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''Caecosphaeroma'' is a troglodytic
They measure from 2–20 mm long. As cave dwellers, they have lost their vision, but remain sensitive to light, which they shun. They are capable of volvation (rolling themselves into a ball) to protect themselves, rest, or sleep. During copulation the male and female embrace takes the form of two concentric spheres.
isopod
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...
genus in the family Sphaeromatidae found in caves of NE and SW France. The genus was split off from Monolistra by Adrien Dollfus
Adrien Frédéric Jules Dollfus (21 March 1858, in Mulhouse-Dornach – 19 November 1921, in Paris) was a French carcinologist known for his work with terrestrial isopods, including crustaceans and trilobites.
Life and career
Adrien Dollfus was th ...
in 1896; in both genera, the female carries about 10 fertilized eggs in its external marsupium (brood pouch); they are white in ''Monolistra'' but bluish-green in ''Caecosphaeroma''. ''C. burgundum'' is the most studied species.
Description
They measure from 2–20 mm long. As cave dwellers, they have lost their vision, but remain sensitive to light, which they shun. They are capable of volvation (rolling themselves into a ball) to protect themselves, rest, or sleep. During copulation the male and female embrace takes the form of two concentric spheres.
Development
Larva remain in the marsupium about 12 months, and the animals continue growing for several years, reaching a final length of 10–20 mm.Evolution
The marine ancestors of ''Caecosphaeroma'' are believed to have migrated up the course of rivers and adapted to a subterranean environment that was relatively stable; meanwhile the marine environment of their ancestors changed, so ''Caecosphaeroma'' continued to differentiate as a separate lineage.Volvation in ''C. burgundum''
''C. burgundum'' has evolved in ways to improve its ability to curl into a ball. The mandibular palps and antennae are able retract into two deep grooves of the face, and the posterior margin ofpleotelson
The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...
(the last body segment fused with the "tail") provides greater mechanical support for the head. Evolution of volvation is seen in other subterranean isopods, but only ''C. burgundum'' is able to roll up into a hermetic sphere without any outward projections, and thus "approaches perfection in volvation". (Article has English abstract.)
References
External links
{{Portal, Arthropods Sphaeromatidae Cave crustaceans Fauna of France Isopod genera