External nasal gland morphology of Eurycea bislineata (Amphibia, Urodela, Plethodontidae).

Plethodontid salamanders possess numerous courtship glands. Previous studies have shown that the glands are more prominent in male individuals than females, and often experience periods of atrophy and hypertrophy throughout the year that correlate to the nonmating and mating seasons, respectively. We sampled male and female Eurycea bislineata throughout the year to test the hypothesis that external nasal glands are courtship glands. External nasal glands are paired, branched tubular glands that extend from excretory ducts dorsal to the nares to terminal secretory units posterior to the eyes. We found that the glands hypertrophy and stain/react more intensely with histochemical procedures during the mating season. Hypertrophy of the glands is more pronounced in males, and seasonal variation in epithelial height of external nasal glands of males is significantly correlated to that of seasonal variation in mental gland epithelial height, a known courtship gland found in males, when compared throughout the year. This correlation was not as strong in females, confirming sexual dimorphism of external nasal glands in terms of seasonal variation. We found no ultrastructural differences between male and female external nasal glands. In all specimens, the glandular tubules were lined by a simple, columnar epithelium that was packed with secretory granules that often obscured other cytoplasmic contents.

Modification of genital kidney nephrons for sperm transport in a plethodontid salamander, Eurycea longicauda.

Salamanders possess kidneys with two distinct regions: a caudal pelvic portion and cranial genital portion. Nephrons of the pelvic region are responsible for urine formation and transport. Nephrons of the genital region transport sperm from testes to Wolffian ducts; however, nephrons of the genital region possess all the same functional regions found in pelvic kidney nephrons that are involved with urine formation and transport (renal corpuscles, proximal tubules, distal tubules, and collecting ducts). Morphological similarities between pelvic and genital regions stimulated past researchers to hypothesize that nephrons of genital kidneys possess dual function; that is, sperm transport and urine formation/transport. Considering size of glomeruli is directly related to the total amount of blood plasma filtered into the Bowman's space, we tested the hypothesis that nephrons of genital kidneys have reduced urine formation function by comparing glomerular size between nephrons of pelvic and genital kidney regions in Eurycea longicauda with general histological techniques. Light microscopy analysis revealed that glomeruli of pelvic kidneys were significantly larger than those measured from genital kidneys. Transmission electron microscopy analysis also revealed modifications in genital kidney nephrons when compared to pelvic kidney nephrons that suggested a decrease in urine formation function in genital kidneys. Such modifications included a decrease in basal and lateral plasma membrane folding in genital kidney proximal and distal tubules compared to that of pelvic kidney proximal and distal tubules. Genital kidney proximal tubules were also ciliated, which was not observed in pelvic kidney proximal tubules. In conclusion, although structurally similar at the histological level, it appears that nephrons of genital kidneys have decreased urine formation function based on glomerular size comparison and nephron ultrastructure.

Ultrastructure of spermatid development within the testis of the Yellow-Bellied Sea Snake, Pelamis platurus (Squamata: Elapidae).

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 2009. 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.

Ultrastructural analysis of spermiogenesis in the Eastern Fence Lizard, Sceloporus undulatus (Squamata: Phrynosomatidae).

Studies on reptilian sperm morphology have shown that variation exists at various taxonomic levels but studies on the ontogeny of variation are rare. Sperm development follows a generalized bauplan that includes acrosome development, nuclear condensation and elongation, and flagellar development. However, minute differences can be observed such as the presence/absence of manchette microtubules, structural organization during nuclear condensation, and presence/absence of a nuclear lacuna. The purpose of this investigation was to examine sperm development within the Sceloporus genus. The process begins with the development of an acrosomal complex from Golgi vesicles followed by nuclear condensation and elongation, which results in the presence of a nuclear lacuna. As the acrosomal complex differentiates, flagellar development commences with elongation of the distal centriole. Spermatid development culminates in a mature spermatid with a highly differentiated acrosomal complex, a condensed nucleus with a nuclear lacuna, and a differentiated flagellum. Although the overall developmental pattern is consistent with other squamate species, minute differences are observed, even within the same genus. For example there is variation in the presence/absence of an endoplasmic reticulum complex during acrosome development, presence/absence of a nuclear lacuna, and presence/absence of manchette microtubules within the three species of Sceloporus studied to date. Future studies concerning sperm morphology in closely related species will aid in our understanding of variation in sperm development and may prove to be useful in testing phylogenetic and evolutionary hypotheses.

Agkistrodon piscivorus spermatogenesis addendum: The effect of Hurricane Katrina on spermatogenesis of the western cottonmouth snake.

