Table 2.

The merits and limitations of selected model organisms.

Model organisms	Advantages	Limitations
Drosophila melanogaster (fruit fly)	Rapid generation time, highly prolific, low cost, and provides excellent genetic tools to study human-related disorders including cancer and tumor [100–101].	Morphological differences between fruit flies and humans represent a limitation in the use of the former in new drug discovery studies [101]. Due to the small body size of the fruit fly a microscope is required in the experimental trials [102].
Danio Rerio (zebrafish)	Zebrafish exhibits complex behaviors and can be used as an animal model to study human behavior. It has a rapid embryonic development and it is used in innate and adaptive immunity studies [103–104].	Difficulties in establishing cell cultures and lack of a conventional knockout technology [104]. Zebrafish cannot be used to study infectious human diseases because bacterial pathogens require a temperature of 37 °C and zebrafish is maintained at 28 °C. This may result in inaccurate data as a low temperature may lead to an attenuated virulence of mammalian infectious agents [104].
Caenorhabditis elegans (nematode)	Short generation time, prolific, transgenic strains available, and are self-fertilizing organisms [105–106].	C. elegans does not exhibit complex behavior due to the presence of fewer mammalian gene homologs [107]. It has a functioning innate immune system but lacks adaptive immunity [108–109].
Mus musculus (mouse)	Used as a model organism in stem cell research [110] and to study human-related diseases including cancer, hypertension, diabetes, osteoporosis, and glaucoma [111].	The housing of mice requires a large infrastructure and this is a problem when the laboratory space is limited. The inability of mice to mimic certain human disease phenotypes, despite the presence of human homolog genes [112], is documented.
Bombyx mori (silkworm)	Silkworm has not sparked any controversies and it is considered a safe and economical animal model [99,113]. Complete genomic sequences are available. Organs such as the midgut, silk gland, and fat bodies are easy to be obtained for research purposes [114].	Despite its genetic traits, having a complete genome and protein database available, the silkworm cannot be used as a model organism to study human-related diseases such as neurogenerative disorders and cardiovascular-related complications [115].