TAXONOMY , ECOLOGY , AND GEOGRAPHICAL DISTRIBUTION OF THE SPECIES OF THE GENUS Thermocyclops KIEFER , 1927 ( COPEPODA , CYCLOPOIDA ) IN SÃO PAULO STATE , BRAZIL , WITH DESCRIPTION OF A NEW SPECIES

The taxonomy and ecology of the cyclopoid copepod genus Thermocyclops were studied. Samples were collected in 207 water bodies located in the 22 hydrographic basins of São Paulo State, Brazil, including large reservoirs, small and shallow lakes, and ponds and rivers. The genus Thermocyclops inhabits mainly water bodies within a limnetic region. Four species were found, of which one is new: Thermocyclops iguapensis, which occurred in the reservoirs of the Ribeira do Iguape and Paraíba do Sul basins. The description of the new species and the geographical distribution of all four species in São Paulo State are presented. Thermocyclops decipiens was the most frequent species, occurring in 71% of the water bodies within a limnetic region. This species is characteristic of eutrophic environments where it can occur in great abundance, whereas Thermocyclops minutus is characteristic in oligotrophic systems. Thermocyclops inversus and Thermocyclops iguapensis n. sp. were not common but can occur together with Thermocyclops decipiens.


INTRODUCTION
The genus Thermocyclops Kiefer, 1927 (Copepoda, Cyclopoida) originated in the tropical region, in which it presents a high diversity of species (Dumont & Decraemer, 1977).In many tropical water bodies, this genus represents the most important component of the zooplankton biomass (Margalef, 1983).Despite the presence of the genus in South America, high diversity has not been recorded in this continent, as compared to the African and Asian continents (Rocha et al., 1995).In the Western Hemisphere, nine species and subspecies have been recorded (Reid, 1989), four of them occurring in Brazil (Rocha & Botelho, 1998).
The aim of this work was to evaluate the occurrence of the species of the genus Thermocyclops in the water bodies of São Paulo State, located in 22 basins that are under hydrographic management and which are referred to as hydrographic management units (HMU).

Fig. 1 includes two maps of São Paulo State
showing its 22 hydrographic basins as well as the hydrographic network with the main rivers where several reservoirs have been constructed in cascade to generate hydroelectricity.
Samplings were carried out during the period of 1999-2002.For each UHGRH, a minimum of 3 and maximum of 29 water bodies were sampled, including the limnetic and littoral regions of large and small reservoirs, as well as ponds and rivers.Geographical coordinates were determined at each site using a Garmin III GPS.
Zooplankton was collected by making vertical and horizontal hauls using a standard plankton net of mesh size 68µm.The samples were preserved in 4% formaldehyde and deposited in the Plankton Museum of the International Institute of Ecology.Species identifications were performed using only adult females.Drawings and measurements were made using an optical microscope with image acquiring system and drawing software (TurboCAD Version 6.5).
Samples obtained from Barra Bonita Reservoir during the period of September 1983 to October 1984 at fortnightly intervals, were analyzed to study the seasonal fluctuations of two species of Thermocyclops.

Description of the male
Fig. 3a shows the general aspect of the male.Antenna (Fig. 3b): 17 segments with geniculation in the 9 th and 15 th segments.Leg 5 (Fig. 3c): internal apical spine passing leg 6 insertion.
Etymology: A reference to the Ribeira do Iguape Hydrographic Basin where this species was found in high abundance.
Differential diagnosis: Thermocyclops iguapensis n. sp.differs from other American Thermocyclops species by a combination of characteristics such as intercoxal sclerite of legs 1-4 without spinular ornamentations on distal margins; ratio between the terminal spines of endopodite 3 of leg 4; and principally, the difference in the morphology of the receptaculum seminis.
Remarks: T. iguapensis n. sp. was recorded in the reservoirs of the Ribeira do Iguape Basin and in reservoirs of the Paraíba do Sul hydrographic basins by Sendacz & Kubo (1982) but was identified as T. minutus.
The figures (51 to 56) presented by the authors show characteristics similar to those presented by T. iguapensis n. sp. and differing from the characteristics of T. minutus, especially in the morphology of the receptaculum seminis.

Differential diagnosis and key for São Paulo
Thermocyclops species Fig. 4 shows the main differences presented by the four species of Thermocyclops found in São Paulo State: T. decipiens, T. inversus, T. minutus and T. iguapensis n. sp.
Thermocyclops iguapensis n. sp.: 4 th leg (Fig. 4-a4): intercoxal sclerite without ornamental spines in prominences on distal margins, 3 rd endopodite with outer apical spine 3.5 times longer than the inner (Fig. 4-b4).Receptaculum seminis (Fig. 4-c4): lateral arms slightly curved on the distal margin, pore canal short, and posterior margin located in the middle of the lateral arms.Caudal rami (Fig. 4-d4): 3.1 times as long as wide, lateral spine on the middle of the caudal rami, internal setae 2.6 times longer than the external.

