THERMOCYCLOPS

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THERMOCYCLOPS, KIEFER, 1927, (syn. Mesocyclops Thermocyclops) (subgenus)

First antenna with 17 segments reaching beyond the
cephalothorax. Last segment of fifth leg of female with
2 long setae. Inner setae on caudal branch more than twice
as long as outer setae. Last segment of fifth leg of female with two terminal setae. First antenna without hyaline plate. Planktonic.
Copepodits feed on zooplankton and phytoplankton when
it is abundant. Mainly tropical species. Often found together with Mesocyclops in the plankton, e.g. Laguna de Bay (Petersen, 1981e). It is presumed that the smaller and larger species use different food sources. See Ueda & Reid (2003a) for at comprehensive key of the genus.

142 a. Connecting plate on fourth pair of legs without spines on outgrowth. Caudal branch 2 times as long as wide. Longest terminal setae not curved in Lanao material, but slightly curved in Papua New Guinea material. Receptaculum seminis with thin head, curved slightly posteriorly. Size 560-600 μm. Differ morphologically from T. crassus in Lake Lanao only with regard to length and length ratio. Thermocyclops wolterecki thus appears to be a sibling species of T. crassus or possible even just a morphotype (Lewis 1979b). Herbst 1986 (se Herbst 1986c) however, accept the status as species in his key of Thermocyclop. Planktonic in lakes. Endemic for Mindoro and Papua New Guinea.
- Lake Lanao, Mindanao.
   Thermocyclops wolterecki, (KIEFER, 1938)
             [1938a, 1941a, 1969, 1986c, 2002a, 2003a]

142 b. Connecting plate on fourth pair of legs with spines on
outgrowth..................................................143

143 a. Longest terminal seta curved at the tip and is 120-230 μm. The wings of receptaculum seminis with broad head, not bended backwards. Caudal branch 2-2 ¹/2 times as long as wide. Connecting plate on fourth pair of legs with spines on outgrowth. Size 560-800 μm. Feeds on diatoms (e.g. Nitzchia),bluegreen algae (e.g. Anabaena) and cryptomonads. A preference for elongate filaments or unicels has been found in Lake Lanao (Lewis 1979b, se also Fernando 1980).
The abundance per unit area increased towards deeper water in Lake Lanao. The ephemeral patchiness increased with progressive stages in life history (Lewis, 1978d). Dominating the zooplankton biomass and production in Laguna de Bay together with Mesocyclops leuckarti in 1980 (Petersen, 1981e). Eurytherm. Planktonic in ponds and lakes. Very common all over the Philippines. (Figures 143a¹, 143a², 143a³, 143a⁴, 143a⁵, 143a⁶, 143a⁷, 143a⁸, 143a⁹)
- Laguna de Bay (nauplii, copepodits C2+C3, C4,
female C5, female, male C6), Paoay Lake, La Mesa Dam,
Bunot Lake, Calibato Lake, Taal Lake, Naujan, Lake Lanao
   Thermocyclops crassus, (FISCHER, 1853)
   (syn. Mesocyclops (Thermocyclops) hyalinus)
             [1938a, 1941a, 1978a+b, 1978d (T. hyalinus),
             1979b, 1980, 1984a, 1986a, 1986c, 2001a,

                     2008e,2011a]

T. crassus Female from Laguna de Bay

143 b. Longest terminal setae not curved at the tip.
The wings of receptaculum seminis with thin head,
bended slightly backwards...............................144

144 a. The membrane connecting the bases of the fourth pair of
legs (swimming feet) has two rounded processes, with a
number of small spines on. Caudal branch 3 times as
long as wide. Longest terminal setae not curved.
Longest setae not curved. Receptaculum seminis with
thin head. In freshwater. Abdomen covered with small
dots in rows. Size of female 900-1000 μm.
- Manila area
   Thermocyclops philippinensis (MARSH, 1932)
   (syn. Mesocyclops Thermocyclops philippinensis)
             [1932, 1986c, 2002a, 2003a]

144 b. The membrane connecting the base of the fourth pair
of legs (swimming feet) has two high and slime
outgrowth with bigger spines on. Caudal branch
2½ times as long as wide. Longest setae not curved.
Receptaculum seminis with thin head. Size of
female 760-790 μm. Planktonic in alkaline
lakes and reservoirs.
- Naujan Lake
   Thermocyclops decipiens, (KIEFER, 1938)
             [1938a, 1941a]

144 c. In Lake Mainit is found a fourth species, different from the species mentioned above.
- Lake Mainit
              [1973]

Note:   Thermocyclops species in the "vicinity" of the Philippine Islands are:
T. operculifer (KIEFER, 1930) [Indonesia: Lesser Sunda Islands, Cambodia, and Vietnam],
T. trichophorus, KIEFER 1930 [Java],
T. taihokuensis (HARADA 1931) (syn. T. asiaticus (KIEFER 1932) [Taiwan (Formosa), China, Vietnam],
T. ianthinus (HARADA, 1931) [Taiwan],
T. orientalis DUSSART & FERNANDO, 1985 [Sri Lanka, Malaysia, and Indien (?)].
(See 2003a, Herbst 1986c)

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