Midterm

Question 1

What is the order, suborder, family, and genus of rats

Answer 1

rodentia
myomorpha
muridae
rattus

Question 2

what is the most common rat you will see in practice

Answer 2

Rattus norvegicus (the norway rat)

Question 3

What is the order, suborder, family, genus and species of mice

Answer 3

rodentia
myomorpha
muridae
mus
musculus

Question 4

t/f: rodent incisors grow continuously throughout life

Answer 4

true. if maloccluded, they won’t wear normally and will need to be trimmed

Question 5

what is the purpose of brown fat deposits in rats and mice? what are they sometimes called?

Answer 5

used to generate heat (“non-shivering” thermogenesis)
also called the hibernating gland, although they do not hibernate

Question 6

what is unique about the rat and mouse brain

Answer 6

it lacks gyri and sulci
don’t confuse this for edema on necropsy

Question 7

what does the harderian gland produce? when might it over-produce?

Answer 7

secretes porphyrin, an iron containing reddish pigment
stress causes hypersecretion (“red tears”)

Question 8

t/f: rats and mice lack a gallbladder

Answer 8

false. the rat lacks a gallbladder, but the mouse has one

Question 9

t/f: rodents cannot vomit

Answer 9

true

Question 10

what is unique about the rat/mouse GIT

Answer 10

they have a large cecum which is important to digestion of plant materials

Question 11

where is the opening of the urethra in female rats/mice? males?

Answer 11

in the genital papilla near the base of the clitoris (not in the vagina like with other animals. important for catheterization)

in the penis for males

Question 12

what animals have a harderian gland?

Answer 12

rats, mice, and gerbils

Question 13

what is a sperm plug and what is its purpose

Answer 13

secretions from the sex glands of male rats and mice form this plug in the vagina after mating to prevent rebreeding. it is also useful for tracking pregnancy. day 1 = the day the plug forms

Question 14

you can’t find the testicles on a male rat. does this mean he has been neutered or is cryptorchid?

Answer 14

no. rats have open inguinal rings that allow the testes to be withdrawn into the abdomen when cold or fighting

Question 15

how is the female rat’s repro system different from other rodents?

Answer 15

she has 2 cervices. others also have a bicornuate uterus, but with only one cervix

Question 16

when is the vaginal closure membrane present in rats and mice? guinea pigs?

Answer 16

in rats and mice, it is present in immature females and disappears prior to sexual maturity.
in guinea pigs, it is present all the time, except when receptive to breeding or near parturition

Question 17

how can you differentiate between sexes in rats and mice

Answer 17

anogenital distance is shorter in females than males

Question 18

how many pairs of nipples do rats and mice have?

Answer 18

6 in rats. 5 in mice

Question 19

describe the distribution of mammary tissue in rats and mice. what is the clinical relevance

Answer 19

widely distributed and may extend onto the lateral and dorsal areas of the abdomen and thorax. tumors on the dorsolateral aspect of the animal could be a mammary tumor

Question 20

how long do rats and mice live

Answer 20

2-3 years for rats
1.5-3 years for mice

Question 21

how much urine do rats and mice produce

Answer 21

3.3 mL/100g BW/day for rats
0.5-1 mL/day for mice

Question 22

when are rats and mice most active

Answer 22

at night. nocturnal

Question 23

are male or female rats/mice more aggressive

Answer 23

males

Question 24

t/f: group housed female rats and mice often fight

Answer 24

false. rarely fight

Question 25

describe barbering in mice. how can it be managed

Answer 25

social dominance may be manifested by excessive grooming of the lower mice. the dominant mouse (the one without bald spots) can be treated with N-Acetylcysteine or housed alone

Question 26

how should rats and mice be fed

Answer 26

food provided ad libitum
good practice to measure feed consumption
standard is pelleted feed

Question 27

what are the downsides to powdered/mash feed for rats and mice

Answer 27

may lead to incisor tooth overgrowth
may dig food out of feeder, making consumption measurement difficult