Podonomus itatiaia , Shimabukuro, Erika Mayumi, Pepinelli, Mateus & Trivinho-Strixino, Susana, 2017

Shimabukuro, Erika Mayumi, Pepinelli, Mateus & Trivinho-Strixino, Susana, 2017, Two new species of Podonomus Philippi (Diptera: Chironomidae: Podonominae) from mountains of Southeastern Brazil, Zootaxa 4290 (1), pp. 155-166: 163-165

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Podonomus itatiaia

sp. nov.

Podonomus itatiaia  sp. nov.

Type material. Holotype: male adult with pupal exuvia, Brazil, Rio de Janeiro State, Itatiaia  , Pico das Agulhas Negras, first –order stream/ madicolous habitat, 22°22′55.2″S / 44°40′40.8″W, 2.419 m a.s.l. 10.vii.2012., leg. M. Pepinelli (N1-31, LEIA-UFSCar).GoogleMaps 

Etymology. Refers to the name of the type –locality: Itatiaia  . The specific epithet is treated as a noun in apposition.

Diagnostic characters. The new species can be separated from other Podonomus  species by the combination of the following characters. Male: complete absence of subapical lobe and also without any trace of swelling; gonostylus long (66 µm) and relatively slender, entirely covered by microtrichia; R4+5 straight; antennal plume normally developed. Pupae: large ventral lamella on segment II; five sinuous setae on each side of anal lobe; lateral processes of all segments straight; presenting two equal distal macrosetae at each side of the anal lobe; presence of a large anal spur distally in anal lobe.

Descriptions. Male (n = 1). Total length 1.28 mm. Wing length 1.18 mm. Total length/wing length. 1.08. Wing length/length of profemur 2.4.

Colouration: Black; wings light brown; legs uniformly dark brown

Head. Antenna with 14 flagellomeres, AR 0.4. Presence of scapal setae (46 µm long) and strong setae under pedicel 100 µm long. Last flagellomere 46 µm long; XIII flagellomere: 138 µm long. Temporal setae 19. Clypeus with 4 setae. Palp segment lengths (II –V in µm): 43, 92, 51, 63 µm. Third palpomere with 4 sensilla clavata, 12–25 µm long. Eyes bare.

Thorax ( Figure 5aView FIGURE 5). 21 acrostichals, 6 antepronotals, 28 dorsocentrals, 20 prealars, scutellum with 4 setae, 4 prescutellars.

Wing. Membrane with a patch of perpendicular setae on r cell ( Figure 1View FIGURE 1 b). r1 cell 83 µm wide, r4+5 cell 118 µm wide. R with 20 setae. R1 with 2. R4+5 straight and without setae. Brachiolum with 4 and squama with 5 setae.

Legs. Spur of fore-tibia 42 µm long ( Figure 5bView FIGURE 5. 1View FIGURE 1). Spurs of mid tibia 23 µm and 27 µm long ( Figure 5bView FIGURE 5. 2View FIGURE 2). Spurs of hind tibia 36 µm and 69 µm long ( Figure 5bView FIGURE 5. 3View FIGURE 3). Long setae on tibiae 160 µm long. Tibial comb with 8 bristles. Lengths and proportions of legs as in Table 4.

Hypopygium ( Figure 5cView FIGURE 5). Gonocoxite 138 µm long. Phallapodeme 83 µm long; transverse sternapodeme 49 µm long. Gonostylus 66 µm long ( Figure 5dView FIGURE 5); subapical lobe and swelling absent; P, x and y setae present but not conspicuous; short apical lobe 6 µm long, tooth (t setae) of normal type 12 µm.

Pupa (n = 1). Total length 1.84 mm. Exuviae brown.

Cephalothorax. Frontal setae as in Figure 5eView FIGURE 5. Thoracic horn ( Figure 5fView FIGURE 5) 263 µm long and 162 µm maximum width. Plastron plate square-shaped 143 µm long, respiratory atrium 155 µm long. Dc1 35 µm long, Dc2 29 µm long, Dc3 42 µm long. Sa 11 µm long. Longest median antepronotal 28 µm long. Lateral antepronotal 22 µm long. Precorneals 5 µm long. Distance between Dc1 and Dc2 8 µm, between Dc2 and Dc3 58 µm, between Dc3 and Sa 129 µm.

