Studi Trent. Sci. Nat., Acta BiolBiol..,, 81 (2004): 53-77 ISSN 0392-054253 © Museo Tridentino di Scienze Naturali, Trento 2005

The water mites of the genus Acherontacarus (Acari, Acherontacaridae): a revision

Reinhard GERECKE1* & Daniele BENFATTI2

1Biesingerstraße 11, D-72070 Tübingen, Germany 2Quistello, Mantova, Italy, 31.08.1957-06.07.2004 *E-mail of the correspondence author: [email protected]

SUMMARY - The water mites of the genus Acherontacarus (Acari, Acherontacaridae): a revision - The taxonomy of the water mites of the genus Acherontacarus is revised and new locality records are published for A. rutilans Angelier (Corsica, Sardinia, Spain, Morocco), A. vietsi Angelier (Corsica, Sardinia) and A. tuberculatus Bader (Morocco, Spain). Three species are described as new to science: Acherontacarus raphani from the Peloponnes, A. cyprioticus from Cyprus and A. ruffoi from Andalusia. The larval stage is described for the first time for A. vietsi, A. tuberculatus, A. raphani and an undefined species from southern Italy, and redescribed for an unknown species (A. halacaroides K.Viets / A. fonticolus K.Viets?) from Macedonia. Larvae of all studied species display distinct characters that allow for discrimination at species level. They parasitize water beetles of the families Dytiscidae and Hydraenidae, attaching with their mouthparts to the outer surface of the hosts body, not in the subelythral space.

RIASSUNTO - Idracari del genere Acherontacarus (Acari, Acherontacaridae): una revisione - Nel presente lavoro si presenta la revisione tassonomica delle idracnelle del genere Acherontacarus, segnalando nuovi dati sulla distribuzio- ne per A. rutilans Angelier (Corsica, Sardegna, Spagna, Marocco), A. vietsi Angelier (Corsica, Sardegna) e A. tuberculatus Bader (Marocco, Spagna). Vengono descritte tre specie nuove per la scienza: A. raphani del Peloponneso, A. cyprioticus di Cypro e A. ruffoi dell’Andalusia. Viene fornita inoltre la prima descrizione dello stadio larvale per A. vietsi, A. tuberculatus e A. raphani e di una specie ancora da definire trovata in Italia meridionale. Viene ridescritta inoltre la larva di un’altra specie finora sconosciuta (A. halacaroides K.Viets / A. fonticolus K.Viets?) della Macedonia. Le larve di tutte le specie studiate sono determinabili a livello di specie. Sono parassite di coleotteri acquatici appartenenti alle famiglie Dytiscidae e Hydraenidae, sulla cui superficie corporea esterna (non nello spazio subelitrale) si fissano con il loro apparato boccale.

Key words: Mediterranean, interstitial and spring waters, water beetles, water mites, new species Parole chiave: Mediterraneo, acque interstiziali e sorgive, coleotteri acquatici, acari acquatici, specie nuove

1. THE WATER MITE GENUS ACHERONTACA- Africa (Hydrovolziella Walter, 1935) merit further RUS K.VIETS, 1932 investigation (Tuzovskij et al. 2001). Last not least, records of Acherontacarus species are rare events and Water mites of the genus Acherontacarus are come generally from particular groundwater-influen- exciting animals from several points of view: At first, ced habitats such as springs, deep wells, and hyporheic the aspect of their idiosoma, covered by a harmonious sediments. While K. Viets (1934) in his first description pattern of sclerite plates which appear assembled like of an Acherontacarus larva in view of its large size a cabinet-maker’s tongue and groove system (e.g. Figs hypothesized a direct development excluding a 2A, 7), is highly esthetic. Secondly, unique character parasitic-phoretic stage, Benfatti & Gerecke (1999) states found in all species of the genus Acherontacarus described the parasitism of several species on beetles indicate a high phylogenetical age of this clade. of the families Dytiscidae (Agabus, Deronectes) and Tuzovskij et al. (2001) proposed therefore ranking the Hydraenidae (Hydraena) and proposed to explain the genus in a family Acherontacaridae, as the sister group existence of a rather high number of localized of Hydrovolziidae in the monophyletic superfamily Acherontacarus species with a particular selectivity Hydrovolzioidea. Phylogenetic relationships between of their larvae for hosts with a delimited flight activity. this family and members of two Hydrovolzioid genera So far, Acherontacarus species have been recorded only from India (Bharatovolzia Cook, 1967) resp. tropical from a restricted part of the western palaearctic (central 54 Gerecke & Benfatti Water mites of the genus Acherontacarus and western mediterranean basin and Makaronesia). SMNH= Swedish Museum of Natural History Stock- Our new record from Cyprus extends the distribution holm; W= width. If no collector is named, specimens area to the eastern Mediterranean. of new records were taken by Gerecke. The aim of this paper is to summarize new records from field work during the past two decades, to revise and discuss the diagnostic features of all previously 3. RESULTS AND DISCUSSION known species, and to describe three new species from various parts of the Mediterranean area. Furthermore, Genus Acherontacarus K. Viets, 1932 we give first insight into the particular morphological Acherontacarellus Lundblad, 1962; Acherontacaropsis diversity at the larval stage. In striking contrast to Cook, 1967; Neoacherontacarus Bader, 1989 (Benfatti representatives of the sister family Hydrovolziidae and & Gerecke 1999) other early derivative families, acherontacarid larvae are (Figs 1-17) “aquatic” (vs. attacking their host under water, attaching to the external surfaces of their hosts, and bathed by Diagnostic features (following Tuzovskij et al. 2001) water when the host is submerged). For this reason Larva (Figs 16, 17) parasitic larvae are more easily detected than the “terrestrial” larvae of members of Eylaoidea and Unique among water mites due to the presence of Hydryphantoidea which parasitize in the subelythral numerous acetabula on the coxae (in other clades one, space, attacking water beetles from the water surface. rarely more than one pair(s) of so called “urstigmata”, At the early beginning of our studies stood the always restricted to the interspace between Cx-1 and submission of parasitized water beetles by Ignacio Cx-2), legs with terminal segments not narrowed Ribera (Madrid) to the senior author. The publication distally and with a claw furrow (in other clades found of this paper has been announced since several years only in deutonymphs and adults) and the pedipalp (Benfatti & Gerecke 1999). It has been postponed again tarsus bearing a high number of long setae. Lateral and again due to new records that contemporarily eyes located along with two setae on platelets at the enlarged and complicated our scenario. Several field level between I-/II-L insertions; mouth opening trips undertaken unsuccessfully in order to detect adults surrounded by a ring of membranous papillae, with a of populations observed in southern Italy further delayed pair of fine postoral, and a pair of stronger, variously our investigations. The very sad sudden death of the modified, preoral setae. junior author in summer 2004 induced now the senior Deutonymph (Fig. 15) author to summarize the work done until now. These results are published in the memory of my dear friend Similar to larvae and adults in the presence of Daniele. Together we projected this paper in the hope to acetabula on the coxae, to adults furthermore in the encourage further investigation about the open questions presence of three or more pairs of dorsolateral platelets concerning the mites of this family, as they are outlined (in Hydrovolziidae only two pairs); as typical for this in the following revision. stage in all hydrovolzioids, genital field completely lacking sclerotized structures. Adults (Figs 1-14) 2. MATERIALS AND METHODS Differing from hydrovolziids in (1) a stable number This study is based both on slide-mounted material of ten paired circumdorsal platelets, (2) ventral sclerite from several museum collections, and fresh material, plates (coxae, genitalia 1-3, excretale, postexcretale) mostly (if no collector name is given) from the author’s assembled to a continuous shield covering the whole own collections. The terminology of the ventral plates ventral surface, and (3) secondary sexual differences follows Bader (1989): genitale 1= the medial platelet in the distal segments of male IV-L and (as in deuto- located anterior to the genital field, genitale 2= lateral nymphs and larvae) the presence of numerous aceta- platelet anterior to the genital field (in deutonymphs, bula in the lateral parts of the coxae; dorsal shields only one pair of sclerite plates is present in the area with eight setae (four on predorsale, four on postdor- between Cx-1+2 and excretale, here called “genitale sale) on the postdorsale arranged or at the very edge 1/2”), genitale 3= plate flanking the genital field, of the shield (in species bearing regularly arranged excretale = plate located caudally from the genital field, marginal tubercles), or distanced from the edge (in postexcretale= plate located posterior from the species with smooth plate margins); basal segments excretale. The following abbreviations are used: Cx= of all appendages globuliform (often remaining in situ coxa(e); L= length; I-L-1= first leg, first segment; during detaching of palps and legs); legs robust, with MNHA= Museum of Natural History, Amsterdam; particularly elongated segments 2 and 6, covered by NHMB= Naturhistorisches Museum Basel; P-4= palp high numbers of differentiated setae, each bearing a segment 4; SMF= Senckenberg Museum Frankfurt; pair of long simple claws, I-/II-L-6 with a dense collar Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 55 of fine setae and one peg-like seta near the claw furrow; Female palps without sexual differences, P-4 with two peg- Maximum W in the lateral idiosoma margin like setae on the mediodistal surface, P-5 with anterior from Cx-3 or on the level of Cx-3, but these numerous long, knife-like claws. not strongly projecting; genitalia 1 medially separated Male from each other by the elongated genital field, genital flaps generally subdivided into four pairs, the anterior Maximum W on the level of the strongly projecting one bearing one, the posterior two pairs of setae, su- Cx-3; genitalia 1 medially in touch anteriorly from the ture line Cx-3/4 running to the lateral margin of ge- nearly round or subrectangular genital field, genital nitale 3 (and therefore medial margins of Cx-3 in flaps continuous, with two to six pairs of setae, suture touch with the circumgenital field), excretale line Cx-3/4 running into the suture Cx-2/3 (and quadrangular. therefore Cx-3 not in direct contact with the circumgenital field); genital field round; excretale hexagonal (with truncated lateral edges); IV-L Acherontacarus halacaroides K. Viets, 1932 modified, obviously as a grasping organ for mating: (Figs 2, 6A, 9C, 15A) as a ground pattern (variously modified in a manner important for species recognition), IV-L-3 shortened Material examined and with a pair of hair-like setae, IV-L-4/5 in the basal Type series, SMF “Jugoslawien Skopje Karaman part each with a more or less developed longitudinal coll.”, lectotype, here designated SMF 4585 female furrow flanked by lamellar extensions and bearing two “Typus”; paralectotypes: SMF 4586, 4705, 4893, to five hair-like setae, IV-L-5 distally with one to three 5332; further material: SMF 4704, 5644a, 5644b, strong posterior setae, IV-L-6 with three lines of 7616. This species was originally described in the modified setae on the dorsal, posterior, and ventral female sex only, based on more than one specimen, surface. but without giving detailed information on the collecting site and date (“Brunnen bei Skoplje, Karaman”) and without a holotype designation. Later on, the author published also the male, but all slides with male specimens, independently of the text of their labels, cannot be regarded as syntypes. No further published records.

