Amerodectes gracilisimilis, Hernandes, 2023

Hernandes, Fabio Akashi, 2023, Feather mites (Acariformes: Astigmata) from the yellow-rumped cacique, Cacicus cela (Linnaeus, 1758) (Passeriformes: Icteridae) in Brazil, with description of four new species, Journal of Natural History 57 (2), pp. 257-284 : 264-268

publication ID 10.1080/00222933.2023.2174459


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scientific name

Amerodectes gracilisimilis

sp. nov.

Amerodectes gracilisimilis sp. nov.

( Figures 4 View Figure 4 –6,13(d))

Type material

Holotype male (#5388), paratypes 13 males and 22 females (#5389–5397) from Cacicus cela (Linnaeus, 1758) ( Passeriformes : Icteridae ), BRAZIL, Bahia State, Ilhéus, campus of UESC, 14.7597222°S, 039.2302778°W, found dead, 14. December 2020, Anibal R. Oliveira coll GoogleMaps .


Male, holotype (range for 6 paratypes in parentheses). Idiosoma, length × width 401 (380– 402) × 148 (129–151). Prodorsal shield: entire, lateral margins with shallow concavities at level of scapular setae, posterior margins unevenly sinuous, length 132 (123–134), width 107 (95–111), surface with sparse circular lacunae, median region near posterior border with a darker patch of sclerotisation ( Figure 4 View Figure 4 (a)); bases of scapular setae se separated by 65 (55–64). Setae ve present, rudimentary. Scapular shields poorly developed dorsally. Humeral shields present, bearing setae cp; c2 on striated tegument. Subhumeral setae c3 lanceolate, 32 (28–31) × 8 (7–8). Hysteronotal shield: greatest length 272 (255–264), width at anterior margin 104 (85–100), anterior margin almost straight, surface with numerous small, circular lacunae as in prodorsal shield. Distance between prodorsal and hysteronotal shields 11 (11–13). Opisthosomal lobes almost parallel-sided, posterior margins rounded. Terminal cleft shaped like an inverted V, 31 (29–32) long. Supranal concavity present. Setae f2 dorsal, located anterior to level of setae ps2. Setae h1 situated at anterior level of supranal concavity. Setae h3 long setiform, 77 (75–88) long; setae ps2 76 (86–100) long; setae ps1 filiform, about 8 long, situated slightly anterior to bases of setae h3. Distances between dorsal setae: c1:d2 102 (98–108), d2:h1 119 (110–121), h2:h2 63 (59– 61), h3:h3 41 (38–41).

Epimerites I fused into a narrow V, fused part with transverse extensions connected with or free from epimerites II ( Figure 4 View Figure 4 (b)). Coxal fields I closed or open, coxal fields II–IV open, without extensively sclerotised areas. Rudimentary sclerites rEpIIa absent. Epimerites IVa absent. Genital arch 19 (15–17) in width; aedeagus bending into a posterior shaft around the level between trochanters III and IV, 163 (155–167) long from the anterior bend to tip, extending to about the base of setae h3. Genital papillae connected at bases. Genital and adanal shields absent. Adanal suckers 20 (18–21) in diameter, distance between centres of discs 27 (24–30), corolla smooth, surrounding membrane with radial striae. Opisthoventral shields wide, occupying lateral areas and posterior halves of opisthosomal lobes; inner margins of these shields with blunt extension bearing setae ps3 at level of anterior margin of adanal suckers. Setae 4b and 3a situated roughly at the same transverse level. Distance between ventral setae: 1a–4b 132 (125–130), 4b–4a 44 (39–46), 4a–g 52 (50–55), g–ps3 56 (50–63), ps3–ps3 61 (57–63).

Femora I, II without ventral crests or flanges ( Figure 6 View Figure 6 (a,b)), other segments of legs I–IV without processes. Solenidion σ of genua I, III situated at distal half of segment. Genual setae cG I, II, mG I, II like short spines, cG I inserted basally, cG II at midlevel of segment. Seta d of tarsus II half as long as corresponding seta f; seta d of tarsi III 2–3 times shorter than corresponding seta f ( Figure 6 View Figure 6 (c)). Tarsus IV 29 (27–31) long, without claw-like apical process; setae d and e button-like, seta d situated at basal third of segment, setae e situated apically (subapically) ( Figure 6 View Figure 6 (d)). Ambulacral discs with median apical projection. Length of solenidia: σ of genu I 7 (6–7), σ of genu III 7 (6–8), φ of tibia I 73 (68–78), φ of tibia II 55 (52–57), φ of tibia III 26 (26–28), φ of tibia IV 37 (33–37), ω1 of tarsus I 16 (12– 17), ω3 of tarsus I 43 (35–39), ω1 of tarsus II 8 (5–8).

