Gnathostomulida from Hawaii

As thc second in a series on Gnathostomulida from the Pacific Ocean this paper describes an additional eight species from Hawaii of which four are new to science. All are accommodated within existing genera: Haplognathia asymmetrica sp.n., Haplognathia ruberrima (Sterrer, 1966), Haplognathia rufa sp.n., Cosmognathia arcus Sterrer, 1991, Cosmognathia manubrium sp.n., Pterognathia ctenifera Sterrer, 1970, Pterognathia hawaiiensis sp.n., and Austrognathia novaeze landiae Sterrer, 1991.     

New phenotypes of the drought-tolerant cbp20 Arabidopsis thaliana mutant have changed epidermal morphology

This paper provides a detailed phenotypic analysis of the abscisic acid (ABA) hypersensitive Cap Binding Protein 20 (cbp20) mutant. Some hitherto undescribed changes were found in the tissue structure and epidermal morphology of this mutant. These include more and smaller cells in the epidermis, a thicker cuticle and more frequent occurrence of trichomes on leaf surfaces. Some of these traits may contribute to the physiological processes responsible for the water-saving behaviour of the mutant. Abnormal spatial patterns between stomatal pore complexes were also found on various organs of the mutant. All these observations indicate profoundly disturbed development of epidermal tissue in the cbp20 mutant, which has not previously been reported for this class of mutants. A potential connection between the new phenotypes and disturbed miRNA metabolism and mRNA splicing of the mutant is discussed.     

New characters in the Gnathostomulid mouth parts revealed by scanning electron microscopy

An analysis with SEM of the mouth parts of 16 species belonging to 10 genera of Gnathostomulida resulted in the following new characters and conclusions: 1) At least in the genus Haplognathia, jaw teeth that are visible by conventional light microscopy are composed of the same aggregated needle-like denticles that are found, often in large numbers, on the basal plates of many filospermoid species. 2) Other new ultrastructural tooth features include the tricuspid basal plate teeth in Problognathia minima, tripartite teeth in Austrognathia and Austrognatharia, and the clear separation, in the Gnathostomula basal plate, of a mediodorsal set of teeth from a more extensive rostroventral set. 3) Three rows of teeth, as typical for Gnathostomulidae and Austrognathiidae, are also present in the filospermoid Haplognathia filum. 4) The wide range of geographic variation in Haplognathia ruberrima is confirmed by significant differences in jaw teeth between specimens from Belize and Bermuda. 5) A compartmentalized involucrum is present in Labidgonathia longicollis. 6) A pair of lamellae addentales, until now only known from Valvognathia pogonostoma, was found in Tenuignathia rikerae, Problognathia minima, and probably also Labidognathia rikerae. 7) In all gnathostomulids, the lamella symphysis is composed of identical rods that are considered homologous with those in the mouth parts of Rotifera and Micrognathozoa.     

Defecation by the ctenophore Mnemiopsis leidyi occurs with an ultradian rhythm through a single transient anal pore

Defecation in the ctenophore Mnemiopsis leidyi is a stereotyped sequence of effector responses that occur with a regular ultradian rhythm. Here I used video microscopy to describe new features and correct previous reports of the gastrovascular system during and between defecations. Contrary to the scientific literature, individuals defecated through only one of the two anal canals which possesses the only anal pore. The anal pore was not visible as a permanent structure as depicted in textbooks, but appeared at defecation and disappeared afterward. Time intervals between repeated defecations in individual animals depended on body size, ranging from ~10 min in small larvae to ~1 hr in large adults. Differential interference contrast microscopy revealed that both the opening and closing of the anal pore resembled a reversible ring of tissue fusion between apposed endodermal and ectodermal layers at the aboral end. Individuals of M. leidyi thus appear to have an intermittent anus and therefore an intermittent through‐gut that reoccur at regular intervals. The temporality of a visible anal pore in M. leidyi is novel, and may shed light on the evolution of a permanent anus and through‐gut in animals. In addition, mirror image dimorphism of the diagonal anal complex occurs in larval ctenophores but not in adults, indicating developmental flexibility in diagonal symmetry of the anal complex.     