Description Male (informations from K. Viets, 1935, completed from SMF 5644b) Idiosoma (Fig. 2) L/W 800/690, colour yellow; praedorsale L/W 189/473 (0.40), with projecting anterior, and straight posterior margins, no lateral eye lenses visible; postdorsale L/W 560/526 (1.06), caudally strongly narrowed and ending in an obtuse angle, without lateral tubercles; setae not visible (probably a preparation artifact), following Viets distanced from the lateral edge. All coxae fused to a horseshoe-shaped shield embracing the genital field and its plates, sutures between coxae obliterated; Cx-1+2 median L/maximum W 224/658 (0.34) (in Fig. 2 A several setae probably lost as preparation artifact); genital field L/W 82/90, with two pairs of genital flap setae; genitale 1 pentagonal, L/W 78/85 (0.92), genitale 2 minute, subtriangular, L/W 50/ 58, genitale 3 L/W 229/138 (1.66), large, with convex lateral margin, excretale L/W 180/243 (0.74), forming an equilateral triangle with truncated edges and a weakly Fig. 1 - Acherontacarus tuberculatus, male (Spain, E 128), concave posterior margin, postexcretale L/W 130/261 distal segments of IV-L. A) anterior, B) posterior view. Bar= (0.50), with straight anterior and strongly convex 100 µm. posterior margins and truncated lateral edges. For Fig. 1 - Acherontacarus tuberculatus, maschio (Spagna, E measurements of IV-L (Fig. 9C) see table 1. IV-L-3 with 128), articoli distali del IV-L. A) vista anteriore, B) vista two long ventral setae arranged close to each other; IV- posteriore. Tratto= 100 µm. L-4 bearing a longitudinal ventral lamella, on the 56 Gerecke & Benfatti Water mites of the genus Acherontacarus

AB Fig. 2 - Acherontacarus halacaroides, male (SMF 5644b), idiosoma. A) ventral view, B) dorsal view. Bar= 100 µm. Fig. 2 - Acherontacarus halacaroides, maschio (SMF 5644b), idiosoma. A) vista ventrale, B) vista dorsale. Tratto= 100 µm. posterior side of this lamella two long setae; IV-L-5 gular, genitale 3 L/W 2.0, excretale L/W 180/238 (0.76), proximally with a ventral protrusion and dorsal forming an equilateral triangle pointed anteriorly, but concavity; two long hairs located posterior from the with truncated posterior edges, postexcretale L/W 148/ ventral protuberance, one further long hair in the distal 256 (0.58); gnathosoma L/W 330/185, rostrum L/W part, two strong posterior setae near distal segment 182/85, with a narrow base; palp measurements (L/H, margin; IV-L-6 dorsally slightly convex, ventral margin ratio): P-1 37/58 (0.64), P-2 183/78 (2.35), P-3 105/62 irregular, with a row of short dorsal setae, a row of seven (1.69), P-4 108/44 (2.45), P-5 46/- (-). very strong posterior peg-like setae, and ventrally one strong proximal seta, more distally a row of two to five Deutonymph (K.Viets 1933, proportions calcula- flattened setae distally extending in a filiform tip; ted from figures) gnathosoma with strong, but not particularly inflated Idiosoma (Fig. 15A) L/W 760/627, predorsale L/ terminal setae; palp (Fig. 6A) measurements (L/H, ratio): W 0.39, with weakly convex posterior margin, P-1 42/54 (0.78). P-2 128/72 (1.78), P-3 80/54 (1.48), postdorsale L/W 1.0, Cx-1+2 medial L/W 0.5, genita- P-4 92/42 (2.19), P-5 12/6 (2.0); P-2-4 rather slender, le 1/2 subtriangular, genitale 3 oval in shape, joined to P-2 with equally diverging dorsal and ventral margins, the excretale by an area of smooth, non lineated mem- bearing two stronger dorsodistal and eight pennated brane; excretale larger than long, subrectangular, lateral setae on the surface; P-3 weakly curved, with excretory pore in the anterior part, postexcretale with parallel dorsal and ventral margins, bearing two straight anterior and strongly convex posterior margins; dorsodistal setae, P-4 with a basal kink, bearing two palp measurements: P-1 20/43, P-2 130/52, P-3 72/ hair-like distal setae in dorsal and ventral position, two 47, P-4 83/29, (P-5 not measured); shape of segments peg like setae inserting close to each other on the as in the adults, but lower number of setae. mediodistal surface; P-5 with a short basal part and seven Larva: unknown. long, weakly curved claws. Female (informations from the original description, Biology completed from SMF 5644b; if no details are given, Acherontacarus halacaroides has been found only morphology as in male) in a 10-12 m deep well. Reduction of lateral eyes Idiosoma L/W 945/740, praedorsale L/W 182-185/ indicates that this species is particularly adapted to 468-479 (0.38-0.39); postdorsale L/W 627-668/538-544 groundwater habitats. (1.17-1.26), more slender than in male; Cx-1+2 median L/maximum W 261/627 (0.42); circumgenital area embraced by the coxal shield subrectangular, Cx-2/3 Acherontacarus fonticolus K.Viets, 1934 separated by a more distinct suture line than in males, (Fig. 15B, 15D) but median suture Cx-1+2 little visible as in males, Material examined genital field L/W 200/90, longish, genital flaps subdivided in two pairs of sclerites; genitale 1 L/W 126/ Holotype deutonymph, SMF 4829 “Jugoslawien, 121 (1.04), enlarged, subtriangular, flanking a large part Berane, Quelle, Aug. 1933”. Locus typicus in Monte- of the genital field, genitale 2 L/W 49/32 (1.53), subtrian- negro (Lim catchment); no further published records. Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 57

Description as taxonomically distant from the deutonymph of A. halacaroides. While some differences could result from Deutonymph (K.Viets 1934, proportions calculated age dependent changes in shape of sclerites (e.g. in A. from figures) halacaroides the coxal margins less projecting in dorsal Idiosoma L/W 740/600, dorsal shields without view, dorsalia, excretale and postexcretale more exten- lateral tubercles, praedorsale L/W 0.33, with conca- ded), other characters are most probably of diagnostic ve posterior margin, postdorsale L/W 1.04, setae value: A. fonticolus differs from A. halacaroides in the distanced from lateral margins; Cx-1+2 stout, excretory pore placed in the centre, not the anterior part completely fused medially, with straight, slightly of the excretale, genitalia 3 more enlarged, and a palp undulating posterior margin, median L/W 1.04; Cx- with much more stout segments P-3 and P-4. The 3+4 narrow; genitale 1/2 transverse oval, genitale 3 diagnostic features of this species should be investigated subtriangular, enlarged; excretale (Fig. 15D) longer on the base of adults collected from the area of the type than large, subrectangular, excretory pore round, locality. surrounded by a sclerite ring in an opening slightly anterior from the centre of the plate, postexcretale Biology roundish, anteriorly truncated; gnathosoma with Unknown; A. fonticolus has been found in a finely pointed apical setae, palp measurements: P-1 rheocrenic spring. 19/37, P-2 107/58, P-3 43/48, P-4 51/29, P-5 35/15 (segments 3 and 4 very compact and stout). Larva and adult Acherontacarus vietsi E. Angelier, 1951 (Figs 3, 16A) Unknown. For unclear reasons and without giving morphological details, Schwoerbel (1963) published Material examined the detection of a larva of this species collected from an undefined hyporheic habitat in Macedonia. In his Italy, Sardinia, I 336 I Sarrabus (CA). Riu di Cannas collection (SMF) a slide is conserved containing two downstr. cofluence Riu de su Perdosu, 400 m, NJ 39 Acherontacarus larvae from Macedonia. The speci- 56, 02.05.1986, interstitial dig, 1 deutonymph mens in question will be discussed and described at (damaged); I 389 I, Gerrei (CA). Dolianova. Riu the end of this paper (“Acherontacarus sp.”). Lassini at Case Porru, 380 m, NJ 21 64, 01.06.1986, interstitial dig, 1 female; 1165 I, same collecting site, 17.09.1991, interstitial dig, 1 male, 3 females, 1 larva Discussion attached to Hydraena sp. (Coleoptera Palpicornia). Viets was surely right in considering this specimen Location of type series unclear.

D

B

E B-F

A

C F

A

Fig. 3 - Acherontacarus vietsi (Sardinia, I 1165 Int.) A-D male. A) idiosoma, partial ventral view; B) palp medially; C) IV-L- 2-6; D) gnathosoma, ventral view. E, F female. E) genital field and surroundings; F) palp, medial view. Bars= 100 µm. Fig. 3 - Acherontacarus vietsi (Sardegna, I 1165 Int.) A-D maschio. A) idiosoma, vista parziale ventrale; B) palpo, vista mediale; C) IV-L-2-6; D) gnathosoma, vista ventrale. E, F femmina. E) area genitale e dintorni; F) palpo, vista mediale. Tratti= 100 µm. 58 Gerecke & Benfatti Water mites of the genus Acherontacarus

Published records males; genitale 1 L/W 56/67 (0.84), genitale 2 L/W 20/ 26 (0,77), subquadratic, genitale 3 L/W 154/78 (1.97), France, Corsica, Haute-Corse, Golo, R. Casaluna excretale L/W 112/154 (0.73), elongated, postexcretale at S. Lorenzo, 500 m, 31.08.1950 (locus typicus, E. L/W 105/163 (0.64); palp measurements (L/H, ratio): Angelier 1959); Haute-Corse: Asco, Bevinco, Fango, P-1 not measured, P-2 103/54 (1.91), P-3 56/405 (1.40), Ficarella, Fium Alto, Fium Orbo, Golo, Tavignano; P-4 72/27 (2.66), P-5 31/14 (2.21). Corse-du-Sud, Ortolo, Porto, Rizzanese, Sagone, Solenzara, Taravo (without information about specific Deutonymph localities, specimen numbers, collecting dates: San- Idiosoma L/W 300/170, predorsale L/W 78/94 tucci 1975). (0.83), postdorsale L/W 209/168 (1.24), Cx-1+2 median L /W 128/224 (0.57); genitale 3 L/W 144/45 Description (Material from Sardinia) (3.2), excretale (Fig. 15F) L/W 56/58 (0.97), Sclerotisation and porosity of all sclerite parts rather postexcretale L/W 72/65 (1.11) with weakly convex fine; dorsal shields with lateral tubercles (predorsale: posterior margin, genitale 1 and 2 roundish, genitale 3 one pair, postdorsale: six pairs, caudally decreasing in oval in shape, joined to the excretale by an area of size); lateral eye lenses visible at anterior margin of smooth, non lineated membrane; excretale larger than praedorsale; glandular openings not visible at light long, subquadratic, excretory pore in the anterior part microscope; Cx-1+2 medially not fused and also of the plate, postexcretale with straight anterior and separated from Cx-3+4 by a well visible suture line; strongly convex posterior margins; palp measurements: gnathosoma (Fig. 3D) enlarged and with a robust P-1, P-2, P-3, P-4, P-5. rostrum bearing a pair of inflated dorsodistal setae; Larva palpus (Fig. 3C, 3F) slender, P-2 basally laced, distally strongly enlarged, with straight ventral and convex Idiosoma (Fig. 16F) L/W 338/265 (1.28), dorsale dorsal margins, P-3 subrectangular, P-4 ventral margin L/W 238/207 (1.15), longish and with equally convex with a strong basal kink, mediodistal margin pointed, caudal margin; Cx-1+2 L/W 171/220 (0.78), medially from here a fine lamella extending over the distal fourth with truncated caudal margin; excretale L/W 148/121 of the segment, roofing over the knob-shaped (1.22), strongly enlarged, with straight anterior and medioproximal seta; the mediodistal seta near the distal convex posterior margins, excretory pore located segment margin, only slightly thickened, P-5 with anteriorly; gnathosoma (Fig. 16A) L/W 94/85 (1.11), relatively short claw setae. strongly enlarged basally, distally narrowed with convex lateral margins, mouth opening minute, no Male particularly modified preoral setae visible; palp Idiosoma (Fig. 3A) L/W 550/370; predorsale L/W insertions covered by the lateral margins of a “ventral 94/216 (0.44), with projecting anterior, and straight platform” which is restricted to the basal part of the posterior margins; postdorsale L/W 365/234 (1.56), gnathosoma, not extending to the area of the mouth parabola-shaped; Cx-1+2 median L/maximum W 135/ opening as in other species (see below); palp club- 324 (0.42); genital field L/W 35/35; genitale 1 L/W shaped, P-1 not visible, P-4 spherical and bearing 58/56 (1.04), genitale 2 L/W 27/25 (1.08), subtrian- numerous fine and long setae, covered by a dorsodistal gular, genitale 3 L/W 161/58 (2,78), large, with nearly extension of P-3. straight lateral margin, excretale L/W 116/116 (1.0), forming an equilateral triangle, postexcretale L/W 112/ Discussion 145 (0.77), with straight anterior and strongly convex As far as informations are available, the populations posterior margins; for measurements of IV-L (Fig. 3 from Sardinia agree well with the specimens known C) see table 1; IV-L-4 ventrodistally with a lamellar from Corsica. After the first description, based on a extension, IV-L-5 with a little visible longitudinal keel single male, further records were published by Santucci on the posterioventral surface, IV-L-6 with only two (1975), who provided also first information on the or three dorsal setae, two posterolateral setae extremely morphology of the female and deutonymph. Acheron- thickened and night-cap shaped, and a row of strong tacarus vietsi differs from A. halacaroides in a high ventral setae; palp (Fig. 3B) measurements (L/H, ratio): number of very distinctive characters: Apart from the P-1 not measured, P-2 125/67 (1.87), P-3 56/45 (1.24), generally by far minor dimensions and more slender P-4 85/31 (2.74), P-5 34/18 (1.89). shape of many idiosoma sclerites, important characters Female regard the presence of tubercles on dorsal shields, coxal plates Cx-1+2 not fused, gnathosoma stout and with Idiosoma L/W 570/335, predorsale L/W 94/206 thickened dorsal setae, palp slender, P-4 with (0.46); postdorsale L/W 392/224 (1.75), more slender mediodistal lamella and only one peg-like medial seta than in male; Cx-1+2 median L/maximum W 153/297 (the second medial seta being hair-like), male IV-L with (0.52); genital field L/W 96/52, genital flaps subdivided only two, but extremely thickened, posterior setae. in two pairs of sclerites, bearing two pairs of setae as in Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 59

The attribution of deutonymphs (one found by Santucci in Corsica together with adults, one taken in B Sardinia from a sample where no adult specimens were found) leaves few doubts because they agree with adults not only in minute dimensions and slender shape, A-C but also in the unfused Cx-1+2 plates. Agreement C should be expected also in the gnathosoma morpho- logy, but no informations was published by Santucci, and the specimen from Sardinia is damaged (distal leg segments and gnathosoma lacking). In the idiosoma characters, they are easily distinguished from A deutonymphs of A. halacaroides and A. fonticolus (both characterized e.g. by a much more enlarged postdorsale and postexcretale). Also the attribution of larvae (which were found in Sardinia at the same site as the population of adults) is corroborated by particular minute dimensions which probably characterize all developmental stages of this taxon. As in the adult, also at the larval stage there are found several highly derivative characters (distal extension of P-4, particular enlargement of the gnatho- soma, presence of a large excretory plate). As will be documented in the further course of this revision, D Acherontacarus vietsi obviously has a rather isolated phylogenetical state within the genus.

