Ultrastructural and functional aspects of the spermatheca of the African Migratory Locust Locusta migratoria migratorioides (Reiche and Fairmaire) (Orthoptera: Acrididae)

The insect spermatheca: an overview.

Abstract: In the female insect, the spermatheca is an ectodermal organ responsible for receiving, maintaining, and releasing sperm to fertilize eggs. The number and morphology of spermathecae vary according to species. Within the spermathecal lumen, substances in the semen and secretions from the spermathecal gland nourish the sperm. Thus, the spermatheca provides an appropriate environment that ensures the long-term viability of sperm. Maintaining sperm viability for long periods within the spermatheca is crucial for insect reproductive success; however, the details of this process remain poorly understood. This review examines several aspects of and gaps in the current understanding of spermatheca biology, including morphology, function, reservoir filling, development, and biochemistry. Despite the importance of the spermatheca in insects, there is little information on the gland secretions and their role in the maintenance and protection of male gametes. Furthermore, in this review, we highlight the current information on spermathecal gland secretions and the likely roles they play in the maintenance and protection of sperm.

Neural and hormonal control of muscular activity of the spermatheca in the locust, Locusta migratoria.

Abstract: The spermatheca in insects is a tubular structure within the female that acts as a repository for spermatozoa deposited by the male during copulation. The spermatozoa remain viable within the spermatheca for extended periods of time, and are then delivered to the site of fertilization during oviposition (egg-laying). Thus, the production of viable offspring is dependent upon the coordination of events associated with fertilization, including the passage of the egg through the lateral and common oviducts and the passage of spermatozoa along the spermathecal duct. The egg and the spermatozoa are propelled along their respective tracts by contractions of the visceral muscles intrinsic to the oviduct and spermatheca. The neural and hormonal control of muscular activity of the locust oviducts has been well reviewed, with more recent studies examining the control over the spermatheca. This review highlights more recent literature, including new data, for neural and hormonal control of muscular activity of the spermatheca of the locust, Locusta migratoria, making reference to examples in other insects where relevant. A variety of neuronal types project to the spermatheca in L. migratoria, and a variety of neuroactive chemicals, including neuropeptides and amines, influence contraction. A comparison is made between the control of oviducts and spermatheca in L. migratoria with regard to their neural substrate and the composition of neuroactive chemicals.

Morphological and morphometrical assessment of spermathecae of Aedes aegypti females

Abstract: The vectorial capacity of Aedes aegypti is directly influenced by its high reproductive output. Nevertheless, females are restricted to a single mating event, sufficient to acquire enough sperm to fertilize a lifetime supply of eggs. How Ae. aegypti is able to maintain viable spermatozoa remains a mystery. Male spermatozoa are stored within either of two spermathecae that in Ae. aegypti consist of one large and two smaller organs each. In addition, each organ is divided into reservoir, duct and glandular portions. Many aspects of the morphology of the spermatheca in virgin and inseminated Ae. aegypti were investigated here using a combination of light, confocal, electron and scanning microscopes, as well as histochemistry. The abundance of mitochondria and microvilli in spermathecal gland cells is suggestive of a secretory role and results obtained from periodic acid Schiff assays of cell apexes and lumens indicate that gland cells produce and secrete neutral polysaccharides probably related to maintenance of spermatozoa. These new data contribute to our understanding of gamete maintenance in the spermathecae of Ae. aegypti and to an improved general understanding of mosquito reproductive biology.

The association of crustacean cardioactive peptide with the spermatheca of the African migratory locust, Locusta migratoria

Abstract: Crustacean cardioactive peptide (CCAP)-like immunoreactivity was identified in neurons of the VIIIth abdominal ganglion and in axons in the nerves that project to the spermatheca of 3–4 week old adult female locusts. In addition, lightly stained CCAP-like immunoreactive processes were localized over the spermathecae. The amount of CCAP in the spermathecal tissue was quantified using an enzyme-linked immunosorbent assay (ELISA) performed on extracts of the whole spermatheca, and on its constituent parts, namely the sperm sac, coiled duct and straight duct. The spermatheca contains 920±273 fmol (mean±SE) of CCAP equivalents, with the majority localized in the coiled duct. There are age-related differences in the amount of CCAP present in the spermathecae with less content in spermathecae from 1 to 5 day old and greater content in spermathecae from 3 to 4 week old adults. There was also no difference in CCAP content of spermathecae in mated and virgin 3 to 4 week old adults. Reversed phase-high performance liquid chromatography (RP-HPLC) followed by ELISA further confirmed the presence of CCAP-like material in extracts of locust spermathecae. Physiological assays demonstrated that CCAP increased the basal tonus and frequency of spontaneous contractions of the spermatheca, with thresholds between 10−10 and 10−9 M and maxima at 10−7 M CCAP. CCAP also increases the amplitude of neurally evoked contractions with a threshold less than 10−11 M and a maximum of 10−7 M CCAP. The present study suggests that CCAP acts as a neuromodulator/neurotransmitter at the spermathecal visceral tissue of female Locusta migratoria.

