Morphological analysis of the male reproductive accessory glands of the bat Artibeus lituratus (Phyllostomidae: Chiroptera)

Bats are distributed worldwide from tropical to temperate regions. Despite their wide geographical radiation and advances in studies using evolutionary approaches, aspects related to the reproduction of these animals remain poorly explored, especially those related to the male reproductive accessory glands (RAGs). Thus, the aim of this study was to analyze the morphophysiology of the male RAGs in the bat Artibeus lituratus. The RAGs in A. lituratus are composed of a compact intra‐abdominal glandular complex, consisting of the prostate with two prostatic regions (ventral and dorsal), plus Littre glands and a pair of extra‐abdominal bulbourethral glands. The ventral region of the prostate has an epithelium with variable morphology, due to its holocrine type of secretion. In contrast, the dorsal region has a typical cubic‐to‐columnar pseudostratified epithelium. Both regions contain two cell types, basal and secretory cells. Similar to the epithelial morphology, the secretion also varies, with the ventral region containing numerous PAS‐positive globular vesicles, whereas the dorsal region has a more fluid, hyaline and PAS‐negative secretion. Littre glands are dispersed in the connective tissue of the urethra, while the bulbourethral glands are located in the penile root, both glands with cubic‐to‐columnar pseudostratified epithelium and globular PAS‐positive secretion. The results demonstrate that the RAGs of A. lituratus are composed of two prostatic regions, ventral and dorsal, and urethral and bulbourethral glands, with no seminal vesicles. Each prostatic region has unique and distinctive characteristics, with the ventral region presenting an exclusive holocrine nature and the dorsal region having similarities to the ventral prostate of rodents.     

Comparative analysis of the male reproductive accessory glands of bats Noctilio albiventris (Noctilionidae) and Rhynchonycteris naso (Emballonuridae)

In eutherian mammals, the male reproductive accessory glands (RAGs) comprise the prostate, bulbourethral glands, ampullary glands, and the seminal vesicles. Their composition, anatomy and function vary widely between species. This study aimed to characterize histologically and compare the RAGs of bats. The RAGs of Noctilio albiventris (Noctilionidae) and Rhynchonycteris naso (Emballonuridae) were studied using anatomical and histological methods, and were reconstructed three dimensionally. The RAGs of N. albiventris and R. naso are composed of a compact glandular complex that surrounds the urethra and a pair of bulbourethral glands, which are extra‐abdominally located in the inguinal region. In both species, the glandular complex is composed of two well‐defined prostatic regions (ventral and dorsal). The ventral region showed an atypical epithelium (holocrine), where no obvious cellular limits were observed, and PAS‐positive secretion. The dorsal region had a pseudostratified cuboidal epithelium, with basal and secretory cells, and PAS‐negative secretion. Noctilio albiventris also had urethral glands (Littre glands) surrounding the urethra, however, R. naso had only muscles. Both species had bulbourethral glands, with simple columnar epithelium and PAS‐positive secretion. In conclusion, the RAGs of N. albiventris and R. naso comprised a pair of bulbourethral glands and an intra‐abdominal complex, composed of a prostate with two different regions (ventral and dorsal), while the ampullary glands and seminal vesicles were missing in both species. This morphology was more closely related between N. albiventris and R. naso, and to species of the family Phyllostomidae than to families Molossidae and Vespertilionidae. J. Morphol. 277:1459–1468, 2016. © 2016 Wiley Periodicals, Inc.     

The structure of the cutaneous pedal glands in the banded snail Cepaea hortensis (Müller, 1774)

Although gastropods have been crawling through the ocean and on the land for 60 million years, we still know very little about the sticky mucus produced in their foot. Most research has been focused on marine species in particular and, to a lesser extent, on the well‐known terrestrial species Arion vulgaris and Cornu aspersum. Within this study, we aim to characterize the foot anatomy of a smaller representative of the family Helicidae, the banded snail Cepaea hortensis. We are particularly interested in the microanatomy of the foot glands, their position, and the histochemical nature of their secretory content. Characterization of the dorsal foot region of Cepaea hortensis reveals four glands, differing in their size and in the granules produced. Histochemically, three of them react positively for sugars (PAS staining and lectin affinity tests for mannose, glucose and N‐acetyl‐d ‐glucosamine) and acidic proteins (positive Alcian blue and Toluidine blue staining), indicating the presence of acidic glycosaminoglycans. The fourth gland type does not react to any of these dyes. The ventral pedal region includes two different gland types, which are positive for the presence of acidic glycoproteins, with a lectin affinity for mannose only. A comparison with Helix pomatia indicates differences regarding the number of glands and their contents. In Helix, only three gland types are described in the dorsal region of the foot, which show a similar granular appearance but nevertheless differ in their chemical composition. Congruently, there are two gland types in the ventral region in both species, whereas in Helix an additional sugar moiety is found. This raises the question whether these differences between the pedal glandular systems of both helicid species are the result of protection or size‐related adaptations, as they occur in the same habitat.     

