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THE ANATOMY of NEOPILINA GALATHEAE LEMCHE. 1957 (Molluscs Tryblidiacea)

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THE ANATOMY of NEOPILINA GALATHEAE LEMCHE. 1957 (Molluscs Tryblidiacea) THE ANATOMY OF NEOPILINA GALATHEAE LEMCHE. 1957 (Molluscs Tryblidiacea) By HENNING LEMCHE and KARL GEORG WINGSTRAND Zoological Museum. Institute for Comparative Anatomy and Zoological University of Copenhagen Technique. University of Copenhagen CONTENTS Introduction ......................... 10 The Lateral Nerve Cords ................ 47 Material and Methods .................... 10 The Pedal Nerve Cords .................. 48 General Description ..................... 12 The Nerves to the Postoral Tentacles and to The Outer Epithelia ..................... 13 the Statocysts ....................... 49 Slightly Specialized Epithelia .............. 13 Comparative Remarks .................. 50 Specialized Ciliated Epithelia .............. 13 Senseorgans ........................ 50 Glandular Epithelia .................... 14 Connective Tissue and Blood Cells ............ 51 Cuticle-Carrying Epithelia ................ 14 The Vascular System .................... 52 The Shell and the Pallial Fold .............. 15 General Morphology .................. 52 The Gills ........................... 19 The Efferent Gill Vessels and the Arterial Mantle TheFoot ........................... 21 Sinuses .......................... 52 The Mouth Region ...................... 22 The Atria .......................... 52 The Preoral Tentacles .................. 22 The Ventricles ....................... 53 The Velum ......................... 23 The Atrio-Ventricular Ostia ............... 53 The Postoral Tentacle Tufts ............... 23 The Aorta ......................... 54 The Feeding Furrow ................... 24 The Blood Sinuses .................... 54 TheLips .......................... 24 Comparative Remarks .................. 54 Comparative Remarks .................. 24 The Coelomic System .................... 55 The Digestive System .................... 25 The Pericardial Sacs .................... 55 The Oral Cavity and the Subradular Sac ........ 25 The Dorsal Body Coelom ................ 55 The Pharynx and the Radula Apparatus ........ 25 Comparative Remarks .................. 56 The Oesophagus ..................... 29 The Nephridia ........................ 57 The Stomach and the Liver ............... 29 The Structure of a Nephridium ............. 57 The Intestine ....................... 30 Mutual Connections of the Nephridia ......... 58 Comparative Remarks .................. 31 Connections with the Coelom .............. 58 The Muscular System .................... 31 Comparative Remarks .................. 59 Histological Remarks .................. 32 The Genital Organs ..................... 59 The Muscles of the Body Proper ............ 33 The Female Organs .................... 59 The Segmental Foot Retractors ............ 33 The Male Organs ..................... 61 The Circular (Longitudinal) Systems ......... 34 Comparative Remarks .................. 61 The Smaller Muscles of the Gills, Mantle and Foot 36 Ecological Remarks .................... 63 The Muscles of the Anterior Body Region ...... 37 Concluding Remarks .................... 64 The Subepithelial Muscles of the Body Wall .... 37 TheProtoconch ...................... 64 The Retractors in the Mouth Region ........ 38 The Adult Shell ...................... 64 The Buccal Muscles .................. 39 The Foot and the Pallial Groove ............ 65 The Muscles of the Radula Apparatus ...... 39 Structures around the Mouth .............. 65 The Muscles of the Pharynx ............ 42 TheGills .......................... 65 The Insertion Pattern on the Shell ............ 42 Internal Organs ...................... 66 Comparative Remarks .................. 43 The Metamerism ...................... 66 The Nervous System .................... 46 Relations to the Fossil Tryblidians ........... 67 General Anatomy ..................... 46 Neopilina and the Systematics of Molluscs ...... 67 Histology ......................... 46 References .......................... 68 The Circum-Oral Nerve Ring .............. 46 Index .............................. 