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STRUCTURE and FUNCTION of the DUCT of KÔLLIKER in PARALARVAE of LOLIGO VULGARIS LAM. (CEPHALOPODA) S Stelzner, G Sundermann, P Fioroni

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STRUCTURE and FUNCTION of the DUCT of KÔLLIKER in PARALARVAE of LOLIGO VULGARIS LAM. (CEPHALOPODA) S Stelzner, G Sundermann, P Fioroni STRUCTURE AND FUNCTION OF THE DUCT OF KÔLLIKER IN PARALARVAE OF LOLIGO VULGARIS LAM. (CEPHALOPODA) S Stelzner, G Sundermann, P Fioroni To cite this version: S Stelzner, G Sundermann, P Fioroni. STRUCTURE AND FUNCTION OF THE DUCT OF KÔL- LIKER IN PARALARVAE OF LOLIGO VULGARIS LAM. (CEPHALOPODA). Vie et Milieu / Life & Environment, Observatoire Océanologique - Laboratoire Arago, 1997, pp.161-164. hal-03103554 HAL Id: hal-03103554 https://hal.sorbonne-universite.fr/hal-03103554 Submitted on 8 Jan 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. VIE MILIEU, 1997, 47 (2) : 161-164 STRUCTURE AND FUNCTION OF THE DUCT OF KÔLLIKER IN PARALARVAE OF LOLIGO VULGARIS LAM. (CEPHALOPODA) S. STELZNER, G. SUNDERMANN, P. FIORONI Institut fur Spezielle Zoologie und Vergleichende Embryologie der Westfàlischen Wilhelms-Universitàt, Hufferstrafle 1, 48149 Munster, Germany CEPHALOPODA ABSTRACT. - Newly hatched paralarvae of Loligo vulgaris have a well developed DUCT OF KÔLLIKER duct of Kolliker, composed of two cell-types. It is divided into seven différent LOLIGO VULGARIS. régions. The duct is not a rudimentary organ but seems to have hydrostatic PARALARVA functions. The duct has an external opening into the connective tissue. CEPHALOPODES RÉSUMÉ. - Les nouveau-nés (paralarves) de Loligo vulgaris possèdent un canal CANAL DE KÔLLIKER de Kolliker qui se compose de deux types cellulaires ; il se divise en sept régions LOLIGO VULGARIS distinctes. Il ne s'agit donc pas d'un organe rudimentaire ; le canal semble avoir PARALARVE des fonctions hydrostatiques. Il s'ouvre vers le tissu conjonctif. INTRODUCTION trathin sections were stained with 1 % lead citrate and examined with a Zeiss EM 900 transmission électron microscope (TEM). The spatial orientation follows the During formation of the statocysts of Loligo swimming position of the adult squid : arms = anterior, vulgaris a duct develops on either side of the mantle tip = posterior, funnel = ventral. embryo by invagination of the epithelium. This duct persists after the séparation of the statocysts from the epidermis, as an appendix of the latéral RESULTS walls of each of the statocysts. It was discovered by Kolliker (1844) in Loligo vulgaris, Sepia offi- cinalis Linné, 1758 and Argonauta argo Linné, Structure of the duct 1758 and consequently named "duct of Kolliker". Since its discovery it received only little attention According to their intensity of staining in se- and it was considered to be an ontogenetic relict mithin sections and variable électron density in of the ectodermal invagination. In L. vulgaris it TEM the cells of the single-layered epithelium of has been described to have a closed end in the the duct of Kolliker can be described as two cartilage surrounding the statocyst (Hamlyn-Har- différent types : the type-1 cells which are élec- ris, 1903). Stephens and Young (1982), however, tron light and the type-2 cells which are électron showed that the duct crosses the cartilage and dense (Fig. 1). The type-1 cells are highly pris- opens ventrally into the connective tissue. The matic and have more numerous interdigitations following morphological and ultrastructural data apically than basally. describe the course of the duct, answer the ques- tion wether the duct opens to the connective tis- The type-2 cells have an irregular shape sue, and give a survey of its ultrastructure. (Fig 1). Because of their high électron density the total content of cell organelles is difficult to dé- termine. In both cell types, the large number of MATERIALS AND METHODS mitochondria and Golgi vesicles indicates a high energy turnover. Latéral interdigitations are more numerous between type-1 and type-2 cells than 18 hatchlings of Loligo vulgaris [stage XX of Naef 1921/28)] from Banyuls-sur-Mer, western Mediterra- between type-2 cells only. Mitochondria are found nean sea, France, were examined. The spécimens were regularly in ail interdigitations. Intermediary fila- ment strings, which are clearly distinguishable in fixed in 2% Os04 dissolved in 0,5% K2Cr207 in 80% seawater, pH 7,2-7,4, embedded in Durcupan (Fluka, the plasma of type-1 cells, are not seen in type-2 Switzerland), and eut on a LKB-Ultrotom III. The ul- cells. Both cell types bear long cilia, except the 162 S. STELZNER, G. SUNDERMANN, P. FIORONI Fig. 1-4. - TEM-sections through the duct of Kolliker. Fig. 1, 5175x. Part C, surrounded by cartilage, with type-1 and type-2 