Biology Fig. 4 - Acherontacarus rutilans, male (Corsica F 79). A) IV-L-4-6; B) palp lateral view, C) palp medial view; D) Obviously preferring habitats of the hyporheic idiosoma, dorsal view. Bars= 100 µm. interstitial, but following Santucci (1970, 1971) during Fig. 4 - Acherontacarus rutilans, maschio (Corsica F 79). A) the estival periods of temperature rise and oxygen IV-L-4-6; B) palpo, vista laterale, C) palpo, vista mediale; depletion in deeper sediments appearing in surface D) idiosoma, vista dorsale. Tratti= 100 µm. waters. Larvae parasitic on hydrophilid beetles of the genus Hydraena. one larva on Agabus didymus female, prosternum; one larva on Agabus nebulosus female, prosternum Acherontacarus rutilans E. Angelier, 1951 laterally; Spain: E TAR Aragon, Horta de San Juan, (Figs 4, 10A, 15E, 17A) Rio Canaletas, 25.01.1998, Ribera, Aguilera & Hernando, four larvae on Agabus biguttatus, anterior Material examined margin of Mesosternum; E 128 Aragon, Horta de San France, Corsica: F 35 Calacuccia (2B), Castirla. Juan, Faixa de la Carrasca N Mas de Josepó, spring, spring eastern slope Capo d’Alici, 390 m, 30.09.1991 650 m, 17.04.1998, two larvae. two deutonymphs; F 76 Cargése (2A), Forêt d’Esigna, Location of type series unclear. stream Bocca di Gradella, 300 m, 29.05.1993, one lar- va; F 79 Ota (2B), Ruisseau de Furtolaccia in Gorges Published records de Spelunca, 250 m, 02.06.1993, two males; F 83a France, Corsica, Haute-Corse, Golo, R. Tartagine, Albertacce (2B), Capu â Rughia spring brook exp. SE, forêt de Tartagine, 880 m, 13.08.1950 (locus typicus, 1350 m, 05.06.1993, one male, one larva; F 88 Porto Angelier 1959); Haute-Corse: Casaluna (Golo) (2B), Ruisseau d’Enova N Crète d’Andatone, 390 m, (without specific localities and collecting dates: five 08.06.1993, one male; F 90 Curzu (2B), Punta Salisei, males, one deutonymph, Santucci 1975). fountain SW slopes, 800 m, 10.06.1993, five larvae. Italy, Sardinia: I 350 Bosa (NU). Riu Mesu NW Description Montresta, 270 m, MK 57 70, 09.05.1986, one deuto- nymph, one larva; Morocco: MAR 4 Djebel Tazzeka, Male (specimens from Corsica F 79 and Morocco E Bab Ferrich (panorama), 1300 m, 30.03.1997, leg. MAR 4) Ribera et al., one larva; same site, 04.04.1997, leg. Idiosoma (Fig. 4D, 10A) L/W 1020/670, colour Gerecke et al., one male, two larvae on Agabus yellow to red, glandular pores well visible; predorsale brunneus female, prosternum, last abdominal sternite; L/W 108-160/450-470 (0.24-0.34), with equally 60 Gerecke & Benfatti Water mites of the genus Acherontacarus rounded, slightly irregular anterior and slightly conca- Female (original description) ve posterior margins, lateral eye lenses well visible; Idiosoma L/W 1040/750, praedorsale L/W 140/500 postdorsale L/W 605-650/430-475 (1.32-1.51), caudal (0.28); postdorsale L/W 740/520 (1.42). Circumgenital part parabola-shaped, regularly arranged lateral area embraced by the coxal shield subrectangular; coxal tubercles on praedorsale (one pair, a similar structure plates well separated as in males; genital field L/W medially on the posterior margin) and postdorsale 160/105, genital flaps subdivided in two pairs of (about ten pairs, caudally diminuishing in size); dorso- sclerites; genitale 1 trapeziform, genitale 2 subqua- lateral platelets not strongly differing in size; coxal dratic, genitale rather large, excretale longish; suture plates Cx-1+2 completely separated medially from lines surrounding excretale straight, not undulating as each other and laterally from Cx-3+4; Cx-1+2 median in males; gnathosoma L/W 250/185, palp measure- L/maximum W 174-198/575-635 (0.29-0.31), posterior ments (L/H, ratio): P-1 25/45 (0.55), P-2 100/63 (1.59), margin convex, forming an obtuse angle at the mee- P-3 100/60 (1.66), P-4 90/50 (1.8), P-5 55/- (-); setation ting point of Cx-3+4 and genitale 2; acetabula well generally similar to males, but no information visible on the coxae anteriorly from III-/IV-L insertions concerning the position of medial setae on P-4. and in a line at the medial margin of Cx-4; genital field L/W, 81/98 (0.9), with four pairs of genital flap setae; Deutonymph (original description, specimens from genitale 1 L/W 90-103/103-127 (0.75-1.00), pentago- Sardinia and Corsica, measurements F 35) nal, genitale 2 minute, L/W 30/35/35-55, rectangular, Idiosoma L/W 950/730, predorsale L/W 135/392 transverse, genitale 3 L/W 350-370/144-160 (2.25- (0.34), postdorsale L/W 515/358 (1.44), Cx-1+2 2.55), with undulating lateral margin, excretale L/W median L/W 252/468 (0.54), genitale 1/2 transverse 279-300/193/205 (1.45-1.46), elongated, anterior oval, with well visible glandular porus; genitale 3 lon- margin slightly convex, posterior margin medially con- gish, anteriorly and posteriorly rounded; excretale (Fig. cave, laterally slightly convex, postexcretale L/W 157- 15 E) L/W 180/126 (1.43), elongated, subrectangular, 168/247-260 (0.62-0.67), anterior margin correspon- with weakly convex anterior margin, excretory pore in ding to the posterior margin of the excretale medially the anterior part of the plate, postexcretale L/W 166/ with a convex extension flanked by concave lateral 193 (0.86), with slightly concave anterior and truncated parts, posterior margin convex, laterally more strongly posterior margins, laterally convex; palp measure- curved than in the centre, surface irregular. For leg ments: P-1 18/35 (0.51), P-2 75/52 (1.44), P-3 75/51 measurements of IV-L (Fig. 4A) see table 1. IV-L-4 (1.47), P-4 63/37 (1.70), P-5 38/- (-); general morpho- distally bearing a flat longitudinal groove, and four to logy as in adults, with stout segments 2-4, proximome- six long ventral setae, IV-L-5 proximally concave, in dial seta of P-4 distanced from distal segment margin. the distal part slightly convex, with a group of long Larva (specimens from Corsica, Spain and Moroc- hairs in the basal part and two to three strong posterior co) setae near distal segment margin; IV-L-6 dorsally nearly straight, ventral margin indented near the base, Idiosoma L/W 325-505/175-405, dorsale L/W 215- nearly parallel to the dorsal margin in the distal part, 315/220-305 (0.73-1.18), enlarged, distally projecting with several long hair setae in the basal part and a in an obtuse triangle; Cx-1+2 L/W 217-275/255-325 bristle formed by high numbers of densely arranged (0.79-0.88), caudal margin medially protruding, short setae on the posterior and ventrodistal surface, laterally concave; excretale L/W 28-36/42-50 (0.60- dorsal setae and peg-like thickened lateral setae 0.74), triangular, with maximum W anteriorly, excre- completely absent. Gnathosoma L/W 262/163 (1.61), tory pore located anteriorly; gnathosoma (Fig. 17A) robust, with strong, but not particularly inflated L/W 123-198/88-166 (1.10-1.40), strongly enlarged terminal setae; palp (Fig. 4C, 4D) measurements (L/ basally, distally equally narrowed with convex lateral H, ratio): P-1 27-35/45-50 (0.54-0.78). P-2 100-105/ margins, mouth large, surrounded by a ring of membra- 68-72 (1.39-1.50), P-3 90-100/67-70 (1.29-1.49), P-4 nous papillae, a pair of dorsoventrally flattened preoral 76-85/45-48 (1.69-1.78), P-5 50-52/22-25 (2.00-2.27), setae sickle-shaped, with their medial edges slightly P-2 with slightly convex dorsal and ventral margins, overlapping, with their lateral extensions paralleling bearing one dorsodistal and four lateral setae; P-3 the anterior margin of the mouth opening; palp inser- relatively large, with parallel dorsal and ventral tions ventrally covered by sclerite folds as a “ventral margins, bearing seven setae, mostly on the lateral platform” anteriorly extending to the area of the mouth surface, P-4 stout, with a basal kink, bearing two hair- opening; palp slender, equally enlarged from segment like setae inserting dorsally resp. ventrally in the distal 1-3, P-3 not forming a distal extension, P-4 elongated, fouth, medial setae strong and short, the proximal one with four fine and long setae and seven thickened distal inserting in the middle of the segment, the distal one “claw setae”. near, but clearly distanced from, the distal segment margin; P-5 with a short basal part and seven very long, Discussion weakly curved claws. After the first description, based on one female and Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 61 one deutonymph, this species was found only once (L/W 1.51 vs. 1.32-1.36) and a more stout P-3 (L/H again by Santucci (1975) who gave a scetchy 1.29 vs. 1.43-1.49), larvae from Corsica have a more description of the male. A redescription of all stages, enlarged dorsal shield (L/W 0.73) than those from based on material listed here was published by Spain and Morocco (L/W 1.0-1.18). At least the latter Tuzovskij et al. (2001). Deutonymphs in some difference is best explained by differences in allometric localities found together with adult A. rutilans can be growth on individual or population level; the agreement attributed to this species on the base of the palp in important characters such as the male IV-L and the morphology and setation, but also due to their rather morphology of the larval excretale and preoral setae large dimensions. Larvae attributed to A. rutilans were indicates that all these populations belong to a single, taken in several occasions together with adults, in other widespread species. occasions together with deutonymphs. Their rather large dimensions confirm this attribution at least in Biology confront to A. vietsi, a species at the adult stage only a Obviously preferring rheocrenic springs and spring little larger than the larvae described here. streams, more rarely in the hyporheic interstitial of Both sexes of A. halacaroides differ from A. rutilans higher order streams. Larvae parasitic on dytiscid in the absence of lateral tubercles on the dorsal plates, beetles of the genera Agabus and Deronectes. The the coxal plates Cx-1+2 fused medially to each other capacity to parasitize widely distributed, flight active and laterally to Cx-3+4, the more stout excretory plate, beetle species of the genus Agabus explains how gene and the slender palp with a higher number of setae on flow between remote areas can be maintained also in P-2, but a reduced number of setae on P-3, and the species at the adult stage bound to patchy, groundwater medial setae of P-4 located at the distal segment influenced habitats. This observation falsifies our margin. The male differs furthermore in the presence former hypothesis concerning the restricted distribu- of a single posterior row of strong peg like setae on tion areas of Acherontacarus species, resulting from IV-L-6 instead of the bristle of densely arranged setae an assumed preference for little flight active host beetle found in A. rutilans. species (Benfatti & Gerecke 1999). Acherontacarus fonticolus, known only from a deutonymph, differs from the corresponding stage of A. rutilans in the medially fused Cx-1+2, minor excre- tale with central excretory pore, larger and shorter Acherontacarus cedro Lundblad, 1962 genitalia 3 and a yet more stout palp, with shorter P-3 (Fig. 5) and medial peg-like setae on P-4 in distal position. Material examined Adult A. vietsi are similar to A. rutilans in the unfused coxal plates, presence of tubercles on the Holotype female, SMNH 5983, Gomera, stream in dorsal plates, the gnathosoma with strongly inflated forest El Cedro, pool, 1000 m, 7.4.1957, Lundblad; dorsodistal setae, a more slender palp with the paratype (“Nymphotypus”) deutonymph, SMNH 5990, medioproximal seta on P-4 knob-shaped and associated same collecting site and date. No further published with a longitudinal lamella; the male differs further- records. more in the presence of only two extremely thickened peg-like seta instead of the bristle found in A. rutilans. Description Deutonymphs of this species are distinguished from Female (holotype, most measurements from the A. rutilans in the generally minor dimensions and more original description; male unknown) slender shape of the idiosoma, a subquadratic excretale with the excretory pore in central position, and Idiosoma (Figs 5A, 5B) L/W 1310/870 (1.5), colour probably also more slender palp segments. At the larval pale red; predorsale L/W 243/586 (0.48), with anterior stage, A. vietsi differs from A. rutilans in by far minor margin forming an obtuse angle, posterior margin dimensions, the large, subquadratic excretale, straight, lateral eye lenses weakly developed but gnathosoma distally more narrowed and with a minu- visible; postdorsale L/W 948/637 (1.49), large, te mouth opening, absence of sickle-shaped anterior caudally equally rounded, on each side bearing 18 setae and P-4 covered by laminar distal extensions of regularly arranged lateral tubercles posteriorly P-3. decreasing in size. Cx-1+2 median L/W 300/810 Our records extend noteworthy the known distribu- (0.37), well separated medially from each other and tion of A. rutilans, a species until now considered laterally from Cx-3+4; genital field L/W 207/96, with endemic to Corsica. Notwithstanding some variation bipartite flaps bearing 4 pairs of setae; genitale 1 L/W in dimensions, more rarely also proportions, between 168/136 (1.24), trapeziform, genitale 2 L/W 58/71 the populations from Corsica, Spain and Morocco, no (0.82), subrectangular, genitale 3 L/W 500/253 (1.98), clear differences could be found that indicate genetical lateral margin slightly convex, medial margin slightly separation. The male from Morocco differs from concave, excretale L/W 396/268 (1.48), elongated, Corsican specimens in a more slender postdorsal plate postexcretale L/W 268/375 (0.71), with straight 62 Gerecke & Benfatti Water mites of the genus Acherontacarus

