Order CTENOPODA G.O. Sars, 1865

Museums

Regional Maps

• Ctenopoda Sars, G.O. 1865. Norges ferskvandskrebsdyr. Første Afsnit. Branchiopoda. 1. Cladocera Ctenopoda (Fam. Sididae & Holopedidae) [Norway's freshwater crustaceans. First part. Branchiopoda. 1. Cladocera Ctenopoda (Fam. Sididae & Holopedidae)]. Christiania : Brøgger & Christie's Bogtrykker pp. i-viii, 1-71, pls 1-4. [https://wellcomecollection.org/works/s4qp43x7] [vii, 27].

Introduction

Ctenopodans are mostly freshwater, but Penilia is marine (or, at least, in the zone of mixing of fresh with sea water, as in estuaries and coastal lagoons). They are found worldwide, with more species in the tropics than in the temperate zone but not in Antarctica. Olesen (1998) could find no synapomorphies for the Ctenopoda.

Diagnosis

Body short, composed of few, indistinct segments and ending in a postabdomen with an apical pair of claws, never articulated to the trunk. Carapace not calcified, bivalved, without hinge, enclosing only trunk and appendages. Head large, without head shield. Labrum fleshy. Eyes single, internal, always fused in adults, with many lenses. Ocellus small or absent (Diaphanosoma, Penilia). Antennules tubular and movable in females, elongated and modified for clasping usually in males. Antennae biramous, natatory (uniramous only in females of Holopedium). Both branches of 2–3 segments, armed with between 13 and 27 natatory setae. Mandibles of the grinding type. Maxillules with numerous spines (minimum 4 in Penilia) . Maxillae simple lobes with or without setose seta. Six pairs of trunk limbs, filtratory and showing much serial similarity, although the sixth pair is more reduced. Exopodites present. All limbs beat with a metachronal rhythm. First trunk limb of male with distal hook, or with modified distal region. Food groove deep and narrow. Alimentary canal straight. Anterior caeca found only in Latona parviramis, where they are ventrally located. Ovaries paired; ovarian cells originate anteriorly. Penes paired, except in Sida. Vasa deferentia open immediately behind trunk limbs. Resting eggs invested by oviductal secretion Carapace not modified to an ephippium. Parthenogenetic eggs large, passed into dorsal brood space formed by carapace where they develop to miniature replicas of adults. Nahrboden present only in Penilia. Reproduct1on by gamogenesis alternates with parthenogenesis. No larval stages; young released from resting eggs are replicas of adults. Length up to 4 mm, usually 1–3 mm in females and 0.7–1.5 mm in males.

Diagnosis References

Dumont H.J. & Negrea, S.V. 2002. Introduction to the Class Branchiopoda Guides to the Identifcation of the Microinvrtebrates of the Continuental Waters of the World. Leiden : Backhuys Publishers Vol. 19 398 pp. [258]

General References

Olesen, J. 1998. A phylogenetic analysis of the Conchostraca and Cladocera (Crustacea, Branchiopoda, Diplostraca). Zoological Journal of the Linnean Society 122: 491–536

History of changes