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© Sociedad Española de Malacología Iberus , 19 (2): 23-30, 2001 The presence of Simrothiella borealis (Odhner, 1921) (Mollusca, Solenogastres: Simrothiellidae) in waters off the Iberian Peninsula Presencia de Simrothiella borealis (Odhner, 1921) (Mollusca, Solenogastres: Simrothiellidae) en aguas de la Península Ibérica Óscar GARCÍA-ÁLVAREZ *, Luitfried v. SALVINI-PLAWEN ** and Victo - riano URGORRI* Recibido el 10-XI-2000. Aceptado el 31-VII-2001 ABSTRACT This paper offers a description of a species hitherto unknown in Iberian waters, Simrothie - lla borealis (Odhner, 1921), and which has only been cited off the Norwegian coast. The genera of the family Simrothiellidae are discussed and the species of the genus Simrothie - lla are compared. RESUMEN En este trabajo se estudia una especie desconocida para las aguas ibéricas, Simrothiella borealis (Odhner, 1921), que solamente estaba mencionada en las costas noruegas. Se discuten los géneros de la familia Simrothiellidae y se comparan las especies del género Simrothiella . KEY WORDS: Simrothiella borealis , Mollusca, Solenogastres, Galicia, Iberian Peninsula. PALABRAS CLAVE : Simrothiella borealis , Moluscos, Solenogastros, Galicia, Península Ibérica. INTRODUCTION Simrothiella borealis (Odhner, 1921) is a rothiella minima (Nierstrasz, 1903) is species hitherto known only off the Nor - known from the Gulf of Naples ( NIERS - wegian coasts ( ODHNER , 1921), its pre - TRASZ AND STORK , 1940) ; and Simrothiella sence in Galician waters (NW Spain) schizoradulata Salvini-Plawen, 1978 and extends its known distribution conside - Simrothiella (?) rhynchota Salvini-Plawen, rably. At present, four species of the 1978 have been located in Antartic and genus Simrothiella Pilsbry, 1898 are Subantartic zones ( SALVINI -P LAWEN , known, all of them have a geographical 1978 ). The family Simrothiellidae Salvini- distribution restricted to clearly defined Plawen, 1978, characterised by: hollow or areas and depths between 75 and 5931 m. solid acicular spicules; a biserial radula; a Simrothiella margaritacea (Koren and partially paired radular sac; type C epit - Danielssen, 1877) has been cited from helial ventral foregut glandular organs Norwegian waters ( ODHNER , 1921) ; Sim - (GARCÍA -Á LVAREZ , S ALVINI -P LAWEN AND * Laboratorio de Zooloxía Mariña. Departamento de Bioloxía Animal. Facultade de Bioloxía. Universidade de Santiago de Compostela. 15706 Santiago de Compostela. España. E-mail [email protected], [email protected] ** Institut für Zoologie. Universität Wien. Althanstrasse, 14. A-1090 Wien IX. Austria. 23 Iberus , 19 (2), 2001 URGORRI , 2001), is at present formed by manganesic nodules, calcareous plates six genera (Table I) with regard to which and coal slag stones of terrigenous there are, as in the cases of Helicoradome - origin, at a depth of 835 m. The speci - nia y Birasoherpia , serious doubts about men was fixed and preserved in 70% their appropriate classification. alcohol. The spicules were studied by separation of small pieces of cuticle from the central dorsal area of the body MATERIAL AND METHODS and from the ventral groove. These pieces were treated with 5% sodium The specimen studied, of 4.2 mm in hypochlorite for 12 hours in order to length and 1.5 mm in width at the ante - isolate the spicules; they were them rior part and 1 mm at the posterior part rinsed with distilled water, dried under (sectioned in seriated cuts), comes from a heater at 40ºC and mounted using the fishing bank A Quiniela, situated to synthetic resin. For the anatomical the West of the Galician coast (NW study, the specimen were decalcified in Spain), station M-5 (43° 15’ 90” N; 09° an ethylenediaminetetracetic acid 36’ 36” W) of the CANGREXO I campaign (EDTA) solution 12 hours, embedded in for the study of the brachyuran decapod paraffin and a series of 10 µm cross sec - Chaeceon affinis (A. Milne Edwards and tions cut. which were stained with Azan Bouvier, 1894) (“cangrexo real”), carried of Heidenhain. The anatomy was out in June 1991, on bottoms with ferro - reconstructed from the serial sections. RESULTS Order CAVIBELONIA Salvini-Plawen, 1978 Family SIMROTHIELLIDAE Salvini-Plawen, 1978 Genus Simrothiella Pilsbry, 1898 Simrothiella borealis (Odhner, 1921) Description of the specimen below the pharynx (Fig. 2A), which is studied . Habitus : This animal has a thick connected to the outside by a narrow body, which is somewhat flat dorso-ven - opening. The pedal groove has a ciliated trally, no lumps and no keel (Fig. 1A). fold, which begins in the pit and enters The spicules project radially from the the pallial cavity. cuticle, those located right at the back Pallial cavity : The pallial cavity (Fig. are longer and project backwards. It has 3A) is connected to the outside by a a clearly visible pedal groove. In narrow ventro-terminal opening. It has alcohol, its colour is yellowish white. 