B

A

C

Fig. 5 - Acherontacarus cedro, holotype. A) idiosoma, partial ventral view; B) idiosoma, partial dorsal view; C) gnathosoma, ventral view. Bars= 100 µm. Fig. 5 - Acherontacarus cedro, olotipo. A) idiosoma, vista parziale ventrale; B) idiosoma, vista parziale dorsale; C) gnathosoma, vista ventrale. Tratti= 100 µm. anterior and lateral, and strongly convex posterior tuberculation of the dorsal shields, separation of the margins; gnathosoma (Fig. 5C) L/W 300/211,with coxal plates, and also in the shape and setation of the minute terminal setae; palp measurements (L/H, ratio): palp (with relatively short P-2 and P-4, but long P-5, P-1 45/63 (0.71). P-2 127/82 (1.55), P-3 132/72 (1.83), proximomedial seta of P-4 far distanced from the distal P-4 102/ 53 (1.92), P-5 56/31 (1.81), P-2 with slightly segment margin). As possible diagnostic differences convex dorsal and ventral margins, P-3 elongated, he regarded the more slender genitale 3 and excretale, subrectangular, P-4 stout, with a strong basal kink, and the genital field larger and more strongly rounded. proximomedial seta lacking; P-5 with rather long claw However, as all these plates are interlocked, having setae. often a more narrow appearance in surface, but being more extended internally, figures can often give a Deutonymph (paratype, measurements from the misleading impression of these structures. The original description) mentioned differences cannot be judged before further Idiosoma L/W 1000/650, shape of dorsal shields females of A. rutilans become available for variability as in the holotype, but with lower numbers of tubercles; studies. The absence of the proximomedial seta, found praedorsale L/W 160/465, postdorsale L/W 672/448, as a stable component in all other species studied, in genitale 1/2 transverse oval, genitale 3 longish, with the female of A. cedro, is surely an artifact, as is rounded anterior and posterior edges; excretale L/W demonstrated also by its presence in the deutonymph. 239/186 (1.28), elongated, subrectangular, with convex The far proximal location of this seta in the deuto- anterior margin, excretory pore in the anterior part of nymph, a character state within the genus found only the plate, postexcretale L/W 221/214 (1.03), with in A. rutilans, suggests that A. cedro is a closely related straight anterior and truncated posterior margins, sister species or a synonym of the latter. With regard laterally convex; palp morphology as in the holotype, to a further presumptively diagnostic character P-4 stout, proximomedial seta present, distanced from described by Lundblad, the shape of the deutonymphal distal segment margin. excretale and postexcretale, in the newly collected Larva: unknown. deutonymphs of A. rutilans we could observe character states which are intermediate or more similar to A. Discussion cedro. In view of the now documented wide distribu- tion and dispersal capacity of A. rutilans, the presence In the original description, Lundblad was aware of this species on Makaronesia is not unprobable. about the strong similarity of this species with A. Biology rutilans, a species that he knew only from the original description. Acherontacarus cedro agrees with A. Unknown. The only known record refers to a rheo- rutilans in generally large dimensions, shape and crenic spring. Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 63

Acherontacarus bicornis Cook, 1974 of lateral tubercles, lateral eye lense little visible, but (Figs 10B, 10C) distinct; postdorsale L/W 694-729/509-547 (1.32), in the caudal part parabola-shaped, with regularly arranged Material examined lateral tubercles; Cx-1+2 median L/maximum W 238/ 630 (0.38) well separated by suture lines medially from Paratypes male, female SMF K.O.Viets 6081, each other and laterally from Cx-3+4; genital field L/ Spain, Rio Triacastela, one mile from Triacastela W 80-86/79-85, with four pairs of genital flap setae; (Lugo), Spain, 18.05.1968 Cook. No further published genitale 1 L/W 40/56 (0.71), roundish, genitale 2 L/W records. 49/22 (2.23), longish subtriangular, genitale 3 L/W 293/ 62 (4.65), slender, with convex lateral and medial Description margins, excretale L/W 275-327/234-256 (1.18), Male (Paratype and data from the original descrip- forming a longish triangle with truncated laterocaudal tion) edges, postexcretale L/W 202/302 (0.67), with slightly convex anterior and strongly convex posterior margins, Idiosoma L 970-1020; predorsale L/W 206-221/ 456- lateral edges truncated. Leg IV (Figs 1, 10B, 10C) 516 (0.47), anterior margin projecting and forming an measurements: see table 1. IV-L-3 with two long obtuse angle, posterior margin straight, bearing one pair ventrodistal setae arranged close to each other; IV-L-4 with a deep ventral furrow flanked by axe-like extensions, in the groove two long setae; IV-L-5 with a little developed ventral protrusion in the proximal part, dorsally straight, with seven hair-like setae on the ventral and posterior surface; IV-L-6 slightly S-shaped, in the E basal part dorsally concave, ventrally convex, viceversa in the distal part, dorsally with a row of short setae, on the posterior surface a row of setae (nine very strong, peg-like, in the basal part, further six normally developed in the distal part, ventrally a row of 10-15 setae (the two basal ones hair-like, five to six central setae flattened D and distally extending in a filiform tip, five distal setae short, nomally developed); gnathosoma L 304-334, with C a pair of strong, mitten-like terminal setae with two blunt tips; palp (Fig. 6C) measurements (L/H, ratio, in brackets range from original description): P-1 (41-42), P-2 163 (155-159)/87 (1.87), P-3 100 (106-112)/74 (1.35), P-4 128 (121-130)/48 (2.67), P-5 63/27 (2.33), P-2-4 rather slender, P-2 with equally diverging dorsal and ventral margins, bearing two dorsodistal and one lateral setae; P-3 subrectangular, with slightly diverging dorsal and ventral margins, bearing two dorsodistal setae, P-4 with a basal kink, bearing two hair-like setae, the dorsal one B arranged distally, the ventral one in the distal quarter; of the two peg-like medial setae the distal one larger A and close to the segment margin, the proximal one by far minor, distanced from the margin and directed ventrally; P-5 with a relatively long basal part and seven weakly curved claws (the shorter L measurements given by Cook - 50-52 - obviously not including claw length). Female (Paratype and data from the original description) Fig. 6 - Acherontacarus, palps. A) A. halacaroides, male (SMF Idiosoma L 1030-1125, predorsale L/W 198-206/ 5644b); B) A. cicolanii, holotype female; C) A. tuberculatus, 410-440 (0.49); postdorsale L/W 680-760/460-520 male (Spain, E 128); D) A. tuberculatus, paratype male; E) A. (1.48), more slender than in male; circumgenital area ruffoi sp. nov. holotype female Bars= 100 µm. embraced by the coxal shield subrectangular, Cx-1+2 Fig. 6 - Acherontacarus, palpi. A) A. halacaroides, maschio (SMF median L/maximum W 246/560 (0.44); genital field 5644b); B) A. cicolanii, olotipo femmina; C) A. tuberculatus, L/W 166-174/90-93; genital flaps subdivided in two maschio (Spagna, E 128); D) A. tuberculatus, paratipo maschio; pairs of sclerites, bearing three pairs of setae; genitale E) A. ruffoi sp. nov. olotipo femmina Tratti= 100 µm. 1 L/W 103/81 (1.27), medially a little longer than 64 Gerecke & Benfatti Water mites of the genus Acherontacarus laterally, genitale 2 L/W 63/38 (1.66), subrectangular, laterally (in the region of the visible, but little developed genitale 3 L/W 302/162 (1.86), excretale L/W 200- lateral eye lenses) slightly concave, posterior margin 251/197-258 (1.0), forming a longish triangle truncated straight, with a distinct central indentation leading to anteriorly, but with pointed posterior edges, postex- a little pit, no lateral tubercles visible; postdorsale L/ cretale L/W 247/297 (0.83). IV-L without particular W 560/381 (1.47), with an equally convex caudal setae on distal segments. Gnathosoma L 304, without margin, dorsal setae distanced from the lateral margins differences to males in shape and setation; palp (as depicted in Bader’s Fig. 2a), margins on each side measurements (L/H, ratio, in brackets range from with about 25 lateral tubercles nearly equal in size from original description): P-1 45 (44-45)/56 (0.88), P-2 145 the anterior to the posterior edge; circumgenital area (156-162)/72 (2.01), P-3 99 (110-119)/61 (1.62), P-4 embraced by the coxal shield with maximum W on 112 (117-121)/40 (2.80), P-5 47 (48-51)/20 (2.35). the level of the genital field; Cx-1+2 median L/ maximum W 193/530 (0.36); genital field L/W 175/ Deutonymph and larva: unknown. 80, longish, genital flaps subdivided in two pairs of sclerites, bearing three pairs of setae; genitale 1 L/W Discussion 175/94 (1.86), trapeziform, flanking a large part of the Acherontacarus bicornis is characterized by the genital field, genitale 2 L/W 67/36 (1.86), subrectan- genitalia 1 and 2 rather similar in size (genitale 1/2 L gular, genitale 3 L/W 288/135 (2.13), excretale L/W ratio in males 0.82, other species > 1.50, females 1.63, 225/189 (1.19), forming an equilateral triangle other species >2.0, by the name-giving “horn-like” truncated anteriorly, but with pointed posterior edges, thickened distal setae of the gnathosoma and by the postexcretale L/W 157/261 (0.60); for figures and proximomedial seta on P-4 reduced in size and directed measurements of legs, see Bader (1983); gnathosoma ventrally. It can be furthermore distinguished from A. L/W 225/160, rostrum basally narrowed, with peg-like, vietsi and A. rutilans, two species similar in the but not particularly inflated terminal setae; palp (Fig. presence of dorsal tubercles and the separation of the 6B) measurements (L/H, ratio): P-1 22/45 (0.49), P-2 anterior coxal plates, in the different shape and setation 154/58 (2.66), P-3 81/52 (1.56), P-4 90/36 (2.50), P-5 of the male mating legs. These legs are found princi- 43/20 (2.15), P-2-4 slender, P-2 very elongated, with pally similar (with three rows of modified posterior equally diverging dorsal and ventral margins, with two setae) in A. halacaroides, but there with less developed dorsodistal setae and two setae in the distal fourth of ventral furrow on IV-L-4 and lower numbers of the ventral margin; P-3 in the basal fourth narrowed, posterior setae on IV-L-6. Furthermore, that species, distally thickened, bearing two dorsodistal setae, P-4 as well as the little known A. fonticolus, differs from with a basal kink, with both the dorsal and ventral hair- A. bicornis in the lateral and medial fusion of coxal like setae distanced from the distal segment margin, plates Cx-1+2. Acherontacarus cedro, a further species the two peg like medial setae equal in size and shape, similar in dorsal tuberculation and fusion of coxal the proximal one little distanced from the segment plates, is known in the female sex only. margin; P-5 with a short basal part and seven long, weakly curved claws. Biology Deutonymph and larva: unknown. The only record of this species derives from the interstitial of a stream. Life cycle unknown. Discussion Acherontacarus cicolanii differs from all formerly Acherontacarus cicolanii Bader, 1983 described species in the slender shape of the palp, (Fig. 6B) namely P-2 (L/W 2.66, other species female P-2 L/W < 2.4). Further diagnostic characteristica are the geni- Material examined tale 1 slender in shape (L/W 1.86, other species < 1.50) and the medial setae of P-4 pointed, little differentiated, Holotype female, NHMB, “Sardinien 3.11.1979 and inserting close to the distal margin. From A. Coll. Cicolani SA 29”. Locus typicus following original halacaroides, the species next similar in palp description: Sardinia, Gonasfanadigo, road Cagliari - proportions (P-2 L/H 1.53, L ratio P-2/4 about 1.7, all S. Gavino, well, depth 6.5, temperature 19.1°C, pH other species < 1.5), and from the little known A. 6.8, 03.11.1979 coll. Pesce, Maggi et Silverii. No fonticolus, A. cicolanii differs in the presence of dorsal further published records. tubercles and separated coxal plates Cx-1+2. Description Biology Female (holotype, male unknown) The only record of this species derives from a deep Idiosoma L/W 860/610; predorsale L/W 135/320 groundwater well; it has never been detected in (0.42), with anterior margin medially projecting, interstitial or spring habitats. Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 65

