Stud Neotrop Fauna & Environm 35: 157–160 (2000)
0165-0521/00/3502-0157$15.00 © Swets & Zeitlinger
Description of Macrochaetus kostei n.sp (Rotifera, Trichotriidae) from a coastal lagoon of Rio de Janeiro, Brazil Susana José de Paggi1, Christina W.C. Branco2 and Betina Kozlowsky-Suzuki3 1National
Institut of Limnology, Santo Tome, Argentina of Natural Sciences,UNIRIO, Brazil 3Department of Ecology, Federal University of Rio de Janeiro, Brazil 2Department
Abstract A new rotifer is described and figured based on females taken from Comprida lagoon, Rio de Janeiro State, in southeastern Brazil. This new animal belongs to the Genus Macrochaetus which includes several species recorded in South America. A key to species of the Genus Macrochaetus of the Neotropical Region is presented. Keywords: Macrochaetus kostei n.sp., rotifer key, taxonomy, coastal lagoon, Brazil. Correspondence: C.W.C. Branco, Departamento de Ciências Naturais, Universidade do Rio de Janeiro, Rua Voluntários da Pátria 107, 22270-000, Rio de Janeiro RJ, Brazil. E-mail:
[email protected]
INTRODUCTION The Family Trichotriidae Bartos 1959 comprises genera with loricate head and body, foot freely moveable or with stiff joints and generally occurring among aquatic macrophytes and in plankton only as migrants (Koste & Shiel, 1989). In this paper a new species of Macrochaetus is described from plankton samples taken from Comprida lagoon. It is separated from the sea by a 50 m wide sand barrier and its littoral region is almost completely covered by aquatic macrophytes. RESULTS Macrochaetus kostei n. sp. (Fig. 1) Type material Populations of 乆乆 found in plankton samples of a coastal lagoon, State of Rio de Janeiro, collected in October and December of 1992, preserved in 4% formol. Type locality Comprida lagoon (22°17′S, 41°39′W), a Brazilian freshwater brown-colored shallow coastal lake which contains high concentrations of humic compounds, located in the coast of the State of Rio de Janeiro, southeastern Brazil. This lagoon has a surface area of 0.11 km2 and a maximum depth of 3.0 m. M. kostei was found in months characterised by low transpar-
ency of water (0.32–0.4m), average temperature of 23°C, suspended matter ranging between 1.2–4.8 g/l, low pH (3.27–4.3), water conductivity ranging between 0.12–0.18 mS/cm, and chlorophyll-a content of 1.2–1.5 µg/l. Holotype 乆 with contracted head in a permanent, glycerine glass slide mount, deposited in the type collection of the Museu de Zoologia da Universidade de São Paulo (MZUSP n.5835). Paratype One loose specimen vialed in 70% alcohol with glycerine, Museu de Zoologia da Universidade de São Paulo, MZUSP n.5836. Diagnosis This species resembles M. aspinus Segers and Sarma 1983, recorded from Roraima, Brazil, because of the total absence of any large spine. M. kostei differs from M. aspinus by its larger size, concave anteroventral and antero-dorsal margins, median longitudinal ridge on the dorsal plate, beginning with a triangular field under the anterior margin, the arched foot opening with lateral folds, and long second pseudosegment of the foot. Description 乆: lorica oval, transparent, surface covered with granules, without shoulder hooks, and no spines.
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Fig. 1. Macrochaetus kostei n. sp., A. dorsal view; B. ventral view. C. transversal section.
Dorsal and ventral margin concave. Lorica margin with minute spicules only on posterior region. Posterior part of body spineless. Dorsal ridge beginning with a triangular field under the anterior margin and extending the whole length of the lorica. Ventral plate flat. Anal segment absent. Foot with two pseudosegments, the first short, the second very long with a terminal short border, toes spindle shaped and very pointed.
