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An elongating spermatid nearing the climax of elongation. (A) The acrosomal vesicle (AV) envelops the entire nuclear (NU) apex. Bar 5 1 lm. (B) The acrosomal shoulders (white arrowheads) are found ~1/3 of the way down the lateral aspect of the nucleus. There is a very thin line of dark protein accumulation just deep to the outer acrosomal membrane (black arrow). The subacrosomal space (*) can be visualized separating the nucleus (NU) and the acrosome on the rostral portion of the developing spermatid and appears to be made up of large granular proteins. Bar 5 1 lm. The insert shows further spiraling condensation of the chromatin and the nuclear spaces have been reduced significantly. Bar 5 0.2 lm. (C) A cross-sectional view of the apical portion of a late elongate showing the acrosomal vesicle (AV) surrounding the nucleus (NU) with the subacrosomal space (*) separating the nucleus from the vesicle. The subacrosomal space is occupied by a dense layer of granulated proteins (*) and the inner and outer acrosomal membranes are easily visualized (white arrowheads). Several layers of Sertoli cell membrane encircle the outer acrosomal membrane (black arrowhead). Bar 5 0.2 lm. (D) A cross-sectional view of the caudal portion of a late elongating spermatid nucleus (NU). The principal piece of the flagellum (white arrow) is seen in cross section near the nucleus and numerous mitochondria (black arrow) are accumulating between the nucleus and the flagellum. There is a large accumulation of degrading cytoplasm (CD) with a lipid droplet core (LD). Bar 5 0.5 lm.
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To date multiple studies exist that examine the morphology of spermatozoa. However, there are limited numbers of data detailing the ontogenic characters of spermiogenesis within squamates. Testicular tissues were collected from Cottonmouths (Agkistrodon piscivorus) and tissues from spermiogenically active months were analyzed ultrastructurally to d...
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Context 1
... the peak of elongation, the acrosome ves- icle envelops the entire nuclear apex (Fig. 4A, AV). The shoulders of the acrosome vesicle have migrated caudally and lay superficial to the apical nucleus. Just inside of the outer acrosome mem- brane is a continuous band of protein accumula- tion that spans the entire length of the acrosome vesicle ( Fig. 4B, black arrow). The subacrosomal cum-cylindrical (black arrowhead) ...
Context 2
... the peak of elongation, the acrosome ves- icle envelops the entire nuclear apex (Fig. 4A, AV). The shoulders of the acrosome vesicle have migrated caudally and lay superficial to the apical nucleus. Just inside of the outer acrosome mem- brane is a continuous band of protein accumula- tion that spans the entire length of the acrosome vesicle ( Fig. 4B, black arrow). The subacrosomal cum-cylindrical (black arrowhead) aligning micro- tubules can be found surrounding the length of the nucleus beginning just caudally to the shoulders of the acrosomal vesicle. The nucleus is reduced into a thin rostrum apically, which extends up into the acrosome complex (Fig. 5B). A protein absent space ...
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Tubulobulbar complexes (TBCs) are actin-based structures that help establish close contact between Sertoli-Sertoli cells or Sertoli-mature germ cells (spermatids) in the seminiferous tubules of the testes. They are actin-rich push-through devices that eliminate excess spermatid cytoplasm and prepare mature spermatids for release into the tubular lu...
Citations
... During Chara vulgaris spermatid differentiation, structures built out of microtubules, i.e., the microtubular manchette in the cytoplasm and two flagella between the plasmalemma and cell walls of antheridial filaments, are formed [43]. The microtubular manchette has also been discovered in spermatids of certain groups of animals, such as mammals [44,45], birds (poultry [46] and ostriches [47]), reptiles [48,49], and octopuses [50]. However, the process of manchette formation and the period of time for which it is present differ [6,43,[51][52][53]. ...
