Crustaceans - Large Branchiopoda
> Triops vicentinus
Order: Notostraca (“tadpole shrimp”)
These organisms are known as living fossils because they existed more than 200 million years ago. They are temporary freshwater crustaceans called tadpole shrimps.
Photo of Elisabete Rodrigues | Sul Informação
The genus Triops is named because it has 3 eyes (2 compound eyes and 1 nauplian). These animals also have 57 pairs of appendages called thoracopods. These toracopods, characteristic of the Brachiopods have several functions, that is, some serve for breathing (gills in the feet), others help the animal to move (locomotion) and others still help him to feed.
Photo of José Pacheco
The Triops live in the bottom of the temporary ponds, next to the sediments but can be found to swim across the water column.
Photo of Vasco Flores Cruz
These animals have the sexes separated but the males and the females are very similar. One of the main differences is that in females the eleventh toracopod is slightly modified to accommodate cysts, as the following image illustrates.
cortesy of Luís Quinta
Another difference is that the carapace of the males is slightly rounder than that of the females but the carapace of the females is larger than the carapace of the males.
It has a maximum length of 68mm, excluding the cercopodia (56mm for the carapace). They have separate sexes.
Ref: Adaptado de Alonso, M.1996. Crustacea, Branchiopoda. In Fauna Ibérica (eds, Ramos, M.A., Alba, J., Bellés, X., Gonsálbes, J., Guerra, A., Macpherson, E., Martin, F., Serrano, J. & Templado, J.), 7: 1-486. Museo Nacional de Ciencias Naturales-CSIC, Madrid.
images of the Triops vicentinus moving. Courtesy from Horácio Costa
The cysts, as they are called, the eggs (Image A), are very resistant to desiccation and therefore able to survive for years or decades until the rain arrives at adequate levels. Thus, as soon as the ideal conditions exist, the cysts hatch giving rise to juveniles, as picture B shows.
The active stage of the life-cycle occurs throughout the flooding period of the biotope, which can last between 4 to 5 months.
Image A - Cyst of Triops vicentinus
Image B - Juvenil of Triops vicentinus
Throughout the growth, this crustacean also changes de shells.
At an early stage of development, these Triops are detritivores or scavengers, feeding on debris and bacteria or from corpses of aquatic organisms. Throughout their development they become omnivores and carnivores at a later stage of life. They are predators of small crustaceans such as copepods and ostracods, worms or tadpoles of amphibians.
Image of copepods
Sexual maturation occurs after around 4 weeks, with a shell length of 14-15mm. Fecundation is internal and may occur several times throughout the lifetime of each adult female. It was also verified that the female can lay several egg (cysts) batches . Cysts are spherical and red-brownish.
The females dig the bottom, release the cysts that they have been carrying for some hours in the double receptacles located at the 11th pair of thoracopods, and then cover them with sediment. The number of cysts in each batch is directly related to the size of the female.
Freshwater temporary ponds, namely the Mediterranean Temporary Ponds (priority habitat 3170 - Directive 92/43/CEE).
It is an endemic specie of the farthest south-west Portugal and has a limited distribution extending from the municipality of Vila do Bispo until Faro.
The threats to this species are directly related with the loss and degradation of its habitat.
Up to this date it has no legal protection status.