An ultrastructural study of the larval integument of the midge,Chironomus riparius meigen (Diptera: Chironomidae)

Summary The larval integument of the midge, Chironomus riparius Mg., is unusually thin although it conforms with the normal insect pattern. The cuticle of the post-cephalic segments is about 3 m thick and overlies an epidermis which has an irregular basal plasma membrane resulting in spaces occurring between it and the basement membrane. The ventral tubuli have a similar epidermis but the cuticle is somewhat thinner. The anal papillae have the thinnest cuticular covering with a uniquely folded epicuticle of variable thickness, and their epidermis has the characteristics of a transporting epithelium. No evidence of pore canals could be found in the cuticle of any part except the head capsule which has a remarkably smooth epicuticle and a distinct layer which may represent the exocuticle. There are no spaces between the basement membrane and basal plasma membrane of the epidermis in the head. Ultrastructural evidence would suggest that gaseous exchange can occur across most of the post-cephalic integument.The author is indebted to Mrs. L. Rolph and Mr. R.L. Jones for their technical assistance     

The morphology of the club glands on the dorsal fin of mature male shannies, Lipophvys pholis (L.) (Blenniidae: Teleostei)

The pelvic, pectoral, anal and dorsal fins of mature male, female and immature male Lipophrys pholis (L.) were examined by light microscopy for the presence of club glands. All fins except the dorsal showed a highly stratified epidermis and a thick cuticle. Club glands were present on the dorsal fin of mature male fisH but only during the breeding season. The development and decline of the club glands corresponds to the period of gonadal build-up and spawnout. Each club gland comprises several thousand bundles ofcolumnar cells. The columnar cells surround acentral pore which opens to the outside through a layer of Malpighian cells. The substance produced by the gland includes mucopolysacchdride. The function of the secretion is unknown and is discussed in relation to studies on similar glands in several Mediterranean blenniids.     

Ultrastructural organization of the anal organs in the anal capsule of Craterostigmus tasmanianus Pocock, 1902 (Chilopoda, Craterostigmomorpha)

We describe the ultrastructural organization of the anal organs of Craterostigmus tasmanianus, which are located on the ventral side of the bivalvular anal capsule. Each part of the capsule bears four pore fields with several anal pores. The pores lead into a pore canal, which is surrounded by the single-layered epithelium of the anal organs. Each anal organ is composed of four different cell types: transporting cells of the main epithelium, junctional cells, isolated epidermal glands, and the cells forming the pore canal. The transporting cells exhibit infoldings of the outer cell membranes, forming a basal labyrinth and a poorly developed apical complex. The cells are covered by a specialized cuticle with a widened subcuticular layer. Only the cuticle of the main epithelium is covered by a mucous layer, secreted by the epidermal glands. The ultrastructural organization of the anal organ is comparable to the coxal and anal organs of other pleurostigmophoran Chilopoda. It is likely that the coxal and anal organs of the Pleurostigmophora are homologous, due to their identical ultrastructural organization. Differences concerning the location on the trunk of Pleurostigmophora are not sufficient to reject a hypothesis of homology. Anal organs are found not only in Craterostigmomorpha, but also in most adult Geophilomorpha, and in larvae and most adults of Lithobiomorpha. The anal organs of C. tasmanianus are thought to play an important role in the uptake of atmospheric water. J. Morphol.     

Fine structure of the epidermis in Gnathostomulida

Summary The fine structure of the epidermis in Haplognathia simplex, Haplognathia rosea, Pterognathia meixneri (Filospermoidea) and Gnathostomula paradoxa (Bursovaginoidea) has been investigated. The epidermis in the filospermoidean species is uniform, consisting of epidermal cells with a single locomotory cilium. The structure and development, including ciliogenesis, of these epidermal cells are described. In G. paradoxa additional epidermal elements have been found: mucous cells with a presumably apocrine secretion modus are scattered in a strip-like arrangement within the epidermis. Their deverlopment is separate from epidermal cells with locomotory function. Two further types of glandular cells with either a single cilium or a diplosome are located ventrally. It is assumed that they represent an adhesive system.Abbreviations (used in figures) ac accessory centriole - ap appendix of accessory centriole - ax axoneme - bb basal body - bf basal foot - bl basal lamina - c cilium - cA ciliary adhesive cell - ce centriole - cp ciliary pit - d diplosome - dy dictyosome - dA diplosomal adhesive cell - E epidermal cell with locomotory cilium, epidermis - ev epidermal vesicle (epitheliosome) - gv gland vesicle - m mitochondrion - ma microvillus of apical cell membrane - mp microvillus of ciliary pit - mv microvillus - n nucleus - ps prosecretory-vesicle - R receptor - r ciliary rootlet - rc caudal ciliary rootlet - rr rostral ciliary rootlert - sv secretory vesicle - v vesicle - v _i central vesicle of multivesicular body - v _o surrounding vesicle of multivesicular body - z cisternae     

