Tiny Cave Snails Have Enormous Kidneys and Huge Seasonal Penis

Posted on December 7, 2015

Large organs of Zospeum isselianum

Researchers have examined organs in cave snails smaller than 2 mm in a new study. The study found there are strikingly huge organs underneath the tiny cave snail shells. Researchers have found the tiny snails have enormous kidneys and a huge seasonally present penis for their size. The snails also have grooved three-pointed teeth.

The research was conducted by conducted by Adrienne Jochum, Naturhistorisches Museum der Burgergemeinde Bern, Switzerland, and an international team of researchers. The researchers say the large organs may help the miniaturized snails survive in the subterranean realm. A scan of the cave snail species Zospeum isselianum is shown above.

Unique adaptations to cave life can include characteristics like blindness, loss of pigmentation, temperature sensitivity and transparent shells. The huge organs are another adaptation acquired by the snails.

Jochum says in a statement, "Studying adaptations in extreme environments such as those found in snails of subterranean habitats can help us to understand mechanisms driving evolution in these unique habitats."

A tiny species of glassy cave snails fro Northern Spain have tiny hearts but an enormous kidney that extends from one to two thirds of the total length of their shells. They have also developed elaborate muscular plates that surrounds the gizzard in their digestive tract. The researchers say the muscular gizzard helps the tiny snails grind the grainy stew of microorganisms and fungi found in the cave mud. Some of the the tiny cave snails are also protandric hermaphrodites. They possess male sexual features initially that later disappear. They possess a large retractable, pinecone-shaped penis for mating in the summer.

A research paper on the study of the tiny cave snails was published here in the journal, Subterranean Biology.

Photo: Dr. Marian Kampschulte & Gunhild Martels