Structure of the female gonoduct of the viviparous teleost Poecilia reticulata (Poeciliidae) during nongestation and gestation stages

Female teleosts do not have oviducts because Müllerian ducts do not develop. Instead, the caudal region of the ovary, the gonoduct, connects to the exterior. Because of the lack of oviducts in viviparous teleosts, the embryos develop in the ovary, as an intraovarian gestation, unique in vertebrates. This is the first study to address the histology of the gonoduct in a viviparous teleost. The gonoduct of Poecilia reticulata was analyzed during previtellogenesis, vitellogenesis, and gestation. The gonoduct lacks germinal cells. From deep to superficial, the wall has simple cuboidal or columnar epithelium, loose connective tissue, longitudinal layer of smooth muscle, and visceral peritoneum. Cells of the immune system occur in the lumen and in the mucosa. The gonoduct was divided in three regions: 1) cephalic, 2) middle, and 3) caudal. At the initial part of each region, thin mucosal folds extend into the lumen. The cephalic region forms a tubular structure with light and irregular folds. The middle region has a wider lumen and is more irregular due to ventral invaginations and irregular and short mucosal folds; beneath the epithelium there are melano‐macrophage centers. The caudal region is delimited from the middle region by folds; however, they are thinner than these of the other regions. Ventral invaginations form exocrine glands, and the smooth muscle is thicker than in the other regions. During gestation, cells of the immune system are abundant; melano‐macrophage centers become larger and the glands exhibit desquamated cells. These observations suggest roles of the gonoduct in reducing the diameter of the lumen; receiving sperm during vitellogenesis; producing secretions, more abundant during vitellogenesis; and in immunological activity throughout the reproductive cycle. The ciliated epithelium and the thick muscle of the caudal region may be involved during birth. J. Morphol. 275:247–257, 2014. © 2013 Wiley Periodicals, Inc.     

Functional morphology of the gonoduct of the viviparous teleost Poeciliopsis gracilis (Heckel, 1848) (Poeciliidae)

Female teleosts do not develop Müllerian ducts; consequently, the ovary of teleosts contains two zones: germinal and gonoduct. The gonoduct lacks germinal cells, but has relevant functions in the reproductive process. We describe the functional morphology of the gonoduct in the viviparous teleost Poeciliopsis gracilis during nongestation and gestation stages. This study tests the hypothesis that the gonoduct functions as a barrier between the germinal zone and the exterior. By providing information about morphology and function of the gonoduct we show that this part of the ovary has an essential role in the reproduction of teleosts. The ovaries were processed by histological technique and stained with hematoxylin‐eosin (H‐E), Masson's trichrome, toluidine blue and periodic acid‐Schiff (PAS). The gonoduct is divided into three regions: cephalic, middle, and caudal. In the cephalic and middle regions there are mucosal folds that extend into the gonoductal lumen, forming structures similar to a cervix. The caudal region has two portions: the anterior contains a dorsal invagination and exocrine glands among columnar cells; the posterior has a ventral flexion and stratified epithelium with apical secretory cells. The morphology of this epithelium indicates two functions: (a) secretory by the apical columnar cells, and (b) protection through the stratification. Another peculiarity of the caudal region is that both ducts, reproductive and digestive, converge in a common cavity at their caudal ends, forming a cloacal region. The histology of the gonoduct indicates relevant functions including: (1) the control of the luminal diameter by the muscle and the presence of mucosal folds, like a cervix; (2) the relationship with the spermatozoa during insemination and storing them in mucosal folds; (3) the support of immunological processes; (4) secretory activities; (5) forming the duct during birth; and (6) possibly, acts as a barrier against parasite infestations.     

