A NEW WATER MITE OF THE GENUS TORRENTICOLA PIERSIG , 1896 ( ACARI , TORRENTICOLIDAE ) FROM CENTRAL SPAIN

The water mite Torrenticola eureka n. sp. is described from streams of the Sierra de Guadarrama, in the center of the Iberian Peninsula. This species belongs to the subgenus Megapalpis Halbert, 1944, characterized by a long, curved rostrum and P-II longer than PIV. T. eureka n. sp. can be separated from the other species of the subgenus by the proportions of the palp segments, the size of the palp in relation to body size and the length of the cheliceral claw.


Introduction
Water mites of the genus Torrenticola Piersig, 1896 show great evolutionary success, with several hundred species and subspecies described worldwide (K.O. Viets, 1987).Sixteen species are known from the Iberian Peninsula including those found in the Pyrenees (Valdecasas, 1988).In the present work a new species of the subgenus Megapalpis Halbert, 1944 is described.This subgenus was later synonymised with Torrenticola by Lundblad (1956) and reinstalled by Gerecke and Di Sabatino (1996).

Methods and sampled habitat
Sampling was carried out on the 13 July 1978.Samples were taken by "kicking" the stream bottom    (1974).Measurements of the holotype are given first, with the range found for 3 additional males in brackets.The measurement range for the female is based on 4 specimens.Ratios can be problematic for discrimination purposes (e.g. Simpson et al., 1960;Atchley et al., 1976;Sokal & Rohlf, 1981).I avoid them in this work.No derivatio nominis is provided, name given is arbitrary.
The ventral shield is narrowed towards the anterior end; ventral length up to the anterior end of the first coxae 700 µm (720-750 µm), width 460 µm (470-488 µm); the capitular bay is U shaped, 110 µm (102-110 µm) in depth and 65 µm (65 µm) in width; the distance between the posterior end of the capitular bay and the anterior end of the genital area is 205 µm (205-210 µm); the disposition of the ventral glandularia is illustrated in (Fig. 1B); the extended depth of focus for the ventral shield of the holotype is shown in Fig. 2B; the genital area is irregular elliptical in shape, 138 µm (138-152 µm) in length, 110 µm (110-124 µm) in width; Fig. 1F, shows the ejaculatory complex and Fig. 2C, its extended depth of focus image; the delimitation line of the fourth coxae has a curved prolongation towards the posterior end in an ample arch, at the end of this arch there is a muscular mark.The excretory pore lies slightly anterior to the glandularia beside them; the distance between the posterior end of the genital area and the excretory pore is 195 µm (195-225 µm).
Fig. 1E shows the ventral shield; total ventral length up to the anterior end of the first coxa 765-858 µm; the capitular bay is 120 µm deep and 70 µm wide; the distance between the posterior end of the capitular bay and the anterior end of the genital area is 165 µm; the genital field is 170-195 µm long and 160-183 µm wide; the distance between the posterior end of the genital field and the excretory pore is 215 µm.
Torrenticola pugionirostris, T. rampha and T. rampha malayensis have been found in Java, Burma, Malaysia and Thailand.T. distans has been found in South Africa.T. macerirostris was described from Israel and T. jasminae from Iran.T. thori was described from Ireland.The other species inhabit the Mediterranean basin (Di Sabatino et al. 2003).
The present species is close to T. tenuirostris, but can be clearly distinguished from it by the smaller size of the palp segments despite the larger body size.It is distinguished from the other species of the subgenus by the different size relations of the palp segments.Besides this, the body length/width combinations, lengths of capitulum and chelicera have a range of values that is not present in any other species of the group.Additional characters to distinguish this species from the other species are that T. thori, T. andrei, and T. rampha have a P-IV of similar or longer size than P-II and that T. distans and T. andrei have a cheliceral claw that is almost half the size of the chelicera.T. fagei, T. trinacriae and T. pugionistris have a longer palp.T. remyi has a much longer capitulum and chelicera than the present species.T. macerirrostris is slender and has a longer rostrum.T. thori and T. andrei (considered as synonymous by Lundblad, 1956) have a long, narrow body.T. fagei and T. remyi have a body length/width proportion that makes them more rounded in comparison.T. jasminae has a small ventral tubercle at setae insertion site in P-II and P-III.