Anatomic,Histologic and Certain Enzymatic Studies on the Male Genital Organs of Hemiechinus auritus collaris Gray,the Indian Long Eared Hedgehog

Anatomically the male reproductive organs of Hemiechinus auritus collaris are of considerable interest and present a unique pattern of arrangement of different glands. The testes are inguinal and a true scrotum is absent. A pair of accessory glands, the seminal vesicles, are situated dorsal to the bladder. A pair of obviously lobulated glands, ventral to the bladder, represent the internal prostate and a pair of compact glands situated outside the pelvis in para-anal position the external prostate. The Cowper's gland and the gland of ampulla are absent. The present studies also concern enzymes of the phosphatase group, including both specific and non-specific phosphatases, in the testes and the sex accessory glands during both active and inactive periods in this insectivore.     

Fine structure of the male reproductive system in two species ofHaplognathia sterrer (Gnathostomulida,Filospermoidea)

Summary The structure of the male reproductive systems of two species ofHaplognathia cf.lyra andH. cf.rosacea was described. The structure of the testes and the anterior portions of the sperm ducts in both species was found to be similar. However, considerable species differences were found between the structures of the glands and muscles associated with the reproductive systems. These were more elaborate inH. cf.lyra than inH. cf.rosacea. The former species possessed an H-shaped sperm duct gland, three distinct groups of penis muscles and a penis with two cell types and with a lumen. The latter species had paired sperm duct glands, no specialized penis muscles and a penis with only one cell type and without a detectable lumen. No open gonopore was observed in either species. The sperm presumably exit through a ventral tissue connection observed connecting the penis and the ventral epidermis. These findings were discussed in the light of Mainitz's (1977) theory concerning the primitive penis type within the Gnathostomulida.Abbreviations ap anterior-posterior penis muscles - bm basement membrane - csd common sperm duct - dl dorsal lumen of the penis - dp dorsal gland cells of the penis - dv dorsoventral muscles anterior to the penis - dw sperm duct wall cell - e epidermis - ex exit cell - g intestine - gl gut lumen - n nerve - p penis - sd sperm duct - sdg sperm duct gland - tw testes wall cell - vl ventral lumen of the penis - vp ventral gland cells of the penis This project was supported by NSF grant #GB 42211 (R.M. Rieger P.I.). The line drawings have been executed after our design by Ms. Linda McVay     

Functional anatomy of the female reproductive systems of two spider crabs (Decapoda,Majoidea)

To better understand the mating systems of majoid crabs, we studied the functional anatomy of the female reproductive systems of the spider crabs Leurocyclus tuberculosus and Libinia spinosa, comparing them with those of other Majoidea. Adult females were measured and dissected, and their reproductive systems described macroscopically and histologically. In females of both species, the seminal receptacles are paired globular structures of ecto‐mesodermal origin. The mesoderm‐derived region is lined by a stratified epithelium. The anchoring, proliferative, and secretory strata are clearly recognizable . The ectoderm‐derived region is lined by a simple cylindrical epithelium underlying a cuticle that increases in thickness toward the vagina. The transition between the ectoderm and mesoderm‐derived regions is abrupt, with differences between the studied species: Li. spinosa has a “velum,” whereas Le. tuberculosus presents prominent “folds.” In both species, the position in which the oviduct is connected to the seminal receptacles is intermediate between the dorsal and ventral types previously described in other eubrachyurans. The seminal receptacles of the studied species show four different conditions, which can be distinguished macroscopically based on their shape and amount of sperm stored. We compare our data with those from other Majoidea in an attempt to determine whether the morphology of the seminal receptacles is related to different mating strategies or behaviors.     