Geographical distribution and frequency of occurrence of Thermocyclops species of São Paulo State
Among the Cyclopoida, the genus Thermocyclops is characteristic of the limnetic region of lakes.
Table 1 shows the number of water bodies studied in the 22 hydrographic basins of São Paulo State, the number of water bodies that present a limnetic zone, and the frequency of occurrence of the four species in each hydrographic basin.
Thermocyclops decipiens was the most frequent species, having been found in 71% of the water bodies with a limnetic region, and occurring in all the hydrographic basins with the exception of the Mantiqueira.Thermocyclops minutus was found in 25% of the water bodies with a limnetic region.This species occurred in a large number of the water bodies considered oligotrophic.It was distributed in the three largest river basins: Tietê, Parapanema, and Rio Grande, but was not found in the Mantiqueira, Litoral Norte, Baixada Santista, and Ribeira do Iguape basins.
Thermocyclops inversus and the new species, Thermocyclops iguapensis, were rare, the former occurring in 8% and the latter in 6% of the limnetic samplings.Both species occurred in several reservoirs of the Ribeira do Iguape Basin.Thermocyclops inversus was recorded also in water bodies from the Pardo, Alto Tietê, Mogi, Tietê/ Jacaré, Turvo Grande, and São José dos Dourados basins.Thermocyclops iguapensis was recorded only in the Ribeira do Iguape and Paraíba do Sul basins, so that its distribution was restricted to the hydrographic basins, which are coastal basins, located n. sp. in the east of São Paulo State where the rivers flow to the Atlantic Ocean.

Seasonal fluctuation of Thermocyclops populations in Barra Bonita Reservoir
Barra Bonita Reservoir is the first of six reservoirs constructed in cascade in the Middle Tietê River Basin (Fig. 1).The reservoir receives from the Tietê River all the domestic and industrial sewage produced in the metropolitan area of São Paulo, SP, as well as pollution from the Piracicaba River, another tributary.The reservoir presents eutrophic characteristics with high concentrations of phosphorus, nitrogen, and chlorophyll, and frequent presence of cyanobacterial blooms.The abundances in this reservoir of two species of Thermocyclops, T. deciepiens, and T. minutus, from September 1983 to September 1984, were analyzed at a time when the reservoir was meso-eutrophic.Both populations showed high abundances during the same periods (November-December and March-April).However, while Thermocyclops minutus disappeared completely in some periods (the end of July to October), Thermocylops decipiens occurred throughout the period (Fig. 6).

DISCUSSION
Thermocyclops iguapensis n.sp.was found only in two basins of São Paulo State: the Ribeira do Iguape and Paraíba do Sul.Sendacz & Kubo (1982) found it in the water bodies of those basins, but identified the species as Thermocyclops minutus.T. iguapensis n. sp. as well as T. inversus have narrow geographical distributions, being restricted to the hydrographic basins in the eastern part of São Paulo State.
The most frequent species, Thermocyclops decipiens, has wide geographical distribution occurring in many types of water bodies in all of the hydrographic basins, whereas Thermocyclops minutus is less widely distributed, thus indicating more restrictive ecological requirements.The occurrence of these two species in Barra Bonita Reservoir (which this time was meso-eutrophic) with similar abundances in some periods of the year and complete disappearance of Thermocyclops minutus in other periods (mainly in the winter and spring) indicates that the two species probably present some different ecological requirements.Much evidence shows that Thermocyclops minutus is common in oligotrophic and mesotrophic environments (Matsumura-Tundisi & Tundisi, 1976;Tundisi et al., 1997).Silva & Matsumura-Tundisi (2002) recorded clear patterns of dominance of Thermocyclops minutus over Thermocyclops decipiens in oligo-mesotrophic reservoirs and dominance of T. decipiens over T. minutus in eutrophic reservoirs.
The co-occurrence of Thermocyclops inversus and Thermocyclops decipiens in some eutrophic water bodies of the Ribeira do Iguape Basin (Iporanga and Jurupará reservoirs) showed that Thermocyclops inversus outnumbered Thermocyclops decipiens (Table 1).Thus, the former species probably has better adaptive strategies than does Thermocyclops decipiens in eutrophic systems.