Copelatus alternatus Sharp, 1882

Alarie, Yves, Michat, Mariano C., Watanabe, Kohei, Shaverdo, Helena, Wang, Liang-Jong & Watts, Chris H. S., 2022, An outlook on larval morphology of Copelatinae diving beetles with phylogenetic considerations (Coleoptera: Adephaga, Dytiscidae), Zootaxa 5175 (2), pp. 151-205 : 157-161

Copelatus alternatus Sharp, 1882

Source of material. All instar larvae studied were associated with adults collected at the following locality: Argentina, Tucumán Province. El Cochuna Provincial Park, 3/ 9-XII-2007, roadside pond; M. C. Michat leg. The identification is firm as C. alternatus is the only Copelatus species known from that locality.

Diagnosis (instar III). The third instar of Copelatus alternatus can easily be distinguished from that of the other species studied in this paper by the following combination of characters: HL = 0.90 mm; L3 <2.00 mm; U <0.40 mm; head capsule rounded, slightly constricted at level of occipital region ( Fig. 15 ) with scale-like sculpticels present over frontoclypeus and parietale; anterior margin of frontoclypeus narrowly convex, extending mesally at about level of adnasalia ( Fig. 15 ); adnasalia margined with a mix of bluntly rounded and truncated teeth ( Fig. 63 ); MP2/MP1> 1.50; GA/MP1> 1.50; 1.30 <LP2/LP1 <1.90; inner margin of stipes lacking a dorsal linear row of spinulae; profemur with less than 3 PV and 4 AV secondary setae; metafemur with less than 3 AV secondary setae; urogomphus composed of one urogomphomere; U/HW <0.40; U/LAS <0.50; Neotropical.

Description, instar I ( Figs 1–14 )

Body: Measurements and ratios aimed to characterize body shape are shown in Table 2 .

Head ( Figs 1–9 ): HL = 0.45–0.47 mm; Head capsule rounded, lacking a clear constriction at level of occiput; occipital suture absent; anterior margin of frontoclypeus lightly convex, extending mesally at about level of adnasalia; A/MP = 1.48–1.60; MP/LP = 1.70–1.79; MP2/MP1 = 1.96–2.17; GA/MP1 = 2.50–3.04; LP2/LP1 = 2.27–2.50; MNL/MNW = 2.75–2.88.

Thorax ( Figs 10–11 ): L3 = 0.83–0.88 mm.

Abdomen ( Figs 12–14 ): LAS = 0.30–0.32 mm; LAS subcylindrical, not constricted posteriorly at point of insertion of urogomphi. Urogomphus: U = 0.18–0.19 mm, composed of one urogomphomere; U/HW = 0.36–0.39; U/LAS = 0.56–0.65.

Chaetotaxy ( Figs 1–14 ): Position and number of additional setae on legs are shown in Table 3 and Figs 10– 11 .

Description, instar II. As first-instar larva except as follows:

Body: Measurements and ratios aimed to characterize body shape are shown in Table 4 .

Head: HL = 0.65 mm; anterior margin of frontoclypeus more narrowly convex; scale-like sculpticels welldeveloped over frontoclypeus and parietale; adnasalia margined with short bluntly rounded and truncated teeth (see Fig. 63 ); occipital suture present; A/MP = 1.59–1.64; MP/LP = 1.64–1.76; MP2/MP1 = 2.00–2.14; GA/MP1 = 2.38–2.57; LP2/LP1 = 1.78–1.89; MNL/MNW = 2.60–2.78.

Thorax: L3 = 1.32–1.34 mm.

Abdomen: LAS = 0.43–0.44 mm; LAS subcylindrical to subconical, less abruptly converging posteriorly at point of insertion of urogomphi. Urogomphus: U = 0.23–0.24 mm, composed of one urogomphomere; U/HW = 0.31–0.32; U/LAS = 0.54–0.56.

Chaetotaxy: Parietale with 3–5 temporal spines; position and number of secondary setae on legs are shown in Table 5 .

Description, instar III ( Figs 15–16 , 63 ). As second-instar larva except as follows:

Body: Measurements and ratios aimed to characterize body shape are shown in Table 6.

Head ( Figs 15 , 63 ): HL = 0.88–0.89 mm; A/MP = 1.52–1.56; MP/LP = 1.77–1.90; MP2/MP1 = 1.58–1.75; GA/MP1 = 1.83–2.00; LP2/LP1 = 1.42–1.58; MNL/MNW = 2.43–2.83.

Thorax: L3 = 1.74–1.81 mm.

Abdomen ( Fig. 16 ): LAS = 0.68–0.73 mm; U = 0.27–0.30 mm; U/HW = 0.27–0.32; U/LAS = 0.37–0.44.

Chaetotaxy: Parietale with 3–7 temporal spines. Position and number of secondary setae on legs are shown in Table 7 .

Figures

FIGURE 63. Anterior margin of left adnasalia of selected species of Copelatinae; magnification of 500x except CALT drawn at 400x. Species codes as in Table 1.

FIGURES 15–16. Copelatus alternatus Sharp, 1882, instar III: (15) head capsule, dorsal aspect (scale-like microsculptures not represented); (16) abdominal segment VIII, dorsal aspect. Scale bars = 0.2 mm.

FIGURES 1–2. Copelatus alternatus Sharp, 1882, head capsule, instar I: (1) dorsal aspect; (2) ventral aspect. EB, egg bursters; FR, frontoclypeus; LC, lamellae clypeales; PA, parietale; TP, tentorial pits. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale-like sculptures not represented. Scale bar = 0.1 mm.

FIGURES 3–5. Copelatus alternatus Sharp, 1882, head appendages, instar I: (3–4) antenna; (3) dorsal aspect; (4) ventral aspect; (5) mandible, dorsal aspect. AN, antenna; MN, mandible; sp, spinula. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bars = 0.05 mm.

FIGURES 6–9. Copelatus alternatus Sharp, 1882, head appendages, instar I: (6–7) maxilla; (6) dorsal aspect; (7) ventral aspect; (8–9) labium; (8) dorsal aspect; (9) ventral aspect. LA, labium; MX, maxilla. Numbers and lowercase letters refer to primary setae and pores, respectively; * = additional sensilla. Scale bars = 0.05 mm.

FIGURES 10–11. Copelatus alternatus Sharp, 1882, metathoracic leg, instar I: (10) anterior surface; (11) posterior surface. CO, coxa; FE, femur; PT, pretarsus; TA, tarsus; TI, tibia; TR, trochanter. Numbers and lowercase letters refer to primary setae and pores, respectively; * = additional sensilla. Scale bar = 0.05 mm.

FIGURES 12–14. Copelatus alternatus Sharp, 1882, instar I: (12–13) abdominal segment VIII; (12) dorsal aspect; (13) ventral aspect; (14) urogomphus, dorsal aspect.AB, abdominal segment VIII; UR, urogomphus. Numbers and lowercase letters refer to primary setae and pores, respectively. Spine-like spinulae on abdominal segment VIII not represented. Scale bars = 0.05 mm.