Cellular Differentiation in a Highly Specialized Insect Secretory Organ

The colleterial glands of insects are accessory reproductive structures which produce secretions that are applied to eggs after fertilization and which serve a number of protective functions. The colleterial glands of lepidoptera are of particular interest in the study of the events of cellular differentiation because they undergo rapid development, generally during the pupal adult transformation, and contain highly specialized cells which produce large amounts of a restricted variety of secretory products. The extreme specialization of these organs facilitates parallel studies of differentiation at the biochemical and morphological level. This communication describes the changes in the ultrastructure of cells which will form the protein-secreting segment of the colleterial gland of the moth Actias luna during the period of transition from the undifferentiated state to the acquisition of secretory ability.
An initial stage of general cellular proliferation by mitosis in the presumptive colleterial tissue mass is followed by differentiation of the cells in the absence of further mitosis. Four distinctive cell types are recognized during the phase of differentiation. These types include a chitogenous cell which forms the chitin lining of the main duct, and three cells which cooperate in the formation of a secretory apparatus. Cell A forms two temporary flagella-like structures which assist in the formation of a ductule, which eventually leads from the secretory cell to the main duct. Near the end of the differentiative phase, Cell A degenerates and is phagocitized by Cell B. Cell B becomes the actual secretory element, and acquires cytoplasmic features such as extensive rough endoplasmic reticulum and Golgi apparatus which are associated with synthesis and secretion of protein. The final element, Cell C, remains associated with the ductule which it helps to construct and which traverses its cytoplasm.     

The fine structure of colleterial glands in two cockroaches and three termites, including a detailed study of Cryptocercus punctulatus (Blattaria, Cryptocercidae) and Mastotermes darwiniensis (Isoptera, Mastotermitidae)

The colleterial glands of insects are organs associated with the female genital apparatus. In cockroaches, these glands produce secretions that cover two parallel rows of eggs during oviposition, and in oviparous species, these secretions become the tanned, sculpted, rigid outer casing of the ootheca. The goal of this study was to compare the gross anatomy of the colleterial glands and the ultrastructure of their component tubules in the phylogenetically significant genera Cryptocercus (Blattaria) and Mastotermes (Isoptera). Recent studies indicate that cockroaches in the genus Cryptocercus are the sister group of termites, and Mastotermes is the only termite known to produce a cockroach-like ootheca. One additional oviparous cockroach, Therea, and two additional termites, Zootermopsis and Pseudacanthotermes, were also examined. As in other cockroaches, the colleterial glands of Cryptocercus and Therea are asymmetrical, with a well developed bipartite left gland and a smaller right gland. In the termites Mastotermes, Zootermopsis, and Pseudacanthotermes, the colleterial glands are composed of a well-developed, paired, anterior gland and a small posterior gland; histological staining and cytological evidence suggest that these are homologues of the left and the right colleterial glands of cockroaches, respectively. At the ultrastructural level, colleterial gland tubules are made of cells belonging to a modified class 1 type cell in the cockroaches, in Mastotermes, and in Zootermopsis; the latter lays its eggs singly, without a surrounding ootheca-like structure. In the advanced termite Pseudacanthotermes, the tubules are made of secretory units belonging to the class 3 cell type. This study demonstrates that the cytological characteristics of colleterial glands in basal termites are similar to those of cockroaches, whether the termite secretes an oothecal casing that covers two parallel rows of eggs, as in Mastotermes, or lays its eggs singly, as in Zootermopsis. The function of colleterial glands in non-mastotermitid termites is unknown.     

Morphology of sternum V glands in three caddisfly species, Stenopsyche marmorata, Eubasilissa regina and Nemotaulius admorsus (Insecta: Trichoptera)

The present study describes the morphology of the sternum V gland of three caddisfly species, Stenopsyche marmorata Navas, Eubasilissa regina (McLachlan) and Nemotaulius admorsus (McLachlan), each of which belongs to a different family of the order Trichoptera, using light and scanning electron microscopy. In both sexes of these three species, the gland orifices are located on the sides of the sternum V as crescent-shaped slits, and are connected with the glandular tissue via cuticular gland ducts. The shapes of glands differ greatly among species; a slender ampullar form in S. marmorata , a flattened saccular form (horseshoe shape) in E. regina and a kidney shape in N. admorsus . The glands are composed of four essential components: large secretory cells, small reservoir cells, the lining of the reservoir and the gland duct. In S. marmorata and E. regina , additional components, muscle fibers, are present around the small reservoir cells. The secretory cells covering the whole outer surface of the gland are very large, and form many bunches in S. marmorata and E. regina , but do not form them in N. admorsus . The small reservoir cells lie inside the layer of the secretory cells and are tightly connected with the cuticular lining of the reservoir. The linings become thick cuticular ducts near the gland orifices. Histological features suggest that the secretory cells of the sternum V gland of Trichoptera belong to the type of class 3 cells in insect epidermal glands.     