How can nematodes mate without spicules? Function of the male gonoduct glands in the roundworm Myolaimus

Males of roundworms (Nematoda) usually possess cuticular copulatory organs (spicules) that are inserted in the female's vulva to attach the male to the female and to widen the vulva against the inner body pressure for sperm transfer. Among free-living nematodes, the only exception of this rule is Myolaimus where the males lack spicules. Until now there exist no reports on how mating is achieved in Myolaimus. Here we show that sperm transfer in Myolaimus apparently involves at least six different secretions of the male gonoduct that are pumped into a sack-like cuticular protrusion of the female's vulva to form a spermatophore-like capsule. The role of gonoduct glands in male nematodes (even in the model organism Caenorhabditis elegans) is poorly understood. Here we present the first study explaining the role of different vas deferens gland products in nematodes and argue that Myolaimus males lost their spicules as a result of sperm competition.     

Chemical Defence in Cephalaspidean Gastropods: Origin, Anatomical Location and Ecological Roles

Within the opisthobranchs, the cephalaspideans are traditionallyconsidered a transitional group between typical testacean prosobranchsand shell-less opisthobranchs. The cephalaspidean anatomy, includingthe presence of a cephalic shield, is related to burrowing throughsoft sediment. Recent studies have shown that some herbivorousand carnivorous cephalaspideans contain secondary metabolites.The micro-herbivorous bubble snails of the Bullidae and Haminoeidaefamilies are known to have secondary metabolites which have differentecological roles. The polypropionates isolated from Bulla gouldianaand B. striata were deterrent to fishes while the secondarymetabolites of Haminoea callidegenita, H. fusari, H. hydatis,H. navicula, H. orbignyana and H. orteai were alarm pheromonesemployed during cross copulation. In Bulla gouldiana and B.striata, the defensive secretion was located mainly in a whitegland along the margin of the mantle. In Haminoea species, alarmpheromones were located in external parts (cephalic shield,parapodial lobes and posterior pallial lobe). The carnivorous cephalaspideans Navanax inermis and Philinopsisdepicta employ chemotaxis to follow the slime trail of theirprey, which include other cephalaspideans or even congenericindividuals. N. inermis and P. depicta sequester alarm pheromonesand allomones from their cephalaspidean prey, which are ejectedwhen N. inermis and P. depicta are disturbed. The specific metabolic patterns of Mediterranean cephalaspideanssuggest that these patterns can be used as chemotaxonomic markers.We propose the use of a single Thin Layer Chromatography todifferentiate among Mediterranean Haminoea species. (Received 3 February 1997; accepted 22 May 1998)     

Reproduction in the genus Limacina (Opisthobranchia: Thecosomata)

Reproductive mechanisms in the seven species of the thecosomatous pteropod genus Limacina are described and compared. All species are protandrous hermaphrodites. Five species– L. bulimoides, L. helicina, L. lesueuri, L. retroversa and L. trochiformis –have a similar reproductive anatomy in which the gonoduct leading from the gonad to the common genital pore functions as a seminal vesicle in the male and is elaborated into mucous and albumen glands in the female. The male system consists of a prostate gland and penis connected to the common genital pore by an external ciliary tract. All five species have a free-swimming veliger stage which hatches from free-floating egg masses. Limacina helicoides has the same reproductive anatomy but is ovoviviparous, with embryos retained in capsules in the mucous gland until they are juveniles of 50 mm in shell diameter. Limacina inflata lacks mucous and albumen glands and a penis; a spermatophore formed by the prostate gland is used in aphallic sperm transfer. This species exhibits brood protection with un-encapsulated embryos retained in the mantle cavity until they are released as veligers measuring 0067 mm in diameter. L. inflata is the most abundant of the seven species despite lowered fecundity; reasons for its ecological success are discussed.     