The dorsal tail tubercle of Mertensiella caucasica and M. luschani (Amphibia: Salamandridae)

Males of the two species of Mertensiella (M. caucasica and M. luschani) possess a tubercle projecting from the skin of the dorsal tail base, the single morphological character that defines the genus. The dorsal tail tubercle functions during courtship, and its role is similar in both species. The tubercle is inserted into the cloaca of the female during ventral amplexus, shortly before the male deposits a spermatophore. Histological examination, however, revealed that the dorsal tubercles differ structurally between the two species. In M. caucasica, the tubercle consists primarily of elongate mucous glands, with granular glands occurring only at the base. Both mucous and granular glands of the tubercle are larger than those in typical skin. Unlike typical skin, however, mucous glands are larger than granular glands. In M. luschani, mucous glands and granular glands occur throughout the tubercle, and the granular glands are larger than the mucous glands, although both types are larger than those in typical skin. The dorsal tubercles of M. caucasica and M. luschani may not be homologous structures and may have resulted from convergent evolution. J Morphol 232:93–105, 1997. © 1997 Wiley-Liss, Inc.     

Position of enigmatic miniature trichomycterid catfishes inferred from molecular data (Siluriformes)

Trichomycteridae is a well‐corroborated catfish family that comprises about 300 valid species distributed in eight subfamilies. The phyletic status of the Trichomycterinae is uncertain, with different hypothesis regarding the position of the miniaturized Trichomycterus hasemani group. This group comprises four valid species, and neither its monophyly nor its positioning among the Trichomycteridae was tested in a phylogenetic framework. Bayesian Inference and Maximum Likelihood analyses of a molecular data set comprising the mitochondrial genes 12S and 16S and the nuclear genes H3, MYH6 and RAG2 (2983 bp) for 26 taxa highly supported the miniature catfish T. hasemani group as monophyletic and sister to the Tridentinae, consequently recognized as a new genus of this subfamily. Potamoglanis gen. nov. is diagnosed by seven character states: an angle of 35–40° between the main longitudinal axis of the head and the main axis of the autopalatine; thin tubular shape of the second ceratobranchial; presence of six or seven anal‐fin rays; eyes dorsally placed on head; opercular and interopercular odontodes patches not juxtaposed; absence of a distal process on the hyomandibula and presence of a long process on the anterior region of the hyomandibula. Potamoglanis gen. nov is similar to the Tridentinae genera by the presence of a wide cranial fontanelle; presence of a short ventral process in the opercular bone and by the origin of the dorsal fin placed in a vertical through the anal‐fin origin.     

Observations on the production of purple pigments in the egg capsules,hypobranchial and reproductive glands from seven species of Muricidae (Gastropoda: Mollusca)

Summary

Tyrian purple is a well-known colourant that can be obtained from the hypobranchial glands of muricids. Here we investigate the presence of purple and related pigments in the hypobranchial glands, reproductive glands and egg capsules of three Rapaninae, three Ocenebrinae and one Muricinae species. Observations on the dissected specimens revealed the presence of purple pigmentation in the hypobranchial glands of all species. All of the Rapaninae and the Muricinae, but only some species of Ocenebrinae, appear to transfer the pigment precursors to their egg capsules. This provides evidence that the precursors of Tyrian purple are not produced for the sole purpose of protecting the egg masses as has been previously suggested. In all the subfamilies, the hypobranchial and reproductive (capsule and prostate) glands lie adjacent to one another. Colour changes in the reproductive glands, indicating the presence of dye precursors, were observed in two species of Rapaninae. In Dicathais orbita, colour changes could be seen in both the capsule glands of females and prostrate glands of males. The final colour was more red in the reproductive glands than the purple observed in the hypobranchial glands. Preliminary observations of detached hypobranchial gland sections in both D. orbita and Pterynotus triformis indicate a different suite of colour reactions occur when compared to sections that are intact and attached to the reproductive glands. This demonstrates that the reproductive glands can influence the chemical conversions of dye precursors synthesized by these species. Further studies on the secondary metabolism occurring within the hypobranchial glands and reproductive organs of Muricidae are ongoing, including histological sectioning and confirmation of the chemistry behind the colours observed and functional analysis of Tyrian purple precursors.     

