There are many physiological processes our bodies need calcium for, like building bones, contracting muscles (including the heart) and operating neurons. Calcium concentration in our bodies is typically regulated by the endocrine system using parathyroid hormones (PTH) and calcitonin.

PTH releases calcium from bones when blood calcium is low to maintain these functions. But what happens when you don’t have bones?

Well until now, it’s been a mystery.

A new study from the University of Tsukuba, Japan, published in Nature, has discovered that peptide hormone Capa regulates calcium in the body fluid of the fruit fly Drosophila melanogaster.

“The team further discovered that Capa is secreted by specific neurons in the cranial nervous system and acts on the apical region of the Malpighian tubules — organs analogous to vertebrate kidneys — to mobilize calcium from “pearl-like calcium granules,” says the University of Tsukuba Research News.

This discovery offers the first evidence that animals without bones contain an endocrine system regulating calcium concentration.

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