Sperm morphology in Ascothoracida (Crustacea: Maxillopoda): confirmation of generalized nature and phylogenetic importance

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Abstract
A comparative spermatological survey of ascothoracid crustaceans is presented. They have the most generalized sperm morphology known in Crustacea. Several species of Dendrogaster have flagellate sperm with short heads and midpieces; their sperm may be secondarily shortened, and therefore less generalized than previously thought. The flagellate spermatids of Petrarca okadai and Ulophysema oeresundense have cup-shaped acrosomes, elongate nuclei and midpieces, and sheaths of microtubular organelles. Seminal receptacles in female Gorgonolaureus sp. are lined with a chitinous cuticle and contain flagellate sperm. The anterior basal body in sperm of the subclasses Cirripedia s.s., Mystacocarida, and Branchiura may be interpreted as a synapomorphy linking them within the class Maxillopoda, and Ascothoracida should be recognized as a subclass distinct from Cirripedia.