Tenrecs and their cloaca

Cloaca

What are cloaca? The cloaca is the rear orifice in an organism that serves as the only opening for digestive, reproductive, and urinary tracts. The cloaca is most commonly observed in amphibians, reptiles, and birds. Very few mammals possess a cloaca. The majority of mammals are placental, and have two to three orifices for evacuation, though all mammals have a cloaca during the earlier phases of their embryological development.

Cloaca in Tenrecs

Tenrecs are from the class mammalia, but unlike the majority of mammals, they have just one orifice that serves as the opening for their digestive, urinary, and reproductive tracts. This opening is referred to as the cloaca. In the study of tenrec anatomy, there have been arguments by many authors that tenrecs have a “false” cloaca ,not true, and that it is essentially a fold of skin or possibly a secondary structure as opposed to primary. These arguments support that the cloaca of tenrecs may not be homologous to the cloaca found in reptiles and monotremes.

Cloacal anatomy

The cloaca in tenrecs is a bowl shaped pouch at the rear of the body, close to the tail. The intestinal, urinary, & genital tract open into the cloaca. For both male & female, the intestinal tract opening is regulated by a sphincter muscle. In females, the genital & urinary tract open into a shared urogenital sinus, which is a sub-compartment of the cloaca. The cloaca of females also contains urethral and Bartholin glands. In males, the penis is sheathed within the cloaca. The cloaca of males contains a prostate gland, Cowper’s glands, and strongly pigmented seminal vesicles. Both male and female possess a cloacal gland and a peri-cloacal gland.

Sex determination

The fact that the cloaca contains the genitals of both sexes makes it difficult to determine tenrec sex from a simple physical examination. Physical examination can provide clues to the sex of the tenrec, and one may even attempt to express male genitals from the cloaca. However, the most accurate way to sex a tenrec is a DNA test, most commonly collected through the saliva.

Article by Chelsey Vermillion.