The ultrastructure of the mastax of Filinia longiseta (Flosculariaceae, Rotifera): Informational value of the trophi structure and mastax musculature

The study contributes to the discussion of mastax evolution within Rotifera by giving an insight into the ultrastructure of the mastax in the rotifer species Filinia longiseta (Flosculariacea) and additionally into the bdelloid rotifer species Adineta vaga and Zelinkiella synaptae. The existence of cuticularized jaw elements (trophi) in the mastax, a muscular pharynx, is one of the defining rotiferan characters and the basis on which the monophyletic taxon Gnathifera Ahlrichs 1995a, comprising Rotifera, Gnathostomulida, Micrognathozoa and Acanthocephala, was erected. By means of SEM observations of the trophi and ultrathin serial sections (TEM) of the mastax, the internal and external organization of the jaw elements of F. longiseta is reconstructed. TEM sections of the incus of Filinia demonstrate that the fulcrum and the rami are built up by multitudes of tiny cuticular tubes. While tubular substructures in the rotiferan fulcrum have been described previously, distinct cuticular tubes as a substructure of the ramus have only been described for species belonging to the taxa Seisonidea and Bdelloidea so far ( [Koehler and Hayes, 1969] and [Ahlrichs, 1995b]). By comparing the appearance and arrangement of the cuticular tubes in the rami of F. longiseta to those found in species of Seisonidea and Bdelloidea, a higher degree of resemblance between the structures in F. longiseta and Bdelloidea can be reported. The occurrence of the ramus substructures in species of Seisonidea (Paraseison annulatus and Seison nebaliae) is given consideration to represent an intermediate between the ramus substructure of Bdelloidea/Flosculariacea and Ploima. Additionally, the mastax musculature of F. longiseta, being associated with the trophi, is described: A total of seven muscles are found that directly insert the jaw elements or are indirectly associated with them via muscle-to-muscle connections.     

Combining confocal laser scanning and transmission electron microscopy for revealing the mastax musculature in Bryceella stylata (Milne, 1886) (Rotifera: Monogononta)

The rotiferan jaw apparatus (mastax) is characterized by enormous plasticity and according to morphology and feeding strategy, different mastax types can be distinguished. The cuticular hard parts (trophi) of the mastax are often highly specialized and have both a major taxonomic and phylogenetic relevance. Owing to numerous light and scanning electron microscopic studies, the morphology of the trophi is well known but only few attempts have been made to analyze the morphology and functionality of the mastax as a whole. Particularly, the complex muscular system connecting the individual trophi elements and moving them against each other was disregarded in the past. Therefore, the subject of the present study is a detailed analysis of the mastax musculature of the proalid rotifer Bryceella stylata using a combination of transmission electron and confocal laser scanning microscopic techniques, previously applied for revealing the somatic musculature in rotifers exclusively. Based on ultrathin serial sections and phalloidin-dyed specimens, a total number of six paired and two unpaired individual mastax muscles have been identified for the modified malleate trophi system of B. stylata. Possibly homologous muscles in other, so far investigated rotifer species are discussed as well as functional considerations of the individual mastax muscles and their interaction when moving the trophi elements are suggested.     

Combining confocal laser scanning and transmission electron microscopy for revealing the mastax musculature in Bryceella stylata (Milne, 1886) (Rotifera: Monogononta)

The rotiferan jaw apparatus (mastax) is characterized by enormous plasticity and according to morphology and feeding strategy, different mastax types can be distinguished. The cuticular hard parts (trophi) of the mastax are often highly specialized and have both a major taxonomic and phylogenetic relevance. Owing to numerous light and scanning electron microscopic studies, the morphology of the trophi is well known but only few attempts have been made to analyze the morphology and functionality of the mastax as a whole. Particularly, the complex muscular system connecting the individual trophi elements and moving them against each other was disregarded in the past. Therefore, the subject of the present study is a detailed analysis of the mastax musculature of the proalid rotifer Bryceella stylata using a combination of transmission electron and confocal laser scanning microscopic techniques, previously applied for revealing the somatic musculature in rotifers exclusively. Based on ultrathin serial sections and phalloidin-dyed specimens, a total number of six paired and two unpaired individual mastax muscles have been identified for the modified malleate trophi system of B. stylata. Possibly homologous muscles in other, so far investigated rotifer species are discussed as well as functional considerations of the individual mastax muscles and their interaction when moving the trophi elements are suggested.     