10-12 longitudinal respiratory folds, Mantle : The cuticle is up to 40 µm which are long, thin and radially thick, below it is the epidermis with arrayed (Figs. 3A, C). It possesses a papillae. The spicules are arrayed in couple of strong copulatory spicules, several layers within the cuticle and which are situated ventro-laterally to many of them project radially from it. the spawning duct. At the distal end, The spicules are hollow and acicular in each copulatory spicule has two smaller form (Fig. 1B), some of them are curved lateral spicules, which very closely and up to 390 µm in length and others follow the path of the central copulatory are slightly sigmoidal and up to 230 µm spicule. Besides, each copulatory spicule in length. On the pedal groove there are is accompanied by a voluminous mid - blade shaped scales of up to 100 µm in dorsal diverticle, which emerges from length (Fig. 1C). the front of the pallial cavity (Figs. 3A, Pedal groove : The pedal groove B). The spawning duct open unpaired in begins in a ciliated pedal pit situated the centre of the frontal wall of the 24 GARCÍA -Á LVAREZ ET AL .: Simrothiella borealis in the Iberian Peninsula Table I. A comparative table of the generic traits of the genera belonging to the family Simrothie - llidae. Tabla I. Tabla comparativa de las características de los géneros pertenecientes a la familia Simrothielli - dae. Simrothiella Cyclomenia Biserramenia Birasoherpia Helicoradomenia Spiomenia Cuticle Thick Thick Thin Thick Thin Thick Hollow acicular Hollow acicular Spicules Hollow acicular Hollow acicular Hollow acicular Massive acicular Hollow harpoon-like Hollow knife-like at the end Mouth In the atrium Not in the atrium Not in the atrium In the atrium In the atrium In the atrium Biserial. Plates Biserial. Plates Biserial. Plates Biserial. Plates Biserial. Plates Biserial. Plates with 1 large with larges and Radula with small lateral with small lateral with small lateral a with few large distal denticle and small lateral denticles denticles denticles lateral denticles small lateral denticles denticles Postbuccal glandular No No No Yes No No organs Ventral foregut Tipo C Tipo C Tipo C No Tipo C Tipo C glandular organs Globular Globular Short Globular Short tubular Large tubular Dorsoterminal sense Yes Yes No Yes Yes Yes organ Copulatory spicules Yes Yes No Yes Yes Yes Respiratory folds Yes Yes No Yes Yes Yes pallial cavity, and the anus is located pharyngeal glands (Fig. 2A). The radula dorsally to the genital pore (Fig. 3A). is located in a ventral groove of the Sense organs and nervous system : On pharynx, it has strong ventral muscula - its dorsal and lateral walls, the atrium ture with massive cells situated longitu - has numerous, long, narrow papillae, dinally along both sides of the radular which may be individual or form groove (Figs. 2A, B). The radula is bise - groups of two or four (Fig. 2A). The rial and each row is formed by pairs of only atrio-buccal space is connected to pectinated plates, of about 50 µm in the outside ventro-anteriorly via a length with 60 small denticles (Fig. 1D). narrow longitudinal opening. It has just A short narrow radular sac (30-40 µm in one dorsoterminal sense organ, situated length) is situated ventrally to the above the middle part of the pallial oesophagus (Figs. 2A, C). The short cavity (Figs. 3A, C). The only part of the ventral foregut glandular organs are nervous system that it was possible to epithelial (type C) ( SALVINI -P LAWEN , see was a short cerebral ganglion (40-50 1978), and opens laterally in the µm), situated above the pharynx (Fig. pharynx on both sides of the beginning 2A). of the radula (Figs. 2A, B). The structure Digestive tract : The mouth opens of these organs is tubular at the front from the posterior area of the atrium near the opening, whilst at the rear it (Fig. 2A). It continues in a pharynx has a globular aspect which continues which has longitudinal folds on its below the oesophagus. The pharynx walls. The back of the pharynx is continues into a short oesophagus surrounded by musculature and has which opens through a sphincter in the 25 Iberus , 19 (2), 2001 1 mm A B D C 100 µm 20 µm Figure 1. Simrothiella borealis (Odhner, 1921). A: habitus; B: acicular spicules; C: spicules along the edges of the pedal groove; D: radula plates. Figura 1. Simrothiella borealis (Odhner, 1921). A: habitus; B: espículas huecas aciculares; C: escamas de los bordes del surco pedio; D: placas radulares. centre of the midgut (Figs. 2A, C). The dorsal wall of the pericardium (Fig. 3A). midgut has a short dorso-rostral caecum The pericardioducts (Fig. 3A) begin at (Fig. 2A), and has seriated lateral cons - the back of the pericardium, and curve trictions due to the dorso-ventral mus - forwards until they join the anterior part culature. The digestive tract opens into of the spawning duct. The two spawning the pallial cavity through the anus, ducts have a lobular frontal wall, which situated dorsally to the genital pore (Fig.