Acherontacarus tuberculatus Bader, 1989 prosternum one larva. The records given here from (Figs 6C, 6D, 7, 16D) Morocco and Spain are the first records since the first description. Material examined Description Holotype female, NHMB, Algeria, “Wilaya Saida, 28.4.1983, Algerien 3” (locus typicus following Male (paratypes, specimens from Spain and original description: Sta. 83-76, Wilaya Saida, captured Morocco) spring 4 km E Saida, 1000 m, temperature 14.2°C, coll. Idiosoma (Fig. 7C) L/W 880/550, colour yellow to Speleo Nederland); paratypes, same locality and orange red; predorsale L/W 138-157/351-405 (0.36- collecting date, two males (one of them mounted 0.41), anterior margin forming an obtuse triangle, together with a female and omitted in the type material posterior margin straight, lateral eye lenses visible, one list of the original description), six females, two pair of tubercles in lateral position; postdorsale L/W deutonymphs on nine slides, many of them damaged 514-582/424-475 (1.17-1.37), caudal part parabola- and/or lacking appendages; further slides “Extr.” and shaped, with about 15 pairs of tubercles posteriorly “palp” containing legs and palps of at least two further not decreasing in size, arranged at irregular distances: males of which the idiosomata are lacking and of an two to three in the anterior part, two to three at the unknown number of further specimens possibly insertion level of III-L, two to three at the insertion omitted in the type material list; NHMB “Algerien 36 level IV-L, six to eight at the posterior edges of the Wilaya Tlemcen, 18.4.1983” (original description: Sta. plate; genital field and its plates forming a slender 83-32, Wilaya Tlemcen, Karaman Chappuis dig on the trapezoidal unit, Cx-1+2 median L/maximum W 156- banks of Sidna Youcha, 7 km ENE Ghazaouet, tempe- 178/482-570 (0.29-0.34); genital field L/W 69/72, with rature 18.2°C), two females, not labeled as types; six pairs of genital flap setae; genitale 1 L/W 40-50/ Morocco: MAR 4b Djebel Tazzeka, E Bab Ferrich (pa- 29-40 (1.25-1.55), parallelogram-shaped, with norama), 1300 m, 04.04.1997, one male, nine larvae; projecting laterocaudal edges; genitale 2 L/W 30-45/ Spain: E TAR Aragon, Horta de San Juan, Rio 18-25 (1.36-2.00), drop-shaped, with maximum W Can~aletas, 25.01.1998, Ribera, Aguilera & Hernando, caudally, genitale 3 L/W 224-245/48-68 (1.36-2.00), two larvae on Agabus biguttatus, anterior margin of slender, with slightly convex lateral and medial Mesosternum (together with larvae of A. rutilans!); E margins, excretale L/W 220-275/170-202 (1.09-1.33), 128 Aragon, Horta de San Juan, Faixa de la Carrasca with slightly concave anterolateral margins and N Mas de Josepó, spring, 650 m, 17.04.1998, six males, extended straight posterolateral margins facing the seven females, two larvae; E 136 Agabus biguttatus posterior part of Cx-4, postexcretale L/W 148-180/225-

C

A B

Fig. 7 - Acherontacarus tuberculatus, type series. A) holotype female, idiosoma, dorsal view; B) paratype female, idiosoma, partial ventral view; C) paratype male, idiosoma, ventral view. Bar= 100 µm. Fig. 7 - Acherontacarus tuberculatus, serie tipica. A) olotipo femmina, idiosoma, vista dorsale; B) paratipo femmina, idiosoma, vista parziale ventrale; C) paratipo maschio, idiosoma, vista ventrale. Tratto= 100 µm. 66 Gerecke & Benfatti Water mites of the genus Acherontacarus

256 (0.61-0.73), with straight anterior and convexely setae flag-like, flattened and laterally extending; palp rounded posterior margins and truncated lateral edges; without distal extension of P-3. for measurements of IV-L (Fig. 1) see table 1; in most details of shape and setation as described for A. bicornis Discussion (Figs 10B, 10C), for differences see discussion; Apart from mentioning a “certain similarity” in the gnathosoma L/W 212-247/158-193, with a long, rather setation of the I-L, Bader did not explain his reasons for slender rostrum and inflated terminal setae; palp (Fig. regarding A. tuberculatus closely related to A. cicolanii. 6 D) measurements (L/H, ratio): P-125-36/49-50 (0.50- 0.70). P-2 103-134/65-70 (1.49-2.06), P-3 85-100/56- Obviously he considered the name giving tuberculation 60 (1.47-1.79), P-4 100-112/35-40 (2.50-3.09), P-5 38- as diagnostic and overlooked that this character is found 45/18-20 (2.11-2.39); shape and setation as described in several other species as well. Acherontacarus for A. bicornis. cicolanii, known only from the female, differs from A. tuberculatus in the longer and more slender genitale 1, Female (holotype, paratypes, specimens from Spain the P-2 more slender, the P-4 with the two medial peg and Morocco) setae similar in size and located close to each other, and Idiosoma (Fig. 7A, 7B) L/W 860/550, predorsale the distal setae of the gnathosoma not particularly L/W 124-157/305-355 (0.41-0.48); postdorsale L/W thickened. With regard to the latter character and also 465-593/355-426 (1.24-1.51); circumgenital area from most other points of view, A. tuberculatus is very embraced by the coxal shield subrectangular, Cx-1+2 similar to A. bicornis, and it differs from all other species median L/maximum W 188-207/436-545 (0.36-0.44); in the same manner as discussed there. Males and genital field L/W 150/170; genital flaps subdivided in females of A. bicornis are generally major in size (e.g., two pairs of sclerites, bearing three pairs of setae; ge- postdorsale L > 650, Cx-1+2 median L/W > 200/600 in nitale 1 L/W 74-94/58-85 (1.11-1.47), medially longer males, > 250/550 in females), and in males several than laterally, genitale 2 L/W 45-59/25-40 (1.20-2.00), idiosoma sclerites are more slender, except for the ge- subrectangular, L ratio genitale 1/2 1.37-2.09; genita- nitale 1 which is more stout (L/W 0.71). Also in the le 3 L/W 207-261/98-126 (2.01-2.28), excretale L/W taxonomically important shape of the male IV-L, only 138-180/148-202 (0.83-1.00), forming a longish minor metric differences are found (Tab. 1: A. bicornis triangle truncated anteriorly, but with pointed posterior with segments 2, 4 and 5 more slender, segment 3 more edges, postexcretale L/W 234-175/217-275 (0.54- stout), but the setation pattern is merely identic. For the 0.66); gnathosoma L 194-227, without differences to moment, our data from topographically distant males in shape and setation; palp measurements (L/H, populations in Spain, Morocco and Algeria furnish a ratio): P-1 25-40/42-49 (0.60-0.82), P-2 112-132/63- series of minor, but obviously stable differences between 67 (1.67-2.10), P-3 77-100/48-50 (1.56-2.04), P-4 78- these two surely closely related taxa. However, it is well 100/31-34 (2.29-3.23), P-5 35-38/16-19 (1.84-2.38). possible that the limits between measurement values used here for separating the two species could be blurred Deutonymph after further investigations on geographical variability. Idiosoma L/W 820/600, praedorsale L/W 120/325 The deutonymph, attributed to this species due to (0.37), with convex anterior margin, postdorsale L/W the detection at the type locality, is still little 383/333 (1.15); Cx-1+2 median L/W 189/450; geni- documented (one of the two specimens of the type tale 1/2 oval, transverse, genitale 3 L/W 100/45 (2.22); series lacking gnathosoma, the other one mounted excretale L/W 126/94 (1.34), longish subrectangular, without detaching appendages). In the rather large excretory pore in the anterior part of the plate, dimensions, presence of tubercles on dorsal shields and postexcretale L/W 162/157, subquadratic with rounded a medial suture line on Cx-1+2 it is most similar to A. angles (both postgenital plates not round as given in rutilans, A. cedro, and possibly A. bicornis and A. Bader’s Fig. 2). cicolanii, two species not yet known at the deutonym- phal stage. Our measurements indicate that it can be Larva (specimens from Spain) distinguished from A. rutilans and A. cedro by the less Idiosoma L/W 404-483/383-424 (1.06-1.20); dor- slender postdorsale and postexcretale. Furthermore, we sale L/W 247-275/277-295 (0.86-0.93); Cx-1+2 L/W can expect a difference in shape and position of the 252-285/324-354 (0.78-0.82); excretale (Fig. 17C) L/ proximal peg seta of P-4, as described for the adults. W 98-112/94-113 (0.87-1.20), very extended, with The larva, ascribed to this species because found slightly concave anterior and equally rounded posterior together with adults in several localities, is characte- margin, setae and excretory pore near the anterior ristic in the shape of the gnathosoma with strongly margin; gnathosoma (Fig. 16D) L/W 153-168/125-138 narrowing margins of the “ventral platform”, and the (1.11-1.23); palp insertion covered by a “ventral particular shape of the anterior setae. The latter platform” rhombic in shape, with maximum W on the character was observed only in one of the investigated level of palp insertion and from here to the mouth specimens: obviously, these tiny setae are easily lost opening equally converging lateral margins; preoral during preparation of these larvae. In the presence of Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 67