Electron microscope studies of the digestive tract ofBrachionus plicatilis (Rotifera)

Summary The rotiferBrachionus plicatilis was immobilized in an extended state by treatment with acrylamide. Longitudinal sections through whole animals were studied by transmission electron microscopy, and in addition animals were cut in different planes and studied by scanning electron microscopy. By these techniques several structures were characterized which seem to be relevant to the processes of enzymatic digestion and resorption in this species. The inner surfaces of both the stomach and the intestine are provided with rootless cilia, which show different densities, alignments, structures and properties in different compartments. The syncytial wall of the anterior part of the stomach is flat; its plasma membrane toward the stomach lumen is smooth and bears relatively few cilia. The posterior part of the stomach consists of voluminous cells. Their plasma membranes lining the stomach cavity show pits and infoldings that are continuous with a system of vacuoles within the cells containing membrane material probably derived from food organisms. The density of cilia in the posterior part of the stomach is about three times that in the anterior part. The stomach glands contain ribosomes, glycogen granules and secretory bodies, which are accumulated toward the region where these glands drain into the stomach cavity. The orifice of the stomach glands occurs in a permanent intercellular gap between the syncytial anterior stomach and three cells of the posterior part of the stomach. The cells of the intestinum are relatively flat and are characterized by mitochondria, narrow intercellular spaces between shingle-like overlapping wall cells and cilia differing in structure and properties from those of the stomach. The observations confirm the existence of functional differences between stomach and intestine. Digestion of nutrients, supported by secretions of the stomach glands, seems to be performed mainly within the stomach, and resorption of particulate food seems to occur almost exclusively in this part of the alimentary tract. The structural features of the intestine, on the other hand, indicate that small molecules may be transported through its wall and that here, perhaps, processes may take place which demand active transport.Abbreviations ast anterior part of the stomach - bm basal membrane toward pseudocoel - cb cell border between stomach cells - cwh rooted cilia of the wheel organ - dm desmosome structure between intestinum cells - e esophagus - gc glycocalyx (fuzzy coat) - gl gastric gland - isp intercellular space - it intestinum - itl intestinum lumen - m mitochondrion - mbl membranelles in the esophagus - mx mastax - pc pseudocoel - pst posterior part of the stomach - sb secretory bodies - SEM scanning electron microscopy - st stomach - stl stomach lumen - TEM transmission electron microscopy - v (food-) vacuole in cells of the posterior stomach wall - x small vesicle or grana-like structures on the lumen side of the opening of the gastric gland Dedicated to Dr. h.c. Walter Koste on the occasion of his 80th birthday     

Functional morphology of the developing alimentary canal in the holothurian Eupentacta fraudatrix (Holothuroidea, Dendrochirota)

Development of the digestive tract of the holothurian Eupentacta fraudatrix was examined using light and transmission electron microscopy. After the blastopore closes, the gut rudiment loses its connection with the blastoderm and becomes an enclosed, tubular chamber, ending blindly at both ends. The differentiation of the digestive and coelomic epithelia is mainly completed by day 12. Since no transient cell types are observed, this differentiation is definitive. By day 20, the mouth and anal openings appear. The cuticular lining in the anterior part of the gut rudiment has an endodermal origin and differentiates before the mouth is formed. The rest of the gut lining is composed of enterocytes typical of holothuroid intestine. At the early stages of development, mitotic figures are encountered among nonspecialized cells of the gut primordium. In more developed digestive epithelium, vesicular enterocytes are capable of mitotic division. Dividing enterocytes retain secretory vacuoles; thus mitosis occurs in actually differentiated cells. After mouth and anus formation, the oesophagus, stomach, intestine and rectum can be distinguished. In the wall of the stomach, powerful musculature is formed.     

