Dynamene bidendata
ARTHROPODA
Isopoda
Have you ever heard of isopods?
๐๐๏ธย Open your eyes, because this species, ๐๐บ๐ฏ๐ข๐ฎ๐ฆ๐ฏ๐ฆ ๐ฃ๐ช๐ฅ๐ฆ๐ฏ๐ฅ๐ข๐ต๐ข, is one of the most commonly found in the intertidal zone on the NE altantic coast! They are typically found on a wide variety of mid- to lower littoral algae, and also in rock pools in the upper littoral zone.
๐๐ต๏ธโโ๏ธย I absolutely love the beautiful color pattern of the exoskeleton, perfectly blending with the seaweed, and ideal for camouflage!
๐ฑ๐ As you maybe guessed, ๐๐บ๐ฏ๐ข๐ฎ๐ฆ๐ฏ๐ฆ ๐ฃ๐ช๐ฅ๐ฆ๐ฏ๐ฅ๐ข๐ต๐ข is herbivorous, and they eat on the algae that they are found on. Like many animals of the intertidal zone, their life follow the rhythm of tides and they eat only when they are covered by the high tide.
๐ฆ๐ฆฟ Isopods belong to crustaceans, just like shrimps and crabs, and they also have a hard exoskeleton. There are over 10,000 identified species worldwide, both terrestrial or marine! Their name comes from the fact that they have segments carrying typically 7 similar (โiso-โ= equal) pairs of legs (-โpodโ = foot).
๐๐ชฒ This small isopod of the intertidal zone is 6 to 7mm long, and also called horned isopod. You can easily guess why!
๐ฆท๐ฆทย The name ‘bidentata’ (latin for ‘two-toothedโ) comes from the two tooth-like projections on its back, which are unique to males of this species. It makes the pleotelson a key feature for the identification of the sex and the species. In ๐๐บ๐ฏ๐ข๐ฎ๐ฆ๐ฏ๐ฆ ๐ฃ๐ช๐ฅ๐ฆ๐ฏ๐ฅ๐ข๐ต๐ข males, the 6th segment is longer and have this typical pointy shape.
โง๏ธโง๏ธ This is a great exemple of ๐๐ฒ๐ ๐๐ฎ๐น ๐ฑ๐ถ๐บ๐ผ๐ฟ๐ฝ๐ต๐ถ๐๐บ, that refers to differences in appearance, size, or other characteristics between males and females of the same species. Sexual dimorphism can be observed in many animal species, including mammals, birds, reptiles, fish, and insects.
๐โโ๏ธ๐ฆถUropods are paired appendages found at the rear end (posterior) of crustaceans, such as lobsters, crabs, shrimp, and isopods. Their structure and function can vary widely but they are typically used for locomotion and swimming.
Sources

- Doris
- MarLIN
- Arrontes, J. Diet, food preference and digestive efficiency in intertidal isopods inhabiting macroalgae. Journal of Experimental Marine Biology and Ecology 139, 231โ249 (1990).
- Vieira, P., Queiroga, H., Costa, F. & Holdich, D. Distribution and species identification in the crustacean isopod genus Dynamene Leach, 1814 along the North East Atlantic-Black Sea axis. ZooKeys 635, 1โ29 (2016).
- Wieser, W. Adaptations of two intertidal isopods I. Respiration and feeding in Naesa bidentata (Adams) (Sphaeromatidae). Journal of the Marine Biological Association of the United Kingdom 42, 665โ682 (1962).