Those specimens to the right are two-centimeter-long male Phallostethus cuulong, or a species of "priapiumfish" that swims Vietnam's Mekong River. These fish are renowned in the animal kingdom for having their genitals — and their anuses — squarely under their throats. If only we could all be so evolutionarily blessed.
Biologists haven't observed P. cuulong deliver its throat-mance, but related species and P. cuulong's morphology offer clues as to how this tiny casanova operates. When it comes time to mate, this little fish swims under the female's head and manipulates both its saw-shaped ctenactinium and rod-like toxactinium to fertilize the female right below her face. As a recent paper in the journal Zootaxa explains:
Male phallostethids have a unique complex copulatory organ, termed the priapium, under the throat (thus the fishes of this family are commonly called "priapiumfish"). The priapium is a bilaterally asymmetric organ for holding or clasping onto females and fertilizing their eggs internally; following internal fertilization, phallostethid females do not give birth to live young, but instead lay fertilized eggs [...]
To deliver their terrible, terrible love, the priapiums of Phallostethus cuulong tend to favor either the right or left side. And to make matters all the more hilarious, the fish's anus loops around in its body, causing it to excrete out of the priapium. Phallostethus cuulong, you are definitely in the running for "the G.G. Allin of the animal kingdom."
Zootaxa via Zoologger. Images: L.X. Tran. Hat tip to Shai Hulud.