CriCotopus ( s . str . ) latellai sp . n . , a new rheophilic species of the tremulus-group from the italian and french maritime alps ( diptera : chironomidae )

Cricotopus (Cricotopus) latellai sp. n. is described and diagnosed based on material comprising male and female pharate adults, pupal exuviae and larvae recently collected in some glacial streams in both the Italian and French Maritime Alps. Taxonomic notes provided in this paper include: description of C. latellai sp. n. as male and female adults, pupal exuviae and last instar larvae. The diagnosis of the Cricotopus tremulus-group is supplemented with additional characters in the male adult and pupal exuviae. Cricotopus latellai sp. n. keys near C. mantetanus Moubayed-Breil, 2016 and C. storozhenkoi Makarchenko & Makarchenko, 2016. Geographical distribution of C. latellai sp. n. is currently restricted to the Italian and French Maritime Alps. It belongs to the Tyrrhenian community of glacial relic species, which are considered to be indicators of climate change in this biogeographical region. Remarks, taxonomic position, and ecology of the new described species are given.


Methods
Morphological terminology and measurements follow that of Saether (1980) for the imagines and pupal exuviae.For a better examination of the specific features and more accurate description of the various taxonomic details of the pupa, the pupal abdomen was mounted not only in dorsal and ventral view but separately in lateral view, which facilitates proper examination and illustration of all the relevant taxonomic characters.Remarks and discussion on some related species and comments on the ecology and geographical distribution of the new species are given.

Results
Cricotopus latellai sp.n. belongs to the tremulusgroup based on characters found in the male adult (distribution pattern of median setae on tergites II-V; shape of tergite IX, inferior volsella and gonostylus) and pupal exuviae (chaetotaxy and granulation of thorax; armament of abdominal segments, shape and size of anal macrosetae) and keys near C. mantetanus and C. storozhenkoi.The new species is only known from high and middle mountain streams located in both the Italian and French Maritime Alps.The 766 valid species known from continental France (Moubayed-Breil & Ashe own observations, Moubayed-Breil 2016) increases to 767 with the description of a new species of Propsilocerus Kieffer from eastern France (Moubayed-Breil, in press).Consequently, the description of C. latellai sp.n. increases the total number to 768 species known from continental France.
The tremulus-group was first emended by Hirvenoja (1973) then modified by Moubayed & Hirvenoja (1986), Casas & Vilchez-Quero (1992) and most recently by Moubayed-Breil (2016).The diagnosis of the tremulus-group is refined by including features found in the male adult and pupal exuviae: Adult male.Palpomere 3 with 2-3 sensilla coeloconica placed distally; presence of lateral and occasionally median antepronotals; apex of femur and base of tibia of fore-, mid-, and hind leg blackish; tergites I-II whitish, remaining tergites blackish; chaetotaxy and distribution pattern of setae on median part of tergites II-V; gonocoxite with rounded or truncated apex, bearing or lacking a sub-triangular to rounded setiferous projection placed dorsally close to base of inferior volsella; inferior volsella: (i) pointing downwards at an acute angle, narrow and finger-like (C.nevadensis), (ii) a projecting lobe with outer margin gradually bent downwards and lacking strong dorsal setae on outer edge (C.latellai, C. royanus and C. tremulus), (iii) a projecting lobe with outer margin abruptly bent downwards at a right angle and with 2 strong dorsal setae on outer edge (C.mantetanus); crista dorsalis medium to large, toothlike, with pointed or rounded apex, moderately to strongly projecting orally.

Pupal exuviae.
Colouration brownish or contrasting whitish to blackish; frontal apotome with wrinkles and granulation, occasionally domed, frontal setae inserted on prefrons, ventral to antennal sheaths; cephalothorax with moderate to dense wrinkles and granulation, bearing or lacking a transverse posteromedian blackish shading placed between the thoracic suture (Dc 3 and Dc 4 ) and base of wing sheath, dorsocentrals are all setaelike or include 1-2 bristle-like setae; thoracic horn tube-like, foliate to ellipse-shaped with or without narrowing apex, toothed in general, occasionally smooth, teeth are pointed or occasionally smooth; anterior and posterior fields of spines on tergites III-VI clearly separated; median field of spines on tergite VI circular, diamond-like to sub-oval, posterior area of sternites V-VI with or without a faint transverse median patch of spines which, when present, are more concentrated and markedly larger on VI; anal lobe with distal part narrowing or distinctly swollen, apical rows of small spines restricted to apical area or extending well above insertion of anal macrosetae; macrosetae short and pin-like with a slightly curved apices.Holotype (on 2 slides, including the male adult and its pupal exuviae) with 1 additional paratype are deposited in the collections of the Zoologische Staatssammlung München (ZSM), Munich, Germany.Remaining paratypes are deposited in the senior author's collection.Type material was preserved in 80-85% alcohol, and later mounted in polyvinyl lactophenol.For each adult, the head, thorax and abdomen were cleared in 90% lactic acid then washed in about 60% ethanol before mounting on slides.

