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Lowe, Jessica M.

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Morehead State University

Jessica M. Lowe and Sean O’Keefe, mentorDepartment of Biology and Chemistry, College of Science Using Oribatid Mites as a Measure of BiodiversitySpring 2019Department of Biology & Chemistry,College of ScienceABSTRACTOribatid, or beetle, mites constitute an extremely diverse and numerous groupof leaf-litter inhabiting arthropods. A good leaf-litter sample may include some 50 to100 different species of mites that may number a few thousand individual specimens.Adult beetle mites range in size from a staggering 1.5 mm to 0.25 mm. This greatdiversity of species and abundance of specimens within most samples makes beetlemites a potentially useful group in which to assess biodiversity; however, the quitesmall body size and potentially thousands of individuals, makes a challenge to sort andidentify all of the specimens that may occur in a single sample. The objective of thisproject was to develop a foundation in the collection, processing, and preparation ofbeetle mites in order to establish a basis from which biodiversity comparisons could beimplemented. Beetle mites from Kentucky, California, Arizona, Alabama, Florida,South Carolina, and Costa Rica were used to build an initial synoptic series of oribatidmite diversity.ACKNOWLEDGEMENTSWe would like to thank Morehead State University’s Biology and ChemistryDepartment for the laboratory space and equipment for this research. Linedrawings were reproduced from Krantz and Walter.REFERENCESMarshall, V.G., R. M. Reeves, and R.A. Norton. 1987. Catalog of the Oribatida (Acari) ofContinental United States and Canada. Memoirs of the Entomological Society ofCanada No, 139. Ottawa, Canada. vi + 418 pp. This source is the only catalog of allof the species of oribatid mites known to occur within the United State and Canada,along with all literature of the known species. The catalog treats 1177 speciesorganized in 329 genera of 108 families. Other species have been described sincethen, but this catalog has not been updated.Balogh, J. 1972. The Oribatid Genera of the World. Akademia Kiado, Budapest, Hungary.188 pp plus 71 plates. This source is the only reference in which oribatid mites ofNorth America can be identified to genus. The genera recognized here fairly closelymatch those listed in Marshall et al. 1987. Oribatids are identified to superfamilyfirst, then to the worldwide genera within each superfamily. Balogh did not use thefamily category within his text.Moldenke, A.R., and B.L. Fichter. 1988. Invertebrates of the H.J. AndrewsExperimental Forest, Western Cascade Mountains, Oregon: IV. The OribatidMites (Acari: Cryptostigmata. Gen. Tech. Rep. PNW-GTR-217. Portland, Oregon. vi+ 118 pp. This source is a final report of a long-term biodiversity study in westernOregon that covers the oribatid mites. The mites collected were identified andillustrated with scanning electron micrographs. Many of the families, and many ofthe genera collected in Oregon are also found in California, Kentucky, Alabama, andSouth Carolina.Norton, R. 1990. Acarina: Oribatida, pp. 779 – 804. In Dindal, D.L. (ed.) Soil BiologyGuide. John Wiley & Sons, New York, NY. This source provides a key to the 50 orso most commonly encountered families of oribatid mites known to occur in NorthAmerica. The key works for many of the mites encountered in our samples, but doesnot include several relatively uncommon species that we captured.Norton, R.A. and U..M. Behan-Pelleticer. 2009. Suborder Oribatoda, pp. 430-564.. InKranz, G., and D.E. Walter (eds.). A Manual of Acarology, 3rd ed. Texas TechUniversity Press. 816 pp. This source provides an identification key to the 180 or sofamilies of oribatid mites from around the world. This represents the most currentarrangement of families.Gulvik, M. 2007. Mites (Acari) as indicators of soil biodiversity and land use monitoring :a review. Polish Journal of Ecology, 55: 415-440.Walter, D and Proctor, H. 1999. Mites: Ecology, Evolution, and Behaviour. Queenland,Australia. vi+ 322 pp.MATERIALS and METHODSCollection of Mites:In a wooded area we obtained a large amount of leaf litter,usually near downed logs or tree buttresses. We placed this leaf litterinto the sifter (Fig. 2). The material is then sifted by briskly shakingthe sifter from side to side as well as up and down. Large items,such as leaves or rocks, remained on the screen while fine organicmatter and organisms fell into the collection bag. This occurred as Imoved one handle clockwise and the one handle counterclockwise.We continued to collect soil and place it onto sifter until the desiredamount of sample was collected.INTRODUCTIONBiodiversity refers to the variety of species within a group of organismsfound in a specific habitat or ecosystem. Biodiversity is important to humansbecause it can be an indicator of possible environmental decay and sustainabilityof an area. Groups that are suitable for biodiversity often contain organisms thatare easily affected by the environment, easily identified, and are well known.Mammals, birds, and plants are often used to measure and monitor biodiversity.Although, these organisms are usually studied, in a small area these organismsare few in species and have few number of individuals. Oribatid mites, referredto as beetle mites, armored mites or moss mites, can be indicators ofenvironmental health because they have long life spans, low fecundity, slowdevelopment, low dispersion ability, with a large number of species and anextreme number of individuals in a small area (Gulvik. 2007). Oribatids canshow humans the direct impact that they have on the environment.Oribatid mites constitute 172 families that include some 9,000 species(Norton and Behan-Pelleticer. 