Tab. 1 - Acherontacarus males, measurements of IV-L segments. Tab. 1 - Acherontacarus maschi, misurazioni degli articoli di IV-L. dividuus halacaroides tuberculatus tuberculatus tuberculatus bicornis bicornis IV-L Ht Pt E 128 E 128 MAR 4 Pt Pt 2 L 329 338 203 210 218 235 280 2 H 139 45 90 84 75 85 94 2 L/H 2.37 7.51 2.26 2.50 2.91 2.76 2.98 2 relative L 28 32 23 24 25 26 26 3 L 144 135 138 134 133 134 139 3 H 103 81 80 78 74 78 85 3 L/H 1.40 1.67 1.73 1.72 1.80 1.72 1.64 3 relative L 12 13 16 16 15 15 13 4 L 247 202 164 154 162 174 211 4 H 108 81 94 68 70 90 85 4 L/H 2.29 2.49 1.74 2.26 2.31 1.93 2.48 4 relative L 21 19 19 18 19 19 20 5 L 220 166 142 140 140 145 175 5 H 85 58 80 73 78 72 72 5 L/H 2.59 2.86 1.78 1.92 1.79 2.01 2.43 5 relative L 19 16 16 16 16 16 16 6 L 220 220 233 225 218 224 275 6 H 63 63 60 55 58 56 67 6 L/H 3.49 3.49 3.88 4.09 3.76 4.00 4.10 6 relative L 19 21 26 26 25 25 25 Total 1160 1061 880 863 871 912 1080 a large, anteriorly truncated excretory plate, A. tuber- Description culatus larvae are similar to larvae of A. vietsi, which Male (holotype, female unknown) differ in minor dimensions, the more enlarged gnathosoma, and the P-3 with dorsal projections. Idiosoma (Figs 8A, 8B) L/W 920/820, predorsale L/W 121/423 (0.29), anterior margin forming an obtuse Biology triangle laterally slightly convex, posterior margin medially indented, lateral eye lenses not clearly Acherontacarus tuberculatus is obviously a identifiable; dorsal shields without lateral tubercles; crenobiont with a preference for rheocrenic spring postdorsale L/W 710/538 (1.32), lateral margins in the habitats. Notwithstanding this restricted habitat caudal half slightly concave, caudal margin equally preference, parasitism on flight active dytiscid species rounded, dorsal setae not clearly visible, following Bader such as Agabus biguttatus obviously allows to this (1989, Fig. 3A) distanced from the shield margin; species to maintain a rather large goegraphic postdorsale not divided in two parts as erroneously distribution in the SW Mediterranean area. described and depicted by Bader (Benfatti & Gerecke 1999). Cx-1+2 medial L/W 224/658 (0.34), separated medially from each other and laterally from Cx-3+4 by Acherontacarus dividuus (Bader, 1989) distinct sutures; genital field L/W 100/106, round, with Neoacherontacarus dividuus Bader, 1989 four pairs of genital flap setae; genitale 1 L/W 58/85 Acherontacarus dividuus (Bader, 1989) Benfatti & (0.68), pentagonal, with medial and lateral margins Gerecke 1999 parallel to the idiosoma axis, caudal margin forming an (Figs 8, 9A, 9B, 15C) obtuse angle, genitale 2 L/W 25/45 (0.56), subtriangular; genitale 3 L/W 324/121 (2.68), large, with convex lateral Material examined and medial margins; excretale L/W 275/333 (0.83), Type series, NHMB: Holotype male. Locus typicus: forming an equilateral triangle with concave lateral Sta. 83-26, 17.04.1983. Wilaya Tlemcen, cascades near margins, truncated tips, and a slight concavity in the El-Ourit, 5 km ESE Tlemcen, small pool fed by water centre of the caudal margin; postexcretale L/W 130/306 dripping out of shallow cave, 980 m, coll. Speleo Ne- (0.42), subtrapezoidal, anterior margin slightly derland (state: heavily damaged by inflation of the idio- projecting in the centre, laterally slightly concave; for soma and partly distruction of sclerites, right I-L la- measurements of IV-L (Figs 9A, 9B) see table 1; IV-L- cking, left III-L-5/6, left III-L and both IV-L detached; 3 with two long ventral setae arranged close to each paratype deutonymph, same site as holotype. No other; IV-L-4 in the basal part of the segment with a further published records. triangular ventral lamella flanking the insertion of two 68 Gerecke & Benfatti Water mites of the genus Acherontacarus

C

E

A D

B

Fig. 8 - Acherontacarus dividuus, holotype. A) dorsal plates; B) genital field and surroundings, partial view; C) part of the gnathosoma and palp, lateral view; D) P-5; E P-4/5, medial view. Bars= 100 µm. Fig. 8 - Acherontacarus dividuus, olotipo. A) placche dorsali; B) area genitale e dintorni, parzialmente; C) parte del gnathosoma e palpo, vista laterale; D) P-5; E P-4/5, vista mediale. Tratti= 100 µm.

long setae, distally enlarged; IV-L-5 with maximum H in the basal fourth, posteriorly with a lamella flanking the insertion of three long setae, in the distal part one further long hair and two stronger posterior setae near distal segment margin, some minor setae on the dorsal C and anterior segment surface; IV-L-6 with straight dorsal and ventral margins, a row of short dorsal setae, a row of ten posterior peg-like setae which are basally very strong, but apically curved and finely pointed, and a further row of ventral setae from the basal part of the segment to the claw furrow decreasing in size; gnathosoma (Fig. 8C) following Bader (squeezed in the preparation) L/W 250/206, with a normally developed rostrum bearing strong, mitten-like terminal setae with two blunt tips; palp (Figs 8C-8E) measurements (L/H, B ratio): P-1 72/94 (0.77), P-2 178/87 (2.05), P-3 89/67 A (1.33), P-4 112/52 (2.15), P-5 58/25 (2.32), P-2 robust, with convex dorsal and straight ventral margins, bearing two stronger dorsodistal and 4 lateral setae; P-3 subrectangular, with a slight kink in the basal part, bearing two dorsodistal setae, P-4 in the basal part with strongly concave ventral margin, the hair-like distal setae in dorsal and ventral position distanced from the distal margin, the peg like medial setae strong and pointed, inserting close to each other near the distal segment margin; P-5 with a short basal part and 7 long, weakly Fig. 9 - Acherontacarus, males. A, B A. dividuus holotype, curved claws. A) IV-L-4-6 anterior view; B) IV-L-2-6 posterior view; C) A. halacaroides male (SMF 5644b) IV-L, posterior view. Deutonymph (paratype) Bars= 100 µm. Fig. 9 - Acherontacarus, maschi. A, B A. dividuus olotipo, A) Idiosoma (Fig. 15C) L/W 745/620, praedorsale L/ IV-L-4-6 vista anteriore; B) IV-L-2-6 vista posteriore; C) A. W 135/387 (0.35), anterior margin laterally protruding, halacaroides maschio (SMF 5644b) IV-L, vista posteriore. in the centre truncated, lateral eye lenses well visible, Tratti= 100 µm. postdorsale L/W 475/405 (1.17), strongly enlarged and Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 69

B

C

A

Fig. 10 - A) Acherontacarus rutilans male, idiosoma ventral view; B, C A. bicornis paratype male. B) IV-L-2-6 posterior view; C) IV-L-3-6 anterior view. Bars= 100 µm. Fig. 10 - A) Acherontacarus rutilans maschio, idiosoma vista ventrale; B, C A. bicornis paratipo maschio, B) IV-L-2-6 vista posteriore; C) IV-L-3-6 vista anteriore. Tratti= 100 µm.

with equally rounded posterior margin, lateralia large; The deutonymph is attributed to this species Cx-1+2 medial L/W 260/620 (0.42); genitale 1/2 because it was collected together with the holotype. transverse oval, genitale 3 L/W 139/54 (2.57), rod- It agrees with the male adult in enlarged idiosoma shaped, with rounded anterior and posterior margins; sclerites and differs from the deutonymph of A. excretale L/W 171/157 (1.09), subquadratic, with tuberculatus in a more slender genitale 3, a more convexely projecting anterior, and slightly concave enlarged excretale and the different shape and lateral margins, excretory pore in the anterior part of insertion of the peg setae on P-4 as described for the the plate, postexcretale L/W 225/225, pentagonal; adults. gnathosoma and its appendages in situ, shape and position of peg setae on P-4 as described for the male. Biology Larva: unknown. The only known record of this species refers to a groundwater-influenced hygropetric habitat. Life cycle Discussion unknown. The original description does not provide correct diagnostic features for A. dividuus. This species is most similar to A. bicornis and A. tuberculatus in the following Acherontacarus raphani sp. nov. character combination: (1) Cx-1+2 separated medially (Figs 11, 12, 13A, 17B, 17D, 17E; Tab. 2) from each other and laterally from Cx-3+4 by distinct sutures; (2) gnathosoma with large, mitten-like anterior Material examined peg setae; (3) male IV-L with three rows of setae, those Type series of the posterior row very large and stout. Acherontacarus dividuus differs from both species in the genitalia 1 Holotype male, GR 60 Achaia (PA) Erymanthos, distinctly larger than genitalia 2, palp segment P-4 Ano Vlassia, riparian spring 1 Selinous, 1000 m, relatively shorter (L ratio P-2/4 1.59, in the compared 25.05.1992, undissected, slide mounted in Hoyer’s species < 1.35) and more stout, predorsale, excretale fluid; paratypes: same collecting site and date, one and postexcretale less slender, and the peg setae on P-4 male, GR 63 Achaia (PA) Erymanthos, Ano Vlassia, homoiomorphic and directed distally (in the compared riparian spring 2 Selinous, 1000 m, 27.05.1992, one species, the proximal one reduced in size and directed male, one female, variously dissected, slide mounted ventrally). Furthermore, the male IV-L-5 is more slender, in Hoyer’s fluid. Further material not included into the but IV-L-6 more stout and the peg setae on the posterior type series: GR 60 (as holotype) 15 larvae, partly slide surface of IV-L-6 are more elongated and characterized mounted, partly mounted for SEM studies; GR 9 Ipiros by extending, pointed tips. (PRE) Preveza, Bunà Zalongu, affluent 2 km upstr. 70 Gerecke & Benfatti Water mites of the genus Acherontacarus

Mirsíni, 180 m, QW 78 93, 20.05.1991 one larva, slide margin largely rounded, setae in the central part of the mounted. shield, far distant from lateral margins; lateralia very irregular in shape, 7th pair strongly elongated, pairs 2 Description and 8-10 particularly reduced in size; all coxae fused to a shield embracing the subrectangular circumgenital Male (holotype, in parentheses paratypes) field, sutures between coxae visible, but indistinct; Cx- Idiosoma (Fig. 11) L/W 1060/900, colour yellow; 1+2 median L/maximum W 291/706 (291/660-706, dorsal shields without tubercles, predorsale L/W 134/ 0.41-0.44); genital field L/W 100/100, with five pairs 44 (134-148/414-448, 0.30-0.34), with anterior margin of genital flap setae; genitale 1 L/W 72/85 (67-72/85- in the centre equally convex, laterally concave posterior 90, 0.74-0.85), pentagonal, caudal margin forming an margin medially deeply indented; lateral eye lenses angle, with a more extended medial and a shorter lateral visible, but little projecting; postdorsale L/W 661/515 part; genitale 2 L/W 36/41 (36-45/40-41, 0.88-1.13), (627-661/470-515, 1.27-1.33), anterior margin subquadratic, genitale 3 L/W 324/139 (288-324/117- medially slightly projecting, lateral margins slightly 139, 2.33-2.54), large, with slightly convex lateral and undulating (with concave and convex areas), caudal medial margins, genital sceleton: Figs 12D, 12E; excretale L/W 265/342 (234-265/300-342, 0.69-0.82), forming an equilateral triangle with truncated tips, Tab. 2 - Acherontacarus raphani male, measurements of IV- lateral margins straight, posterior margin in the centre L segments. slightly indented, postexcretale L/W 166/387 (139-166/ Tab. 2 - Acherontacarus raphani maschio, misurazioni degli 329-387, 0.39-0.43), anterior margin medially slightly articoli di IV-L. projecting, posterior margin slightly convex, lateral I-L II-L III-L IV-L edges truncated; for measurements of IV-L (Fig. 12A) 1 L 76 72 72 121 see table 1; IV-L-3 with one long ventral seta; IV-L-4 1 relative L relative L 07 07 07 10 with a little conspicuous ventral groove in the basal 2 L 279 306 297 324 part bearing two long hair-like setae; IV-L-5 with two 2 relative L 27 29 28 26 little projecting ventral lamellae flanking five hair-like 3 L 139 135 126 148 setae and a strong, “raphanus-like” ventrodistal seta, 3 relative L 14 13 12 12 some further minor setae on the distal surface; IV-L-6 4 L 153 166 166 238 with distally little diverging dorsal and ventral margins, 4 relative L 15 16 15 19 an irregular row of minute dorsal setae restricted to 5 L 162 166 180 220 the basal 2/3 of the segment, a row of strong peg-like 5 relative L 16 16 17 18 setae on the posterior surface and a row of long, but 6 L 207 211 238 189 less thickened ventral setae restricted to the distal part 6 relative L 20 20 22 15 of the segment; gnathosoma (Fig. 11A) L/W 288/216, Totale 1016 1056 1079 1240 with well projecting lateral extensions at the palp