Rosette glands in the gills of the grass shrimp,Palaemonetes pugio. I. Comparative morphology,cyclical activity,and innervation

Two types of exocrine rosette glands (called type A and type B), located in the gill axes of the grass shrimp Palaemonetes pugio, are described. The type A glands are embedded within the longitudinal median septum of the gill axes, whereas the type B glands typically project into the efferent hemolymph channels of the gill axes. Although both glands have certain common characteristics (i.e., a variable number of radially arranged secretory cells, a central intercalary cell, and a canal cell that forms the cuticular ductule leading to the branchial surface), they differ in the following respects. The type B gland is innervated, but the type A gland is not; axonal processes, containing both granular (ca. 900–1300 Å) and agranular (ca. 450–640 Å) vesicles, occur at a juncture between adjacent secretory cells and the central cell of the type B gland. The secretory cells of type A and type B glands differ in their synthetic potential and membrane specializations. These differences are more pronounced in well-developed, mature glands, most frequently encountered in larger (24–28 mm, total length) grass shrimp, than in the underdeveloped, immature glands that are most abundant in smaller (14–18 mm, total length) grass shrimp. Thus, in mature glands, the secretory cells of the type A rosette glands are characterized by extensive RER, abundant Golgi, and numerous secretory granules, whereas the secretory cells of the type B gland are characterized by extensively infolded and interdigitated basal plasmalemmas and by the presence of numerous mitochondria. In general, both types of glands exhibit increased secretory activity soon after ecdysis. The central and canal cells in both glands seem to have a role in the modification of the secreted materials. The possible functions assigned to the type A gland and the type B gland include phenol-oxidase secretion and osmoregulation, respectively.     

Ultrastructural features of the salt gland of Tamarix aphylla L.

Summary The salt gland in Tamarix is a complex of eight cells composed of two inner, vacuolate, collecting cells and six outer, densely cytoplasmic, secretory cells. The secretory cells are completely enclosed by a cuticular layer except along part of the walls between the collecting cells and the inner secretory cell. This non-cuticularized wall region is termed the transfusion are (Ruhland, 1915) and numerous plasmodesmata connect the inner secretory cells with the collecting cells in this area. Plasmodesmata also connect the collecting cells with the adjacent mesophyll cells.There are numerous mitochondria in the secretory cells and in different glands they show wide variation in form. In some glands wall protuberances extend into the secretory cells forming a labyrinth-like structure; however, in other glands the protuberances are not extensively developed. Numerous small vacuoles are found in some glands and these generally are distributed around the periphery of the secretory cells in association with the wall protuberances. Further, an unusual structure or interfacial apparatus is located along the anticlinal walls of the inner secretory cells. The general structure of the gland including the cuticular encasement, connecting plasmodesmata, interfacial apparatus, and variations in mitochondria, vacuoles, and wall structures are discussed in relation to general glandular function.     

Development of female accessory glands of Chrysomya putoria (Wiedemann) (Diptera: Calliphoridae) during oogenesis

Females of Chrysomya putoria (Diptera: Calliphoridae) have two sexual accessory glands, which are tubular and more dilated at the distal extremity. The glands open independently into the common oviduct. Two morpho-physiological regions were distinguished in the longitudinal semi-thin sections of the glands. The secretory region is constituted by three layers: a cuticular intima, lining the lumen, followed by a layer of small cells, and then a layer of very large secretory cells. The ductal region of the gland presents only two layers: the cuticular intima and a cellular layer. In both regions a basement membrane is present. Each secretory cell has in its apical region a reservoir, which enlarges throughout oogenesis; in its basal region there is a large nucleus. The ductal cells are cylindrical and smaller than the secretory cells. The glandular secretion is synthesized in the cytoplasm of the secretory cells, stored and/or modified in the reservoir, then drained to the lumen through an end apparatus seen in the apical region of the secretory cell. Histochemical tests indicate that this secretion is a glycoprotein. Measurements of the glands from females at different physiological conditions and fed on different diets correlate with the results obtained for changes in the ovary during oogenesis. Cell number averaged 561.2 ± 77.54 per gland. There was no increase in cell number during oogenesis.     