Light and electron microscopy study of the salivary glands of the carnivorous opisthobranch Philinopsis depicta (Mollusca, Gastropoda)

Cephalaspideans are a group of opisthobranch gastropods that comprises carnivorous and herbivorous species, allowing an investigation of the relationship between these diets and the morphofunctional features of the salivary glands. In this study, the salivary glands of the carnivorous cephalaspidean Philinopsis depicta were observed by light and electron microscopy. The secretory epithelium of these ribbon-shaped glands is formed by ciliated cells, granular cells and cells with apical vacuole. In ciliated cells the nucleus and most cytoplasmic organelles are located in the wider apical region and a very thin stalk reaches the base of the epithelium. These cells possess significant amounts of glycogen. Granular cells are packed with electron-dense secretory granules and also contain several cisternae of rough endoplasmic reticulum and Golgi stacks. The other type of secretory cell is mainly characterized by the presence of a large apical vacuole containing secretion. These cells possess high amounts of rough endoplasmic reticulum cisternae and several Golgi stacks. Vesicles with peripheral electron-dense material are also abundant, and seem to fuse to form the apical vacuole. The available data point out to a significant difference between the salivary glands of carnivorous and herbivorous cephalaspidean opisthobranchs, with an intensification of protein secretion in carnivorous species.     

Histology and ultrastructure of the salivary glands in Bulla striata (Mollusca, Opisthobranchia)

Abstract. The ribbon‐shaped salivary glands in Bulla striata were studied with light microscopy and transmission electron microscopy (TEM). Secretion is produced in tubules formed by two types of secretory cells, namely granular mucocytes and vacuolated cells, intercalated with ciliated cells. A central longitudinal duct lined by the same cell types collects the secretion and conducts it to the buccal cavity. In granular mucocytes, the nucleus is usually central and the secretory vesicles contain oval‐shaped granular masses attached to the vesicle membrane. Glycogen granules can be very abundant, filling the space around the secretory vesicles. These cells are strongly stained by PAS reaction for polysaccharides. Their secretory vesicles are also stained by Alcian blue, revealing acidic mucopolysaccharides, and the tetrazonium reaction detects proteins in minute spots at the edge of the vesicles, corresponding to the granular masses observed in TEM. Colloidal iron staining for acidic mucopolysaccharides in TEM reveals iron particles in the electron‐lucent region of the vesicles, while the granular masses are free of particles. In vacuolated cells, which are thinner and less abundant than the granular mucocytes, the nucleus is basal and the cytoplasm contains large electron‐lucent vesicles. These vesicles are very weakly colored by light microscopy techniques, but colloidal iron particles could be observed within them. The golf tee‐shaped ciliated cells contain some electron‐dense lysosomes in the apical region. In these cells, the elongated nucleus is subapically located, and bundles of microfibrils are common in the slender cytoplasmic stalk that reaches the basal lamina. The morphological, histochemical, and cytochemical data showed some similarities between salivary glands in B. striata and Aplysia depilans. These similarities could reflect the phylogenetic relationship between cephalaspidean and anaspidean opisthobranchs or result from a convergent adaptation to an identical herbivorous diet.     

A molecular phylogeny of the Cephalaspidea sensu lato (Gastropoda: Euthyneura): Architectibranchia redefined and Runcinacea reinstated

The monophyly and phylogenetic relationships of the Cephalaspidea sensu lato ( sensu   Burn and Thompson 1998 ) have been investigated by means of Bayesian, parsimony and distance analyses of nuclear (18S rRNA and 28S rRNA) and mitochondrial cytochrome oxidase I (COI) genes.
Results revealed the presence of three monophyletic groups among the Cephalaspidea s. l. (i) Architectibranchia ( sensu   Haszprunar 1985 , in part: including Acteonidae and Aplustridae, but excluding Diaphanidae), (ii) Cephalaspidea including Diaphanidae but not Runcinidae (both previously of uncertain systematic affinity), and (iii) Runcinacea.
The monophyly of the architectibranch families Acteonidae (represented by Acteon and Pupa ) and Aplustridae ( Hydatina and Micromelo ); of the runcinacean family Runcinidae ( Runcina ); and of the cephalaspidean families Aglajidae ( Chelidonura , Aglaja , Odontoglaja , Navanax and Philinopsis ), Bullidae ( Bulla ), Gastropteridae ( Siphopteron and Sagaminopteron ), Haminoeidae ( Atys , Haminoea , Phanerophthalmus and Smaragdinella, but not Ventomnestia ), and Retusidae ( Retusa and Pyrunculus , but not Volvulella ) is suggested. The families Scaphandridae ( Scaphander ) and Rhizoridae ( Volvulella ) are reinstated as valid. A new phylogenetic classification of the Cephalaspidea is proposed.     