Recent studies detailed the spermatogenic cycle of the Western Cottonmouth Snake, Agkistrodon piscivorus and noted that spermatogenesis is bimodal, with active periods during March-June and August-October in southeastern Louisiana. However, only spermatogonia were present in September in the only specimen that was captured and the authors state that the individual "should have a high testis volume and also show spermiogenic activity." The specimen in their study was caught immediately following Hurricane Katrina outside of its normal habitat. Therefore, in order to verify their assumption, individuals were captured during September of 2008 and the testes were spermatogenically active with spermatogonia, spermatocytes, and mature spermatozoa being present in the seminiferous epithelium of the testes. These data indicate that Hurricane Katrina could have had an impact on the spermatogenic cycle in Cottonmouths, resulting in stress-induced testicular regression.

Spermatogenic cycle of a plethodontid salamander, Eurycea longicauda (Amphibia, Urodela).

Previous investigators have described the spermatogenic cycles of numerous species of plethodontid salamanders. Most studies describe a fairly stereotypical cycle with meiotic divisions of spermatogenesis commencing in the spring/summer. However, many studies lack details obtainable from histological examination and/or testicular squashes and, instead, provide only mensural data from the testes. Studies that lacked microscopic evaluation often revealed spermatogenic cycles that varied greatly from that of the stereotypical cycle with meiotic divisions commencing in the fall/winter. Those studies hamper comparisons between the spermatogenic cycles of different species and their environments, as they do not provide a correlation between testicular size and any aspect of the spermatogenic cycle. In the following manuscript, we elucidate the spermatogenic cycle of Eurycea longicauda longicauda in an effort to outline an appropriate protocol for analyzing spermatogenesis in salamanders that will facilitate future comparative studies. Like many Nearctic plethodontids, E. l. longicauda exhibits a meiotic wave that travels through the testes during the summer; this process is followed by spermiogenesis, spermiation, and recrudescence in the fall, winter, and spring.

Seasonal spermatogenesis in the Mexican endemic oviparous lizard, Sceloporus aeneus (Squamata: Phrynosomatidae).

Oviparous species of Sceloporus exhibit either seasonal or continuous spermatogenesis and populations from high-elevation show a seasonal pattern known as spring reproductive activity. We studied the spermatogenic cycle of a high-elevation (2700 m) population of endemic oviparous lizard, Sceloporus aeneus, that resided south of México, D.F. Histological analyses were performed on the testes and reproductive ducts from individual lizards collected monthly. This population of S. aeneus showed a seasonal pattern of spermatogenesis, with 4 successive phases common in other lizards. These include: 1) Quiescence in August, which contained solely spermatogonia and Sertoli cells; 2) Testicular recrudescence (September-January) when testes became active with mitotic spermatogonia, spermatocytes beginning meiosis, and the early stages of spermiogenesis with spermatids; 3) Maximum testicular activity occurred from March to May and is when the largest spermiation events ensued within the germinal epithelia, which were also dominated by spermatids and spermiogenic cells; 4) Testicular regression in June was marked with the number of all germs cells decreasing rapidly and spermatogonia dominated the seminiferous epithelium. February was a transitional month between recrudescence and maximum activity. The highest sperm abundance in the lumina of epididymides was during maximum testicular activity (March-May). Thus, before and after these months fewer spermatozoa were detected within the excurrent ducts as the testis transitions from recrudescence to maximum activity in February and from maximum activity to quiescence in June. Maximum spermatogenic activity corresponds with warmest temperatures at this study site. This pattern known as spring reproductive activity with a fall recrudescence was similar to other oviparous species of genus Sceloporus.

Testicular histology and germ cell cytology during spermatogenesis in the Mississippi map turtle, Graptemys pseudogeographica kohnii, from Northeast Arkansas.

