Meaning of gerbil
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09 Feb 2023 05:59:58 pm.
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Meaning of gerbil
Mature gerbils are smaller than rats, but larger than mice. Mongolian gerbils are attracted to saliva and use salivary cues to discriminate between siblings and nonsiblings, and females use oral cues in the selection of sociosexual partners. Gerbils have been used as experimental models in a number of areas of biomedical research. Gerbils are excellent subjects for laboratory animal research as they are susceptible to bacterial, viral, and parasitic pathogens that affect humans and other species. Gerbils may have spontaneous seizures secondary to stress such as handling, cage change, abrupt noises, or changes in the environment.
Cystic ovaries are seen commonly in female gerbils over 1 year of age. Gerbils have unique characteristics, which make them appropriate for a number of animal models. Classically, gerbils have been used in research involving stroke, parasitology, infectious diseases, epilepsy, brain development and behavior, and hearing.
The chapter provides an overview of the taxonomy, history, and origin of the Mongolian gerbil. It provides quick, easy-to-use information on anatomy, physiology, and behavior as well as management and husbandry practices. It assists in the humane care and use of gerbils by including details on basic experimental methods for investigators, veterinary care, and the commonly seen diseases. Some more common uses of gerbils in research are described.
The introduction and development of the Mongolian gerbil, Meriones unguiculatus, as a laboratory animal is recent, compared to other rodents. The gerbil is usually non-aggressive and is one of the easiest rodents to maintain and handle. Its disposition, curious nature, relative freedom from naturally occurring infectious diseases, and adaptability to its environment have contributed to its popularity as a laboratory animal (Wagner and Farrar, 1987). It has several interesting anatomical and physiological characteristics that make it a useful model in biomedical research. Several other species of gerbils (e.g. Meriones libycus, Meriones crassus) have been used as experimental animals (Belhocine et al., 2010, Khokhlova et al., 2009). However, the Mongolian gerbil (Meriones unguiculatus), on which this chapter will focus, is the most common species of gerbil used in biomedical research (Schwentker, 1963).
It should be noted that mammalian taxonomy is a rapidly changing field. The following description outlines a classification of the Mongolian gerbil based on morphology as well as more recent molecular techniques. Gerbils are in the class Mammalia and order Rodentia. Rodents are divided into five major suborders (Musser and Carleton, 2005). Gerbils are part of the suborder Myomorpha, originally so named because the deep and lateral masseter muscles attach to the front of the muzzle, giving it a forward thrust. Myomorphs also lack premolar teeth (Hurst, 1999). Gerbils belong to the superfamily Muroidea, family Muridae, and subfamily Gerbillinae based on morphology and on evaluation of nuclear protein coding sequences of the Lecithin Cholesterol Acyl Transferase gene and the von Willebrand factor gene (Michaux et al., 2001, Robinson, 1975b). The genus Meriones was first described by Illiger in 1811, and Meriones unguiculatus was first identified in 1867 by Milne-Edwards (Robinson, 1975; Thiessen and Yahr, 1977). Chaworth-Musters and Ellerman (1947) provided a comprehensive description of the genus Meriones which was updated by Ellerman and Morrison-Scott (1951), Corbet (1978), and Pavlinov et al. (1990).
The genus name, Meriones, was derived from a Greek warrior who wore a battle helmet decorated with boar tusks (Robinson, 1975). The species name, unguiculatus, is Latin for clawed or fingernail leading to one of the common names, clawed jird. The name gerbil is from the Arabic word, yarbu, which refers to saltatorial, desert-inhabiting rodents. Yarbu was translated into Latin as gerbo and into English as gerbil (Robinson, 1975).
Origin, Domestication, and Geographical Distribution
Approximately 15 genera and 81 species of gerbils are known (Agren, 1986). Gerbils are found in deserts and semi-arid geographical regions of the world (Field and Sibold, 1999; Thiessen and Yahr, 1977). They are native to northern Africa, India, Mongolia, southwestern and central Asia, northeastern China, and regions of Eastern Europe (Robinson, 1976). Because wild gerbils live in arid habitats they dig burrows that extend between 50 cm and 1.5 m below the surface so the temperature is relatively constant throughout the day and night. The burrows may be small and simple with one entrance or complex with eight to 14 entrances (Agren, 1986, Brain, 1999).
The domestication of the Mongolian gerbil is a relatively recent occurrence. They were found by a French missionary, Father Armand David, who traveled extensively in Mongolia and China in the 1860s. Some wild-caught stock were sent to Japan, where they were bred freely (Alderton, 1986). The Mongolian gerbils that are available today originated from 20 pairs of captured animals that were maintained in 1935 by Dr. C. Kasuga in a closed, random-bred colony at the Kitasato Institute in Japan. In 1949 a sub-colony of gerbils was established at the Central Laboratories for Experimental Animals in Tokyo by M. Nomura. In 1954 Dr. V. Schwentker imported 11 pairs from Japan. Five females and four males from this group were successfully bred and formed a foundation colony which produced gerbils for distribution throughout the United States (Robinson, 1979). This foundation colony was established at Tumblebrook Farm at Brant Lake, NY, founded by Dr. Schwentker. After his retirement in 1971, the Brant Lake facilities were phased out, and the Tumblebrook Farm gerbil production colony was relocated to new facilities in West Brookfield, MA under the ownership of D.G. Robinson. The name “Tumblebrook Farm†was retained (Robinson, 1974). A sub-colony established from seven pairs of animals by Dr. J.H. Marston at the Worcester Foundation for Experimental Biology in Shrewsbury, MA during 1961–62 was the origin of the sub-colony established at the University of Birmingham, England in 1964. This breeding stock produced the animals used in laboratories throughout the United Kingdom and Europe. Charles River Laboratories purchased Tumblebrook Farm in 1996 giving rise to the Crl:(MON)BR strain.
Genetics
There is a low amount of genetic variability present in laboratory gerbils compared to wild gerbils as a result of their origination from a few founder animals (Razzoli et al., 2003). Recently, Neumann et al. (2001) identified the first polymorphic dinucleotide repeat loci in Mongolian gerbils by a microsatellite technique. These studies demonstrated that there has been minimal genetic variability identified in the Mongolian gerbil used in research, even though there are several different lines or strains. Razzoli et al. (2003) confirmed these results using an amplified fragment length polymorphism technique to characterize and detect strain-specific polymorphisms in gerbils. Prior to these studies, relatively few genetic studies had been performed.
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