Morphological analysis of the female reproductive system of Stenorhynchus seticornis (Brachyura: Inachoididae) and comparisons with other Majoidea

We examined the female reproductive system of the yellowline arrow crab Stenorhynchus seticornis by means of histological and histochemical techniques. Mature specimens obtained in the field were kept in the laboratory for mating experiments. After 24 h, newly mated females were dissected, and their reproductive trait routinely processed for embedding in historesin. The specimens examined each possessed a pair of kidney‐shaped seminal receptacles (SR), and these we classified as ventral type, based on the location of the oviduct opening. The mesodermal dorsal region (DR) of SR consisted of a stratified epithelium with scaly cells, while the ectodermal ventral region (VR) was composed of a simple epithelium covered by a cuticle. The oviduct opened at the transition region (TR) between DR and VR and had no velum. The simple epithelium of TR had more folds on the face of the oviduct opening. The vagina exhibited the same features as the TR epithelium and was contiguous to VR, anchored by muscles. In the lumen, from one to three strata of sperm packets were observed, the dorsal one containing free sperm, and the most ventral stratum, spermatophores. An acidophilic glycoprotein layer enclosed the strata. Spermatophores in the ventral stratum were enclosed in a voluminous secretion, composed by acid polysaccharides most likely from the last male mated. The ventral‐type receptacle, stratified sperm packets, and polyandry, usually observed in females of Majoidea, suggest the occurrence of sperm competition in S. seticornis, favoring the sperm of the last male mated, as its sperm mass is located near the opening of the female oviduct.     

Histology and lectin-binding patterns in the skin of the terrestrial horned frog Ceratophrys ornata

The terrestrial horned frog, Ceratophrys ornata, lives on a wet substratum and absorbs water through the ventral epidermis; water is lost by evaporation from the dorsal skin. Thus, this species may be useful as a model for determining whether or not skin histology and lectin-binding patterns, indicative of glycoconjugates, are related to skin functions such as osmoregulation and water balance. With this in mind, a histological and lectin-histochemical study was carried out on dorsal and ventral skin of aquatic tadpoles and of a young terrestrial frog of C. ornata. Sections of skin were stained with various dyes to demonstrate general histological features and with two horseradish peroxidase (HRP)-conjugated lectins, Ulex europaeus agglutinin (UEA 1) and soybean agglutinin (SBA) which bind to specific terminal sugar residues of glycoconjugates, namely L-fucose and N-acetyl-D-galactosamine or D-galactose, respectively. In early stage tadpoles both lectin-binding patterns were similar in the bilaminar epidermis of dorsal and ventral skin (i.e., each lectin stained the apical cell layer). However, metamorphic changes resulted in a young frog with typical adult-type skin composed of a stratified squamous epidermis and three distinct types of glands containing glycoconjugates in their secretions. Strikingly different lectin-binding patterns were evident in the epidermis from dorsal and ventral regions of the body. The epidermis from the dorsal region was stained by both lectins; in contrast, that from the ventral region although stained strongly by HRP-SBA, did not react with HRP-UEA 1 indicating that few, if any, fucose residues were present in the ventral epidermis. These findings, as suggested in the discussion, indicate that different glycoconjugate patterns in dorsal and ventral skin may be associated with the regulation of water balance in the frog.     

SALMFamide2 and serotonin immunoreactivity in the nervous system of some acoels (Xenacoelomorpha)

Acoel worms are simple, often microscopic animals with direct development, a multiciliated epidermis, a statocyst, and a digestive parenchyma instead of a gut epithelium. Morphological characters of acoels have been notoriously difficult to interpret due to their relative scarcity. The nervous system is one of the most accessible and widely used comparative features in acoels, which have a so‐called commissural brain without capsule and several major longitudinal neurite bundles. Here, we use the selective binding properties of a neuropeptide antibody raised in echinoderms (SALMFamide2, or S2), and a commercial antibody against serotonin (5‐HT) to provide additional characters of the acoel nervous system. We have prepared whole‐mount immunofluorescent stainings of three acoel species: Symsagittifera psammophila (Convolutidae), Aphanostoma pisae, and the model acoel Isodiametra pulchra (both Isodiametridae). The commissural brain of all three acoels is delimited anteriorly by the ventral anterior commissure, and posteriorly by the dorsal posterior commissure. The dorsal anterior commissure is situated between the ventral anterior commissure and the dorsal posterior commissure, while the statocyst lies between dorsal anterior and dorsal posterior commissure. S2 and serotonin do not co‐localise, and they follow similar patterns to each other within an animal. In particular, S2, but not 5‐HT, stains a prominent commissure posterior to the main (dorsal) posterior commissure. We have for the first time observed a closed posterior loop of the main neurite bundles in S. psammophila for both the amidergic and the serotonergic nervous system. In I. pulchra, the lateral neurite bundles also form a posterior loop in our serotonergic nervous system stainings.     