Microtubules are cytoskeletal cell elements that also build flagella and cilia. Moreover, these structures participate in spermatogenesis and form a microtubular manchette during spermiogenesis. The present study aims to assess the influence of propyzamide, a microtubule-disrupting agent, on alga Chara vulgaris spermatids during their differentiation by means of immunofluorescent and electron microscopy methods. Propyzamide blocks the functioning of the β-tubulin microtubule subunit, which results in the creation of a distorted shape of a sperm nucleus at some stages. Present ultrastructural studies confirm these changes. In nuclei, an altered chromatin arrangement and nuclear envelope fragmentation were observed in the research as a result of incorrect nucleus–cytoplasm transport behavior that disturbed the action of proteolytic enzymes and the chromatin remodeling process. In the cytoplasm, large autolytic vacuoles and the dilated endoplasmic reticulum (ER) system, as well as mitochondria, were revealed in the studies. In some spermatids, the arrangement of microtubules present in the manchette was disturbed and the structure was also fragmented. The observations made in the research at present show that, despite some differences in the manchette between Chara and mammals, and probably also in the alga under study, microtubules participate in the intramanchette transport (IMT) process, which is essential during spermatid differentiation. In the present study, the effect of propyzamide on Chara spermiogenesis is also presented for the first time; however, the role of microtubule-associated proteins in this process still needs to be elucidated in the literature.
... Interestingly, the dense collar is absent in Agkistrodon piscivorus ( Gribbins et al. 2010). In C. durissus (Cunha et al. 2008), Oxyuranus microlepidotus, Boiga irregularis ( Oliver et al. 1996) and S. pygaea , no data on the sinuous tubular mitochondria and its zigzagged arrangement was available to show the para- sagittal longitudinal sections of the spermatozoa. ...
Identifying the polymorphism of the spermatozoon ultrastructure of squamates is vital for improving the accuracy of phylogenic analyses. Multiple studies have been conducted to distinguish the similarities and differences among the sperms of squamates, but these studies have mainly focused on lizards. Thus, there is a need to update the database of the ultrastructure of snake spermatozoa. Myrrophis chinensis is a protected snake in China because of its economic and scientific value. In this study, we examined the ultrastructure of the M. chinensis epididymal spermatozoon. The ultrastructure of the M. chinensis spermatozoon was found to have the following characteristics: dense collar, multilaminar membranes, extracellular microtubules and extraordinary elongation of the midpiece, all of which are typical sperm characteristics of the synapomorphies of Serpentes. Although no unique trait was identified, the current findings could still provide valuable data for phylogenetic analysis.
... The ductus deferens from the right reproductive tract was isolated and prepared for TEM analysis. Following isolation, the ductus deferens was washed in a buffer solution three times (×10 min each), postfixed in 2% osmium tetroxide, dehydrated in a graded series of ethanol solutions, cleared with propylene oxide, and embedded in Spurr's plastic, following the procedures outlined by Gribbins et al. (2010). Samples were viewed using a JEOL JEM-1200 EX II TEM (Jeol Inc., USA) and photographed using an attached digital camera. ...
Previous studies demonstrated that variation in sperm morphology exists below the species level in a variety of organisms. However, most of the studies focus on invertebrates with only a few recent studies on vertebrates with a majority on birds and mammals. Understanding variation at various taxonomic levels is necessary for comparative studies. Therefore, to test the hypothesis that sperm shows little variation between and within closely related taxa, sperm morphology was analyzed in multiple populations of two sister species of lizards, Sceloporus consobrinus and Sceloporus undulatus. The ultrastructure of the sperm did not differ intraspecifically nor interspecifically, but differences were observed in sperm morphometrics between populations. The data gathered in this study show that the ultrastructure of the spermatozoa is consistent with other squamates, and although no variation was observed between the two taxa, slight variations were observed when compared to other members of Phrynosoma. The observed differences in sperm morphometrics show that sperm size differs despite variation in ultrastructure and there may be differences in selection on sperm size between the populations.