Fine structural aspects of secretory processes in a pentastomid arthropod parasite in its mouse and rattlesnake hosts

The histology and development of three extensive glands in the porocephalid pentastomid Porocephalus crotali is described by light and electron microscopy, during growth of the parasite to an infective stage in the tissues of mouse; the infective stage in rattlesnake definitive hosts is also included. These glands elaborate excretory/secretory components which are channelled, via chitin-lined efferent ductules, on to the parasite cuticle. Hook and frontal glands are relatively compact, and within each gland ductules serving individual secretory lobules collect into common ducts which discharge over each of the four hooks, or at the anterior margin of the cephalothorax respectively. Subparietal gland cell lobules, composed of two large and two small secretory cells, are distributed under the cuticle and each is served by a single efferent ductule; these erupt over the entire cuticle. The large cells in subparietal glands secrete lamellate droplets which coat the cuticle with thin layers. Identical cells are found in hook and frontal glands, in addition to to three morphologically distinct types of protein secretory cell. Preliminary data on the composition and immunological properties of the various secretory products are presented.     

The ultrastructure of the female accessory gland,the cement gland,in the insect Rhodnius prolixus

The cement gland of Rhodnius prolixus is an epidermally derived tubular gland consisting of a distal synthetic region and a proximal muscular duct region. The synthetic region consists of numerous secretory units joined to a central chitinous duct via cuticular ductules. Proteinaceous secretion, synthesized by the goblet-shaped secretory cell, passes through the delicate cuticular lattice of a ductule-end apparatus and out through fine ductules to the central duct. Secretory cells are rich in rough endoplasmic reticulum and mitochondria. Light microscopy, SEM and TEM reveal the delicate lattice-like end apparatus structure, its formation and relationship to the secretory cell. The secretory cell associates via septate junctions with a tubular ductule cell that encloses a cuticle-lined ductule by forming an elaborate septate junction with itself. The ductules are continuous with the cuticle lining of the large central duct that conveys secretion to the proximal area. The proximal muscular duct has a corrugated cuticular lining, a thin epithelium rich in microtubules and thick longitudinal, striated muscles which contract during oviposition, forcing the secretion out. Histochemistry and electrophoresis reveal the secretion as proteinaceous.     

Colleterial glands of Sesamia nonagrioides as a source of the host-recognition kairomone for the egg parasitoid Telenomus busseolae

Abstract.  The maize stemborer Sesamia nonagrioides glues its egg masses under the leaf sheaths or ear bracts using colleterial gland secretion. In spite of such concealed oviposition sites, these eggs are parasitized by Telenomus busseolae. The colleterial glands of S. nonagrioides are investigated as a possible source of the host-recognition kairomone for T. busseolae . This secretion, applied on glass beads, elicits intense antennal drumming and oviposition probing behaviour in the parasitoid. Through an histochemical study, neutral and acid glycoconjugates are identified as components of the secretion. Finally, using ultrastructural techniques, the colleterial glands are described and classified as comprising class 3 secretory cells.     

The comparative morphology of epidermal glands in Pentatomoidea (Heteroptera)

The Heteroptera show a diversity of glands associated with the epidermis. They have multiple roles including the production of noxious scents. Here, we examine the cellular arrangement and cytoskeletal components of the scent glands of pentatomoid Heteroptera in three families, Pentatomidae (stink bugs), Tessaratomidae, and Scutelleridae (shield-backed bugs or jewel bugs). The glands are; (1) the dorsal abdominal glands, (2) the tubular glands of the composite metathoracic gland, and (3) the accessory gland component of the composite metathoracic gland. The dorsal abdominal glands are at their largest in nymphs and decrease in size in adults. The metathoracic gland is an adult-specific gland unit with a reservoir and multiple types of gland cells. The accessory gland is composed of many unicellular glands concentrated in a sinuous line across the reservoir wall. The lateral tubular gland is composed of two-cell units. The dorsal abdominal glands of nymphs are composed of three-cell units with a prominent cuticular component derived from the saccule cell sitting between the duct and receiving canal. The cuticular components that channel secretion from the microvilli of the secretory cell to the exterior differ in the three gland types. The significance of the numbers of cells comprising gland units is related to the role of cells in regenerating the cuticular components of the glands at moulting in nymphs.     