Autoradiographic observations on the incorporation of amino acids into oesophageal,gastric and pancreatic glands in the leopard frog,Rana pipiens

Summary The uptake and incorporation of L-³H-leucine and L-³H-serine in the oesophageal, gastric and pancreatic exocrine glands of Rana pipiens was examined using light microscopic autoradiographic techniques. At 1/2 h, 1 1/2 h and 3 h following injections of amino acids, silver grains are observed over the basal region of the cells comprising the glands. At 6 h after injection, silver grains occur over the apical region of the cells and by 24 h the grains can be observed over the cytoplasm of the cells adjacent to the lumen of the glands, collecting ducts, oesophagus and stomach. These observations indicate that the amino acids are being incorporated into proteins that are then discharged into the lumen of the pancreatic ducts, oesophagus and stomach. The secretory picture observed in the oesophageal glands closely resembles that of the gastric glands. This autoradiographic study supports the suggestion that the two glands are homologous and that they both secrete pepsinogen granules.     

The Structural Adaptation of Aerial Parts of Invasive <Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis> to Water Regime

Alternanthera philoxeroides has successfully invaded diverse habitats with considerably various water availability, threatening biological diversity in many parts of the world. Because its genetic variation is very low, phenotypic plasticity is believed to be the primary strategy for adapting to the diverse habitats. In the present paper, we investigated the plastic changes of anatomical traits of the aerial parts of A. philoxeroides from flooding to wet then to drought habitat; the results are as follows: A. philoxeroides could change anatomical structures sensitively to adapt to water regime. As a whole, effects of water regime on structures in stem were greater than those in leaf. Except for principal vein diameter and stoma density on leaf surfaces, all other structural traits were significantly affected by water regime. Among which, cuticular wax layer, collenchyma cell wall, phloem fiber cell wall, and hair density on both leaf surfaces thickened significantly with decrease of water availability, whereas, pith cavity and vessel lumen in stem lessened significantly; wet habitat is vital for the spread of A. philoxeroides from flooding to drought habitat and vice versa, because in this habitat, it had the greatest structural variations; when switching from flooding to wet then to drought habitat, the variations of cuticular wax layer, collenchyma cell wall, phloem fiber cell wall, pith cavity area ratio, diameter of vessel lumen, and hair density on both leaf surfaces, played the most important role. These responsive variables contribute most to the adaptation of A. philoxeroides to diverse habitats with considerably various water availability.     

Light and electron microscopic study of the anterior oesophagus of Bulla striata (Mollusca,Opisthobranchia)

Lobo‐da‐Cunha, A., Oliveira, E., Alves, Â., Coelho, R. and Calado, G. 2010. Light and electron microscopic study of the anterior oesophagus of Bulla striata (Mollusca, Opisthobranchia). —Acta Zoologica (Stockholm) 91 : 125–138. The anterior oesophagus of Bulla striata was investigated with light and electron microscopy. In the most anterior region, the ridges of the oesophageal wall are covered by a ciliated columnar epithelium forming large apical blebs which are released into the lumen, an activity that is particularly intense in the oesophageal pouch. In the last two‐thirds of the anterior oesophagus, the epithelium is covered with microvilli embedded in a cuticle, but apocrine secretion and cilia are absent. Subepithelial secretory cells are very abundant in the oesophageal wall, except in the roof of the pouch. They have a long neck that crosses the epithelium, whereas the cell body containing the nucleus is embedded in the connective tissue. Large electron‐lucent secretory vesicles and many Golgi stacks fill most of their cytoplasm. The histochemical and cytochemical assays show that these cells secrete acid mucopolysaccharides. With the current and future studies we aim to obtain data for the establishment of relationships between morphofunctional features of the digestive system and food types in cephalaspideans. Additionally, the new data about the oesophageal pouch of B. striata may be useful for the establishment of eventual homologies with the oesophageal diverticula of other opisthobranchs.     