Morphology and function of reproductive organs in Neodasys chaetonotoideus (Gastrotricha: Neodasys) with a phylogenetic assessment of the reproductive system in Gastrotricha

The reproductive system of the important basal gastrotrich Neodasys chaetonotoideus is described and reconstructed on the basis of light microscopy, serial ultrathin sections (ultrastructure) and scanning electron microscopy. Starting frontally, the hermaphroditic reproductive system consists of paired and tube shaped lateral testes that do not possess elongated seminal ducts but most likely open directly via paired ventral pores. The unpaired, medio‐dorsal ovary region contains early oogenic stages that mature caudally towards the uterus region, where the most mature egg is positioned laterally to the midgut. The ovary region is not covered with an epithelial lining whereas the uterus region possesses a distinct epithelial wall. Between ovary and uterus region, we have detected a conspicuous section of the female gonad, the vitellogenic oviduct that consists of a thick epithelial wall which forms cellular protuberances into the developing oocytes passing the oviduct. We interpret this as a special, hitherto undescribed mode of vitellogenesis in Gastrotricha. Further caudally, the uterus continues with the fronto‐caudal organ, a complex of two substructures that are apparently homologous to the frontal organ and the caudal organ of many species of the Gastrotricha Macrodasyida. Neodasys chaetonotoideus obviously engages in spermatophore formation and transfer. In this study we develop a morpho‐functional scenario for the gonads and accessory organs in terms of spermatophore production, exchange and oviposition. We compare our newly obtained data with already published results on the reproductive organs of several species of Gastrotricha by means of a species‐character matrix and provide a computer aided evaluation by a parsimonious character optimization. A reconstruction of the reproductive system of the stem species of Gastrotricha on the basis of three recent phylogenetic analyses is presented. These reconstructions give support for a Neodasys‐like reproductive system in the ground pattern of Gastrotricha with slight morphological differences and direct transfer of spermatozoa rather than spermatophore transfer. The evolution of selected characters is traced thus revealing some incidents of convergent evolution as well as the evolutionary replacement of the ancestral frontal organ by the derived frontal sac in at least two separated lineages.     

The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). II. Male

Guillaume, O. 2000. The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). II. Male. —Acta Zoologica (Stockholm) 81 : 223–234 Cloacae from male Proteus anguinus were examined for the first time by light and electron microscopy. Male P. anguinus possess anterior and posterior ventral glands, dorsal and lateral pelvic glands, vent glands and Kingsbury’s glands as do Necturus males. However, male P. anguinus also possess the new additional cloacal glands found in females and which the author has called the ventral skin glands. Furthermore, the number, the length and the diameter of these tubular glands are higher in males. Therefore the inference is that these glands are sexually dimorphic glands.     

Morphology and Molecular Phylogeny of Pseudocyrtohymena koreana n. g., n. sp. and Antarctic Neokeronopsis asiatica Foissner et al., 2010 (Ciliophora,Sporadotrichida), with a Brief Discussion of the Cyrtohymena Undulating Membranes Pattern

We discovered a new brackish water oxytrichid Pseudocyrtohymena koreana n. g., n. sp. in South Korea and investigated the new species on the basis of morphology, ontogenesis, and 18S rRNA gene sequences. The new genus has the 18 frontal‐ventral‐transverse cirri of typical oxytrichids with flexible body, cortical granules, Cyrtohymena undulating membranes (UM), and one left and one right marginal cirral row. Ontogenesis of the new species indicated that dorsal kinety anlage 3 stretches within the parental row without any fragmentations (Urosomoida pattern) and exclusively forms all caudal cirri. The new genus is morphologically similar to Cyrtohymena Foissner, 1989, but has the following distinctive features: (i) caudal cirri absent in dorsal kineties 1 and 2 (vs. present in Cyrtohymena); and (ii) dorsal kinety 3 nonfragmented (vs. fragmented in Cyrtohymena). Further, we collected an additional species Neokeronopsis asiatica Foissner et al. 2010, from King George Island, Antarctica, and the species shares the morphology of UM with Cyrtohymena. Herein, we describe the previously unidentified characteristics of N. asiatica (i.e., cortical granules, body flexibility, contractile vacuole, and 18S rRNA gene sequence). In addition, we obtained two 18S rRNA gene sequences from Cyrtohymena muscorum and Parasterkiella thompsoni to expand samples for phylogenetic analysis. Our 18S rRNA gene tree supports the hypothesis that the Cyrtohymena UM pattern might have evolved several times in hypotrichs (e.g., Neokeronopsidae, Oxytrichinae, and Stylonychinae).     

