Cejkaian tubules' in the posterior midgut of terrestrial Enchytraeidae (Oligochaeta) (original) (raw)
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The stick insects or phasmids (Phamsatodea) have a series of pyriform ampulles with long, thin filaments on the posterior end of their midgut referred to as the "appendices of the midgut." Found only in phasmids, their function had never been determined until now. Their similarity to the Malpighian tubules, which are ubiquitous insect organs of excretion, suggested a similar function. To differentiate between the appendices and the Malpighian tubules and compare functional differences between the two tissue types, vital staining (the injection of histological stains into living organisms) was done in conjunction with light and scanning electron microscopy in multiple phasmid species. The results showed that the appendices originated in the basal phasmids (Timematidae) and grew more numerous in derived species. The appendices stain selectively, notably failing to pick up the indicators of the two known systems of invertebrate excretory function, indigo carmine and ammonium carmine. Appendices sequester stains in the ampule portion before eliminating the compounds into the midgut. We conclude by confirming that the appendices do have an excretory function, but one unlike any other known in invertebrates. Their function is likely cation excretion, playing a role in calcium regulation and/or organic alkaloid sequestration. The appendices must thus be considered distinct organs from the Malpighian tubules. J. Morphol. 000:000-000,
2000
Malpighian tubules proper are connected to the gut by ducts called trunks, the organization of which is described at ultrastructural level in the nymphs of various mayfly species, namely Ecdyonurus venosus (Heptageniidae), Ephemerella ignita (Ephemerellidae), Choroterpes picteti (Leptophlebiidae), and Caenis luctuosa (Caenidae). Trunks are luminal tubes varying in arrangement, number, shape, and length. The main cell type of the trunk wall is represented by cells that are bordered by a thin cuticle along their luminal side (type-A cells). Whereas these cells are exclusive in the long trunks (such as those of C. picteti and C. luctuosa), in the shorter ones (such as those of E. venosus and Ephemerella ignita) cells with a microvillous luminal border (type-B cells) are also encountered. These cells are located close to the entrance of the collecting duct of the Malpighian tubules proper, and their long microvilli form a dense filamentous mesh filling up the lumen. Both cell types exhibit fine structural features that are characteristics of ion-transporting epithelia. Ultrastructural investigations show that trunks are not a simple conducting system but are involved in the regulation of the ionic composition of the primary urine for producing a fluid hypo-osmotic with respect to the hemolymph.
Microscopic anatomy of pycnogonida: II. Digestive system. III. Excretory system
Journal of Morphology, 2007
The digestive system of several species of sea spiders (Pycnogonida, Arthropoda) was studied by electron microscopy. It is composed of the foregut inside a long proboscis, a midgut and a hindgut. Lips near the three jaws at the tip of the proboscis receive several hundred ductules originating from salivary glands. These previously undetected glands open on the lips, a fluted, projecting ridge at the external hinge line of the jaws, i.e., to the outside of the mouth. This disposition suggests affinities to the chelicerate line. The trigonal esophagus within the proboscis contains a complex, setose filter device, operated by dedicated muscles, that serves to reduce ingested food to subcellular dimensions. The midgut has diverticula into the bases of all legs. Its cells differentiate from the basal layer and contain a bewildering array of secretion droplets, lysosomes and phagosomes. In the absence of a hepatopancreas, the midgut serves both digestive and absorptive functions. The cuticle-lined hindgut lies in the highly reduced, peglike abdomen.
Acta Zoologica, 2004
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.
2019
A new species of enchytraeids with peculiar characters is described, Enchytraeus demutatus sp. nov. The species differs from all known species of Enchytraeus in features of the oesophageal appendages and the male efferent apparati. The oesophageal appendages insert ventro-laterally below the pharyngeal pad and not dorsally behind the pad, as is usual in the genus; furthermore, their histology is different. The male efferent apparati have each an unusually wide and short vas deferens, and accessory glands are attached to the inner surface of the male glandular bulb, in close vicinity to the male pore. The remaining characters agree with the genus diagnosis of Enchytraeus, notably the presence of testis sacs and oesophageal appendages. The bisetose worms are about 5 mm long and 0.2–0.3 mm wide. The peculiarities of the oesophageal appendages raised the possibility to place the species in a new genus. DNA sequencing was performed to provide molecular identifiers and to assess the gener...
The excretory function of the posteriormost part of the echinoid and holothuroid gut (Echinodermata)
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 1998
In vivo and in vitro experiments demonstrate that the intestinal caecum of the echinoid Echinocardium cordatum and the rectum of the holothuroid Holothuria tubulosa actively excrete chlorophenol red (CPR) from the individual body cavity towards the gut lumen, a function already demonstrated for the rectal caeca of asteroids. Physiological and ultrastructural investigations of the enterocytes of these organs show that they are functionally and structurally analogous to the cells of the proximal tubules of the vertebrate kidney. The results allow to suggest that the capability to eliminate unwanted substances through the posteriormost part of the gut is a generalized feature within the Echinodermata.
Histologic features of the gastrointestinal tract of Laonastes aenigmamus (Rodentia: Diatomyidae
We have carried out histological studies of the gastrointestinal tract of Laotian rock rat Laonastes aenigmamus. Most of the inner surface of the stomach is a cardiac region having reduced glands. Generally the cardiac glands are located near the esophagus. The esophagus and the ventricular groove are lined by keratinized stratified squamous epithelium. The region containing fundic (proper gastric) glands occupies a small area of the stomach. The maximum thickness of the gastrointestinal wall has been determined for the hindstomach and duodenum. The minimum wall thickness has been determined for ileum, colon, and cecum. In the large intestine, the glands are weakly developed and this can mean that there is not an active digestion in this gut site. Our results confirm the fact that foregut fermentation is crucial in digestion for this rodent. The topography of the regions, occupied by different types of mucosa in the stomach, has a convergent similarity to ones that are found in ruminant-like marsupials and points to similar adaptations to the consumption of plant foods. Owing to the small body mass of the rodents, the distribution of foregut fermentation is exceptionally rare in evolutionary history.
North-Western Journal of Zoology
The current study was designed to evaluate some histomorphological and histochemical characteristics of the digestive tract of Ophisops elegans, the most common lizard species in Turkey. The digestive tract was mainly composed of esophagus, stomach, small and large intestine. Each of these consisted of mucosa, submucosa, tunica muscularis and serosa, as in higher vertebrates. The folded esophageal mucosa had ciliated columnar epithelium with mucous secreting goblet cells which stained positive with PAS (Periodic Acid Schiff) and AB (Alcian Blue) procedures. The surface of the columnar cells of the gastric mucosa and gastric glands of stomach were strongly stained with PAS, but did not show any reaction with AB. The mucosa of small intestine was composed of columnar epithelium with goblet cells that exhibited a strong positive reaction to both PAS and AB. Despite the fact that the mucous secreting cells of the large intestine displayed a strong positive reactivity with PAS, they exhibited a weak reaction with AB. In addition, some statistical differences in AB /PAS staining cellular area and epithelial cell/nuclear area among the parts of the digestive tract were noted. The area of PAS positive material in goblet cells was much greater than the area of AB positive mucosubstances (GAGs) in the large intestine.