New insights into the functional morphology of the male copulatory apparatus of bullid gastropods

In this study, semi-thin sections stained with histochemical techniques and transmission electron microscopy were used to obtain new data about the morphology and function of the male copulatory apparatus of the cephalaspidean gastropod Bulla striata. The apparatus comprises a vestibule, a penial papilla and a prostate consisting of a coiled unbranched tube ending in a blind caecum. The penial papilla and the coiled tubular prostate are enclosed by a muscular sheath, which is continuous with the muscular tissue of the vestibule. The epithelium lining the lumen of the vestibule is formed by ciliated and mucus-secreting cells. Two new types of subepithelial secretory cells were discovered in this region. The penial papilla is a muscular structure without secretory cells in the epithelium lining the narrow lumen. The tubule that constitutes the prostate possesses a muscular wall and can be divided in three distinct regions: a non-secretory duct connected to the penial papilla, a glandular region rich in large secretory cells and the terminal caecum containing just a few small secretory cells. In the terminal blind caecum, the muscular sheath is fused with the muscular wall of the tubular prostate. Large numbers of spermatozoa were found in the glandular region and in the terminal caecum of the prostate. A new functional mechanism is proposed to explain penial eversion during copulation. This differs from a previous hypothesis in two main aspects: (1) existence of a permanent penial papilla in mature animals acting as a functional penis and (2) functional role of vestibule during copulation, which everts and surrounds the penial papilla, while the latter protrudes outwards.     

Mating behavior of the hematophagous bug Triatoma infestans: role of Brindley's and metasternal glands

We investigated if Brindley's and metasternal glands are involved in the sexual behavior of Triatoma infestans. In laboratory assays, we analyzed the effect of selective occlusion of Brindley's and metasternal glands of the female (separately and together) on the behavior of males. Control assays without occlusion of glands were also performed. We quantitatively tested if such glands affect mating occurrence, the copulatory attempts of males, and the aggregation of males around a mating couple. The number of mating attempts by males did not differ between treatments, demonstrating that likelihood of males mating did not depend on which gland is occluded in the female. In the absence of any occlusion, T. infestans mated and males aggregated. The proportion of copulations and aggregation behavior of males did not differ between treatments when female's Brindley's glands were occluded. However, when metasternal glands were occluded, the proportion of mating couples decreased and males did not aggregate. We demonstrated that the metasternal glands of the female are involved in the sexual behavior of T. infestans, while Brindley's glands seem to have no effect on mating behavior. Copulation and aggregation behavior of males likely result from the eventual release of volatiles from the female's metasternal glands.     

The Comparative Cellular Architecture of the Female Gonoduct Among Tylenchoidea (Nematoda: Tylenchina)

The cellular architecture of the female gonoduct of 68 nematode populations representing 42 species belonging to Tylenchidae, Belonolaimidae, Hoplolaimidae and Meloinema is shown to have an overall similarity in cellular gonoduct structure. The oviduct consists of two rows of four cells; the spermatheca is comprised of 10 to 20 cells, and the uterus cells, except in the case of Psilenchus, are arranged in four (Tylenchidae) or three (Belonolaimidae, Hoplolaimidae and Meloinema) regular rows. Although the genus Meloinema is classified within Meloidogynidae, its spermatheca is clearly hoplolaimid-like and lacks the spherical shape with lobe-like protruding cells typical of Meloidogyne. Detailed morphology of expelled gonoducts may provide a valuable character set in phylogenetic analysis, and the cellular morphology of the spermatheca appears to be a distinguishing feature at species level, especially in the genera Tylenchus and Geocenamus. Ultrastructural data on the oviduct-spermatheca region of Meloidogyne incognita complement light-microscopic (LM) results. The combination of LM of expelled organs and transmission electron microscopy (TEM) on selected sections is put forward as a powerful tool to combine three-dimensional knowledge with ultrastructural detail.     