cells. Fig. 2, 5175x. Part G, aperture into the surrounding connective tissue. Fig. 3, 5175x. Part A, aperture to statocyst lumen. Fig. 4, 49.500x. Part B, cilia surrounded by microtubular structures (arrows), a = aperture, bl = basai lamina, c = cartilage cell, ci = cilia, se = statocyst cartilage, st = statocyst, tl = type-1 cell, t2 = type-2 cell. STRUCTURE AND FUNCTION OF THE DUCT OF KÔLLIKER 163 peripheral cells of the bulge around the opening Part C : Région between B and cephalic turn ; of the duct into the statocyst lumen (Fig. 3). The lower stags of cilia, type-1 and type-2 cells. ciliature in part B of the duct (see below) is différent Part D : Région of cephalic turn ; lumen narrows from that of other parts. In regular intervais around continually; number of cilia as in C ; type-1 and the cilia are thin, microtubular-like structures (Fig. type-2 cells. 4). They are connected to each other and to the cilia Part E : Transition from cartilage to connective by a substance of médium électron density (Fig. 4). tissue ; thinnest part of duct with smallest lumen Thèse connections combine approximately 150-200 (diameter ca. 1.4|j,m); flattened epithelial cells, cilia to bundles. The number of cilia per cell de- only type-1 cells. creases from part C to part G (Fig. 1 and 2). No Part F : Ampulla-like dilatation of lumen ; number obvious signs of degeneration in the epithelium of of cilia, form and type of epithelial cells as in E. the duct were seen. Part G : Aperture into connective tissue ; only type-1 cells. Course of the duct From the aperture in the statocyst lumen the duct runs into the statocyst cartilage (Fig. 3). DISCUSSION Right after entering into the cartilage, it turns in ventro-caudal direction. In the région underneath The examination of the duct of Kolliker at the the primordium of hamulus 3 it turns in anterior hatching stage proves that the duct shows no signs direction and then leaves the cartilage and its of degeneration but rather represents a well dif- lumen narrows. Surrounded by a thin layer of ferentiated structure. Therefore, it is rather unli- connective tissue it continues in anterior direction kely that it is only an ontogenetic relict without between the outer surface of the cartilage and a any function. haemolymph sinus. At its end, the duct opens into the connective tissue dorsal to the funnel muscle The duct of Kolliker reaches its greatest dia- and ventral to the edge of the statocyst cartilage ; meter in B and C. If there were a metabolic the opening points to the nearby epidermis exchange between the duct epithelium and the (Fig. 2). In this area the lumen of the duct has an fluid inside the canal, endolypmph would most ampulla-like dilatation (Fig. 2). probably occur in this part of the duct. However, no sécrétion vacuoles or anything similar can be The duct can be divided into seven parts (A - found in the apical surfaces of the cells. Also the G), according to the différent width of its lumen, fact that some coated vesicles and sécrétion grains the variation in ciliature of the epithelial cells, of undefinable content can be recognized in the and the cell types (which are highly prismatic in area of the Golgi apparatus of type-1 cells, is not parts A-D) (Fig. 5) : sufficient support for the assumption that the epi- Part A : Aperture to statocyst lumen; only type-1 thelial cells have a secretory function. Therefore, cells. we suppose that the duct of Kolliker is not invol- Part B : Région with widest lumen of entire duct ved in the production of the statocyst endolymph. (diameter ca. 17.4 |a,m), type-1 and type-2 cells. The experiments of Stephens and Young (1982) showed that after injection of coloured substances into the statocyst the fluid in the lumen of the duct also becomes coloured and that, therefore, a transport of endolymph into the duct must exist. Our investigations show that the duct runs a short distance in the surrounding tissue outside the sta- tocyst cartilage and then opens into it very close to the epidermis. Ail thèse facts indicate that the duct of Kolliker receives endolymph from the statocyst. This hypo- thesis is supported by the fact that the ciliary beat is directed from the statocyst lumen into the duct (Budelmann, 1990) and that the lumen of the duct is larger at its beginning (Parts A-C) than at its end. Consequently, it is reasonable to assume that one essential function of the duct of Kolliker is to receive endolymph from the statocyst ; and thus Fig. 5. - Diagram of the course of the duct of Kolliker to regulate the volume of the endolymph inside (parts A - G), (se = statocyst cartilage, arrow = transi- the statocyst. Where the endolymph sécrétion oc- tion from statocyst cartilage to connective tissue).
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