Diagnostic characters
Based on similarity of characters found in the male adult and pupal exuviae of the tremulus-group, three species (C.latellai sp.n., C. mantetanus and C. storozhenkoi) are considered to be sister species.However C. latellai sp.n. can be easily separated with the following characters: Male adult: palpomere 3 with 2 sensilla coeloconica (tubule-like) placed distally; tergites III-IV with 3 median setae placed distally; laterosternite VIII not lobe-like; inferior volsella consists of a projecting lobe-like, with rounded outer margin gradually bent downwards, posterior area bearing two minute lobes, with a distinct rounded setiferous lobe placed close to its base; crista dorsalis large, tooth-like and orally projecting, apex rounded in dorsal view and pointed in lateral view; Pupal exuviae: thoracic horn foliate to ellipselike, narrowing distally with pointed to smooth ending apically, toothed, teeth are smooth in general or occasionally weekly pointed; tergite VI with median dorsal field of spines semi-circular to diamond-like; posterior area of sternite VI with a distinct median patch of spines; distal part of anal lobe narrowing, apical rows of small spines extending well above insertion of anal macrosetae; macrosetae short with markedly curved apices.

Etymology:
The new species is named 'latellai' after our colleague Dr. Leonardo Latella, curator of zoology at the Museum of Natural History of Verona (Italy), who is contributing to preserve the biological and ecological quality of water and environment in Verona and surrounding areas.

Male pupal exuviae
(n = 15: 7 males, 8 females; Figs 31-36, 39-43) Colouration contrasting brownish to dark brown with blackish cephalothorax.Frontal apotome with dense wrinkles and granulation; cephalothorax brown to dark brown with blackish anteromedian area, densely wrinkled and granulose, granulation and wrinkles strongly covering the anteromedian area including the thoracic suture and Dc 1 -Dc 2 zone, granulose area along the thoracic suture reaching Dc 3 -Dc 4 zone, posteromedian area less granulose, presence of a characteristic transversal posteromedian blackish shading extending between Dc 3 -Dc 4 and base of wing sheath.Base of wing sheath covered with blackish bow-like shading.Abdomen including anal segment brown to dark brown; dark brown apophyses distinctly present on segments I/II-VII; muscles marks distinct on segments I-VIII.width, slightly narrowing distally, apical area with small spines extending well above insertion of anal macrosetae.Macrosetae about 100 µm long, stout, pin-shaped and slightly curved apically.Genital sac (Fig. 42) 180-190 µm long, narrowed apically and overreaching apical margin of anal lobe by 65-70 µm.
Total length 3.90-4.00mm, maximum width 0.5-0.6 mm.Colouration contrasting pale greenish to blackish.Head (Fig. 45) blackish with a markedly transparent circular area (clearly visible in lateral view) placed on each side below base of antenna; proximal part of head capsule contrasting brown to dark brown including antennae and epipharyngeal region; mentum totally blackish; anteromedian area of clypeus densely covered with granulation.Thorax, abdomen and anal segment greenish.
In the pupal exuviae: granulation on cephalothorax covering the entire anteromedian area and thoracic suture (Fig. 32), is differently figured in C. mantetanus (Fig. 37); dorsocentrals are all setae-like; thoracic horn foliate to ellipsoidal and narrowed distally ; posteromedian area of sternites VI with a patch of small spines (Fig. 43).

Additional remarks
According to the previously provided key for known male adults and pupal exuviae from the Tyrrhenian Region (Moubayed-Breil 2016) Consequently, the main differentiating morphological features found in the male adults and pupal exuviae of the tremulus-group can be supplemented based on the combination of characters summarized in the following key of known species from the Tyrrhenian Region.

Ecology and geographical distribution
Localities where the larval, imaginal and pupal material of C. latellai sp.n. were collected consist of pristine epirhithral sections located in middle and high sectors of glacial streams (upper basin of the River Po, northwestern Italy, Fig. 50).Environmental data of water are: crystalline to moderately calcareous water, conductivity (about 20-30 µS/cm for dolomitic areas of the upstream of the Po River; 95-100 µS/cm for the calcareous upstream of the Casterino stream); temperature 8-12 °C during late spring and summer.Emergence is observed in June and July but apparently extends to late summer.Geographical distribution (Fig. 51) is delimited by the eastern limit of the Tyrrhenian Region, which covers both the Italian and French Maritime Alps.Moreover, C. latellai sp.n. belongs to a relict glacial element, which is believed to characterize the Tyrrhenian continental Province where other Tyrrhenian elements have previously been documented by Moubayed-Breil & Ashe (2016) and  Moubayed-Breil & Orsini (2016).This highlights the importance of some high local glacial mountain ranges in the Mediterranean Region where constructive plans for conservation and preservation of autochthonous glacial relic species must be implemented.Such relic species are considered as biogeographically representative and biological indicators of global warming and climate change.

Figure 3 .
Figure 3. Emergence pattern of the wintering generation from the Appingedam vase in spring 2014 (black dots and solid line) and hypothetical emergence pattern when larval development would have been interrupted by a diapause (dotted line).Number of pupal exuviae are added up per week.
, C. latellai sp.n. keys near C. mantetanus and C. storozhenkoi based on the following combination of characters: outer margin of inferior volsella is rounded for C. latellai sp.n. and C. storozhenkoi, shape of the thoracic horn for C. latellai sp.n. and C. mantetanus, while a nearly similar shape of anal lobe is observed in both C. latellai sp.n. and C. mantetanus.