The testicular histology and cytology of spermatogenesis in Graptemys pseudogeographica kohnii were examined using specimens collected between July 1996 and May 2004 from counties in northeastern Arkansas. A histological examination of the testes and germ cell cytology indicates a postnuptial testicular cycle of spermatogenesis and a major fall spermiation event. The majority of the germ cell populations in May and June specimens are represented by resting spermatogonia, type A spermatogonia, type B spermatogonia, pre-leptotene spermatocytes, and numerous Sertoli cell nuclei near the basement membrane. The start of proliferation is evident as spermatogonia in metaphase are present near the basal lamina and many of these germ cells have entered meiosis in June seminiferous tubules. Major spermatogenic events occur in the June and July specimens and result in an increased height of the seminiferous epithelium and increased diameter of the seminiferous tubules. The germ cell population during this time is represented by spermatogonia (type A, B, and resting), hypertrophic cells, large populations of early primary spermatocytes, and early round spermatids. By September, the major germ cell population has progressed past meiosis with abundant round and early elongating spermatids dominating the seminiferous epithelium. October seminiferous epithelia are marked by a decreas in height and mature spermatozoa fill the luminal space. Round and elongating spermatids constitute the largest portion of the germ cell population. Following the spermiation event, the testes enter a period of quiescence that lasts till the next spermatogenic cycle, which begins in the subsequent spring. Based on the cytological development of the seminiferous tubules revealed by our study, Graptemys pseudogeographica kohnii demonstrates a temporal germ cell development strategy similar to other temperate reptiles. A single major generation of germ cells progresses through spermatogenesis each year resulting in a single spermiation event with sperm stored within the epididymis until the next spring mating season.

The ultrastructure of spermatid development during spermiogenesis within the rosebelly lizard, Sceloporus variabilis (Reptilia, Squamata, Phrynosomatidae).

Several recent studies have mapped out the characters of spermiogenesis within several species of squamates. Many of these data have shown both conserved and possibly apomorphic morphological traits that could be important in future phylogenetic analysis within Reptilia. There, however, has not been a recent study that compares spermiogenesis and its similarities or differences between two species of reptile that reside in the same genus. Thus, the present analysis details the changes to spermiogenesis in Sceloporus variabilis and then compares spermatid morphologies to that of Sceloporus bicanthalis. Many of the morphological changes that the spermatids undergo in these two species are similar or conserved, which is similar to what has been reported in other squamates. There are six main character differences that can be observed during the development of the spermatids between these two sceloporid lizards. They include the presence (S. variabilis) or absence (S. bicanthalis) of a mitochondrial/endoplasmic reticulum complex near the Golgi apparatus during acrosome development, a shallow (S. variabilis) or deep (S. bicanthalis) nuclear indentation that accommodates the acrosomal vesicle, filamentous (S. variabilis) or granular (S. bicanthalis) chromatin condensation, no spiraling (S. variabilis) or spiraling (S. bicanthalis) of chromatin during condensation, absence (S. variabilis) or presence (S. bicanthalis) of the longitudinal manchette microtubules, and the lack of (S. variabilis) or presence (S. bicanthalis) of nuclear lacunae. This is the first study that compares spermiogenic ultrastructural characters between species within the same genus. The significance of the six character differences between two distantly related species within Sceloporus is still unknown, but these data do suggest that spermiogenesis might be a good model to study the hypothesis that spermatid ontogeny is species specific.

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

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, México, 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.

The testicular sperm ducts and genital kidney of male Ambystoma maculatum (Amphibia, Urodela, Ambystomatidae).

The ducts associated with sperm transport from the testicular lobules to the Wolffian ducts in Ambystoma maculatum were examined with transmission electron microscopy. Based on the ultrastructure and historical precedence, new terminology for this network of ducts is proposed that better represents primary hypotheses of homology. Furthermore, the terminology proposed better characterizes the distinct regions of the sperm transport ducts in salamanders based on anatomy and should, therefore, lead to more accurate comparisons in the future. While developing the above ontology, we also tested the hypothesis that nephrons from the genital kidney are modified from those of the pelvic kidney due to the fact that the former nephrons function in sperm transport. Our ultrastructural analysis of the genital kidney supports this hypothesis, as the basal plasma membrane of distinct functional regions of the nephron (proximal convoluted tubule, distal convoluted tubule, and collecting tubule) appear less folded (indicating decreased surface area and reduced reabsorption efficiency) and the proximal convoluted tubule possesses ciliated epithelial cells along its entire length. Furthermore, visible luminal filtrate is absent from the nephrons of the genital kidney throughout their entire length. Thus, it appears that the nephrons of the genital kidney have reduced reabsorptive capacity and ciliated cells of the proximal convoluted tubule may increase the movement of immature sperm through the sperm transport ducts or aid in the mixing of seminal fluids within the ducts.

Ultrastructure of the spermatozoon of the American Alligator, Alligator mississippiensis (Reptilia: Alligatoridae).

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.

Ultrastructural description of spermiogenesis within the Mediterranean Gecko, Hemidactylus turcicus (Squamata: Gekkonidae).

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.

Reptilian spermatogenesis: A histological and ultrastructural perspective.