Structural investigation of the female genitalia and sperm-storage sites in the terrestrial isopod Armadillidium vulgare (Crustacea, Isopoda)

The cuticular genitalia of the terrestrial isopod, Armadillidium vulgare, have two distinct states during the reproductive cycle of the females. The structural differences between the reproductive and non-reproductive states, and the structure of the sperm storage sites were investigated employing electron and light microscopy. In both states the genitalia consist of a distal segment that connects to the gonopore, and a cuticular tube-like structure lining the lumen of the oviduct in the middle region of the oviduct. Sheath-like projections, apparently consisting of cuticular material, extend laterally along two sides of the cuticular tube. In the proximal region of the oviduct cuticular structures are lacking. In the non-reproductive state the distal segment consists of endo-, exo- and epicuticle. The exocuticle is three layered with unusual spongy and dense layers at the distal side. On one side the endocuticle doubles in thickness to form a cuticular bulge that fills the lumen of the distal segment leaving just a narrow U-shaped space. The cuticular tube consists of endo- and epicuticle only. In the reproductive state the distal segment is funnel-shaped and forms branched cuticular folds that increase in complexity from distal to proximal. In the cuticular tube these folds tightly fill the lumen of the oviduct. At the confluence of the oviduct with the ovary spermatozoa are stored in a seminal receptacle.     

Rotifer digestive enzymes: direct detection using the ELF technique

Hydrolytic enzymes involved in rotifer digestive processes were investigated directly at the sites of enzyme action using the ELF (Enzyme Labelled Fluorescence) technique. After enzymatic hydrolysis of an artificial ELF substrate, the fluorescent product ELF alcohol (ELFA) marked the sites of enzyme action. The time development of ELFA labelling was studied at different incubation times. Phosphatases, β-N-acetylhexosaminidases and lipases were examined in Brachionus angularis, B. calyciflorus, Keratella cochlearis and Lecane closterocerca from fed-batch cultures. We detected activities of all studied enzymes mostly in the stomach and intestine of rotifers. L. closterocerca was the only species showing enzyme activity at the mastax. Lipase activity was observed in the stomach and intestine of all species and in the mastax of L. closterocerca. Phosphatases were frequently located at the corona of B. calyciflorus. In other cases, both phosphatases and β-N-acetylhexosaminidases were rarely detected at the corona, and on the lorica and epidermis of some species. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont and R. Rico-Martínez Advances in Rotifer Research     

A new acuariid nematode, <Emphasis Type="Italic">Syncuaria mackoi</Emphasis> n. sp. (Spirurida), from <Emphasis Type="Italic">Ciconia nigra</Emphasis> (L.) (Ciconiiformes: Ciconiidae) in Europe

Syncuaria mackoi n. sp. is described, based on light and scanning electron microscopy, from the stomach of the black stork Ciconia nigra in Bulgaria. The new species is characterised by: body length 7.18–8.30 mm (males) and 10.13–11.40 mm (females); cordons anastomosing about the level of the middle of the muscular oesophagus and consisting of delicate cuticular plates; bifurcate deirids 7–9 μm long; lateral longitudinal cuticular band-like swellings; nine pairs of pedunculate caudal papillae, i.e. four precloacal and five postcloacal, the latter forming two groups (2 + 3); sixth pair of postcloacal papillae sessile; left spicule 854–907 μm long; right spicule 138–154 μm in length, with a curved distal end resembling a horn and a short lateral projection at some distance from its tip; and vagina vera provided with an anteriorly-directed blind appendix. The specimens identified as S. ciconiae (Gil’bert, 1927) by Macko (1964) from C. nigra in Slovakia are considered as belonging to S. mackoi. A pair of small cupolae situated dorsally and ventrally between bases of cordons of the new species is described for the first time in this genus; they are recognised as homologous to the pair of spines in the same position previously described in S. diacantha Petter, 1961 and S. plegadisi Digiani, 1999.     