... These data have focused on morphological facets that may be beneficial in phylogenetic deduction because gamete ultrastructure has been considered a source for nontraditional character matrices. [1][2][3][4][5][6][7][8][9] However, given the large number of snake species, descriptions of spermatozoa ultrastructure in the Ophidia are still limited at best, 10 and complete descriptions of the entire process of spermiogenesis within snakes are rare., 9,10 There are a few reports that focus on specific parts of spermiogenesis in snakes, [11][12][13][14][15] but to our knowledge the only comprehensive spermiogenic study in ophidians that describes the complete ultrastructural ontogeny of acrosome development, flagellar formation, elongation, and condensation of the spermatid DNA concerned the Cottonmouth (Agkistrodon piscivorus), 10 which is a member of the Viperidae. There also exists a comparative account of spermiogenesis ultrastucturally between Agkistrodon contortrix (though incomplete for the Copperhead) and its sister taxon A. piscivorus, 9 and an earlier study that determines all the major events of spermatid development in the Rock Python, Python sebae. ...
... These data have focused on morphological facets that may be beneficial in phylogenetic deduction because gamete ultrastructure has been considered a source for nontraditional character matrices. [1][2][3][4][5][6][7][8][9] However, given the large number of snake species, descriptions of spermatozoa ultrastructure in the Ophidia are still limited at best, 10 and complete descriptions of the entire process of spermiogenesis within snakes are rare., 9,10 There are a few reports that focus on specific parts of spermiogenesis in snakes, [11][12][13][14][15] but to our knowledge the only comprehensive spermiogenic study in ophidians that describes the complete ultrastructural ontogeny of acrosome development, flagellar formation, elongation, and condensation of the spermatid DNA concerned the Cottonmouth (Agkistrodon piscivorus), 10 which is a member of the Viperidae. There also exists a comparative account of spermiogenesis ultrastucturally between Agkistrodon contortrix (though incomplete for the Copperhead) and its sister taxon A. piscivorus, 9 and an earlier study that determines all the major events of spermatid development in the Rock Python, Python sebae. ...
... These data have focused on morphological facets that may be beneficial in phylogenetic deduction because gamete ultrastructure has been considered a source for nontraditional character matrices. [1][2][3][4][5][6][7][8][9] However, given the large number of snake species, descriptions of spermatozoa ultrastructure in the Ophidia are still limited at best, 10 and complete descriptions of the entire process of spermiogenesis within snakes are rare., 9,10 There are a few reports that focus on specific parts of spermiogenesis in snakes, [11][12][13][14][15] but to our knowledge the only comprehensive spermiogenic study in ophidians that describes the complete ultrastructural ontogeny of acrosome development, flagellar formation, elongation, and condensation of the spermatid DNA concerned the Cottonmouth (Agkistrodon piscivorus), 10 which is a member of the Viperidae. There also exists a comparative account of spermiogenesis ultrastucturally between Agkistrodon contortrix (though incomplete for the Copperhead) and its sister taxon A. piscivorus, 9 and an earlier study that determines all the major events of spermatid development in the Rock Python, Python sebae. ...
Little is known about spermatid development during spermiogenesis in snakes, as there is only one complete study in ophidians, which details the spermatid ultrastructure within the viperid, Agkistrodon piscivorus. Thus, the following study will add to our understanding of the ontogenic steps of spermiogenesis in snakes by examining spermatid maturation in the elapid, Pelamis platurus, which were collected in Costa Rica in 2010. The spermatids of P. platurus share many similar ultrastructural characteristics to that described for other squamates during spermiogenesis. Three notable differences between the spermatids of P. platurus and those of other snakes is a round and shorter epinuclear lucent zone, enlarged caudal nuclear shoulders, and more prominent 3 and 8 peripheral fibers in the principal and endpieces. Also, the midpiece is much longer in P. platurus and is similar to that reported for all snakes studied to date. Other features of chromatin condensation and morphology of the acrosome complex are similar to what has been observed in A. piscivorus and other squamates. Though the spermatids in P. platurus appear to be quite similar to other snakes and lizards studied to date, some differences in subcellular details are still observed. Analysis of developing spermatids in P. platurus and other snakes could reveals morphologically conserved traits between different species along with subtle changes that could help determine phylogenetic relationships once a suitable number of species have been examined for ophidians and other squamates.
