Ctenopoda

Penilia avirostris

The Ctenopoda make an order or subordination of the claws tails ( Onychura ) and thus within the Blattfußkrebse ( Branchiopoda ) dar. It involves small crustaceans that are found mainly in fresh water, only the genus Penilia lives in the sea. The types are limited in their occurrence to the northern hemisphere ( Holarctic ) and the tropical belt.

Construction of Ctenopoda

The Ctenopoda reach a maximum body length of 4 millimeters. The body of the animal is surrounded by the typical for the claws tails shell ( carapace ) and consists of relatively few segments, whose boundaries are not clearly recognizable. It ends in a telson with a short abdomen fork ( furca ). The head bears no separate head shield.

The first antenna is short and tubular, the 2 antennas provide great zweiästige swimming legs with swimming bristles represents the maxilla and mandible which are formed normally. The single compound eye is relatively large and is the front of the head, an unpaired Naupliusauge is also available.

The body carries six limb pairs, with the first five pairs are designed to filter legs. The impact of these legs is metachrom, that is, he wanders wave from one leg to the other, starting with the last pair of legs. This particle can be trapped between the leg bases and are filtered through the bristles on the Enditen and swept into a central channel and sucked through the forming vacuum forward. And characterized by the movement of the legs, these particles then pass into the oral cavity.

Reproduction and Development

The propagation of Onychopoda is mainly parthenogenetic, with the juveniles develop in the brood pouch of the female and are supplied with nutrients there via secretions of a specially developed fabric ( soil ). During the annual cycle, it often comes to bisexual reproduction, resulting from the resting eggs, which are released freely into the water. The development runs directly without Nauplius.

Nomenclature of Ctenopoda

The Ctenopoda were previously together with the Haplopoda (the only representative is the Glaskrebschen ), the Onychopoda and Anomopoda as water fleas ( Cladocera ) summarizes this group is, however, probably not a natural unit ( monophyletic ); actual allocation in the system of claws tails is controversial.

The few representatives of the Central European Ctenopoda are the families Sididae ( Sida crystallina, Latona setifera and Diaphanosoma brachyurum; Mediterranean marine form Penilia avirostris ) and the Holopediidae assignment (only Holopedium gibberum ).