69 A living representative of the ~nolluscanorder Tryb- In order to present a prompt and extensive report lidiacea, captured by the Galathea Expedition, has on the anatomy of Neo/7iIina the present authors been described by LEMCHE(1957a) under the name joined in its preparation. But, as we found ourselves of Neopilina gulutheae. An account of its anatomy entangled in comparisons and phylogenetical spec- was presented to the XVth International Congress ulations as soon as we left the level of pure descrip- of Zoology in London (LEMCHEand WINGSTRANDtion, we soon decided to exclude from our paper 1959), and the phylogenetical implications were almost every reference to the literature. discussed by LEMCHE(1959a, 1959 b). Several other The authors are highly indebted to the Carlsberg comments have been published but do not record Foundation for granting support towards the in- new facts about the original material (BEKLEMISHEVvestigations. The presentation of this paper has 1958, GLASS1957, KNIGHTand YOCHELSON1958, been greatly facilitated through the enthusiastic 1959, LEMCHE1957b,c, 1958a,b, YONGE1957a,b, cooperation of the staff of the Institute for Com- 1958). A chapter summarizing the more important parative Anatomy and Zoological Technique. The features has been prepared for the "Trait6 de painstaking work of preparing the illustrations for Zoologie".l printing is due to Miss J. TESCHand Mr. A. @YE. The preliminary note on the find aroused so Some drawings have been made by Mr. P. WINTHER, considerable interest among zoologists, and the whereas most of the originals have been produced animal proved to be of such importance for the by the authors themselves. Comparison with the interpretation of fossil forms, that it was decided to fossil material was made possible through the lay special stress on a detailed description. As, how- courtesy of Prof. E. STENSIOof the Museum of ever, the uniqueness of the find made it most impor- Natural History, Stockholm, and Mr. E. YOCHEL- tant to distinguish very clearly between the facts SON of the National Museum in Washington, both observed and their theoretical implications, whether of whom have sent us rubber squeezes of fossil systematical or phylogenetical, it was decided to Tryblidians. Prof. STENSIOhas also placed the publish the mere facts about the structure of Neo- beautiful photograph of Pilina unguis (Fig. 134) at pilina in the Galathea Reports at the very first date our disposal. The English text has been revised by possible, whereas the discussion of its consequences Mr. N. HAISLUND.TO all those who have helped us in phylogeny and systematics should be reserved for in these various ways, we wish to extend our most papers to follow elsewhere. cordial thanks. MATERIAL AND METHODS The material was obtained from station 716, 9' 23' sieves, the animals were preserved in 70 % ethyl N., 8gC32' W.%,3,570 m depth (corrected), "dark, alcohol (8 specimens) or 2 % formaldehyde (2 spec- muddy clay, herring otter trawl", on May 6th, 1952. imens). Later, all of them were transferred to one The sample contained 10 specimens with the soft jar with 70% ethyl alcohol. Originally, the empty parts preserved but more or less damaged, and shells were kept in the same jar with alcohol as three empty shells. The specimens were washed out the other specimens, but unfortunately an attempt of the muddy content of the trawl by means of was made afterwards to dry the shells, with the surface water at a temperature of 28"C., which must result that all of them broke to pieces. have killed the animals immediately, if they did not When in the autumn of 1956 the specimens came die already during the transport to the deck of the to be investigated and their importance was realized, ship from the abysses with its temperature of only it was decided very soon to give them individual 2°C. After lying some time on the deck and in the Roman numbers for easier registration, and to keep them apart from each other. Since then, the 1. After our manuscript was sent to the printer, a new species specimens been treated as shown in ~~bl~1. of Neopilinn was described (CLARKEand MENZIES1959). The main part of the investigation has been 2. In the Proceedings of the Zoological Congress (LEMCHE& WINGSTRAND1959) a misprint occurred in the longitude- carried Out on the two sectioned (IT1 and record. IV). These were refixed for three days in 80 % Table 1. The state of preservation and the use of the ipecimeils of Neol1111 -- - - - - - - --- - - - - -- - Spec. ' Length xbreadth State of preservation Use No. x height, mm. 1 Intact shell and intact soft parts. Holotype, untreated. Well preserved. Formalin fixation? Paraffin embedding attempted. An~maldid not stand treatment with acids. Practically lost. Mature $2. Apex preserved in spite of rupture in Cut into transverse sections. See text! Larval the apical region. Larval shell present. Probably shell preserved in a block of celloidin in alcohol. formalin fixation. Mature 3. Apex preserved, but slightly damaged. Cut into horizontal sections. See text! Apical region destroyed, liver collapsed, radula Kept untreated. Used for exhibitions. emerging from the hole. Ventral side relatively well preserved. VI ab. 25 x 22 x 9 Shell broken lengthwise, the right side of the Studies on gill position. animal slightly damaged along the margin. VII 37~35x13 A large hole in the apical region. Anterior end much damaged. VIII 37x ? XI2 Apical region present, but the whole right side Additional studies on the radula. of the animal
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