Abdomen. TI bare ( Figure 5gView FIGURE 5), TII –TVIII with fine and small spinules sparsely distributed. TII –TVII presenting two small patches of shagreen with coarse spinules. TIX with anterior shagreen. SI –SII bare ( Figure 5hView FIGURE 5); presence of lamella on SII ( Figure 5hView FIGURE 5). SIII –SVIII with fine, sparse median spinules; SIX with anterior spinules. Segment VIII with 7 L setae. Lengths (in µm) of L1 to L7 as: 362, 355, 354, 354, 323, 292, 315. Anal lobe 208 µm long with 5 sinuous setae ( Figure 5iView FIGURE 5). Two distal macrosetae on anal lobe with similar size, 41.5 and 46.1 µm long. Anal spur 9 µm long.

Notes on distribution and biology of the species. P. itatiaia  sp. nov. is only known from the type –locality, a madicolous habitat located at 2400 m a.s.l. in Pico das Agulhas Negras. This is the third highest mountain in southeastern Brazil, after Pico das Bandeiras and Pedra da Mina  , and the fourth highest in the country, reaching 2790 m a.s.l. in its summit. 

Taxonomic discussion. The male of P. itatiaia  sp. nov. resembles Podonomus inermis Brundin,1966  , Podonomus nordenskjoldi Brundin, 1966  and Podonomus quito Roback, 1970  , due to the complete absence of subapical lobe and swelling, and the elongated shape of the gonostylus. However, P. itatiaia  sp. nov. differs from P. inermis  by the format of R4+5, which is not S –shaped, and by the markedly smaller size of the wing; the species also differs from P. nordenskjoldi  by the normally developed antennal plume. The differentiation from P. quito  is possible due to the size of the gonocoxite and gonostylus, which are longer in P. itatiaia  sp. nov. Since the P. quito  male was described based on a pharate pupae, a detailed comparison is precluded by the lack of information on some structures, for example wings and legs. A preliminary comparison of female leg sizes suggests that the legs of P. itatiaia  sp. nov. may be distinctly longer than P. quito  .

On the other hand, the differences between P. itatiaia  sp. nov. and P. quito  become more evident when comparing the morphology of the pupa. P itatiaia  sp. nov. possesses a shorter and wider respiratory atrium, squareshaped plastron plate, and only 5 sinuous setae on anal lobe, while P. quito  presents a thinner and larger respiratory atrium, approximately with the same size as the thoracic horn, an oval plastron plate, and 14 sinuous setae on anal lobe. The pupa of P. itatiaia  sp. nov. is completely different from all the pupae described by Brundin, sharing most similarities with P. pepinellii Roque & Trivinho-Strixino, 2004  and P. mina  sp. nov. It differs from P. pepinellii  by the shape of plastron plate, which is conical in P. pepinellii  and square-shape in P. itatiaia  sp. nov., by equal –sized megasetae in anal lobe, and by the larger size of anal spur. The pupae of P. itatiaia  sp. nov. can be differentiated from P. mina  sp. nov. by the absence of abruptly curvature in the distal margin of the respiratory atrium in the former.

P. itatiaia  sp. nov. also does not fit completely in any Podonomus  group species created by Brundin (1966). The male well fits in the albinervis  group, because it does not present any trace of swelling or subapical lobe in his gonostylus, but this placement is discarded by morphological features of the pupae. The known pupae from albinervis  group possesses 11–30 sinuous setae on anal lobe, while P. itatiaia  sp. nov. only 5, and also the appearance of the cephalic horn is completely different from those observed in albinervis  pupae.

Unfortunately, DNA barcoding analysis of P. itatiaia  sp. nov. was precluded by the limited material available (only one specimen). Future sampling and molecular studies are necessary in order to compare P. itatiaia  sp. nov. with other Podonomus  spp.


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