Female, range for 6 paratypes. Idiosoma, length × width 551–570 × 183–199. Prodorsal shield: shape as in male, surface without lacunae, with a distinct darker patch at posterior margin, length × width 151–154 × 127–142, posterior margin roughly sinuous, bases of setae se separated by 80–87 ( Figure 5 View Figure 5 (a)). Setae ve present, rudimentary. Scapular shields developed dorsally. Humeral shields present, bearing setae cp and c3. Setae c2 situated on the striated tegument. Setae c3 lanceolate, 30–33 × 8–10. Hysteronotal shield separated dorsally by a transverse narrow band of soft tegument into anterior and lobar parts. Distance between prodorsal and anterior hysteronotal shields 8–17. Anterior hysteronotal shield roughly rectangular, anterior margin straight, greatest length 300–314, width at anterior margin 103–110, surface with numerous small circular lacunae. Length of lobar region 103–110, greatest width at level of setae h2 95–101. Terminal cleft like a narrow V, 38–46 long. Lobar shield entire; surface with circular lacunae around area of setae h1; supranal concavity present, circular, situated near the anterior margin of lobar shield. Setae h1 and f2 arranged in a low trapezoid. Setae h2 lanceolate with blunt apex, 43– 47 × 9–11. Setae ps1 situated slightly at midline of each lobe, closer to h3 than to h2. Setae h3 11–18 long. Distances between dorsal setae: c1:d2 126–133, d2:h1 178–197, h2:h2 77– 81, h3:h3 40–50.

Epimerites I as in male ( Figure 5 View Figure 5 (b)). Coxal fields I and III almost closed, coxal fields II and IV open. Epimerites IVa absent. Translobar apodemes of opisthosomal lobes present, wide, connected to each other at anterior end of terminal cleft. Epigynum horseshoeshaped, with small lateral extensions at level of setae g, greatest width 61–70; apodemes of ovipore connected with epimerites IIIa. Spermatheca as in Figure 6 View Figure 6 (g); secondary spermaducts 24–31 long. Pseudanal setae ps2 and ps3 filiform, bases of setae ps2 situated posterior to level of anal opening; distance between pseudanal setae: ps2:ps2 33–39, ps3: ps3 22–35, ps2:ps3 30–34.

Femora II with a small ventral flange, other segments of legs I, II without processes. Solenidion σ of genu I situated at midlevel of segment. Solenidion σ of genu III inserted basally. Genual setae cG I, II, mG I, II as in male. Setae d of tarsi I, II 2–3 times shorter than corresponding setae f, setae d of tarsi III, IV 2–3 times shorter than corresponding setae f. Genua IV with dorsal inflation. Ambulacral discs with median apical projection. Length of solenidia: σ of genu I 8–10, σ of genu III 7–12, φ of tibia I 79–87, φ of tibia II 63–65, φ of tibia III 32–39, φ of tibia IV 11–12, ω1 of tarsus I 16–19, ω3 of tarsus I 42–47, ω1 of tarsus II 9–11.

Differential diagnosis

Amerodectes gracilisimilis sp. nov. is very similar in overall appearance to the type species of the genus, A. gracilis ( Trouessart, 1885) , described from Psarocolius decumanus (Pallas, 1769) . In males the new species, the aedeagus is shorter in length (155–167), and has a shorter anterior portion which bends into a long shaft at the level of setae 4a ( Figure 6 View Figure 6 (e)); setae h3 is longer and setiform, about the same length as setae ps2, and longer than the distance se-se. In females, there are numerous small circular lacunae on the anterior hysteronotal shield, and the head of the spermatheca has a longer tube (about 15 long) preceding the bulbous inflation ( Figure 6 View Figure 6 (g)). Males of A. gracilis have the longest aedeagus known in the genus, at 223–237 µm ( Valim and Hernandes 2008), and with a bend almost at the level of setae 4b ( Figure 6 View Figure 6 (h)); setae h3 are lanceolate, 2–3 times shorter than setae ps2, and shorter than distance se-se. Females of A. gracilis have the hysteronotal shield without lacunae, and the head of the spermatheca has a shorter tube (about 10 long) ending with a small inflation ( Figure 6 View Figure 6 (i)).

Remark. Although this was not illustrated by either Berla (1959) or Valim and Hernandes (2008), the female of A. gracilis also has a darker area at the posterior margin of the prodorsal shield, similar to that of the new species.


From Latin similis (= similar, resembling without being identical), referring to the resemblance of the new species to Amerodectes gracilis .


Departamento de Geologia, Universidad de Chile

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