... The nucleus of the S. scincus had uniformly distributed chromatin with a smaller amount of heterochromatin, which is considerably different from Sphenodon heterochromatin (Healy and Jamieson, 1994) and that of chelonians (Zhang et al., 2004). The subacrosome space formed in round spermatids of S. scincus continued to expand during the elongation process, and this space accumulated granules which are dark in color and were reported in other sauropsids (Al-Dokhi et al., 2013;Gribbins et al., 2007;Gribbins et al., 2009). After completion of acrosomal growth, the nuclei of the spermatids linked with the cell membrane. ...
... (Saita et al., 1998); however, in D. zarudnyi, (Al-Dokhi et al., 2013) a visible perforatorium has developed an endonuclear canal, as observed in other worm lizards (Saita et al., 1998). In compare to squamates including that of S. scincus have an extra-nuclear perforatorium (without endonuclear canals or no visible canal was found) present in the subacrosome space within their spermatozoa (Gribbins et al., 2007;Gribbins et al., 2009;Rheubert et al., 2010). ...
Background: Knowledge of spermiogenesis in reptiles, especially in lizards, is very limited. Lizards found in Arabian deserts have not been considered for detailed studies due to many reasons and the paucity of these animals. Therefore, we designed a study on the differentiation and morphogenesis of spermiogenesis, at an ultrastructural level, in a rare lizard species, Scincus scincus.
Results: The spermiogenesis process includes the development of an acrosomal vesicle, aggregation of acrosomal granules, formation of subacrosomal nuclear space, and nuclear elongation. A role for manchette microtubules was described in nuclear shaping and organelle movement. During head differentiation, the fine granular chromatin of the early spermatid is gradually replaced by highly condensed contents in a process called chromatin condensation. Furthermore, ultrastructural features of sperm tail differentiation in S. scincus were described in detail. The commencement was with caudal migration toward centrioles, insertion of the proximal centriole in the nuclear fossa, and extension of the distal centrioles to form the microtubular axoneme. Subsequently, tail differentiation consists of the enlargement of neck portion, middle piece, the main and end pieces.
Conclusions: This study aids in the understanding of different aspects of spermiogenesis in the lizard family and unfurls evolutionary links within and outside reptiles.
... The morphological and ultrastructural features of tail region of D. zarudnyi were similar to those described for other amphisbaenian reptiles. The flagellum of D. zarudnyi develops similarly to that described in other reptiles (Healy and Jamieson, 1992;Al-Dokhi and Al-Wasel, 2002;Rheubert et al., 2012;Gribbins et al., 2010Gribbins et al., , 2013. The proximal centriole rests within the nuclear fossa of D. zarudnyi spermatids. ...
Diplometopon zarudnyi, a worm lizard belongs to amphisbaenia under trogonophidae family. This species exists in limited areas of the Arabian Peninsula and is an oscillating digger found in sub-surface soils. The present study aimed to investigate the sperm tail differentiation in D. zarudnyi. Ten male adults of D. zarudnyi were collected from Riyadh during April–May 2011. To study the sperm tail at the ultrastructural level the testes were fixed in 3% glutaraldehyde, than post fixed in 1% osmium tetaroxide followed by dehydration in ethanol grades; samples were cleared in propylene oxide and embedded in resin. Tail formation begins by the moving of centrioles and mitochondria towards the posterior pole of sperm head. Simultaneously many microtubules of the midpiece axoneme were enclosed by a thick layer of granular material. Mitochondria of midpiece lie alongside the proximal centriole which forms a very short neck region and possess tubular cristae internally and concentric layers of cristae superficially. During this course a fibrous sheath surrounds the axoneme of mid and principal piece. At the end dissolution of longitudinal manchette takes place. The mitochondria then rearrange themselves around the proximal and distal centrioles to form a neck region. Later, the fibrous sheath surrounds the proximal portion of the flagella. This part along with sperm head of D. zarudnyi provides a classical model that could be used in future for evolutionary and phylogenetic purposes of class reptilia.