Measurements µm) M. aspinus M. kostei n.sp. Lorica width Lorica length Foot pseudosegment length Toes length
72–76 76–82
102–108 135–147
17 18–19
43 22–25
NEW SPECIES OF ROTIFER FROM BRAZIL
Etymology M. kostei is dedicated to Dr. Walter Koste, who studied the rotifers of Brazil, and of other countries of South America for many years publishing numerous contributions. As a rotifer specialist, he always helped generously the beginner and advanced students in the identification of species.
DISCUSSION The genus Macrochaetus Perty was characterised mainly by the mobile spines on its loricated body. The total number of spines, including dorsal, posterior and anal spines ranges from 8 to 16 (Wulfert, 1964; Koste, 1978). However, in the last years M. danneeli Koste & Shiel, from Australia, and M. americanus Segers, from Brazil were described, both with only two pairs of posterior spines; M danneeli with rudiments of dorsal spines and M. americanus with a single pair of dorsal spines. Segers & Sarma (1993) described M. aspinus as spineless from Brazil. M. kostei closely resembles the latter, but it has particular characteristics such as the median ridge on the dorsal lorica, the wide foot opening, wider than in M. danneeli. Several species have been recorded in the Neotropical Region (Koste & José de Paggi, 1983; José de Paggi & Koste, 1995): M. altamirai Arevalo, M. americanus Segers & Sarma, M. aspinus Segers & Sarma, M. longipes Myers, M. multispinosus Myers, M. sericus (Thorpe), M. subquadratus, Perty and M. collinsi (Gosse). M. longipes, also recorded in the Neotropical Region, has an uncertain taxonomic status, and probably represents a form of M. collinsi (Wulfert, 1964; Gillard, 1967). The char-
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acter allowing differentiation between M. collinsi and M. longipes is the longer second foot pseudosegment in the latter. However, the ratio lorica length/foot pseudosegment length seems to be quite variable and there is a wide overlap in the specimens assigned to M. collinsi and M. longipes. In the first species the ratio is 2.6-5.0 (Green, 1960; Gillard, 1967; Koste, 1972; Koste & Shiel, 1989) and in M. longipes the ratio is 2.6-3.8 (Myers, 1934; Berzins, 1959; Koste, 1972; Koste, 1974). At present 3 species of the genus are known exclusively from the Neotropical Region (M. aspinus, M. americanus and M. kostei). With the exception of M. subquadratus, all South American species were recorded from Brazil, possibly due to the higher number of faunistic studies carried out there and the existence of environmental conditions which this genus seems to prefer, such as acidic and low salinity waters and warm temperatures (Table 1). M. subquadratus was recorded from colder areas (Thomasson, 1963; Schmid-Araya, 1991).
Key to Species of the Genus Macrochaetus of the Neotropical region: 1. Dorsal spines present .................................. 3 – Total absence of any large spines .............. 2 2 (1). With a dorsal median longitudinal ridge ..... ......................................................kostei n.sp. – Without dorsal median ridge ........................ ............................... aspinus Segers & Sarma 3 (1). With only 2 dorsal spines; 4 posterior spines ......................... americanus Segers & Sarma – With more than 2 dorsal spines .................. 4
TABLE 1. Macrochaetus in the Neotropics: environmental variables of sampling localities. Species
Temperature (°C)
pH
O2 (mg/l)
Conductivity (µS/cm)
