Title: Morphology and ultrastructure of the midgut in Piscicola geometra (Annelida, Hirudinea) Author: Magdalena M. Rost-Roszkowska, Piotr Świątek, Michalina Kszuk, K. Główczyk, A. Bielecki Citation style: Rost-Roszkowska Magdalena M., Świątek Piotr, Kszuk Michalina, Główczyk K., Bielecki A.(2012). Morphology and ultrastructure of the midgut in Piscicola geometra (Annelida, Hirudinea). "Protoplasma" (Vol. Molecular249, iss .identification 4 (2012), s. and1037 chromosomal-1047), doi localization 10.1007/s00709 of new -powdery011-0337 mildew-7 resistance gene Pm11 in oat Protoplasma (2012) 249:1037–1047 DOI 10.1007/s00709-011-0337-7 ORIGINAL ARTICLE Morphology and ultrastructure of the midgut in Piscicola geometra (Annelida, Hirudinea) Magdalena M. Rost-Roszkowska & Piotr Świątek & Michalina Kszuk & Kinga Główczyk & Aleksander Bielecki Received: 1 July 2011 /Accepted: 5 October 2011 /Published online: 21 October 2011 # The Author(s) 2011. This article is published with open access at Springerlink.com Abstract This paper presents information on the organiza- organelles, plays a role in its absorption and secretion. tion of the midgut and its epithelium ultrastructure in Glycogen granules in the intestinal epithelium indicate its juvenile and adult specimens of Piscicola geometra role in the accumulation of sugar. The comparison of the (Annelida, Hirudinea), a species which is a widespread ultrastructure of midgut epithelium in juvenile and adult ectoparasite found on the body and gills and in the mouth specimens suggests that electron-dense granules observed of many types of fish. The analysis of juvenile nonfeeding in the apical cytoplasm of digestive cells take part in specimens helped in the explanation of all alterations in the enzyme accumulation. Numerous microorganisms were midgut epithelium which are connected with digestion. The observed in the mycetome, which is composed of two endodermal portion (midgut) of the digestive system is large oval diverticles that connect with the esophagus via composed of four regions: the esophagus, the crop, the thin ducts. Similar microorganisms also occurred in the posterior crop caecum, and the intestine. Their epithelia are cytoplasm of the epithelium in the esophagus, the crop, the formed by flat, cuboidal, or columnar digestive cells; intestine, and in their lumen. Microorganisms were ob- however, single small cells which do not contact the midgut served both in fed adult and unfed juvenile specimens of P. lumen were also observed. The ultrastructure of all of the geometra, which strongly suggests that vertical transmis- regions of the midgut are described and discussed with a sion occurs from parent to offspring. special emphasis on their functions in the digestion of blood. In P. geometra, the part of the midgut that is devoid Keywords Leeches . Midgut epithelium . Digestive of microvilli is responsible for the accumulation of blood, system . Haem digestion . Endosymbionts while the epithelium of the remaining part of the midgut, which has a distinct regionalization in the distribution of Introduction Handling Editor: Pavel Dráber The digestive tract of invertebrates is composed of three M. M. Rost-Roszkowska (*) : P. Świątek : M. Kszuk : K. Główczyk distinct regions: the foregut, the midgut, and the Department of Animal Histology and Embryology, hindgut. While the foregut and hindgut are of an University of Silesia, ectodermal origin, the midgut is formed by the Bankowa 9, endoderm and is responsible for absorption, enzyme 40-007 Katowice, Poland e-mail: [email protected] secretion, storage of toxic substances (e.g., excessive metals),andevenforexcretionwhenthereareno P. Świątek e-mail: [email protected] excretory organs. It is also the first barrier against any invasion of pathogens because it takes part in homeo- A. Bielecki static maintenance. Depending on its different functions Department of Zoology, University of Warmia and Mazury, and the kinds of food consumed, the midgut may Oczapowskiego 5, 10-967 Olsztyn-Kortowo, Poland possess a tube-like shape, numerous caeca, or it may e-mail: [email protected] be differentiated into distinct regions (Saulnier-Michel 1038 M.M. Rost-Roszkowska et al. 1992; Silva et al. 2006; Rost-Roszkowska et al. 2010a, b, Material and methods 2011). Its digestive functions might additionally be delivered by symbiotic microorganisms which supply Material digestive enzymes, amino acids, fatty acids, or help in the detoxification and neutralization of toxic substances Specimens of P. ge ometr a (Linnaeus, 1758) were used in the (Nakabachi and Ishikawa 1999;Baumann2005;Grafetal. research. Sexually mature specimens were collected from C. 2006). carpio and then bred under laboratory conditions. Mature Among Annelida, Polychaeta, and Oligochaeta sensu