A B

Fig. 11 - Acherontacarus raphani paratype male, idiosoma. A) ventral view, B) dorsal view. Bar= 100 µm. Fig. 11 - Acherontacarus raphani paratipo maschio, idiosoma. A) vista ventrale, B) vista dorsale. Tratto= 100 µm. Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 71

interspace from Cx-3+4; genital field L/W 166/90, genital flaps subdivided in two pairs of sclerites which with their triangular lateral edges submerge far under the medial margin of genitale 3, bearing three pairs of setae; genitale 1 L/W 117/117, quadrangular, with A maximum W anteriorly, flanking a large part of the genital field, genitale 2 L/W 72/58 (1.24), quadran- gular, with maximum W posteriorly; genitale 3 L/ W333/166 (2.01), with slightly convex lateral and slightly concave medial margins, excretale L/W 261/ B 211 (1.24), forming an elongated triangle truncated anteriorly, but with pointed posterior edges, lateral margins slightly convex, posterior margin with a slight shallow indentation; postexcretale L/W 157/270 (0.58), anterior margin in the centre slightly protruding, laterally slightly concave; posterior margin rounded, C in its central part less curved than laterally; gnathosoma L/W 270/215, rostrum L/W 123/110, with a large base; chelicera L 264 (basal segment 206, claw 58), H 43; palp measurements (L/H, ratio): P-1 27/56 (0.48), P-2 DE F 175/81 (2.16), P-3 100/65 (1.54), P-4 96/49 (1.96), P- 5 49/22 (2.23); shape and setation as in males. Deutonymph: unknown. Larva Idiosoma (Figs 17 D, E) L/W 405/356 (1.14), dor- sale L/W 252/279 (0.90), laterally convexely protru- Fig. 12 - Acherontacarus raphani paratype male. A) IV-L; ding, caudal margin forming an obtuse triangle; Cx- B) palp lateral view; C) palp medial view; D) ejaculatory 1+2 L/W 225/333 (0.68), caudal margin forming an complex lateral view; E) ejaculatory complex anterior view; obtuse triangle; excretale L/W 72/63 (1.14), consisting F) chelicera. Bars= 100 µm. only of a minute, longish oval sclerite with excretory Fig. 12 - Acherontacarus raphani paratipo maschio. A) IV-L; pore and a pair of setae arranged very close to each B) palpo vista laterale; C) palpo vista mediale; D) complesso other; gnathosoma (Fig. 17B) L/W 136/130 (1.05), eiaculatore vista laterale; E) complesso eiaculatore vista with distally equally narrowed margins, mouth opening anteriore; F) cheliceri. Tratti= 100 µm. large, preoral setae flattened, disk-shaped; palp insertions covered by the lateral edges of a rhombic “ventral platform” which extends to the area of the insertions, an equally narrowed rostrum and inflated mouth opening; palp with P-4 sphaerical and bearing terminal setae; chelicera (Fig. 12F) L 256 (basal numerous fine and long setae, not covered by a segment 202, claw 54), H 38; palp (Figs 12B, 12C) dorsodistal extension of P-3. measurements (paratype, L/H, ratio): P-1 36/56 (0.64). P-2 175/94 (1.86), P-3 100/76 (1.42), P-4 105/61 Discussion (1.72), P-5 54/22 (2.45); P-2 with equally diverging dorsal and ventral margins, bearing only 3 setae in the Acherontacarus raphani is similar to A. halacaroi- distal part of the segment (dorsally, laterally, ventrally), des, A. fonticolus and A. dividuus in the absence of P-3 subrectangular, ventral margin with a slight basal tubercles from the dorsal shields. Males differ from A. kink, P-4 stout, distally inflated, medial peg setae halacaroides and A. dividuus in the subquadratic pointed, close to each other at the dorsodistal segment circumgenital field with laterally only slightly convex margin, P-4 with short basal part and seven long, little genitalia 3 and subquadratic genitalia 2, and the IV-L- curved claw setae. 5 with a strong “radish-like” distal seta - the latter character unique among all other species of the genus. Female (paratype) Both sexes differ from A. halacaroides and A. dividuus Idiosoma (Fig. 13A) L/W 1000/750, predorsale L/ (known in the male sex only) in the more stout P-4 W 134/420 (0.32); postdorsale L/W 683/515 (1.33); with both medial peg setae inserting at the distal circumgenital area with maximum W on the level of segment margin, females differ from A. halacaroides genitalia 3, caudally narrowed, Cx-1+2 medial L/ in a more slender genitale 3 and excretale. At the maximum W 275/638 (0.43), medial suture little visible moment, the deutonymphal stage of the new species as in males, but clearly separated by membranous being unknown, the distinction from A. fonticolus 72 Gerecke & Benfatti Water mites of the genus Acherontacarus which is described only from a deutonymph is Description problematic. However, it differs from A. raphani in a Female (holotype, male unknown) more stout palp with one of the medial peg setae of P- 4 distanced from the distal segment margin. In all Idiosoma (Fig. 13 B, C) L/W 750/515, predorsale Acherontacarus species known both from adults and L/W 100/325 (1.31), with irregularly projecting, deutonymphs, agreement is found in these character medially truncated anterior margin, lateral eye lenses states within developmental stages. well projecting, a pair of tubercles in laterocaudal Larvae are attributed to A. raphani due to detection position, posterior margin slightly concave, medially together with adults at the same collecting site. They indented; postdorsale L/W 660/360 (1.83), caudally are most similar to larvae of A. halacaroides/fonticolus parabola-shaped, with 11 pairs of lateral tubercles, in (see below) in the “ventral platform” of the gnathosoma the anterior part more distanced, in the posterior part anteriorly extending to the mouth opening and praeoral more close to each other, all setae arranged on the very setae not laterally projecting, and the minute excretale. edge of the plate; setae bearing lateral platelets slightly From these larvae, they can be distinguished in the larger than setae-free platelets, posteriorly decreasing more stout gnathosoma, with the margins of the ventral in size; Cx-1+2 median L/maximum W 200/485 (0.41), platform anteriorly converging and the the praeoral well separated medially from each other and laterally setae circular in shape. from Cx-3+4 by membranous sutures; genital field L/ W 130/63, genital flaps bipartite; genitale 1 L/W 100/ Biology 100, pentagonal, genitale 2 L/W 35/20, minute, longish rectangular, genitale 3 L/W 265/120 (2.21), with nearly The records come from sandy riparian springs straight lateral and medial margins, excretale L/W 185/ (typical “rheopsammocrenes” sensu Gerecke 1996) of 185, forming a slightly elongated triangle, postexcre- a mountain stream. Larvae were found crawling in the tale L/W 160/240 (0.67), with straight anterior and sediment; host preference unknown. strongly convex posterior margins and truncated lateral edges; gnathosoma L/W 184/157 (1.17), stout, with strongly projecting lateral edges basally from the palp Acherontacarus cyprioticus sp. nov. insertions, basal part with rounded lateral margins, (Figs 13B-F) terminal setae strong, but not particularly inflated; palp (Figs 13 D-F) measurements (L/H, ratio): P-1 25/34 Material examined (0.74), P-2 67/52 (1.29), P-3 82/45 (1.82), P-4 90/30 Holotype female, MNHA, Cyprus, E of Lanzanias, (3.00), P-5 37/14 (2.64); P-2 particularly shortened, stream Kiona, 24.04.2002, Smit; slide mounted in with curved dorsal and ventral margins, bearing seven Hoyer’s fluid. No further specimens known. setae (two ventrodistally, two dorsodistally, three

B C

D E A

F

Fig. 13 - Acherontacarus females. A) A. raphani paratype idiosoma ventral view; B-F A. cyprioticus. holotype; B) idiosoma ventral view; C) idiosoma dorsal view; D) palp lateral view; E) P-4/6 medial view; F) P-5. Bars= 100 µm. Fig. 13 - Acherontacarus femmine. A) A. raphani paratipo idiosoma vista ventrale; B-F A. cyprioticus. olotipo; B) idiosoma vista ventrale; C) idiosoma vista dorsale; D) palpo vista laterale; E) P-4/6 vista mediale; F) P-5. Tratti= 100 µm. Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 73 laterally in the basal part of the segment); P-3 elon- gated, dorsal margin slightly convex, ventral margin basally straight, in the distal part slightly concave, bea- ring two dorsodistal setae, P-4 slender, ventral margin basally concave (but not with a distinct kink), dorsal margin equally convex, the two hair-like setae in dorsal and ventral position distanced from the distal segment edge, the two peg like medial setae equal in size, inserting close to each other near mediodistal margin; P-5 with a short basal part and 7 long, weakly curved claws.

Deutonymph and larva: unknown. AB Discussion Fig. 14 - Acherontacarus ruffoi, holotype female. A) dorsal Acherontacarus cyprioticus differs from all so far view, B) ventral view. Bar= 100 µm. known species in the combination of the extremely Fig. 14 - Acherontacarus ruffoi, olotipo femmina. A) vista short P-2 (L/H ratio 1.29, other species females > 1.50, dorsale, B) vista ventrale. Tratto= 100 µm. males > 1.35), the rather long and slender P-4 (relati- ve L 30 %, other species 21-27 %), and consequently, platelets generally larger than setae-free platelets, but an extremely low L ratio P-2/P-4 (0.74, other species size difference little developed (at maximum 2:1); Cx- > 1.0). Acherontacarus rutilans, the species next similar 1+2 median L/maximum W 234/562 (0.42), separated in a relatively stout P-2, differs in the stout P-4, with medially and laterally against Cx-3+4 by well the proximal peg seta placed far distant from the distal developed suture lines; genital field L/W 170/112, one in the centre of the segment surface. Acherontaca- genital flaps bipartite, with two pairs of setae; genitale rus fonticolus and A. dividuus, the two species at pre- 1 L/W 135/103 (1.31), quadrangular, genitale 2 L/W sent unknown in the female sex, are clearly distin- 81/53 (1.53), rectangular, genitale 3 L/W 302/157 guished from A. cyprioticus in the absence of tuber- (1.92), large, with convex lateral and straight culation on the dorsal shield. mediocaudal margins, excretale L/W 216/230 (0.94), forming an equilateral triangle with truncated anterior Biology tip, postexcretale L/W 157/315 (0.50), with straight anterior and weakly rounded posterior margins and The only known specimen was taken by kick truncated lateral edges; gnathosoma L/W 250/180, with sampling in the gravel bed of a stream. little projecting extensions at the base of palp insertions and minute, peg-like terminal setae; palp (Fig. 6E) measurements (L/H, ratio): P-1 25/61 (0.41), P-2 190/ Acherontacarus ruffoi sp. nov. 87 (2.18), P-3 103/76 (1.36), P-4 114/54 (2.11), P-5 (Figs 6E, 14) 49/22 (2.23); P-1 very short, ring-shaped; P-2-4 rather slender, P-2 with equally diverging dorsal (slightly Material examined convex) and ventral (slightly concave) margins, bearing Holotype female, SMF, Spain, E 120, Andalusia five setae in dorsal (two), lateral (two) and mediodistal (CA) Sra. del Endrínal, rheocrenic spring SW Puerto position; P-3 weakly curved, with parallel dorsal and El Boyar, 1000 m, TF 85 69, 08.04.1994; slide mounted ventral margins, bearing two dorsal setae distanced in Hoyer’s fluid; damaged: left palp and part of the left from the distal edge, P-4 with a basal kink, with the gnathosomal rostrum broken, with signs of regenera- two hair-like setae in dorsal and ventral position tion. No further specimens known. distanced from the distal segment margin and the peg like medial setae strongly developed, pointed, inserting Description close to each other near the distal margin; P-5 with a short basal part and seven long, weakly curved claws. Female (holotype, male unknown) Deutonymph and larva: unknown. Idiosoma (Figs 14 A, B) L/W 941/706, colour yellow; dorsal shields without tubercles; predorsale L/ Discussion W 140/311 (0.45), with rounded anterior, and straight, medially weakly concave posterior margins, lateral eye Acherontacarus ruffoi is similar to A. halacaroides, lenses visible; postdorsale L/W 590/423 (1.23), A. fonticolus, A. dividuus and A. raphani in the absence caudally parabola-shaped, maximum distance of setae of tubercles on the dorsal shields. The latter three species from the lateral edge equal to the diameter of lateral differ from A. ruffoi in their by far more stout palps, A. platelets; lateral platelets rather enlarged, setae-bearing dividuus furthermore in the gnathosoma bearing strongly 74 Gerecke & Benfatti Water mites of the genus Acherontacarus