The Fine Structure of the Spermatheca in Anopheles aquasalis (Diptera: Culicidae)

Abstract: The vectorial capacity of mosquitoes is related to the reproductive output, and dependent on the ability of male spermatozoa to survive within the inseminated female. Mosquito females mate once, and immediately after mating, the male spermatozoa are transferred to and maintained in the ectodermic spermatheca. Mosquito spermathecae in culicines, especially of the yellowfever mosquito Aedes (Stegomyia) aegypti (L.), have been characterized in detail. In contrast, not much is known about this organ in anophelines. Here, the morphology of the spermatheca in the saltwater-tolerant mosquito Anopheles aquasalis Curry was investigated for the first time using a combination of light, confocal, and scanning and transmission electron microscopy. The spermatheca in An. aquasalis share many features with the three spermathecae present in Ae. aegypti, including a round-shaped reservoir and spermathecal duct glandular cells. However, differences such as the volume and cell types, as well as their numbers and di...

Fine structure of insect epidermal glands

Abstract: The present review is devoted to the exocrine glands derived from epidermis; glands associated with the preoral cavity (mandibular, salivary, etc) and genital apparatus are not dealt with except for the sake of comparison. As defined, the epidermal glands manifest an exceptional diversity as far as location, morphology, and func­ tion are concerned. In the past, the studies were mainly anatomical, very rarely cytological, but the interest in insect glands was recently renewed by the chemical approach and the recognized importance of the secretions as far as behavior and physiology are concerned. Concurrently, the high resolution of the transmission electron microscope permitted a far more precise elucidation of the structures, with the hope of establishing some correlations between these structures and the func­ tions. Additionally, the scanning electron microscope appeared well suited for the examination of some cuticular differentiations.

Muscle attachment related to cuticle architecture in Apterygota.

Abstract: In Apterygota muscles are attached to the cuticle by a series of discrete structures. The junction of the muscle and epidermal cells is demarcated by regular interdigitations of the two tissues, with desmosomes lining these processes. Within the epidermal cells, microtubules link up the desmosomes of the interdigitated region with dense material associated with cone-like depressions in the apical plasma membranes of the epidermal cells. Each of these ‘conical hemidesmosomes’ is situated opposite a pore canal. From within each cone, an electron-dense ‘muscle attachment fibre’ extends up the corresponding pore canal through the procuticle and is inserted on the epicuticle. There is no direct link between the microtubules and the muscle attachment fibres. The muscle attachment fibres are slightly elliptical in cross-section, and are twisted, this twist being in phase with the orientation of the chitin-protein microfibrils forming the lamellae of the procuticle. The attachment fibres are straight, and not helically arranged; patterns obtained in oblique sections of procuticle including these structures support the twisted ribbon model of pore canal shape. The cuticle, particularly in Thysanuran and Dipluran intersegmental membrane, displays the parabolic patterning typical of softer insect procuticle and procuticle deposition zones. The epicuticular insertion of the muscle attachment fibre is characterized by a pit in the cuticulin layer, the fibre passing through the middle of this pit. The microtubule-associated conical hemidesmosomes appear to be cytoskeletal in function. The muscle attachment fibres are rigid structures which are not digested by the moulting fluid enzymes. New muscle attachment fibres may only become attached to the epicuticle during its formation. The structures described in regions of muscle attachment in Apterygota are similar to those recorded for other arthropods.

Fine structural organization of the spermatheca in the cockroach, Periplaneta americana.

Abstract: . The detailed structure of the cockroach spermatheca is described and discussed firstly as an example of an insect integumentary gland, and secondly, from the standpoint of its role in reproduction. The gland comprises a cortical rank of separate secretory units, each associated with an epithelial duct cell responsible for receiving secreted materials and transporting them through the cuticular intima lining the reproductive tract. Secretory activity is cyclic, and the probable mode of elaboration and release of secretory material is described, together with the fine structure of the markedly differing intimas associated respectively with the glandular and conducting units.