yellow mites viewed from under a dissecting microscope. Yellow mites were <0.5 mm in size. Collected from the edge of ears at San Gerardo Fi gure 6: Octopus mite viewed from under a dissecting microscope. Mites were about 0.5 mm in size. Collected from the at Curi Cancha.
Species specificity between ectoparasites and rats Dao 7 Figure 7: This graph looks at the distribution of mite morphologies in rats with mites The x axis represents e ach species of rat (refer to T able 1). The lightest grey bar indicates the percentage of rats with yellow mites The medium grey bar indicates the percentage of rats with red mites The dark grey bar indicates the percentage of rat s caught with brown mites. The darkest grey bar indicates the percentage of rats caught with octopus mites Furthermore, only one SPM from all 48 rats captured had pseudoscorpions ( Epichernes vickeryae ) (Figure 8). A total of six pseudoscorpions we re counted on the single mouse. Pseudoscorpions are not parasites because they prey on ectoparasites. Figure 8 : Adult (left) and juvenile (right) Epichernes vickeryae found on a Spiny Pocket Mouse in Bajo del Tigre (n=6) About 2 mm in length Hairs of the following rats were also collected: SPM, PRR, MDM, WCR, and HCR This was in an attempt to determine the mechanism behind any species specificity. ASM hair was not 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% SPM WCR PRR MDM ASM octopus brown red yellow
Species specificity between ectoparasites and rats Dao 8 able to be collected because it escaped before its fur could be snipped. All h a irs were viewed under a dissecting microscope at the same magnification. SPM hair was the thickest o f the hairs collected (Figure 9 ). SPM hair was a combination of spiny and thin The spiny hairs were easily 3 4 times the thickness of the other hairs. The hair felt rough to the touch and did not clump when placed into the tube with ethanol. PRR hair, in contrast, was the thinnest of the hairs examined (Figure 10 ). The hair was also shorter and softer. It did not cl ump when placed in the tube MDM and WCR ha irs were fairly similar in thickness (Figure 11 ). Both had fur that was soft to the touch. The hairs matted to clumps when collected in the tube but were thin enough to easily separate. The HCR hair was thick, s econd only to the SPM (Figure 12 hair clumped the most, and was extremely difficult to separate once in the ethanol solution. Figure 9 : Hair collected from a Cloud dwelling S piny P ocket M ouse collected at La Calandria viewed under a dissecting microscope.
Species specificity between ectoparasites and rats Dao 9 Figure 10 : Hair from a Fulvous Pygmy Rice Rat collected at Bajo del Tigre viewed under a dissecting microscope Figure 11 : Hair from a Mexican Deer Mice (left) Climbing Rat (rig ht) collected from La Calandria viewed under a dissecting microscope
Species specificity between ectoparasites and rats Dao 10 Figure 1 2 : Hair from the Hispid Cotton Rat collected at La Calandria viewed under a dissecting microscope. DISCUSSION This data supports my expectation that there is species specificity between ecto parasites and their hosts. Certain species of e ctoparasites were more common in some species of rats over others, showing that ectoparasites are found selectively on particular hosts. Because lice were found present in only the SPM, I have determined that lice are species specific to SPM. Fleas were only found on the MDM, and therefore are specific to MDM. Ticks are specific to both the PRR and the MDM. There is species specificity for yellow mites in SPM, WCR, and MDM. Though red mites are also present on the MDM, the overwhelming majority of mites found were yellow mites on that species Red mites are specific to PRR because they are the only type of mite found on that species. ASM introduced two new categories of mites (brown and octopus) that were not present across any of the other five species of rats. Thus, I conclude that both of these are specific to the ASM Looking at the data, I tried to determine why SPM had less than 50% of the captured ra ts with ectoparasites, and of those that had ectoparasites largely had only yellow mites present. This could in part be due to the presence of pseudoscorpions ( Epichernes vickeryae ) Though E. vickeryae were found on only one of the SPM, they could be a re ason as to why ectoparasite richness was lower in SPM relative to the other species of rats found. In a study by Lucas Lippert, parasite densities in rats reduced as Amblyopinus beetles increased in abundance, an insect which plays a similar role as the E. vickeryae in SPM (Lippert, 2001). E. vickeryae consume the ectoparasites in their fur (Francke and Guzman, 2005). The reason why yellow mites were able to prevail may be due to where they are located. Yellow mites stay burrowed