Until recently, the histology and ultrastructural events of spermatogenesis in reptiles were relatively unknown. Most of the available morphological information focuses on specific stages of spermatogenesis, spermiogenesis, and/or of the mature spermatozoa. No study to date has provided complete ultrastructural information on the early events of spermatogenesis, proliferation and meiosis in class Reptilia. Furthermore, no comprehensive data set exists that describes the ultrastructure of the entire ontogenic progression of germ cells through the phases of reptilian spermatogenesis (mitosis, meiosis and spermiogenesis). The purpose of this review is to provide an ultrastructural and histological atlas of spermatogenesis in reptiles. The morphological details provided here are the first of their kind and can hopefully provide histological information on spermatogenesis that can be compared to that already known for anamniotes (fish and amphibians), birds and mammals. The data supplied in this review will provide a basic model that can be utilized for the study of sperm development in other reptiles. The use of such an atlas will hopefully stimulate more interest in collecting histological and ultrastructural data sets on spermatogenesis that may play important roles in future nontraditional phylogenetic analyses and histopathological studies in reptiles.

Ultrastructure of spermiogenesis in the American alligator, Alligator mississippiensis (Reptilia, Crocodylia, Alligatoridae).

Testicular samples were collected to describe the ultrastructure of spermiogenisis in Alligator mississipiensis (American Alligator). Spermiogenesis commences with an acrosome vesicle forming from Golgi transport vesicles. An acrosome granule forms during vesicle contact with the nucleus, and remains posterior until mid to late elongation when it diffuses uniformly throughout the acrosomal lumen. The nucleus has uniform diffuse chromatin with small indices of heterochromatin, and the condensation of DNA is granular. The subacrosome space develops early, enlarges during elongation, and accumulates a thick layer of dark staining granules. Once the acrosome has completed its development, the nucleus of the early elongating spermatid becomes associated with the cell membrane flattening the acrosome vesicle on the apical surface of the nucleus, which aids in the migration of the acrosomal shoulders laterally. One endonuclear canal is present where the perforatorium resides. A prominent longitudinal manchette is associated with the nuclei of late elongating spermatids, and less numerous circular microtubules are observed close to the acrosome complex. The microtubule doublets of the midpiece axoneme are surrounded by a layer of dense staining granular material. The mitochondria of the midpiece abut the proximal centriole resulting in a very short neck region, and possess tubular cristae internally and concentric layers of cristae superficially. A fibrous sheath surrounds only the axoneme of the principal piece. Characters not previously described during spermiogenesis in any other amniote are observed and include (1) an endoplasmic reticulum cap during early acrosome development, (2) a concentric ring of endoplasmic reticulum around the nucleus of early to middle elongating spermatids, (3) a band of endoplasmic reticulum around the acrosome complex of late developing elongate spermatids, and (4) midpiece mitochondria that have both tubular and concentric layers of cristae.

Ultrastructure of spermiogenesis in the Cottonmouth, Agkistrodon piscivorus (Squamata: Viperidae: Crotalinae).

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 detail the cellular changes that occur during spermiogenesis. The major events of spermiogenesis (acrosome formation, nuclear elongation/DNA condensation, and flagellar development) resemble that of other squamates; however, specific ultrastructural differences can be observed between Cottonmouths and other squamates studied to date. During acrosome formation vesicles from the Golgi apparatus fuse at the apical surface of the nuclear membrane prior to making nuclear contact. At this stage, the acrosome granule can be observed in a centralized location within the vesicle. As elongation commences the acrosome complex becomes highly compartmentalized and migrates laterally along the nucleus. Parallel and circum-cylindrical microtubules (components of the manchette) are observed with parallel microtubules outnumbering the circum-cylindrical microtubules. Flagella, displaying the conserved 9 + 2 microtubule arrangement, sit in nuclear fossae that have electron lucent shoulders juxtaposed on either side of the spermatids basal plates. This study aims to provide developmental characters for squamates in the subfamily Crotalinae, family Viperidae, which may be useful for histopathological studies on spermatogenesis in semi-aquatic species exposed to pesticides. Furthermore, these data in the near future may provide morphological characters for spermiogenesis that can be added to morphological data matrices that may be used in phylogenetic analyses.

Histological analysis of spermatogenesis and the germ cell development strategy within the testis of the male Western Cottonmouth Snake, Agkistrodon piscivorus leucostoma.