Molecular phylogeny of the Tylenchina and evolution of the female gonoduct (Nematoda: Rhabditida)

Tylenchina are a morphologically and functionally diverse group of nematode species that range from free-living bacteriovores, over transitory grazing root-hair feeders to highly specialized plant-parasites with complex host associations. We performed phylogenetic analyses of small subunit rDNA sequences from 97 species including an analysis that account for the RNA secondary structure in the models of evolution. The present study confirms the sister relationship of the bacteriovore Cephalobidae with the predominantly plant-parasitic Tylenchomorpha. All analyses appoint the fungal-feeding Aphelenchidae and Aphelenchoididae as being polyphyletic but the morphology based hypothesis of their monophyly could not be significantly rejected. Within the Tylenchomorpha, the families that exclusively parasitize higher plants are joined in a single clade. However, only the monophyletic position of the (super)families Hoplolaimidae and Criconematoidea were supported; Anguinidae, Tylenchidae, Belonolaimidae and Pratylenchidae appeared to be paraphyletic or polyphyletic. Parsimony and likelihood ancestral state reconstruction revealed that burrowing endoparasitism and sedentary endoparasitism each evolved, respectively, at least six and at least three times independently, mostly from migratory ectoparasitic ancestors. Only root-knot nematodes have evolved from burrowing endoparasitic nematodes. Traditional classifications are partially misled by this convergent evolution of feeding type and associated morphology. Contrastingly, mapping attributes of the gonoduct cellular architecture, including newly obtained data of 18 species belonging to the Aphelenchoidea, Criconematoidea, Anguinidae and Panagrolaimidae, revealed a broad congruence of the gonoduct characters and the molecular phylogenetic hypothesis. Yet, the presence of an offset spermatheca and proliferation of uterus cells has evolved multiple times, the latter associated with derived endoparasitic feeding specialization and resulting reproduction mode. Ancestral state reconstruction further revealed that the gonoduct of the morphologically and ecologically dissimilar tylenchid and cephalobid nematodes evolved from a common ancestor.     

The Harderian gland of the Mexican volcano mouse Neotomodon alstoni alstoni (Merriam 1898): a morphological and biochemical approach

The Harderian glands of rodents are large intraorbital exocrine glands with histologic organization that varies among mammalian species. Here we describe some ultrastructural and biochemical features of the Harderian gland in the Mexican volcano mouse Neotomodon alstoni alstoni, a species of restricted habitat. The Harderian glands from male and female adult mice were dissected, processed and embedded in Epon 812 for light and electron microscopy studies. Porphyrin and total lipids were biochemically determined. The macroscopic appearance of the Harderian gland is similar in the male and female. The gland is a bilobulate structure, situated in the orbit towards the posterior side of the eyeball, of whitish color and is surrounded by a connective tissue capsule. The male gland is slightly heavier (127 mg) than that of the female (113 mg). The Harderian gland shows a tubulo-alveolar organization and is composed exclusively of one type of secretory cells. No branched duct system within the gland was found. Adrenergic nerves endings and mast cell were observed in the interstices of the alveoli. Male and female glands produce similar levels of porphyrins. Triglyceride levels were significantly higher (P < 0.05) in the female compared to the male. Abundance of lipids could induce corneal lubrication of the Harderian gland which may confer a protective and adaptative function to the volcano mouse in its natural habitat during the dry and cold seasons.     