Differentiation of embryonic chick feather-forming and scale-forming tissues in transfilter cultures

The dermal-epidermal tissue interaction in the chick embryo, leading to the formation of feathers and scales, provides a good experimental system to study the transfer between tissues of signals which specify cell type. At certain times in development, the dermis controls whether the epidermis forms feathers or scales, each of which are characterized by the synthesis of specific beta-keratins. In our culture system, a dermal effect on epidermal differentiation can still be observed, even when the tissues are separated by a Nuclepore filter, although development is abnormal. Epidermal morphological and histological differentiation in transfilter cultures are distinct and recognizable, more closely resembling feather or scale development, depending on the regional origin of the dermis. Differentiation is more advanced when epidermis is cultured transfilter from scale dermis than from feather dermis, as assessed by morphology and histology, as well as the expression of the tissue-specific gene products, the beta-keratins. Two-dimensional polyacrylamide gel analysis of the beta-keratins reveals that scale dermis cultured transfilter from either presumptive scale or feather epidermis induces the production of 7 of the 9 scale-specific beta-keratins that we have identified. Feather dermis, although less effective in activating the feather gene program when cultured transfilter from either presumptive feather or scale epidermis, is able to turn on the synthesis of 3 to 6 of the 18 feather-specific beta-keratins that we have identified. However, scale epidermis in transfilter recombinants with feather dermis also continues to synthesize many of the scale-specific beta-keratins. Using transmission and scanning electron microscopy, we detect no cell contact between tissues separated by a 0.2-micron pore diameter Nuclepore filter, while 0.4-micron filters readily permit cell processes to traverse the filter. We find that epidermal differentiation is the same with either pore size filter. Furthermore, we do not detect a basement membrane in transfilter cultures, implying that neither direct cell contact between dermis and epidermis, nor a basement membrane between the tissues is required for the extent of epidermal differentiation that we observe.     

Conidioma development in Ophiodothella vaccinii

The perithecial ascomycete Ophiodothella vaccinii causes a leafspot disease of sparkleberry (Vaccinium arboreum), in which an anamorph is produced early in the life cycle of the fungus. The anamorph forms shiny, black, pulvinate conidiomata that contain a single central pore. After initial infection, fungal hyphae permeate the interior tissues of the leaf, creating lesions. Conidiomata are initiated by the formation of a small layer of intertwined, thicker-walled hyphae beneath the epidermis of the lesion. Near the center of this hyphal layer a subglobose collection of thick-walled hyphae is formed. This hyphal collection grows upward, becoming conical and pressing against the epidermis. Elongation of a columnar apex of the hyphal collection ruptures the epidermis, creating a pore. Subsequent expansion and development of conidiophores and conidia push the epidermis upward, lifting it away from the column, opening the pore and allowing conidia to emerge. The conidioma is regarded as a modified acervulus.     

Transport-active organs within the ’ano-genital’ capsule of Craterostigmus tasmanianus (Chilopoda, Craterostigmomorpha)

 In Craterostigmus tasmanianus, first results of the cellular organization of anal organs within the ’ano-genital’ capsule are presented. Each valve of the ’ano-genital’ capsule bears four pore fields ventrally, each of them consisting of several pore openings of the anal organs. The pores lead into a cuticle-lined pore channel, the base of which is surrounded by a single-layered epithelium that is composed of three different cell types. The main epithelium consists of radially arranged transport-active cells surrounded by exocrine cells, and the cells of the pore channel. The cells of the transporting epithelium show deep invaginations of the apical and basal cell surfaces and plasmalemma-mitochondrial complexes. These cells are covered by a specialized cuticle with a prominent subcuticle. Exocrine glands secrete a mucous layer on the cuticle of the main epithelium. The type of anal organ present in Craterostigmus tasmanianus shows similarities to coxal and anal organs found in other Pleurostigmophora in the chilopods. The possible function of the anal organs in uptaking water vapour is discussed. It is appropriate to call the organs within the ’ano-genital’ capsule of Craterostigmus tasmanianus ”anal organs”, as components of the genital segments are not involved. Accepted: 17 November 1996     