... Although some studies provide ultrastructural descriptions of various aspects of spermiogenesis (acrosome formation, elongation/condensation, and flagellar development) within the 9,0001 species (Reptile-Database, 2012) of lepidosaurians (Clark, 1967;Butler and Gabri, 1984;Hondo et al., 1994;Al-Doki, 2004;Mubarak, 2006), only a few species have complete ultrastructural descriptions of spermatid development across the entire process of spermiogenesis. These comprehensive studies encompass nine families and include 10 species: Sphenodontidae (Sphenodon punctatus; Healy and Jamieson, 1994) Vieira et al., 2001), Lacertidae (Lacerta vivipara; Courtens and Depieges, 1985), Gekkonidae (Hemidactylus turcicus; Rheubert et al., 2011), Scincidae (Chalcides ocellatus; Carcupino et al., 1989; Scincella lateralis; Gribbins et al., 2007), and Viperidae (Agkistrodon piscivorus; Gribbins et al., 2009). The anguimorpha clade (Shinisauridae, Lanthonatidae, Varanidae, Helodermatidae, Xenosauridae, Anguidae; sensu Wiens et al., 2012), to which B. imbricata belongs, has no studies encompassing spermiogenesis and only a single representative with a mature spermatozoon morphological description (Varanus gouldii; Oliver et al., 1996). ...
... Also, endoplasmic reticulum (Fig. 1C, Rer) is seen close to the developing acrosome complex; however, no visual observations from this study suggest it plays any role in acrosome formation as proposed by Ferreira and Dolder (2002) for Iguana Iguana. The majority of morphological observations of the acrosome complex during spermiogenesis in B. imbricata are similar to what has been described in other squamates (Clark, 1967;Furieri, 1970;Jamieson, 1992, Jamieson, 1999;Gribbins et al., 2007Gribbins et al., , 2009Rheubert et al., 2011Rheubert et al., , 2012. These common characteristics included: an elongated nuclear rostrum into the acrosome complex, a highly compartmentalized acrosome complex with an epinuclear lucent zone, subacrosomal space, subacrosomal lucent ridge, basal plate, and perforatorium. ...
... Chromatin condensation begins early in B. imbricata during the mid-round spermatid stage and the nucleus at this time has very distinct round granular nucleoli. Condensation of the chromatin is filamentous even at this early stage, which is different than some squamates and allows chromatin condensation to occur in a granular fashion with later chromatin twisting leading to filamentous condensation such as seen in Iguana iguana (Ferreira and Dolder, 2002), Hemidactylus turcicus , Agkistrodon piscivorus (Gribbins et al., 2009), and Scincella lateralis (Gribbins et al., 2007). The manchette of B. imbricata is similar to that described in other lepidosaurians, in that there is circular and longitudinal microtubules that make up its scaffolding (Gribbins et al., 2007). ...
Although the events of spermiogenesis are commonly studied in amniotes, the amount of research available for Squamata is lacking. Many studies have described the morphological characteristics of mature spermatozoa in squamates, but few detail the ultrastructural changes that occur during spermiogenesis. This study's purpose is to gain a better understanding of the subcellular events of spermatid development within the Imbricate Alligator Lizard, Barisia imbricata. The morphological data presented here represent the first complete ultrastructural study of spermiogenesis within the family Anguidae. Samples of testes from four specimens collected on the northwest side of the Nevado de Toluca, Mexico, were prepared using standard techniques for transmission electron microscopy. Many of the ultrastructural changes occurring during spermiogenesis within B. imbricata are similar to that of other squamates (i.e., early acrosome formation, chromatin condensation, flagella formation, annulus present, and a prominent manchette). However, there are a few unique characteristics within B. imbricata spermatids that to date have not been described during spermiogenesis in other squamates. For example, penetration of the acrosomal granule into the subacrosomal space to form the basal plate of the perforatorium during round spermatid development, the clover-shaped morphology of the developing nuclear fossa of the flagellum, and the bulbous shape to the perforatorium are all unique to the Imbricate Alligator Lizard. These anatomical character differences may be valuable nontraditional data that along with more traditional matrices (such as DNA sequences and gross morphological data) may help elucidate phylogenetic relationships, which are historically considered controversial within Squamata. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.