Cottonmouth (Agkistrodon piscivorus leucostoma) testes were examined histologically to determine the germ cell development strategy employed during spermatogenesis. Testicular tissues from Cottonmouths were collected monthly from swamps around Hammond, Louisiana. Pieces of testis were fixed in Trump's fixative, dehydrated in ethanol, embedded in Spurr's plastic, sectioned with an ultramicrotome, and stained with toluidine blue and basic fuchsin. Spermatogenesis within Cottonmouths occurs in two independent events within a single calendar year. The testes are active during the months of March-June and August-October with spermiation most heavily observed during April-May and October. To our knowledge, this is the first study that describes bimodal spermatogenesis occurring in the same year within the subfamily Crotalinae. During spermatogenesis, no consistent spatial relationships are observed between germ cell generations. Typically, either certain cell types were missing (spermatocytes) or the layering of 3-5 spermatids and/or spermatocytes within the same cross-section of seminiferous tubule prevented consistent spatial stages from occurring. This temporal pattern of sperm development is different from the spatial development found within birds and mammals, being more reminiscent of that seen in amphibians, and has now been documented within every major clade of reptile (Chelonia, Serpentes, Sauria, Crocodylia). This primitive-like sperm development, within a testis structurally similar to mammals and birds, may represent an intermediate testicular model within the basally positioned (phylogenetically) reptiles that may be evolutionarily significant.

Ultrastructural examination of spermiogenesis within the testis of the ground skink, Scincella laterale (Squamata, Sauria, Scincidae).

Although the events of spermiogenesis are commonly studied in amniotes, the amount of research available for lizards (Sauria) is lacking. Many studies have described the morphological characteristics of mature spermatozoa in lizards, but few detail the ultrastructural changes that occur during spermiogenesis. The purpose of this study was to gain a better understanding of the subcellular events of spermiogenesis within the temperate ground skink (Scincella laterale). The morphological data presented here represent the first complete ultrastructural study of spermiogenesis within the Scincidae clade. Samples of testes from 20 specimens were prepared using standard techniques for transmission electron microscopy. Many of the ultrastructural changes occurring during spermiogenesis within the ground skink are similar to that of other saurians. However, there were a few unique characteristics that to date have not been described during spermiogenesis in other lizards. For example, during early round spermatid development within the ground skink testis, proacrosomal granules begin to form within the acrosomal vesicle before making contact with the apex of the nucleus. Also, a prominent microtubular manchette develops during spermiogenesis; however, the circular component of the manchete is absent in this species of skink. This developmental difference in manchette formation may lead to the more robust and straight mature spermatozoa that are common within the Scincidae family. These anatomical character differences may be valuable nontraditional sources that along with more traditional sources (i.e., mitochondrial DNA) may help elucidate phylogenetic relationships, which are historically considered controversial at best, among species within Scincidae and Sauria.

Cytological evaluation of spermatogenesis within the germinal epithelium of the male European wall lizard, Podarcis muralis.

The annual cytological changes to the male germinal epithelium were investigated in an introduced population of European wall lizards (Podarcis muralis). Testicular tissues were collected, embedded, sectioned by an ultramicrotome, and stained with the PAS procedure followed by a toluidine counterstain. Spermatogenesis in the lizard is divided into the proliferative, meiotic, and maturational phases. Wall lizards have a prenuptial pattern of spermatogenesis, where sperm development begins immediately prior to and continues through the months of breeding (April-June). The testis then involutes, undergoes a short period of quiescence, and recrudescence commences in mid-July. Germ cells undergo proliferation, meiosis, and the early stages of spermiogenesis (maturation) from late July through December. However, the late stages of spermiogenesis are retarded from December through February. Spermiogenesis continues at an accelerated pace from March through May, leading to a single massive spermiation event through the month of June. Although spatial relationships are seen between germ cells within the seminiferous epithelium, accumulation of spermatids during winter and acceleration of elongation in spring prevents determination of consistent cellular associations between early and late developing germ cells within the wall lizard testis. This temporal germ cell development is different from the consistent spatial development seen within seasonally breeding birds and mammals and may represent an evolutionary intermediate in terms of amniotic germ cell development.

Cytological evaluation of spermatogenesis and organization of the germinal epithelium in the male slider turtle, Trachemys scripta.

The germ cell development in the slider turtle (Trachemys scripta) testis was investigated by viewing the histology of the seminiferous epithelium in plastic sections with a light microscope. Germ cell morphologies in the slider turtle testis were similar to the morphologies of other vertebrate germ cell types. However, the slider turtle seminiferous epithelium contained germ cells that progress through spermatogenesis in a temporal rather than a spatial pattern, resulting in a single spermatogenic event that climaxed with one massive sperm release in November. Mature sperm then are stored within the epididymis until breeding commences in the following spring. The germ cell development strategy in the slider turtle is different from that of other amniotes and is more reminiscent of the developmental strategy found in the anamniotic testis. This temporal progression of germ cells through spermatogenesis within a tubular testis represents a transitional model that may be evolutionarily significant.