(citados por primera vez para la Argentina) y Metopus es (previamente ... (Córdoba province, Argentina), at depths below 10·14 rn, io oxygeo depleted water.
Rev. Asoc. Cienc. Nat. LiJoral26 (1): 25 - 31 (1995)
CILIATED PROTOZOA FROM OXYGEN DEPLETED WATERS FROM CASSAFFOUSTH RESERVOIR (CORDOBA, ARGENTINA) María Foggetta and Andrés Boltovskoy Instituto de Limnología "Dr. Raúl A. Ringuelet" Casilla de Correo 712, 1900 La Plata, Argentina.
RESUMEN. Protozoos ciliadas oligoaerófilos del embalse Cassaffousth
(Córdoba, Argentina). Cinro especies de protozoos ciliados fueron enrontradas en muestras de plancton del embalse Cassaffousth, en profundidades por debajo de los 1O~14 m, en condiciones de bajo tenor de oxígeno: Plagiophyla nasuta, Saprodinium dentatum, Bruclwnello. spiralis, Caeonomorpha medusula (citados por primera vez para la Argentina) y Metopus es (previamente mencionado como M. sigmoides). Se presentan descripciones e ilustraciones de estos ciliados. ABSTRACT. Five species of ciliated protozoa were recorded in plankton samples collected during the surnmer in Cassaffoustb reservoir (Córdoba province, Argentina), at depths below 10·14 rn, io oxygeo depleted water.:; below the epilimnetic layer. The species in question are: Plagiophyla nosuta, Saprodinium dentatum, Brachonella spiralis, Caeonomorpha medasula (first rerords for Argentina), and Melopus es (previously registered as M. sigmoU1es). Desaiptions and ilIustrations of these ciliates are presented.
INTRODUCTION The ciliates Plagiophyla nasuta, Saprodinium dentatum, Metopus es, Braehonella spiralis aud Caeonomorpha medusula were fouud in plankton samples from CassatIousth reservoir. With the exception of Metopus es, aH are new records for Argentina. M. es was formerly citOO under a different name.
0325-2809195/26(t)-25 $2.00
Cassaffousth reservoir (Córdoba, Central Argentina, 32' 10' S, 64' 25' W) is a small subtropical monomietÍc water body 10eated 1 km downstream from tbe larger Río Tercero Reservoir. Its area is 88 hm, maximum volume 10.5 hm3, maximum deptb 28.7, mean deptb 11.9 m, and retention time 0.01 year (Boltovskoy &
©
Asoc. Cienc. Nat Litoral
25
Foggeta & Boltovskoy
Foggella, 1985). Ouring lhe sampling pe-
1-2% acetic acid, lo a drop of freshly
nad surface water temperature ranged be-
colected material.
tween 10· and 24· C. Secchi-disk readings varied between 3.5 (July) and 1.4 m (March). 10e laxa here described were found only during lhe summer (January and March, 1981), al deplbs below 10 lo
10e c1assification system adopted is that proposed by de Puylorac et al. (1974) and, more recently, by Tbe Commitee on Systemalics and Evolulion of lhe Sociely of Protozoologists (Levine et al., 1980).
14
ffi.
Temperature decreases from tbese
deplhs lo ca. 20 m are approximalely 7··8· C (from 22· C lo 14·-15· C), which points
TAXONOMY
al a stable thennocline, witb restricted
1. P/agiophyla nasula Slein, 1860 (Fig. 1).
water exchange between deep walers and superficia 1, more oxygena ted layers (BoIlovskoy & Foggella, 1985). Ouring lhe summer, below 16 lo 19 m (January and March, respeclively), lhe waler has a slrong hydrogen sulfide (H2S) odor, characteristic of oxygen depleled environments. During lhe studied period Ibis produclive
reservoir was charaeterized by blooms of chlorophytes (Closlerium aciculare and Sphaerocystis schroeteri), dialoms (Aulacoseira granulata) and dinoflagellales (Peridinium gatunense), lhe latter being domina nI during lhe slaguanl phase. MAlERIAL ANO METIIOOS 10e studied material was collecled bimonlhly, al deplbs from O m lo 20 m, be· tween July, 1980, and September, 1981. 40 liters samples were taken al one meter inlervals al between O and 10 m and every 2 m between 10 and 20 m, by means oí a submersihle cenlrifugal pump and fillered lhrough a 33 ~m mesh plankton nel. Samples were fixed with 1% formaldebyde salutian, retaining aliquots Coe
1860 P.n. Stein, Sitz. Ber. B6hm. Ges. Wiss. : 58, seco Levander, 1894, Acta Soco Fauna Flora fenn., 12 : 76. Body shape ovoid, lalerally compressed, wilh slender anlerior region. A slit-like buccal overture on the left side (ventral surface) of lhe body, distanl from lhe apex by 1/4 of lhe lolal body length, and open towards the transverse vestibular area.
10is area is a deep cilialed canal, eJ