The electron microscopy of the left colleterial gland of the cockroach

A study has been made of the cells of the left colleterial gland of the cockroach, Periplaneta americana (L.), using the electron microscope, and the results compared with previous histological and histochemical studies. The colleterial gland consists of an arborescent bunch of long tubules composed mainly of the cells which secrete the structural protein of the egg case ("type 4 cells"). Other types of cells: chitinogenic cells and "type 2 and 3 cells" each with a different cytology are described. The type 4 cells, which form the structural protein, reveal a cytological pattern very similar to that described for mammalian cells in a state of active protein synthesis. There is an elaborate development of particle-studded membranes in the cytoplasm. Smaller, rounded agranular vesicles also occur. The free secretory surface of the secreting cells forms the "end-apparatus" of the light microscopists. The invaginated surface is cast into numerous long narrow processes usually radially arranged and directed into a funnel-like formation derived from the thin intima lining the lumen of the gland (Text-fig. 2). The secretion in the form of small balls may be seen in the cavity of the end-apparatus and sometimes in the narrow processes. The small chitinogenic cells, lying between the protein-forming cells and the thin intima which they secrete, have a different cytology perhaps related to the fact that they form a polysaccharide rather than a protein. There is a very poor development of the particle-studded membranes of the type found in protein-forming cells. The type 2 cells, supposed to form an oxidase, have an end-apparatus that is similar to, but more complex than, those of the type 4 cells and their cytoplasm is almost completely filled with mitochondria. There is some evidence that mitochondria play a part in forming the oxidase and pass into the tubules of the end-apparatus. Type 3 cells resemble both types 2 and 4 and are probably a transient intermediate form.     

The terpene-producing glands of a Phasmid insect. Cell morphology and histochemistry

The defensive glands of Anisomorpha buprestoides produce the terpene toxicant anisomorphal. Each gland consists of a cuticular secretion reservoir surrounded by the secretory epithelium and the musculature which serves to compress the gland and expel the secretion. Two types of cells make up the secretory epithelium: a squamous layer next to the cuticular reservoir and a layer of larger secretory cells responsible for production of the toxicant. The microvilli-laden plasma membrane of each secretory cell is invaginated to form a central cavity. It appears that secretory products pass into the central cavity and then flow out to the gland reservoir via an efferent cuticular ductule contained within the squamous epithelial cell. Histochemical techniques demonstrate lipid reserves, carboxylic esterases, a variety of phosphatases, and an alcohol dehydrogenase, within the secretory cells. It is suggested that the lipid reserves are precursors of the terpenoid toxicant, that a mevalonic kinase has been histochemically demonstrated by the phosphatase test, and that an unusual alcohol dehydrogenase is active in the final steps of toxicant synthesis. The histochemical evidence is consistent with the hypothesis that anisomorphal is produced via the mevalonic acid pathway.     

Organization of unusual idiosomal glands in a water mite, <Emphasis Type="Italic">Teutonia cometes</Emphasis> (Teutoniidae)

The unusual idiosomal glands of a water mite Teutonia cometes (Koch 1837) were examined by means of transmission and scanning electron microscopy as well as on semi-thin sections. One pair of these glands is situated ventrally in the body cavity of the idiosoma. They run posteriorly from the terminal opening (distal end) on epimeres IV and gradually dilate to their proximal blind end. The terminal opening of each gland is armed with the two fine hair-like mechanoreceptive sensilla (‘pre-anal external’ setae). The proximal part of the glands is formed of columnar secretory epithelium with a voluminous central lumen containing a large single ‘globule’ of electron-dense secretory material. The secretory gland cells contain large nuclei and intensively developed rough endoplasmic reticulum. Secretory granules of Golgi origin are scattered throughout the cell volume in small groups and are discharged from the cells into the lumen between the scarce apical microvilli. The distal part of the glands is formed of another cell type that is not secretory. These cells are composed of narrow strips of the cytoplasm leaving the large intracellular vacuoles. A short excretory cuticular duct formed by special excretory duct cells connects the glands with the external medium. At the base of the terminal opening a cuticular funnel strengthens the gland termination. At the apex of this funnel a valve prevents back-flow of the extruded secretion. These glands, as other dermal glands of water mites, are thought to play a protective role and react to external stimuli with the help of the hair-like sensilla.     