... We will also contrast our findings here to the spermatid descriptions provided by Gribbins et al. (2010b) within the testis of A. mississippiensis. General relationships will also be drawn between the products of spermiogenesis of A. mississippiensis to those of the Tuatara (Sphenodon punctatus; Healy and Jamieson, 1994), squamates, (Clark, 1967;Dehlawi et al., 1992;Gribbins et al., 2007;Gribbins et al., 2010a;Rheubert et al., 2010a,b), turtles (Hess et al., 1991), and birds (Jamieson, 2007). ...
... Also, as in A. mississippiensis, the fibrous sheath begins caudal to the midpiece in turtles, other crocodilians, ratites, non-passerines (except parrots and doves), and mammals (Jamieson, 1999(Jamieson, , 2007. In contrast, squamates begin the fibrous sheath within the midpiece (Gribbins et al., 2007;Gribbins et al., 2010a;Rheubert et al., 2010b) and this leads to a shorter distal centriole overall. The early beginning of the fibrous sheath within the THE SPERMATOZOON OF THE A. mississippiensis midpiece is clearly an autapomorphy for Squamata Jamieson and Healy, 1992;Scheltinga, 1993, Jamieson, 1995). ...
This study details the ultrastructure of the spermatozoa of the American Alligator, Alligator mississippiensis. American Alligator spermatozoa are filiform and slightly curved. The acrosome is tapered at its anterior end and surrounded by the acrosome vesicle and an underlying subacrosomal cone, which rests just cephalic to the nuclear rostrum. One endonuclear canal extends from the subacrosomal cone through the rostral nucleus and deep into the nuclear body. The neck region separates the nucleus and midpiece and houses the proximal centriole and pericentriolar material. The distal centriole extends through the midpiece and has 9 × 3 sets of peripheral microtubules with a central doublet pair within the axoneme that is surrounded by a dense sheath. The midpiece is composed of seven to nine rings of mitochondria, which have combinations of concentrically and septate cristae. The principal piece has a dense fibrous sheath that surrounds an axoneme with a 9 + 2 microtubule arrangement. The sheath becomes significantly reduced in size caudally within the principal piece and is completely missing from the endpiece. Dense peripheral fibers, especially those associated with microtubule doublets 3 and 8, penetrate into the anterior portion of the principal piece axoneme. The data reported here hypothesize that sperm morphology is highly conserved in Crocodylia; however, specific morphological differences can exist between species.
... Useful non-traditional characters developed from the ultrastructure of the mature spermatozoa have previously been used in phylogenetic analyses (Jamieson, 1991(Jamieson, , 1995(Jamieson, , 1999Newton and Trauth, 1992;Jamieson et al., 1996;Gribbins and Rheubert, in press), many of which have found sperm characters to be highly conserved among reptilian taxa (Teixeira et al., 1999a,b;Gribbins and Rheubert, in press). Since the developmental characters of spermiogenesis often disclose the final morphological details of the mature spermatozoa (Gribbins et al., 2007(Gribbins et al., , 2010Rheubert et al., 2010c), equal focus on spermiogenesis may add to the robustness of these phylogenetic analyses by providing novel ontogenic characters. ...