specimens were fed on Danio rerio. Juveniles were collected stricto are the groups for which the midgut epithelia are immediately after hatching from a cocoon. Four juveniles and well known (Jamieson 1981; Punin and Lukyanova 1984; about 30 adult specimens were collected, fixed, and studied Saulnier-Michel 1992; Jenkins et al. 2002), although the with the use of light and electron microscopy techniques. ultrastructure of the digestive cells in the midgut of Hirudinea has been analyzed only in four species: Hirudo Light and electron microscopy medicinalis (Hirudinidae), Haementeria depressa, Helob- della triserialis,andTheromyzon rude (Glossiphoniidae) The specimens studied were prepared and fixed in the same (Hammersen and Pokahr 1972a, b; Fernádez et al. 1992). manner as in the case of previously studied clitellate annelids It is also known that species which belong to Rhynchob- (Świątek et al. 2011). Briefly, they were initially fixed with dellida possess the bacterial symbiont-containing organ 2.5% glutaraldehyde in a 0.1 M sodium phosphate buffer called a mycetome that is connected to the esophagus, (pH 7.4). Their bodies were then divided into smaller pieces while it is absent in Arhynchobdellida, where symbionts and fixed in 2.5% glutaraldehyde in the same buffer at room settle in the epithelium of the digestive tract (Siddall et al. temperature for 2 days. After washing in a sodium phosphate 2004; Perkins et al. 2005;Grafetal.2006). Many species buffer, the material was postfixed for 2 h in 1% OsO4 in the of leeches are ectoparasites of invertebrates and verte- same buffer, dehydrated in a graded series of ethanol replaced brates in which they cause diseases and have negative by acetone, and then embedded in an Epoxy Embedding effects on those animals that are commercially raised. A Medium Kit (Sigma, St. Louis, MO). Semithin sections (0.8- precise description of their midgut epithelium at the μm thick) stained with methylene blue were examined under ultrastructurallevelwouldhelpincontrollingthepests an Olympus BX60 microscope equipped with a DP12 digital that belong to Hirudinea. camera and AnaliSIS 3.2 (Soft Imaging System) software. Piscicola geometra is a widespread ectoparasite found Ultrathin sections (80 nm) were cut on a Leica ultracut UCT on the body and gills and in the mouth of many fish, e.g., ultramicrotome. After contrasting with uranyl acetate and lead salmon (Salmo salar), brown trout (Salmo trutta), charr citrate, the sections were examined using a Hitachi H500 (Salvelinus alpinus), bream (Abramis brama), gudgeon electron microscope at 75 kV. In addition, several mature (Gobio gobio), European eel (Anguilla anguilla), perch specimens were first anesthetized in 10% ethanol, then rinsed (Perca fluviatilis), gibel carp (Carassius gibelio), and of any mucus in 50% ethanol, and finally placed in test tubes common carp (Cyprinus carpio) (Bielecki 1997; Arslan with 75% ethanol or a 3% aqueous solution of formalin. and Emiroğlu 2011). P. geometra uses its proboscis to These leeches were then dissected and photographed using an penetrate a host’s tissues and suck its blood. When it is Olympus SZ-ST stereomicroscope. not attached to the body of a host, it can be found free- living, on and beneath stones and macrophytes. This paper presents the first part of our results connected Results with the organization of the midgut and its epithelial ultrastructure in juvenile and adult specimens of P. The endodermal part of the digestive tract in P. geometra, geometra. The aims of this study were: (a) to describe the both in nonfeeding juveniles and adult specimens, is ultrastructure of the endodermal part of the digestive tract composed of four regions: the esophagus, the crop, the (midgut) of the fish leech, P. geometra (Piscicolidae), as a posterior crop caecum, and the intestine (Fig. 1). The representative of Rhynchobdellida; (b) to describe any endodermal epithelium is formed by a single layer of differences in the distribution of organelles in juvenile cuboidal cells which rest on the noncellular basal lamina. nonfeeding and adult feeding specimens; and (c) to The midgut epithelium is surrounded by two layers of determine whether symbionts colonize both the mycetome visceral muscles: the inner circular and the outer longitu- and the midgut epithelium. Analysis of juvenile non- dinal fibers. The following description concerns both feeding specimens was used in order to explain all juvenile nonfeeding and adult feeding specimens of P. alterations in the midgut epithelium which appear after geometra, except in areas where differences between the blood meal. two stages are noted. Morphology and ultrastructure of the midgut in Piscicola geometra 1039 Ultrastructure of
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