Histology and mucin histochemistry of the gastrointestinal tract of the mud loach, in relation to respiration

The gastrointestinal tract of the mud loach Misgurnus mizolepis was divided into an oesophagus, stomach, intestine and rectum which consisted of a mucosa (epithelial layer), lamina propria-submucosa, muscularis and serosa. The intestine and rectum have shorter mucosal folds and a thinner wall than those of the oesophagus and the stomach. Extensive vascular capillary networks were present near the luminal surface of the intestine and the rectum. The diffusion distance between the vascular capillaries and the viscus lumen in the intestinal and rectal mucosal epithelium was 0·7 μm (±0·11). The intestine and rectum of Misgurnus mizolepis probably have a respiratory function to address the deficient oxygen supply within their environment. The epithelial mucous cells contained acidic or a mixture of acidic and neutral mucins, the former being the most common.     

The structure of the postantennal organ in Onychiurus sp. (Insecta: Collembola) and its connection to the central nervous system

Summary The postantennal organ in Onychiurus (group armatus) is a sensory organ comprising one sensory cell, several enveloping cells and cuticular structures.The perikaryon of the sensory cell is located in the central nervous system and distally gives off a dendrite in which one inner and two outer segments are distinguishable. Two ciliary structures connect the outer dendritic segments with the inner segment. The outer segments divide repeatedly, basal to the cuticular structures, into small branches which end distally beneath the cuticular wall. The wall of the cuticular structures is very thin and is pierced by numerous funnel-shaped pores. The pores are filled with electron-dense material which forms a continuous sheath underneath the cuticle. This material encases the small dendritic branches and the processes of the enveloping cells which occupy the lumen of the cuticular structures. There are three types of enveloping cells: one inner, several outer and one basal. Their processes differ in the manner in which they envelop the various regions of the dendrite.At the beginning of moulting outer dendritic branches are not found within the cuticular structures of the organ. They may be assumed to retract inwardly. However, in the later stages, when the cuticle is fully formed, the outer dendritic segments appear to divide. It is assumed that the small dendritic branches reach their targets before ecdysis. The electrondense material which clogs the intermoult cuticular pores is absent until the final stages of the moulting cycle.Supported by a grant from the Deutscher Akademischer Austauschdienst.     

On the oesophagus of ascaris lumbricoides

Summary The oesophagus ofAscaris lumbricoides is built up by a muscular-epithelial part containing the ordinary muscle fibres which run from the three sides of the oesophagus lumen towards the periphery and a system of fibres and fibrous plates at the margin of the triradiate oesophagus lumen. In four complete series ofA. lumbricoides (males and females) the nuclei of both kinds of fibres were constant in arrangement and number. The glandular system of the oesophagus consists of a large dorsal gland and two smaller subventral ones. The opening of the dorsal gland is at the anterior end of the oesophagus in the middle between nerve ring and lips. The openings of the two subventral glands are placed in the posterior end of the oesophagus in the middle of the two subventral slides at the same level. The dorsal gland fills with its ramifications the space between the muscle fibres of the three sectors with the exception of the most anterior end of the oesophagus before the opening of the dorsal gland and the subventral sectors in the posterior end of the oesophagus. The subventral sectors of the posterior end are filled by the ramifications of the two subventral glands. The ramifications of these three glands are connected. The three nuclei of the three glands have their place in the posterior end of the oesophagus, the nuclei of the subventral glands are situated in the most ventral part of each subventral sector close to each other, the nucleus of the dorsal gland has a complicated form and extends over the whole breadth of the dorsal sector. With 10 figures in the text.     