... Lepidosaurs have largely been ignored in terms of describing the complete steps of spermiogenesis although many previous studies regarding sperm development in reptiles focused on specific steps or details of spermiogenesis (i.e., acrosome development, nuclear condensation/elongation, and flagellar development) (Clark, 1967;Butler and Gabri, 1984;Hondo et al., 1994;Al-Dokhi, 2004, 2009Mubarak, 2006). To date, only seven studies provide comprehensive descriptions of spermiogenesis in Lepidosaurs: Chalcides ocellatus (Carcupino et al., 1989), Sphenodon punctatus (Healy and Jamieson, 1994), Tropidurus torquatus (Vieira et al., 2001), Iguana iguana (Ferreira and Dolder, 2002), Scincella lateralis (Gribbins et al., 2007), Agkistrodon piscivorus (Gribbins et al., 2010), and Anolis lineatopus (Rheubert et al., 2010c). These studies have shown that the major events associated with spermiogenesis follow general patterns although specific ultrastructural differences exists, such as presence/absence of a manchette, endoplasmic reticulum involvement in acrosome development, number and composition of acrosomal layers, and location of the acrosome granule upon first appearance. ...
... Protein stratification observed within the subacrosomal space observed in A. lineatopus (Rheubert et al., 2010c) and the snake, A. piscivorus (Gribbins et al., 2010) was not seen in H. turcicus. The subacrosome space in the Mediterranean Gecko is uniformly paracrystalline with a single perforatorium, which is proposed to develop from the acrosome granule (Del Conte, 1976), extending into the subacrosomal cone similar to that of other squamates (Tourmente et al., 2008). ...
We studied spermiogenesis in the Mediterranean Gecko, Hemidactylus turcicus, at the electron microscope level and compared to what is known within other Lepidosaurs. In H. turcicus germ cells are connected via cytoplasmic bridges where organelle and cytoplasm sharing is observed. The acrosome develops from merging transport vesicles that arise from the Golgi and subsequently partition into an acrosomal cap containing an acrosomal cortex, acrosomal medulla, perforatorium, and subacrosomal cone. Condensation of DNA occurs in a spiral fashion and elongation is aided by microtubules of the manchette. A nuclear rostrum extends into the subacrosomal cone and is capped by an epinuclear lucent zone. Mitochondria and rough endoplasmic reticulum migrate to the posterior portion of the developing germ cell during the cytoplasmic shift and the flagellum elongates. Mitochondria surround the midpiece as the anlage of the annulus forms. The fibrous sheath begins at mitochondrial tier 3 and continues into the principal piece. Peripheral fibers associated with microtubule doublets 3 and 8 are grossly enlarged. During the final stages of germ cell development spermatids are wrapped with a series of Sertoli cell processes, which exhibit ectoplasmic specializations and differing cytoplasmic consistencies. The results observed here corroborate previous studies, which show the conservative nature of sperm morphology. However, ultrastructural character combinations specific to sperm and spermiogenesis seem to differ among taxa. Further studies into sperm morphology are needed in order to judge the relevance of the ontogenic changes recorded here and to determine their role in future studies on amniote evolution.
... Although much attention has been paid to the ultrastructure of spermatozoa in the last decade, the number of taxa sampled within the Squamata, and certainly within Serpentes, needs to increase to more thoroughly study evolutionary trends. These spermatozoa characters along with developmental features during spermiogenesis, which are also gaining much needed attention (Healy and Jamieson 1994;Gribbins et al. 2007Gribbins et al. , 2010Rheubert et al. in press), have been considered a rich source of non-traditional morphological characters that can be utilized in phylogenetic analyses (Jamieson 1991;Newton and Trauth 1992;Jamieson et al. 1996;Teixeira et al. 1999;Tavares-Bastos et al. 2002;Vieira et al. 2004;Wiens 2004). ...
... The flagellar structure of the S. pygaea spermatozoon has numerous similarities and differences to other snakes studied to date suggesting this may be a more variable portion of the mature sperm. However, surrounding the neck region and the tail are extracellular microtubules that were observed in all snakes studied to date and have been observed in immature spermatids during spermiogenesis (Gribbins et al. 2007(Gribbins et al. , 2010 and immature teiid sperm (Jamieson 1995). We assume that the extracellular microtubules observed in association with the mature spermatozoa are remnants of the manchette not shed during spermiation. ...
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.