Anatomy of Ricciocarpus natans, with emphasis on fine structure

The amphibious liverwort Ricciocarpus natans has been investigated with regard to structure and differentiation of cells and tissues.
The differentiation of the tissues was determined starting with their origin from the meristem situated in the median furrow. From this zone there is dorsally a differentiation of epidermis and aerenchyma, and ventrally a differentiation of epidermis and scales. Air–chambers arise schizogenously. They become divided by cells, which grow out from lateral walls and form an internal pore.
Parenchyma (aerenchyma and euparenchyma) cells and epidermis cells (including thallus margin and main scale cells) appear similar in ultrastructure. A characteristic localization of heteropycnotic chromatin close to the nucleolus is recognized. Mic–robodies have an extraordinary cap–shape. Vacuoles often contain electron dense bodies. Lipid droplets occur frequently in the cytoplasm. Storage products are not restricted to a certain tissue. Young scales have an apical papilla cell with many dictyosomes. Chloroplasts of the oilbody idioblast are much smaller than those of unspecialized cells. The rhizoids are smooth–walled.     

Elucidating the mechanism of poricidal anther dehiscence in Miconia species (Melastomataceae)

Melastomataceae have porate anthers. However, unlike Solanaceae and many monocots, in which the poricidal dehiscence depends on the presence of a mechanical layer (often the endothecium), most members of Melastomataceae have no evident specialized layer related to the poricidal opening. The goal of this study was to characterize the tissues that form the apical pore of the anther in 10 Miconia species, which may help to understand the nearly unknown mechanism of anther dehiscence in this genus, considered to be one of the largest and most diverse New World genera. Before anthesis, the apical pores of all of the species are closed by a uniseriate epidermis, the cells of which lack a cuticle. In contrast, the epidermis of the remainder of the anther is covered by a thick, ornamented cuticle. Among Myrtales, the Melastomataceae form a clade with Alzateaceae, Crypteroniaceae and Penaeaceae, almost all of which have anthers with endothecium lacking wall thickenings. In these families, the endothecium may or may not be present in the mature anther, with degenerating cells in the latter case. Anther dehiscence does not depend on the endothecium as the mechanical layer, and this process is still not well understood. However, in the Miconia species studied here, the cuticle may prevent tissue dehydration, and the pore opening seems to be due to the passive process of dehydration taking place only in the pore region due to the absence of the cuticle.     

密花香薷花蜜腺的解剖学研究

密花香薷花密腺分布于子房基部和子房表面,属于一朵花中具二种花蜜腺类型,子房基部的盘状蜜腺由分泌表皮、产蜜组织及维管束三部分组成,分泌表皮上角质层局部有小孔。子房蜜腺由分泌表皮和产蜜组织组成。     

Skin structure in the snout of the Australian lungfish,Neoceratodus forsteri (Osteichthyes: Dipnoi)

Many fossil lungfish have a system of mineralised tubules in the dermis of the snout, branching extensively and radiating towards the epidermis. The tubules anastomose in the superficial layer of the dermis, forming a plexus consisting of two layers of vessels, with branches that expand into pore canals and flask organs, flanked by cosmine nodules where these are present. Traces of this system are found in the Australian lungfish, Neoceratodus forsteri, consisting of branching tubules in the dermis, a double plexus below the epidermis and dermal papillae entering the epidermis without reaching the surface. In N. forsteri, the tubules, the plexus and the dermal papillae consist of thick, unmineralised connective tissue, enclosing fine blood vessels packed with lymphocytes. Tissues in the epidermis and the dermis of N. forsteri are not associated with deposits of calcium, which is below detectable limits in the skin of the snout at all stages of the life cycle. Canals of the sensory line system, with mechanoreceptors, are separate from the tubules, the plexus and the dermal papillae, as are the electroreceptors in the epidermis. The system of tubules, plexus, dermal papillae and lymphatic capillaries may function to protect the tissues of the snout from infection.     

Repugnatorial glands with associated striated muscle and sensory cells inMelibe leonina (Mollusca,Nudibranchia)

Summary The nudibranch molluscMelibe leonina is repellant to some seastars and fish, but not to crab predators. Distinctive subepidermal glands, which are particularly abundant within the cerata and dorsal wall of the oral hood, can be easily seen within the translucent body wall of this slug. The glands can be individually discharged by touching the overlying epidermis and the collected secretion is repugnant to seasters. Ultrastructural analysis reveals that each repugnatorial gland is composed of two types of secretory cell encased by cross-striated muscle. Storage of secretory product within a single, large, intracellular vacuole and cytological features of the muscle investment are consistent with a rapid, all-or-none secretion event, as observed in live tissue. The secretory cells empty into a short duct that opens by a pore. The pore is surrounded by ciliated sensory cells that probably act as mechanoreceptors triggering gland discharge. I argue that one of the two secretory cells releases defensive chemical, whereas the second may produce a protein-rich mucin.     

