Fat Body

Fat Body

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Honey bees have what is called a “fat body” which is a section of tissue that holds fat cells, as well as glycogen, protein, and high concentrations of mitochondria and enzymes. The fat body is the equivalent in insect terms of a mix of a liver and fat storage.

During larval state, the fat body covers most of the larvae. The fat body will quickly and efficiently store nutrients during the larval stage to be used during the pupae stage (while the bee is not fed) and the adult bee will emerge with a fat body only in her abdomen.

The fat body is extremely important for winter bees (aka fat bees). Winter bees have a bigger fat body that would allow them to store more energy and nutrients that will last for months. Summer bees have a smaller fat body and in some cases almost non-existent.

Why is fat body important?

Recent studies on the parasitic varroa mite found out that the varroa mite is not actually sucking hemolymph (bee blood) our of the larvae and the honey bee, but it’s actually eating fat body cells, which are higher in nutrients. Different experiments determined that the mite could not extract enough energy by sucking hemolymph (which has a lower concentration of nutrients) and that it would not be as detrimental to bee health to lose some hemolymph.

By taking fat body cells, the varroa mite can take a higher nutritional material that would allow for fast growth and reproduction. Taking fat body is more detrimental to the honey bee colony’s health, especially over the end of the season when the mites feed on what were supposed to become winter bees. The winter bees that fed varroa mites have a smaller fat body and will not be able to survive for as long as the colony intended when raised those bees.

This explains some of the abrupt colony collapses that beekeepers find by the end of fall when stronger hives (big in numbers and resources) end up dying before even getting to winter.


3 thoughts on “Fat Body

  1. I read a few articles about this recently. Fascinating how they discovered this. I think there might be a TED talk on it as well, if I am not mistaken.

    I believe there is likely value to providing supplemental protein going into winter, not for increase, but rather to make the bees “fatter.” See Randy Oliver’s discussion here: http://scientificbeekeeping.com/fat-bees-part-1/

    Thanks for the article.

    1. Hi Greg,
      It’s hard to supplement protein for a colony for two reasons:
      1- Protein substitutes are not as nutritional to honey bees as real pollen. The only way to supplement with good protein at some point (like during queen rearing) would be to harvest some pollen when is abundant and then feed it back to the bees when there’s less pollen (or lower quality pollen available).
      2- Research on fat bees found out that a colony actually makes winter bees when protein sources start to become scarce. Since bees evolved to get ready for winter when the season is slowing down, they take the incoming protein reduction as a trigger to make winter bees. If we supplement protein at this time of the year, we could be pushing the colony out of sync with the season, delaying the production of winter bees until a time that is too late (temperatures too low for brood rearing).
      It seems that the best approach is to provide as good as an environment we can for the colony (as in having plants/weeds around) and let them take resources in on their own.

      The only cases where beekeeper intervention would be recommended is in cases where emergency feeding is necesary. In case of drought (we had some two years ago) or prolonged abnormal weather, a beekeeper may need to step in to keep the colony alive.

      But in other cases, the intervention trying to improve one variable (amount of protein in the fat body) could have some negative consequences in the colony (not producing winter bees because they think the season will be longer).

      Beekeeping certainly stays interesting!

  2. You can find suppliemental information about research on the importance of fat bodies and the destruction of fat bodies by varroa by searching the videos of Samuel Ramsey.

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