Fine Structural Analysis of the Silk Apparatus in the Funnel-web Spider, Agelena limbata (Araneae: Agelenidae)

ABSTRACT Silk apparatus of the funnel-web spider, Agelena limbata was located at the ventral end of the abdominal part, and was composed of internal silk glands and external spinnerets. Among the three pairs of spinnerets, the posterior pairs were highly elongated along the body axis. By the light and electron microscopic inspections, it was found that four types of silk glands were connected through the typical spinning tubes of each spinneret. Anterior spinnerets comprise 2 pairs of the ampullate and 125 to 150 pairs (female) or 110 to 114 (male) of pyriform glands. Another 2 pairs of ampullate glands in both sexes, 5 to 8 pairs of tubuliform glands in females, and 20 to 26 pairs (female) or 15 to 17 pairs (male) of aciniform glands were connected on the median spinnerets. Additional 8 to 10 pairs of tubuliforms in female and 41 to 53 pairs (female) or 27 to 32 pairs (male) of aciniform glands were on the posterior spinnerets, respectively. While the ampullate and tubuliform glands were connected with the spigot-type spinning tubes, the pyriform and aciniform glands with that of spool-type tubes. It has been also revealed that the tubuliform glands were only observed in female spiders, however the flagelliform and aggregate glands which had the function of adhesive thread production in orb-web spiders were not observed at both sexes of this spiders.     

Sexual selection for small size in male mosquitofish (Gambusia holbrooki)

In many poeciliid fishes, large males which court females coexist with small males which sneak-copulate. It is unclear whether these two tactics represent two evolutionarily stable strategies or if sneaking is a conditional strategy adopted by small, unattractive males. We studied the success of sneaky copulation by looking for sperm in the gonoduct of females after they were kept for 48 h with a male. A logistic regression analysis showed that the probability of a female being inseminated increased with female length and decreased with male length. The length of the male relative to that of the female was the best predictor of success. This result was confirmed using virgin females, thereby excluding any possible confounding effect due to the release of sperm from previous copulations. Sperm counts suggested that large males do not compensate for their reduced copulatory success by releasing larger sperm numbers. Behavioural data indicate that the advantages to small males are twofold: they have a greater chance to approach females from behind without being detected, and manoeuvre better when inserting the gonopodium into the female''s gonoduct. The selective advantage of small size might explain male dwarfism in poeciliids. Our results also suggest that small males adopting the sneaky tactic may be as successful as large males adopting courtship, and that alternative mating strategies may be maintained by negative density-dependent selection.     

Anatomy and ultrastructure of the female reproductive system of Pleioplana atomata (Platyhelminthes: Polycladida)

The ultrastructure of the female reproductive system of the polyclad flatworm Pleioplana atomata is described. Numerous ovaries are scattered throughout the entire body but are mainly concentrated on the dorsal side. Within an ovary, a germinative zone with oogonia and prefolicular cells is located in the dorsal part of the ovary. The remaining part of the gonad is filled with previtellogenic and early vitellogenic oocytes enwrapped by follicular cells. During previtellogenesis, oocytes produce numerous eggshell globules, which are distributed into the cortical area of the cell in later stages. Eventually, these globules release their contents into the space between the eggshell cover and oolemma. Similar types of globules are also found in others flatworms, and may represent useful phylogenetic characters. Entolecital, vitellogenic oocytes pass to paired uteri, where vitellogenesis is completed. The remainder of the female reproductive system consists of paired thin uterine ducts that join a vagina. The distal part of the long, curved vagina forms a large Lang's vesicle, while the proximal part is connected to a female atrium leading to a female gonopore. We hypothesize that Lang's vesicle functions in the digestion of excess sperm received. Two kinds of different shell (cement) glands that release their secretion into the vagina are identified. Both are unicellular glands and each gland cell connects to the lumen of the vagina via an individual canal. Similar glands in other acotylean polyclads have been implicated in the formation of eggshell covers. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.