Morphology,fine structure,and functional aspects of the labial gland reservoirs of the subterranean termite Reticulitermes santonensis de Feytaud (Isoptera: Rhinotermitidae)

The morphology and fine structure of the labial gland reservoirs in the subterranean termite Reticulitermes santonensis (Isoptera: Rhinotermitidae) was studied by light and transmission electron microscopy. The reservoir wall consists of a single epithelial cell layer and a cuticular intima. The reservoir ducts are formed by a flat epithelial matrix with cuticular ridges lining the duct lumen. Measurements of the ionic concentrations of reservoir fluids and haemolymph show that the osmolality of reservoir fluid ranges from 7 to 28 mosmol kg⁻¹; the haemolymph osmotic pressure was 201 ± 31 mosmol kg⁻. The reservoir lumen is effectively separated from the haemolymph compartment; a net water flow through the reservoir wall could not be induced in physiological experiments. Moreover, typical epithelial structures associated with a fluid transport against an osmotic gradient are lacking. Thus, our fine structural and physiological data support the view that a water transfer from the haemolymph through the reservoir wall into the reservoir lumen does not occur.     

Old and new data on Seisonidea (Rotifera)

Class Seisonidea consists of one marine genus, Seison, with two species (S. nebaliae and S. annulatus) which are epizoic on the crustacean Nebalia. Seisonidea are the only rotifers whose reproduction is strictly bisexual. They also possess the unusual feature of having well-developed males. In this paper we review the literature concerning biogeographical distribution, relationships with their host, and morphology, and present new information obtained with SEM and optical microscopy of both living animals and serial sections.Some seisonid characters, such as the paired retrocerebral organ, nervous system, and trophi, suggest that they hold a primitive position within phylum Rotifera. However, they do share features with other rotifers: paired gonads and an unusual locomotory behavior with Bdelloidea; lateral antennae, cellular stomach wall, arrangement of intracytoplasmic lamina, and other characters with Monogononta. Some features are peculiar to Seison: obligatory amphimixis, endolecythal eggs, encysted spermatozoa, unique mastax, and absence of copulatory organ in males and of vitellaria in females. Reduction of the corona and absence of resistant stages in Seisonidea may be related to their habitat and to their life style. We propose a closer relationship of Seisonidea to Monogononta than previously asserted.     

Ultrastructure of Enteronephridia and General Description of the Alimentary Canal in Trochonerilla mobilis and Nerillidium troglochaetoides (Polychaeta,Nerillidae)

The alimentary canals of Trochonerilla mobilis and Nerillidium troglochaetoides consist of a ventral pharyngeal organ, oesophagus, stomach, intestine, and rectum. Prominent salivary glands lying lateral to the oesophagus discharge their secretions into the buccal cavity. Ciliated canals, the enteronephridia, embedded in the intestinal epithelium, open into the stomach near its border to the intestine. The ventral pharynx comprises a muscle bulb connected to a tonguelike organ by an investing muscle. The whole alimentary canal is ciliated except for the intestine of T. mobilis. The stomach is built up of absorptive cells and posteriorly also of secretory cells, whereas the intestine consists of only one cell type which is considered to be mainly absorptive. A typical microvillar brush border is present only in the intestine of T. mobilis; elsewhere the density of microvilli is low or the cells have irregular apical processes. In N. troglochaetoides the intestine has a ventral ciliary gutter laterally bordered by cells with highly specialized microvilli. The enteronephridia — 3 in N. troglochaetoides and 13 in T. mobilis — are unicellular tubes up to 130 μm long with a microvillar brush border and other cytological features typical for nephridial ducts. These structures are not known in any other polychaete taxon.     

