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The approximately 13,000 species of copepod are classified into 10 different orders; this blog post is going to explain a little about one of those orders, the harpacticoids which is made up of about 5000 described species, including Tisbe.

The harpacticoids are an order of mostly benthic (living on surfaces) copepods found all over the world; living in the ocean, lakes, moist soil, groundwater…basically anywhere you can find water you can find a harpacticoid copepod, although most species are marine. Because harpacticoids are so abundant in marine waters where a majority of the order’s diversity can be found, they are extremely important primary and secondary consumers and an important food source for larger organisms.

On the morphology front, harpacticoids are small copepods, usually measuring less than a millimeter in length. That’s not to say they’re all small; Tigriopus is quite large for this order, measuring 1 to 1.5 millimeters in length. Harpacticoids tend to have short antennae, the single eye that many copepods are known for, and, relative to other copepod species, a wider urosome (the posterior portion of the body).

Within the harpacticoida the freshwater family of copepods, the Canthocamptidae are unique in that the adult form is able to protect itself from inhospitable environments, such as a pool drying up, by encasing itself in a cyst. By encasing itself the animal enters a state called diapause, a form of dormancy in which metabolic activity and energy consumption are reduced. The copepod can stay encysted for months until the environmental change has subsided and then resume its normal activities. Adult encystment also takes places in the marine copepod Heteropsyllus nunni, the only known marine crustacean to undergo this process.

In the coming weeks you can look forward to posts about the other fascinating copepod orders and families and species within them.





Williams-Howze, J.,1996.The biology and morphology of the marine harpacticoid copepod Heteropsyllus nunni Coull, during encystment diapause.Hydrobiologia.320:179-189

Feature Image: Aidan Long [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons

Copepod Image:H. Limen and H. MacIsaac. (http://www.glerl.noaa.gov/pubs/photogallery/) [Public domain], via Wikimedia Commons

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