The Electron Microscopy of the Left Colleterial Gland of the Cockroach

A study has been made of the cells of the left colleterial gland of the cockroach, Periplaneta americana (L.), using the electron microscope, and the results compared with previous histological and histochemical studies. The colleterial gland consists of an arborescent bunch of long tubules composed mainly of the cells which secrete the structural protein of the egg case ("type 4 cells"). Other types of cells: chitinogenic cells and "type 2 and 3 cells" each with a different cytology are described. The type 4 cells, which form the structural protein, reveal a cytological pattern very similar to that described for mammalian cells in a state of active protein synthesis. There is an elaborate development of particle-studded membranes in the cytoplasm. Smaller, rounded agranular vesicles also occur. The free secretory surface of the secreting cells forms the "end-apparatus" of the light microscopists. The invaginated surface is cast into numerous long narrow processes usually radially arranged and directed into a funnel-like formation derived from the thin intima lining the lumen of the gland (Text-fig. 2). The secretion in the form of small balls may be seen in the cavity of the end-apparatus and sometimes in the narrow processes. The small chitinogenic cells, lying between the protein-forming cells and the thin intima which they secrete, have a different cytology perhaps related to the fact that they form a polysaccharide rather than a protein. There is a very poor development of the particle-studded membranes of the type found in protein-forming cells. The type 2 cells, supposed to form an oxidase, have an end-apparatus that is similar to, but more complex than, those of the type 4 cells and their cytoplasm is almost completely filled with mitochondria. There is some evidence that mitochondria play a part in forming the oxidase and pass into the tubules of the end-apparatus. Type 3 cells resemble both types 2 and 4 and are probably a transient intermediate form.     

Fine structure of the spermatheca and of the accessory glands in Orchesella villosa (Collembola, Hexapoda)

The spermatheca and the accessory glands of the collembolan Orchesella villosa are described for the first time. Both organs exhibit ultrastructural differences, according to the time of the intermolt in which the specimens were observed. A thick cuticular layer lines the epithelial cells of the accessory glands. In the reproductive phase, they are involved in secretory activity; a moderately dense secretion found in the apical cell region opens into the gland lumen. Cells with an extracellular cistern are intermingled with the secretory cells. These cells could be involved in fluid secretion, with the secretory product opening into the cistern which is filled with an electron-transparent material. After the reproductive phase, the gland lumen becomes filled with a dense secretion. The accessory gland secretion may play a protective role towards the eggs. The spermatheca is located between the accessory glands; its epithelium is lined by a thin cuticle forming spine-like projections into the lumen and consists of cells provided with an extracellular cistern. Secretory cells, similar to those seen in the accessory glands, are missing. Cells with a cistern could be involved in the production of a fluid secretion determining sperm unrolling and sperm motility.     

Comparing the secretory pathway in honeybee venom and hypopharyngeal glands

We provide insights into the secretory pathway of arthropod gland systems by comparing the royal jelly-producing hypopharyngeal glands and the venom-producing glands of the honeybee, Apis mellifera. These glands have different functions and different product release characteristics, but both belong to the class 3 types of insect glands, each being composed of two cells, a secretory cell and a microduct-forming cell. The hypopharyngeal secretory cells possess an extremely elongate tubular invagination that is filled with a cuticular structure, the end-apparatus, anchored against the cell membrane by a conspicuous series of actin rings. In contrast, venom glands have no actin rings, but instead have an actin-rich brush border surrounding the comparatively short and narrow end-apparatus. We relate these cytoskeletal differences to the production system and utilisation of secretions; venom is stored in a reservoir whereas royal jelly and enzymes are produced on demand. Fluorescence-based characterisation of the actin cytoskeleton combined with scanning electron microscopy of the end-apparatus allows for detailed characterisation of the point of secretion release in insect class 3 glands.     

Structural and functional aspects of salivary fluid section in Calliphora

Calliphora salivary glands are described, emphasizing correlations between structure and physiology. In vitro studies show that the distal part of each gland produces a potassium-rich primary saliva when stimulated with 5-hydroxytryptamine or cyclic AMP. The secretory cells have elaborate canaliculi opening into the lumen. Stimulation of the secretory region causes a 60-fold increase in fluid secretion rate without affecting cell structure. The proximal part of the gland reabsorbs potassium when stimulated with cyclic AMP, but 5-HT has no effect. Potassium reabsorption from the primary saliva results in formation of a dilute saliva. The structure of the secretory and reabsorptive cells is discussed with regard to the functional role of long narrow channels in transport.     

