The Histology of Fishes by Formicki Krzysztof;Kirschbaum Frank;

Author:Formicki, Krzysztof;Kirschbaum, Frank;
Language: eng
Format: epub
Publisher: Taylor & Francis Group
Published: 2020-01-15T00:00:00+00:00

Uniflagellate Spermatozoa

This type of spermatozoon is the most common in teleosts, and with some exceptions (e.g., spermatozoa of Elopomorpha, see below) it exhibits a simple structure with a spherical nucleus, having, at the base or laterally, invagination called nuclear fossa. Both centrioles, the proximal and the distal ones, could be located inside the nuclear fossa in various mutual arrangements, or outside it, which happens in the case when the flagellum is tangential to the nucleus. The midpiece with mitochondria is located usually at the base of the nucleus. The flagellum arises from the distal centriole forming the basal body. The sperm of Elopomorpha, as shown in Fig. 13(A–C), possesses several unique features being spermatozoal synapomorphies for the orders of Elopiformes, Anguilliformes, and Albuliformes (Jamieson and Mattei 2009). All these unique features were described in the sperm of Anguilla anguilla (Gwo et al. 1992), Albula vulpes (Mattei and Mattei 1973, 1974), Lycodontis afer (Mattei 1970, Mattei and Mattei 1974, Mattei 1991). The sperm has an elongate nucleus, crescentic in shape and with a hook-shaped anterior end, where the only mitochondrion is situated. The centrioles are located at the posterior end. The proximal centriole is extended and dissociated into two bundles of microtubules consisting of five and four triplets, running from the centriolar region towards the anterior tip of the elongated nucleus and forming the pseudoflagellum. Another feature is the striated rootlet, a strong projection supported by a central axis present at the posterior tip near the anterior part of the flagellum. The flagellum arises from the distal centriole and the elopomorph axoneme is composed of nine peripheral doublets and lacks central singlets.

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