M. sericus
12 – 33
5.7 – 8.4
3.0 – 5.0
15 – 550
M. multispinosus M. altamirai M. collinsi s.l.
– 27 23 – 30
5.4 7.0 5.5 – 7.5
– 4.0 1.3 – 5.9
12 63 11 – 1846
M. americanus M. aspinus M. kostei n.sp.
36.6 36.6 21 – 30
5.3 5.3 3.4 – 6.1
7.1 7.1 3.2 – 8.8
5.7 5.7 9 – 340
References
Hauer,1965; Zoppi de Roa et al., 1993; José de Paggi, 1996; Brandorff et al., 1982; Koste & Böttger, 1989; Koste & Böttger, 1989; Dabés, 1995; José de Paggi, 1996; Segers & Sarma, 1993; Segers & Sarma, 1993; this study
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4 (3). With 4 dorsal spines. ................................... 5 – With more than 4 dorsal spines .................. 6 5 (4). With 4 posterior spines and without anal segment .............................. sericus (Thorpe) – With anal segment, some specimens with 2 spines on the foot segment ........................... .......................................... collinsi sensu lato 6 (4). With 6 dorsal spines, 4 posterior spines, and anal segment with 2 spines ........................... ........................................ altamirai (Arévalo) – With more than 6 dorsal spines ................. 7 7 (6). With 8 dorsal spines, 4 posterior spines, anal segment with 2 spines ................................... ....................................... subquadratus Perty – With 10 dorsal spines, 4 posterior spines and anal segment with 2 spines ........................... .................................... multispinosus Myers.
ACKNOWLEDGMENTS We are grateful to Walter Koste (Quakenbrück, Germany) for his helpful drawings and encouragement.
REFERENCES Berzins (1959): Rotatorien aus Französisch West-Afrika. Bull Ifan 21, Ser A3: 921–933. Brandorff GO, Koste W, Smirnov N (1982): The composition and structure of Rotiferan and Crustacean communities of the lower Rio Nhamundá, Amazonas Brazil. Stud Neotrop Fauna & Environm 17: 69–121. Dabés MBGS (1995): Composição e descrição do zooplâncton de 5 lagos marginais do Rio São Francisco, Pirapora/Três Marias/Minas Gerais, Brazil. Revta Brasil Biol 55: 831–845. Gillard AM (1967): Rotiferes de l’Amazonie. Bull Inst r Sci Nat Belg 43: 1–20. Green J (1960): Zooplankton of the River Sokoto. The Rotifera Proc Zool Soc London 135: 491–523.
Hauer J (1965): Zur Rotatorienfauna des Amazonasgebietes. Int Ver Ges Hydrobiol 50: 341–389. José de Paggi S (1996): Rotifera Monogononta diversity in subtropical waters of Argentina. Ann Limnol 32: 209– 220. José de Paggi S, Koste W (1995): Additions to the checklist of rotifers of the Superorder Monogononta recorded from Neotropics. Int Rev Ges Hydrobiol 80: 133–140. Koste W (1972): Rotatorien aus Gewässern Amazoniens. Amazoniana 3: 258–505. Koste W (1974): Über Rotatorien aus einem Ufersee des unteren Rio Tapajós, dem Lago Paroni. Gewässer und Abwässer 53/54: 43–68. Koste W (1978): Die Rädertiere Mitteleuropas (Monogononta) Bestimmungswerk Begründet von Max Voigt. 2 Vols, Borntraeger, Stuttgart, 673 pp. Koste W, José de Paggi S (1983): Rotifera of the Superorder Monogononta recorded from Neotropis. Gewässer und Abwässer 68/69: 71–102. Koste W, Shiel RJ (1989): Rotifera from Australian inland waters. III. Euchlanidae, Mytilinidae and Trichotriidae (Rotifera: Monogononta). Trans Royal Soc South Australia 113: 85–114. Koste W, Böttger K (1989): Rotatorien aus Gewässern Ecuadors. Amazoniana 10: 407–438. Myers FJ (1934): The distribution of Rotifera on Mount Desert Island, Part 5. Amer Mus Novitates 700: 1–16. Segers H, Sarma SSS (1993): Notes on some new or little known Rotifera from Brazil. Revta Hydrobiol trop 26: 175–185. Schmid-Araya J (1991): Distributional aspects of Rotifera in Central and South Chile. Arch Hydrobiol 120: 481– 493. Thomasson K (1963): Araucanian Lakes. Acta Phytogeogr Suec 47: 481–493. Wulfert K (1964): Unsere gegenwärtige Kenntnis der Rotatorien – Gattung Macrochaetus. Limnologica Berlin 2: 281–309. Zoppi de Roa E, Pardo MJ, Vasquez W (1993): Nuevas adiciones a la fauna de rotíferos de Venezuela. Ver Hydrobiol trop 26: 165–173.
Received: 20 April 1998 Accepted: 20 August 1999