Attachment and Feeding Devices of Water-Mite Larvae [Arrenurus spp.) Parasitic on Damselflies (Odonata, Zygoptera)

Water-mite larvae of the subgenus Arrenurus (Acari, Hydrachnellae) act as habitual ectoparasites on zygopteran imagines, mostly attached to the soft membranous cuticle. The powerful larval pedipalp claws grasp the cuticle and the distal sabre-like cheliceral segments tear it, thus obtaining the host's tissue fluids. The chelicerae and palps co-operate to anchor the larva. The attached larva soon produces—in the host's subcuticular epidermis layer, and separated from the haemocoele by the thin sheet of subepidermal connective tissue—an elongated pouch, the stylostome, consisting of an acellular gelatinous substance, apparently secreted by the larva. Presumably, interaction with components in the host's tissue fluids solidifies the stylostome, which becomes firmly fixed to the host's body wall. The stylostome is thought to lengthen by repeated alternation between the suction of tissue fluids from the host and secretion of fresh soft substance forming additional stylostome segments. The resilient stylostome develops in a cleft between the host's cuticle and the subepidermal connective tissue in connection with partial decomposition of the host's epidermis, probably caused by cytotoxins leaking from the stylostome. In attempts to wall off the wound and thus to avoid influx of foreign substances, the host lays down a melanin sleeve around the stylostome at the perforation site. Lodgement of the functional stylostome separated from the haemocoele within the host's tissues might explain why the newly-formed stylostome seems immune from cellular host reactions. However, cellular encapsulation and melanization appear to happen to outworn, non-active stylostomes.     

Morphology and dynamic behavior of anal pores during defecation in the ctenophore Pleurobrachia pileus

Defecation in the lobate ctenophore Mnemiopsis leidyi was recently shown to occur periodically with an ultradian rhythm through a single transient anal pore which suddenly appeared, expelled waste, and disappeared afterward. To discover whether this novel method of defecation occurs in other kinds of ctenophores, I examined individuals of Pleurobrachia pileus and Beroe cucumis. Both ctenophores were found to have two identical and permanent anal pores as described in the scientific literature and textbooks. In P. pileus, both anal pores commonly participated in a defecation, but they did so asynchronously with independent and irregular opening and closing kinetics. Individuals of P. pileus defecated with an ultradian rhythm. Closed anal pores in P. pileus and B. cucumis consisted of a continuous ectodermal epithelium overlying a continuous endodermal epithelium with a cup-shaped group of thickened endodermal cells bearing a tuft of cilia which beats into the anal cavity. The rims of opening or closing pores were smooth and uniform without encircling muscles or fibers. This morphology and the continuity of the epithelial layers between defecations suggest that anal pores may not operate by a contractile sphincter, but by a reversible ring of tissue fusion between apposed ectodermal and endodermal epithelia to create an adjustable hole to expel waste.     

Epidermal-dermal tissue interactions between mutant and normal embryonic back skin: site of mutant gene activity determining abnormal feathering is in the epidermis.

The site of the scaleless gene's activity in the development of abnormal feathers was determined by reciprocally recombining epidermis and dermis between normal and scaleless chick embryos and culturing the recombinants for seven days on the chorioallantoic membrane. When recombined with a common dermal source, feather development is enhanced by scaleless high line as compared to scaleless low line epidermis. Against a common responding tissue, 7-day normal back epidermis, significant differences were not found in feather inducing ability between normal, scaleless high line and scaleless low line dermis. It was concluded that, in relation to abnormal feathering, these tissue interactions reveal that the site of the scaleless gene's activity is the epidermis. A model of tissue interaction in the development of normal and abnormal feathers is presented. According to the model, the focus of the scaleless mutation and the genes accumulated by selection for high or low feather numbers is the epidermis, the effect being that the reactivity of the epidermis to dermal stimuli is altered. Subsequently, the epidermis controls the morphogenetic organization of the dermis. The scaleless dermis is presumed to contain normal positional information for the determination of feather structure and pattern.