Sperm Morphology in Neotropical Primates.

Eliana R Steinberg,Ana M Palermo,María B Ceballos,Virginia Wagner,Adrián J Sestelo,Marta D Mudry

doi:10.3390/ani9100839

Abstract

Simple SummaryThe spermatozoon is a highly differentiated cell, whose morphology has been affected throughout evolution by selective forces such as the competition between the sperm of rival males (sperm competition) and the joint evolution of male and female reproductive tracts (coevolution). The study of its morphology is important when analyzing the relationships between different species. In this contribution we analyzed new specimens and produced a database with all the spermatozoa dimensions recorded to date, comprising 75 individuals from 20 species and 8 genera, representing 2 families of neotropical primates (Cebidae and Atelidae). After an evolutionary analysis, we observed two different trends for the Cebidae and Atelidae families. Narrower and shorter spermatozoa seem to be the ancestral (oldest) form for Cebidae, with an evolutionary trend toward spermatozoa with wider and larger heads in the derived (younger) species. In Atelidae, on the contrary, narrower heads are observed in the more derived groups. We analyzed these results in the context of sperm competition and mating systems in these groups. More studies are needed to improve our knowledge of the evolution of the spermatozoa in neotropical primates.The morphological and morphometric characterization of spermatozoa has been used as a taxonomic and phylogenetic tool for different species of mammals. We evaluated and compared the sperm morphometry of five neotropical primate species: Alouatta caraya, Ateles belzebuth and Ateles chamek of family Atelidae; and Cebus cay (=Sapajus cay) and Cebus nigritus (=Sapajus nigritus) of family Cebidae. After the collection of semen samples, the following parameters were measured on 100 spermatozoa from each specimen: Head Length, Head Width, Acrosome Length, Midpiece Length, Midpiece Width and Tail Length. Considering the available literature on sperm morphometry, we gathered data of 75 individuals, from 20 species, 8 genera and 2 families. These data were superimposed on a phylogeny to infer the possible direction of evolutionary changes. Narrower and shorter spermatozoa seem to be the ancestral form for Cebidae, with a trend toward wider and larger heads in derived groups. The spermatozoa of Atelidae may show an increase in total length and midpiece length. Sperm heads would have become narrower in the more derived groups of Ateles. Sperm length may increase in the more derived species in both families. Our results are discussed in the context of sperm competition and sexual selection.

Highlights

The spermatozoon is a highly differentiated cell, whose morphology and physiology are closely associated with fertilization [1]
Semen was obtained from eight adult males from of neotropical primate species Cebus cay (CCY), Cebus nigritus (CNI), Ateles chamek (ACH), Ateles belzebuth (ABE) and Alouatta caraya (ACA)
In Cebus, the whole ejaculate coagulated after collection (CCY ED08: 100 μL, CCY 4FF6: 500 μL, CCY D000: 50 μL and CNI 911F: 250 μL), except for CCY D000, who produced 100 μL of liquid fraction with 80% of motility and 67.3% of normal spermatozoa

Summary

Introduction

The spermatozoon is a highly differentiated cell, whose morphology and physiology are closely associated with fertilization [1]. Eutherian mammals show a high variation in sperm head morphology [2,3,4,5]. Lemuridae and Loridae, the sperm head varies from bearing a hook emerging from the apical end to extensions emerging from its base [3,6]. In this context, sperm morphology and morphometry are regarded as informative variables useful in phylogenetic and taxonomic studies on different mammal species [4,5,7,8]. Sperm competition has been proposed to shape many sperm features [3,6,12,13]

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