Rotifer muscles as revealed by phalloidin-TRITC staining and confocal scanning laser microscopy

By combining phalloidin‐TRITC staining with confocal scanning laser microscopy (CSLM), the pattern of the musculature in two species of Rotifera, Euchlanis dilatata unisetata and Brachionus quadridentatus is revealed. The same general muscle pattern prevails in both species. The major components of the body wall musculature are: 1. retractor muscles (5 pairs in E. dilatata unisetata and 3 pairs in B. quadridentatus); 2. Two pairs of dorso‐ventral muscles; 3. Two pairs of perpendicular muscles (in E. dilatata unisetata); 4. retractors of the corona (median, lateral and ventral); 5. Foot retractors. In addition, three pairs of cutaneo‐visceral muscles and visceral muscles (including mastax muscles) are described. The sphincter of the corona was found only in B. quadridentatus. The high degree of muscle differentiation points to a high level of development of rotifer muscular system.     

Morphology of female reproductive system of Mediterranean flatheaded peachborer,Capnodis tenebrionis (Linnaeus, 1761) (Coleoptera: Buprestidae)

Capnodis tenebrionis causes damage in many species of Rosaceae. The present study investigates on the morphology of the female reproductive system of C. tenebrionis. The female reproductive system of C. tenebrionis has a pair of ovaries, lateral oviducts, a common oviduct, spermatheca, and bursa copulatrix. Each ovary in C. tenebrionis consists of approximately 24 telotrophic meroistic type ovarioles. The ovarioles of C. tenebrionis have four regions (terminal filament, tropharium, vitellarium, and pedicel). Tropharium have trophocytes, young oocytes, and prefollicular cells. Vitellarium consists of previtellogenic, vitellogenic, and choriogenic oocytes. Previtellogenic oocyte is surrounded by cylindrical epithelial cells. Its ooplasm is homogeneous and basophilic. In vitellogenic oocyte, there are intercellular spaces between monolayered follicle cells. Its ooplasm has yolk granules and lipid droplets. Choriogenic oocyte are surrounded by chorion and single-layered cylindrical cells. There are yolk granules and lipid droplets in its ooplasm which is asidophilic. In C. tenebrionis female, spermatheca and bursa copulatrix wall is surrounded by thin cuticular intima, monolayer epithelial, glandular cells, and muscle layer. Spermatheca lumen contains a large number of spermatozoa. Bursa copulatrix lumen is filled with secretory material. This study may be useful in terms of the morphology of mature female reproductive organs of Buprestidae and other coleopteran species.     

An exaggerated trait in insects: The prothoracic skeleton of Stictocephala bisonia (Homoptera: Membracidae)

The prothoracic skeleton of Stictocephala bisonia was investigated in adults and fifth-instar nymphs on a gross morphological (SEM, maceration) and light microscopic level. In both nymphs and adults, the prothoracic skeleton consists of the pronotum, episternum, epimeron, precoxale, sternum, trochantin, and two endoskeletal characters (furcal arms and pleural apophyses). In nymphs, the entire pronotum is a single-layered outgrowth of the integument communicating with the body cavity and filled with hemolymph and fat body cells (“spine”); the dorsal and ventral processes and the suprahumeral bud are extensions of this single-layered integument. In adults, the pronotum is composed of (1) a proximal, single-layered part, and (2) a larger, distal, double-layered part (“posterior reduplication”) with two cuticular layers separated by a thin lumen. The posterior reduplication is elevated above the body and forms hollow (air-filled) extensions (e.g., suprahumeral horns). Its two cuticular layers are connected through cuticular columns that appear on the external surface as pits. The lumen between these layers communicates with the body cavity and contains nerves and tracheae. In the lumen of newly eclosed adults, intercellular space, epidermal cells with long processes, and hemocytes with nonlipid granules are present. In the lumen of sclerotized adult pronota, the intercellular space has disappeared, together with definite cell boundaries. Several structures are associated with the external cuticle: two types of innervated sensilla trichodea that articulate in the center of external pits, sensilla campaniformia, sensilla coeloconica, and cuticular canals with exterior openings. The morphogenetic implications of pronotal construction, various aspects of adult prothoracic anatomy, and the value of glands and sensilla for an adaptive interpretation of the pronotum are discussed. J. Morphol. 238:157–178, 1998. © 1998 Wiley-Liss, Inc.