2009). Oribatids dwell within the soil-littersystem. Oribatid mites are detritivores, feeding on dead organic material, andfungivores, feeding on fungi, but can also be opportunistic predators. They aredescribed as being “hyper-diverse” due to the range in body size (15 to 2000µm) (Fig. 1). The vast number of species and morphological differences couldbe related to competition or area occupied within the soil.Sorting of samplesOnce our sample was brought back to the lab, it was placedinto a Berlese funnel (Fig. 3). This funnel has a light bulb in the lid.Soil organisms do not like heat or light, therefore they are drivendown through the litter then through the screen into the collectiondish. The collection dish contains ethanol to capture and preserveall organisms that fall out. These organisms will be identified later.Slide mounting of mites:A small selection of mites were mounted on temporaryglycerin slides. This means glycerin is dropped into the center of theslide, the mites were placed in the glycerin with forceps, and a coverslip placed on top of the immersion (Fig. 4). We used these as manyof the features needed to identify mites are difficult to assess. Theglycerin allowed us to move the mites to position them in order tolook at features laterally, dorsally, or ventrally. These slides aremessy and temperamental. If a slide was left unbalanced, thespecimen and cover slip would slide down. This left a mess butmoved the mite under the cover slip with warrant. The slides werevery fragile and if moved too harshly, the specimen could breakapart in the glycerin.Identification of mitesOnce the slide was viewed under a microscope, miteswere identified using the few references in existence (Fig. 5). Alarge portion of the learning curve that came with this researchwas understanding morphological terms. I used figures frommost of the referenced texts, as in Figs. 6, 7, 8, and 9, to learnthis terminology. I could compare these to the slides and learnthe vocabulary associated with the morphology. These keyshelped identify specimens to family, and possibly to genus.DISCUSSIONWe identified 16 different families compromising of 69 differentspecimens. This was just a small number of the collection as many mites arestill unprocessed. The small size and vast amount of mites make it difficult toidentify all mites in the laboratory. The yield of some sites makes theprocessing portion quite strenuous. One site can contain hundreds ofspecimens while another could yield fewer than ten. The sites containinghundreds of specimens often takes many hours to sort through. This researchproject was designed to learn techniques to handle and identify this very largeand diverse group of very small and abundant leaf-litter dwelling organisms.Part of this study focused on the ways on how Oribatids representbiodiversity. As shown in Fig. 10, Oribatid mites take on many differentforms. The differences in morphology can be minute or extremely large .Within a family, two species may have completely different appearances. Thesimilarity may be that they have pteromorphs or segmented body shapes. Thissometimes made identification difficult.Due to the small size of these mites, the leaf litter is dominated withOribatids. These mites show trophic flexibility (Walter. 1999). This means theycan live in many different microhabitats within the forest ecosystem, and theyare found in a variety of ecosystems. The beetle mites of the same family arewidespread across the country. For some areas, it is possible that 100-150species exist in a density of 100,000 mites m-2 (Moldenka and Fitcher. 1988).The dominance of these mites in a forest means a sample can have many ofthese specimens for a study. The great diversity and abundance of Oribatids canassist researchers in measuring the biodiversity within an area.Oribatids’ small size made them very difficult to identify. When viewingunder a dissecting microscope, not all features or relativity of dimension wascompletely seen. Mites within a family can have different characteristics as well.An overall appearance may not fit a specimen into a family but underlyingmorphology may fit them into the family. In order to observe the characters ofthese small organisms, they need to be mounted on microscope slides. The miteswere mounted on temporary slides containing glycerin because often the mitesneed to be rotated to view specific features. The process of identification camewith a steep learning curve because of the techniques for handling such smallorganisms, the ability to view key characteristics, and the learning of a largeword-bank of unfamiliar morphological terms.We were able to use mites from collections that included samples fromKentucky, California, Arizona, Alabama, Florida, South Carolina, and CostaRica. Although we had samples from all these locations, different species fromthe same family were represented in many of these samples. Some mites werespecific to only one location. Some species were in abundance while there wasonly one or two of another species within the entirety of the collection. Thestudy conducted was designed to specifically craft skills when working withmites.Fig. 1. Reference of size variety within Oribatid mitesFig. 2. Jessica with sifterFig. 3. Berlese funnelFig 5. References used to identify mitesFig. 6. Ventral view of mite illustrating key morphological terms. Fig. 7. Anterior dorsal view illustrating key morophological termsFig. 8. Movable vs non-movable pteromorph as compared to absence ofpteromorphFig. 9. Different types of body segmentation among mitesFig. 4. Glycerin SlidesMovable pteromorphNon-movable pteromorphGenital platePreanal plateAnal plateCoxisternumAdanal plateAggenital plateIndividual acetabulumVentral plateTranslamellaLamella cuspPorose area AdPleurophragmaDorsophragmaTrichobothrium with setaPostpedal furrowPygidiumProntaspisDorsoejugalfurrowFused coxisternumCircumgastricscissureFig. 10. Diversity of Oribatid body morphologyThis research was helpful in my learning, understanding of techniquesand interpretation of the specialized terms associated with Oribatid mites. Theidentification of these mites can be later used to help assess the health andsustainability of the areas sampled. Oribatids can give insight into a variety ofdifferent ecosystems and microhabitats.

Using Oribatid Mites as a Measure of Biodiversity

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Using Oribatid Mites as a Measure of Biodiversity

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