Species specificity between ectoparasites and rats Dao 11 microhabit iz ation can potentially explain why the mites were not preyed upon, though the specific mecha nism of interactions between pseudoscorpions and MDM are not well known (Rather & Hassan, 2014) Furthermore, I suspect that like the Pthirus pubis pseudoscorpions could favor the SPM fur over others due to it having the coarsest and thickest hair ( Flinders & Schweinitz, 2004 ) Looking further into other rat species hairs, I tried to determine a trend between hair morphologies and the types of ectoparasites present on the rats. The PRR hair was very thin, possibly making it easier for ectoparasites t o reach its skin and take hold. This is supported by the presence of ticks and red mites ( bodily ectoparasites ) that were abundant on the PRR. In one mouse, t here were a total of 10 ticks on it alone along with several other ectoparasites. In comparison, the MDM had only three. Furthermore, the MDM had thicker hair than the PRR or WCR, but t hinner hair than the BCR and SPM This intermediate hair thickness may be able to appeal to a variety of ectoparasites, as the MDM had the greatest dive rsity of ectoparasites across all six species of rats. Unfortunately, the ASR fur was not collected, though during the collection of the ectoparasites, its fur was noted to be soft and short. I expect that if we were to collect its fur, its thickness would be similar to the PRR. It also had bodily ectoparasites in the form of brown mites. The WCR, however, challenges this possibility of hair morphology playing a part in species specificity It, too, has very thin hairs, second only to the PRR of the hairs e xamined, yet shows no evidence of any bodily ectoparasites. HCR fur was examined and had the second coarsest hair among the rats. It is possible that due to its texture and tendency to get matted, it prevents ectoparasites from being able go through the fur and reach the skin Hair morphology playing a role in species specificity, however, is only a hypothesis. Experiment s would be needed to test this possibility. Overall, my results supported my expectation of there being species specificity between pa r asite s and their rodent host s. This result, however, could have been skewed from a limited sample size. Being able to expand on the number of specimens caught for each rat species would have made this conclusion more solid Perhaps further studies can expa nd on the limited knowledge available about pseudoscorpion and rat relationships, thereby increasing our understanding of parasite host relationships as a whole. Little is known about the mutualistic relationship between Epichernes vickeryae and the SPM. Possibly being able to find the mouse burrows where these pseudoscorpions are suspected to reside and observing their interactions could increase our understanding of these creatures. ACKNOWLEDGEMENTS I would like to than k Federico Chinchilla for being the best advisor I could ask for. His patience, knowledge, and guidance have kept me mentally sane throughout this process. I would also like to thank Noelle Pruett and Emily Parker for sharing their data and struggles with me. Joyce Silva as w ell, who reviewed this paper and gave some great advice Further thanks to confidence in myself. To Emilia who helped me find a love for bugs. To Frank and Katy, for graciously allowing me to use their property as a site to capture rats. To Felix for being the best nanny. And Andres, who I can always turn to for a good laugh. Thank you to the people at San Gerardo station, La Calandria and Curi Cancha for allowing me to use their beautiful reserves to set up traps. An additional thanks to the Estacin Biolgica Monteverde and Monteverde
Species specificity between ectoparasites and rats Dao 12 Institute for allowing me to use their facilities. A thank you to my homestay family, especial ly my tica mother, Haydee Cruz for provi ding me with a lovely home during the duration of this study A final thanks to all of the people involved in the Fall 2017 program, for making my final quarter as an undergraduate student the best I could ever hope for. Pura vida. LITERATURE CITED Coevolution. 2009 In Understanding Evolution. Retrieved online December 1, 2017, from https://evolution.berkeley.edu/evolibrary/article/evo_33 Fli nders, D.C. & Schweinitz, P.D. 2004 Pediculosis and Scabies American Family Physician 69(2), 342 Leawoo d, KA: American Academy of Family Physicians. Francke, O.F. & Guzman, G. A. 2005. Symbiotic Relationships Between Pseudoscorpions ( Arachnida ) and Packrats ( Rodentia). Journal of Arachnology, 34(2), 289. Futuyama,F.J. & Slatkin, M. 1983. Coevolution. Sunderland MA: Sinauer Associates Inc. Lippert, L.I. 2001 Amblyopinus Beetles and their Relationship to Parasites of Mexican Deer Mice ( Peromyscus mexicanus ). UCEAP Tropical Biology Spring 2001. Rather & Hassan 2014 Human Demodex Mite: The Versatile M ite of Dermatological Importance Indian Journal of Dermatology, 59(1), 60. Thoene D.M. 2016 Immune d imorphism in w ild m ice of Monteverde, Costa Rica. UCEAP Tropical Biology Fall 2016.