Ultrastructural investigation of a salivary gland in a centipede: structure and origin of the maxilla I-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora)

The maxilla I-gland of Scutigera coleoptrata was investigated using light and electron microscopy methods. This is the first ultrastructural investigation of a salivary gland in Chilopoda. The paired gland opens via the hypopharynx into the foregut and extends up to the third trunk segment. The gland is of irregular shape and consists of numerous acini consisting of several gland units. The secretion is released into an arborescent duct system. Each acinus consists of multiple of glandular units. The units are composed of three cell types: secretory cells, a single intermediary cell, and canal cells. The pear-shaped secretory cell is invaginated distally, forming an extracellular reservoir lined with microvilli, into which the secretion is released. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cell. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the structure of the glandular units of the salivary maxilla I-gland is comparable to that of the glandular units of epidermal glands. Thus, it is likely that in Chilopoda salivary glands and epidermal glands share the same ground pattern. It is likely that in compound acinar glands a multiplication of secretory and duct cells has taken place, whereas the number of intermediary cells remains constant. The increase in the number of salivary acini leads to a shifting of the secretory elements away from the epidermis, deep into the head. Comparative investigations of the different head glands provide important characters for the reconstruction of myriapod phylogeny and the relationships of Myriapoda and Hexapoda.     

A pair of rosette glands in the embryo and zoeal larva of an estuarine crab Sesarma haematocheir, and classification of the tegumental glands in the embryos of other crabs

A pair of rosette glands (one of the tegumental glands in crustaceans) is present at the root of the dorsal spine of the thorax in mature embryos of the estuarine crab Sesarma haematocheir. Each rosette gland is spherical, 45-50 microm in diameter. This gland consists of three types of cells: 18-20 secretory cells, one central cell, and one canal cell. The secretory cells are further classified into two types on the basis of the morphology of secretory granules. There are 17-19 a cells, and only one b cell per rosette gland. An a cell contains spherical secretory granules of 2-3 microm in diameter. The granules are filled with highly electron-dense materials near the nucleus but have lower electron-density near the central cell. The secretory granules contained in the b cell have an irregular shape and are 1-1.5 microm in diameter. The density of the materials in the granules is uniform throughout the cytoplasm. The secretory granules contained in both the a and b cells are produced by the rough endoplasmic reticulum. Materials in the granules are exocytotically discharged into the secretory apparatus inside the secretory cell, sent to the extracellular channels in the central cell, and secreted through the canal cell. The rosette gland can be distinguished from the epidermal cells 2 weeks after egg-laying and the gland matures just before hatching. Materials produced by this gland are secreted after hatching and secretion continues through five stages of zoeal larvae. These rosette glands were never found in the megalopal larva. Rosette glands are found in the embryos of Sesarma spp. and Uca spp. In other crabs, tegumental glands are also found at the same position as in the embryo of S. haematocheir, but the fine structure of their glands is largely different from that of the rosette gland. On the basis of the morphology of secretory cells (a-g cell types), the tegumental glands of a variety of crab embryos can be classified into four types, including rosette glands (type I-IV). The function of these tegumental glands is not yet known, but different types of the gland seem to reflect the phylogeny of the crabs rather than differences of habitat.     

Ultrastructure of the submandibular gland of the rare white-winged vampire bat, Diaemus youngi

The submandibular gland of the white-winged vampire bat, Diaemus youngi, was examined by electron microscopy. Unlike typical submandibular glands, those in Diaemus have only one type of secretory cell in their endpieces, namely, serous cells. These serous cells are conventional in structure, with an extensive rough endoplasmic reticulum, scattered dictyosomes, and numerous secretory granules. The endpiece lumina, as well as intercellular canaliculi, are fitted with numerous microvilli, which also are present on the otherwise unremarkable intercalated duct cells. Striated ducts are of conventional morphology, but have a brush border-like array of microvilli on their luminal surface. These cells resemble those in the submandibular gland of the common vampire bat, Desmodus rotundus. The presence of an abundance of microvilli in the salivary glands in the two vampire bat species (and their absence from chiropteran species that consume other types of diets) is a strong indication that these structures play a significant role in dealing with the problems posed by a sanguivorous diet.