Transforming growth factor‐β signal regulates gut bending in the sea urchin embryo

During gastrulation, one of the most important morphogenetic events in sea urchin embryogenesis, the gut bends toward the ventral side to form an open mouth. Although the involvement of transforming growth factor‐β (TGF‐β) signals in the cell‐fate specification of the ectoderm and endoderm along the dorsal–ventral axis has been well reported, it remains unclear what controls the morphogenetic behavior of gut bending. Here, using two sea urchin species, Hemicentrotus pulcherrimus and Temnopleurus reevesii, we show that TGF‐β signals are required for gut bending toward the ventral side. To search for the common morphogenetic cue in these two species, we initially confirmed the expression patterns of the dorsal–ventral regulatory TGF‐β members, nodal, lefty, bmp2/4, and chordin, in T. reevesii because these factors are appropriate candidates to investigate the cue that starts gut bending, although genetic information about the body axes is entirely lacking in this species. Based on their expression patterns and a functional analysis of Nodal, the dorsal–ventral axis formation of T. reevesii is likely regulated by these TGF‐β members, as in other sea urchins. When the Alk4/5/7 signal was inhibited by its specific inhibitor, SB431542, before the late gastrula stage of T. reevesii, the gut was extended straight toward the anterior tip region, although the ectodermal dorsal–ventral polarity was normal. By contrast, H. pulcherrimus gut bending was sensitive to SB431542 until the prism stage. These data clearly indicate that gut bending is commonly dependent on a TGF‐β signal in sea urchins, but the timing of the response varies in different species.     

Description of the male of Sclerocypris tuberculata (Methuen, 1910) (Crustacea,Ostracoda, Megalocypridinae)

The male of Sclerocypris tuberculata (Methuen), thus far unknown, is here described. Relying on the morphology of the copulatory appendages and of the prehensile palps, it appears that this taxon belongs to a separate species group, together with S. zelaznyi and perhaps also S. sarsi. There are some interesting sexual dimorphic characters in the valve morphology: males have shorter valves with a dorsal margin which runs nearly parallel to the ventral one (more elongated valves with sloping dorsal margin in females) and there is lobe-like projection of the valve margin on the ventro-caudal corner of the LV in females which is lacking in the male. Furthermore, the female genital region has a very aberrant morphology, and all specimens from the present collection possess the tuberculated and noded valves.     

The influence of aging on androgen dynamics in the male rat

Androgen assimilation was investigated in a variety of accessory sex organs (seminal vesicles and anterior, dorsal, lateral, and ventral prostates) and in several nonaccessory sex organs in male Wistar rats. After administration of a pulse dose of [³H]testosterone in vivo to intact young (3–4 months old) rats, [³H]testosterone was the primary radioactive steroid recovered from most organs examined, except for the secondary sex glands where the reduced metabolites, [³H]5α-dihydrotestosterone (DHT) and [³H]5α-androstanediol(s), predominated. At longer postinjection times, [³H]DHT was preferentially retained in the accessory sex glands, presumably reflecting intracellular metabolism of [³H]testosterone to this compound and subsequent specific binding of [³H]DHT to receptor proteins. At the longest postinjection interval investigated, the ventral prostate retained greater concentrations of [³H]DHT than the lateral prostate which in turn had a higher [³H]DHT concentration than the seminal vesicles or anterior or dorsal prostates. The latter three glands retained approximately equal concentrations of [³H]DHT. Scatchard plot analyses of cytosol binding in 24-h castrates indicated that with one exception, the level of high affinity DHT binding sites was generally correlated with the retention of [³H]DHT in vivo in intact rats. Specifically, while the affinity for DHT binding in all accessory sex organs was the same, the number of high affinity binding sites per mg wet tissue weight was on the order of ventral prostate > anterior prostate ≥ seminal vesicles ≥ dorsal prostate > lateral prostate. Studies of the influence of aging to 22–26 months revealed no apparent differences in the affinity of the DHT receptor for its ligand in any of the accessory sex glands from 24-h castrates when the receptors were present in levels sufficiently high to quantify. The concentration of available DHT receptors with advancing age remained constant in the anterior and dorsal prostates, increased in the seminal vesicles, and declined in the ventral and lateral prostates. The decreases observed in the ventral prostate were only partial, but the receptors of the lateral prostate declined to nondetectable levels.