C

B

A, C-F E F A D

Fig. 15 - Acherontacarus deutonymphs. A) A. halacaroides idiosoma ventral view; B) A. fonticolus II-L; C) A. dividuus idiosoma dorsal view; D-F genitalia and excretale. D) A. fonticolus; E) A. rutilans; F) A. vietsi. Bars= 100 µm. Fig. 15 - Acherontacarus deutoninfe. A) A. halacaroides idiosoma vista ventrale; B) A. fonticolus II-L; C) A. dividuus idiosoma vista dorsale; D-F genitalia e excretale. D) A. fonticolus; E) A. rutilans; F) A. vietsi. Tratti= 100 µm. inflated praeoral setae, A. raphani in the genitale 2 sale L/W 288-293/279-293 (1.00-1.03), in the shape relatively reduced in size, the more slender excretale of a rombus with rounded angles; Cx-1+2 L/W 252- and the medial peg setae on P-4 inserting in a groove 270/347-351 (0.73-0.77), caudal margin forming an near the distal segment edge. Acherontacarus halaca- obtuse triangle; excretale (Fig. 16E) L/W 31-32/29- roides, a species rather similar in gnathosoma and palp 36 (0.89-1.07), consisting of a minute, roundish or morphology, differs in the dorsal shields more enlarged heart-shaped sclerite with excretory pore and a pair of with postdorsal setae much more distanced from the setae arranged very closely to each other; gnathosoma lateral plate edge, lateral platelets more slender, setae (Fig. 16C) L/W 171-202/121-148 (1.36-1.41), with bearing lateral platelets distinctly more longer than setae- distally equally narrowed margins; palp insertions free platelets (maximum ratio 2.0-3.0), minor genitalia covered by the lateral edges of a rectangular “ventral 2 triangular in shape, and the dorsal and ventral setae of platform” which extends to the area of the mouth P-4 inserting close to the distal segment edge. opening; mouth opening large, preoral setae flattened, transverse-oval in shape, medially overlapping, inserted Biology in a shallow bay formed by indentations of the praeoral The only known specimen was collected in a rheo- gnathosoma margin, the lateral margin of this bay crenic spring. Lifecycle unknown. forming a equally curved line; palp with P-4 sphaerical and bearing numerous fine and long setae, not covered by a dorsodistal extension of P-3. Acherontacarus halacaroides/fonticolus? (Fig. 16C, 16E) Discussion As the larvae from coll. Viets and coll. Schwoerbel Material examined agree in much detail, they are treated here together. In SMF, fountain near village Pridvorica, near the Ibar view of the lack of material of postlarval stages from stream 20 km upstr. Kos. Mitrovica, coll. Karaman, the two collecting sites, the question remains open if one larva; SMF in coll. Schwoerbel, “Mazedonien”, they represent a species still unknown to science or collecting site unclear, two larvae. one of the two species just known from Mazedonia, A. halacaroides or A. fonticolus. The larvae are characte- Description ristic in the combination of a rhombic dorsal shield, the minute excretale, the “ventral platform” of the Larva gnathosoma with parallel margins, and the preoral setae Idiosoma L/W 419-440/360-374 (1.16-1.18), dor- laterally weakly extended. Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 75

ABC

F G E

D

Fig. 16 - Acherontacarus larvae. A-D gnathosoma ventral view. A) A. vietsi (Sardinia); B) A. sp. Calabria (I 1112); C) A. sp. Macedonia; D) A. tuberculatus Spain (Pujante); E) A. sp. Mazedonia, excretale; F) A. vietsi, idiosoma ventral view; G) A. vietsi idiosoma dorsal view. Bars= 100 µm. Fig. 16 - Acherontacarus larve. A-D gnathosoma vista ventrale. A) A. vietsi (Sardegna); B) A. sp. Calabria (I 1112); C) A. sp. Macedonia; D) A. tuberculatus Spagna (Pujante); E) A. sp. Macedonia, excretale; F) A. vietsi, idiosoma vista ventrale; G) A. vietsi idiosoma vista dorsale. Tratti= 100 µm.

A-C AB

E

C D

Fig. 17 - Acherontacarus larvae. A, B gnathosoma ventral view. A) A. rutilans (Sardinia, I 350); B) A. raphani (Greece, GR 60); C) A. tuberculatus, Spain (Pujante), excretale; D, E A. raphani (Greece, GR 60), idiosoma; D) ventral view, E) dorsal view. Bars= 100 µm. Fig. 17 - Acherontacarus larve. A, B gnathosoma vista ventrale. A) A. rutilans (Sardegna, I 350); B) A. raphani (Grecia, GR 60); C) A. tuberculatus, Spagna (Pujante), excretale; D, E A. raphani (Grecia, GR 60), idiosoma; D) vista ventrale, E) vista dorsale. Tratti= 100 µm. 76 Gerecke & Benfatti Water mites of the genus Acherontacarus

Acherontacarus sp. Biology (Fig. 16B) The specimens were collected in an area rich in strongly flowing karstic rheocrenes, partly crawling in Material examined the gravel and sand sediment, partly attached to flight Italy, I 1101 Calabria (CS) Pollino, Morano Calabro, active Dytiscid beetles. As intense field work in various spring in Contrada S. Paolo, 600 m, WE 962 127, seasons did not produce any record of postlarval stages, 04.10.1990, one larva; same collecting site, 01.06.1996, we suggest that these larvae belong to an undescribed seven larvae (four of them used for transection series, species at the adult stage having a particular preference see Benfatti & Gerecke 1999); I 1112 Calabria (CS) for deeper layers of the groundwater/surface water Pellegrino, Saracena, spring in Contrada Polignano, 750 ecotone. m, WE 973 063, 07.10.1990, two larvae on Agabus guttatus, first abdominal segment, ventrally. ACKNOWLEDGEMENTS Description Larva This study found support from Ana Pujante, Pedro Aquilera, Carles Hernando, Ignacio Ribera and Harry Idiosoma L/W 360/311 (1.16), dorsale L/W 234/ Smit by submission of specimens collected during 247 (0.95), in the shape of a rombus with rounded zoobenthological field work, and by Julia Altmann angles; Cx-1+2 L/W 211/297 (0.71), caudal margin (SMF), Manfred Graßhoff (SMF), Ambros Hänggi forming an obtuse triangle; excretale L/W 23/25 (0.92), (NHMB), Peter Jäger (SMF), Torbjörn Kronestedt consisting of a minute, round sclerite with excretory (SMNH), Ulrike Schreiber (SMF) and Urs Wüest pore and a pair of setae arranged very closely to each (NHMB) by loan of museum material. Our sincere other; gnathosoma (Fig. 16 B) L/W 134/119 (1.13), thanks go to all of them. with distally equally narrowed margins; palp insertions covered by the lateral edges of a “ventral platform” which extends with slightly converging lateral margins to the area of the mouth opening; mouth opening large, REFERENCES preoral setae flattened, disk-shaped, medially overlap- ping, inserted in a bay formed by indentations of the Angelier E. (ed.), 1959 - Hydrobiologie de la Corse. Vie et preoral gnathosoma margin; the lateral angles of this Millieu, Suppl. 8: 277 pp. bay sharp, nearly rectangular; palp with P-4 spherical Bader C., 1983 - Zwei neue Wassermilben-Arten aus dem and bearing numerous fine and long setae, not covered Interstitial des Mittelmeergebietes. Riv. Idrobiol., 22 (2- by a dorsodistal extension of P-3. 3): 169-177. Bader C., 1989 - Wassermilben (Acari: Hydrovolziidae et Discussion Hydrachnellae) aus Algerien. Bijdr. Dierk., 59 (1): 33-42. Benfatti D. & Gerecke R., 1999 - Remarks on the distribution, Several attempts to collect postlarval specimens life cycle and larval morphology of Acherontacarus K. from the Italian collecting sites were unsuccessful. As Viets (Hydrachnellae: Hydrovolziidae). In: Bruin J., van a single record of a specimen of Acherontacarus from der Geest L.P.S. & Sabelis M.W. (eds): Ecology and Central Italy (Abruzzo: Di Sabatino pers. comm.) is Evolution of the Acari. Kluwer Academic Publishers, based on fragments of a heavily damaged adult, the Dordrecht, The Netherlands: 473-482. question about the identity of the Italian species re- Gerecke R., 1996 - Untersuchungen über die Wassermilben mains open. The larvae from Calabria are a little mi- der Familie Hydryphantidae (Acari, Actinedida) in der nor in size than those reported from Mazedonia, but agree in most proportions. A difference is found in the Westpalaearktis II. Die Wassermilben der Familie Hydry- more stout gnathosoma with anteriorly slightly phantidae in den Mittelmeerländern - Systematik, Fau- narrowed, not rectangular “ventral platform”, the disk- nistik, Zoogeographie. Arch. Hydrobiol., Suppl., 77 (3/ shaped, not laterally enlarged praeoral setae, and the 4): 337-513. bay at the anterior gnathosomal margin set off more Santucci J., 1970 - Contribution à l’étude du comportment distinctly. In the shape of the preoral setae, the Cala- estival de quelques Hydracariens (Hydrachnellae) brian larvae are similar to those of A. raphani, a species psammiques d’un torrent de Corse - Le Porto. Ann. Fac. differing in a larger excretale (L/W > 50/50), the Sci., 44: 191-211. “ventral platform” of the gnathosoma anteriorly more Santucci J., 1971 - Contribution à l’étude de la répartition des tapering, and a very shallow bay embracing the preoral Hydracariens (Hydrachnellae) des eaux superficielles d’un setae insertions. The detection of these larvae prooves torrent de Corse - Le Porto. Ann. Fac. Sci., 45: 81-99. the existence of a species in Italy which is probably Santucci J., 1975 - Contribution à l’étude de deux espèces closely related to, but clearly different from, the popula- du genre Acherontacarus (Hydrachnellae) de Corse. tions so far known at the larval stage from the other Ann. Univ. Provence., Rev. Biol. Ecol. Méditerr., 2 (3): side of the Aegean Sea. 15-18. Studi Trent. Sci. Nat., Acta Biol., 81 (2004): 53-77 77

Schwoerbel J., 1963 - Süßwassermilben aus Mazedonien. unterirdischen Gewässern (Hydrachnellae et Halaca- Acta Mus. Macedon. Sci. Nat., 9 (4): 51-75. ridae, Acari). Zool. Anz., 102 (11-12): 277-288. Tuzovskij P., Benfatti D., & Gerecke R., 2001 - About the Viets K., 1934 - Sechste Mitteilung über Wassermilben aus taxonomical status of the water mite subfamily Acheron- unterirdischen Gewässern. (Hydrachnellae und Halaca- tacarinae and diagnosis of the superfamily Hydro- ridae.). Zool. Anz., 105 (11-12): 273-281. volzioidea Thor, 1905 (Acari, Hydrachnidia). Acarologia Viets K., 1935 - Wassermilben aus unterirdischen Gewässern (Paris), 41: 451-473. Jugoslaviens. (Achte Mitteilung). Verh. Internat. Verein. Viets K., 1933 - Vierte Mitteilung über Wassermilben aus Limnol. Beograd 1934, 7: 74-86.