The taxonomic confusion surrounding Pisidium (Bivalvia, Sphaeriidae): the possible birth of a new taxon
Résumé
The presence of Pisidium shells with an appendiculum,
presenting specific morphological characteristics not yet
described has been observed for several years. Although
their external shell traits appear similar the ligament-pit of
these individuals differs: it is either long and narrow as in
P. supinum, or shorter and thicker as in that of the ponderosa
form of P. casertanum and would therefore belong to one or
the other of these two species. They could also be the result
of hybridisation and constitute a new taxon.genre, and raising one of these alleged forms or varieties to
species rank often gives rise to debate (Dyduch-Falniowska,
1983; Kuiper, 1983; Piechocki, 1989; Araujo & Korniushin,
1998; Glöer & Zettler, 2005). On the contrary, polymorphism
is quite limited in other species such as Pisidium
henslowanum (Sheppard, 1823), P. supinum ( A. Schmidt,
1851) or P. milium Held, 1936. For several years shells with
an appendiculum (a more or less oblique fold located close
to the top of each valve) and resembling P. supinum or forma
plicata Zeissler, 1962, of P. casertanum, but presenting specific
characters have been observed in rivers and canals. The aim
of this article is to describe the particularities of these
individuals that have not yet been mentioned.
Domaines
Sciences de l'environnement
Origine : Accord explicite pour ce dépôt