Histology and morphometrics of testes of the white-sided dolphin (Lagenorhynchus acutus) in bycatch samples from the northeastern Atlantic
Abstract
The testes of 31 Atlantic white-sided dolphins, Lagenorhynchus acutus bycaught in the northeastern Atlantic were studied by histological and morphometric techniques. Twenty specimens were classified as mature, nine as immature and two as pubescent. Between immature and mature specimens there were overlappings in body length and body weight, but clear differences in the diameter of seminiferous tubules (<80 and > 480 μm) and the proportion of seminiferous tubules to interstitial tissue (ST:INT-ratio). Also relative testes weight differed clearly. The pubescent specimens showed intermediate characteristics. Spermatogenetic activity of mature dolphins ranged from quiescent to different degrees of activity and varied even in animals from the same site and capture date. The fact that we found mature males with quiescent testes suggests a seasonal rather than a continuous spermatogenesis. We assume that sexual activity in L. acutus begins at an age of 7-8 GLGs and that the reproductive season of this species in the northeastern Atlantic starts in February. Further, the ultrastructure of the spermatozoon is similar to that of the related Lagenorhynchus obliquidens.
Key words
Lagenorhynchus acutus testis histology morphometricsHistologie und Morphometrie der Hoden von Atlantischen Weißseitendelphinen (Lagenorhynchus acutus) aus Beifängen des nordöstlichen Atlantik
Zusammenfassung
Die Hoden von 31 Atlantischen Weißseitendelphinen (Lagenorhynchus acutus) aus Beifängen des nordöstlichen Atlantik wurden histologisch und morphometrisch analysiert. Zwanzig Exemplare konnten als geschlechtsreif, neun als nicht geschlechtsreif und zwei als pubertär klassifiziert werden. Die nicht geschlechtsreifen und die geschlechtsreifen Tiere zeigten bei der Körperlänge und dem Körpergewicht Überlappungen; beide konnten jedoch anhand des Durchmessers der Tubuli seminiferi (<80mm und > 480 mm) sowie anhand des Verhältnisses von Tubuli seminiferi und interstitiellem Gewebe (ST:INT-Verhältnis) unterschieden werden. Zudem war auch das relative Hodengewicht unterschiedlich. Die entsprechenden Werte für die pubertierenden Exemplare nahmen eine Zwischenstellung ein. Die Spermatogenese der geschlechtsreifen Delphine schwankte von ruhend” bis “aktiv” (verschiedene Intensitäten); sie variierte selbst bei Tieren, die zur gleichen Zeit ” im selben Gebiet gefangen wurden. Der Fang von geschlechtsreifen Männchen ohne Spermatogen-eseaktiviät spricht eher für eine saisonale als für eine kontinuierliche Spermatogenese. Wir vermuten, dass die sexuelle Aktivität von L. acutus in einem Alter von 7-8 GLGs und die Fortpflanzungszeit im nordöstlichen Atlantik im Februar beginnen. Die Ultrastruktur der Spermien ähnelt der des verwandten Lagenorhynchus obliquidens.
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