Ultrastructure of the reproductive system of the black swamp snake (Seminatrix pygaea). VII. spermatozoon morphology and evolutionary trends of sperm characters in snakes

Abstract

This study investigates the evolution of snake spermatozoa within a phylogenetic context, with the addition of a new ultrastructural description from the spermatozoa of the Black Swamp Snake, Seminatrix pygaea. Overall the spermatozoon of S. pygaea is similar to that described for other squamates, whereas some characters such as the electron lucent space separating the cortex and medulla of the acrosome complex may be a unique feature of S. pygaea spermatozoa. This preliminary analysis of sperm evolution within Serpentes leads to the hypothesis that some sperm characters are more plastic than others. Incongruencies are found between the molecular and the morphological topologies utilized, and the phylogeny derived from a morphological data set recovers more unequivocal ancestral states of snake sperm structure. Characters such as the beginning of the fibrous sheath at mitochondrial tier one unite the Colubroidea, whereas characters such as the presence of an acrosome vesicle subdivision, absent vacuity subdivision, and round ⁄ oval mitochondria in transverse section unite all squamates. However, from this analysis it is evident that more taxa need to be studied and taxa with current data need to be more thoroughly investigated to make more conclusive remarks regarding the evolution of sperm structure within snakes.

Spermiogenesis in the imbricate alligator lizard,Barisia imbricata(Reptilia, Squamata, Anguidae)

“…Though our limited spermiogenic data also suggest conservation, like the spermatozoa, in many aspects of spermatid ultrastructure the differences seen could infer evolutionary trends or relationships within squamates and/or other lepidosaurians. For example, Jamieson et al (1995,1996), Vieira et al (2005), and Rheubert et al (2010a,b) all suggest that a single extranuclear perforatorium is a synapomorphy for the Squamata (which our present study supports). Nevertheless, with so few families of lepidosaurians presently represented, these data remain arbitrary and preliminary in nature.…”

“…Interestingly, the acrosomal complex has also been suggested by other studies to be highly conserved in squamates and probably lepidosaurian spermatozoa (Jamieson,1999; Vieira et al,2005; Rheubert et al,2010a,b,2011). However, in B. imbricata the most novel character differences in its spermatid's ultrastructure occur in the acrosomal complex.…”

Ultrastructural differentiation of sperm tail region in Diplometopon zarudnyi (an amphisbaenian reptile)

“…These findings have increased the knowledge of taxon sampling and have provided phylogenetic and evolutionary trends of reptile’s gamete morphology (Vieira et al, 2004; Tourmente et al, 2006; Tavares-Bastos et al, 2008; Rheubert et al, 2010a,b). In recent years, several studies have been published on spermiogenesis of reptiles such as Sceloporus bicanthalis (Rheubert et al, 2012), Agama adramitana (Dehlawi et al, 1992; Ismail et al, 1995), Mauremys caspica (Al-Dokhi and Al-Wasel, 2001a,b), Acanthodactylus boskinus (Al-Dokhi, 2006, 2012), Ptyodactylus hasselquistii (Al-Dokhi, 2009), and Anolis lineatopus (Rheubert et al, 2010a,b). Recently Al-Dokhi et al (2013) has published a paper on sperm head differentiation of D. zarudnyi .…”

Ontogenic development of spermatids during spermiogenesis in the high altitude bunchgrass lizard (Sceloporus bicanthalis)

“…These studies have broadened the taxon sampling and some have even provided phylogenetic and evolutionary perspectives using gamete morphology 1 - 4 . Currently, the Iguania clade is the most highly sampled taxon in terms of ultrastructural characters, 5 , 6 with one study describing spermatozoal data for Uta stansburiana and Urosaurus ornatus 7 within the family Phrynosomatidae.…”

“…Currently, the Iguania clade is the most highly sampled taxon in terms of ultrastructural characters, 5 , 6 with one study describing spermatozoal data for Uta stansburiana and Urosaurus ornatus 7 within the family Phrynosomatidae. These previous studies show that the Squamata contain multiple synapomorphies 8 but relationships between more recently derived taxonomic clades (i.e., genus, family level) are poorly elucidated and contain multiple points of convergence 4 , 8 . Vieira, Colli and Bao 1 showed that the Iguania contain relatively few apomorphic characters and the pleurodonta (Iguanidae, Crotaphytidae, Polychrotidae, Phrynosomatidae, Tropiduridae) only share one character, the presence of a perforatorial baseplate, which is also observed within Scleroglossa and the agamid, Pogona barbata .…”