Morphology and Ultrastructure of the Amazon River Dolphin (Inia geoffrensis) Spermatozoa

Abstract

This is the peer reviewed version of the following article: 'Morphology and ultrastructure of the Amazon river dolphin (Inia geoffrensis) spermatozoa', Anatomical Record, which has been published in final form at http://dx.doi.10.1002/ar.23585. This article may be used for noncommercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. 2 ABSTRACTThe spermatozoa from seven adult Amazon river dolphins (Inia geoffrensis, CETACEA: INIIDAE) were analyzed by light and electron microscopy. The spermatozoa showed an elongated ellipsoid shaped head and a long tail with a well distinguishable midpiece. The head spermatozoa have a smooth surface like other odontocetes examined, with the exception of the Delphinidae family. The mean dimensions of the spermatozoa were within the range already reported for other cetaceans. The spermatozoa midpiece, as in other cetaceans, showed a random pattern of mitochondria, different from that described for other mammals. Further studies of sperm morphology of a wider spectrum of cetacean families could help to better understand the reproductive biology of these animals and the inter-and intra-generic relationships among them, as well as, among other mammals.

Characterization of Bottlenose Dolphin (Tursiops truncatus) Sperm Based on Morphometric Traits

“…The morphometric parameters observed in the present study are similar to previous findings for bottlenose dolphin sperm (see Table 1 [ 16 , 34 , 35 , 36 , 37 , 38 ]) and comparable to those for other cetaceans [ 35 ]. Knowledge of sperm dimensions may provide important information on the evolutionary adaption of spermatozoa [ 55 , 56 ], and the standardization of sperm features in captivity animals may provide information of interest when comparing the same features in wild animals, because external factors (e.g., environmental pollutants) might modify sperm dimensions [ 57 ].…”

“…For these reasons, sperm morphometry may determine subsequent effects on swimming speed [ 30 ], spermatozoa selection in the uterus [ 23 , 31 ] and the ability to fertilize oocytes [ 32 , 33 ]. Sperm morphometry in different species of dolphin (including bottlenose dolphin) has been described previously ( Table 1 [ 16 , 34 , 35 , 36 , 37 , 38 ]); however, whether sperm morphometry traits influence sperm function has not been studied in this species. The morphometry of sperm subpopulations in other mammals is subject to changes in conditions, including sperm refrigeration or freezing [ 39 ].…”

A drastic shift in the energetic landscape of toothed whale sperm cells

“…To further examine the mitochondrial size of mammalian sperm, we collected published photographs of longitudinal sections through the midpiece of the sperm flagellum. [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87] For well-defined mitochondrion, for which we were able to see the boundaries, we took two measurements: one called ''Height,'' defined as the measurement of the mitochondrion parallel to the axoneme, and another called ''Width,'' defined as the measurement of the mitochondrion perpendicular to the axoneme (figshare link in Key resources table). Images for which only magnification was displayed, the height and width of each mitochondrion were calculated from distances measured with a ruler (±0.05 cm).…”

The Amazon River dolphin, Inia geoffrensis: What have we learned in the last two decades of research?

“…This relatively small percentage of testes weight is probably related to the high level of male competition and the promiscuous mating system. The head morphology of spermatozoa is similar to that of some other odontocete species but differs from that of delphinids (Amaral et al, 2017). The placenta is diffuse epitheliochorial, like in other cetaceans (da Silva et al, 2007).…”