Franciscagrion longispinum Machado & Bedê, 2015

Cezário, Rodrigo Roucourt, Vilela, Diogo Silva & Guillermo-Ferreira, Rhainer, 2019, Final instar larva of Franciscagrion longispinum Machado & Bedê, 2015 (Odonata Coenagrionidae), an endemic species from the springs of the São Francisco river, Zootaxa 4657 (3), pp. 581-586 : 582-585

Description of the final instar larvae of Franciscagrion longispinum Machado & Bedê, 2015

Figs. 1–6 .

Material examined. 2 ♂♂ and 1 ♀♀ F0 exuvia ( Fig. 1a ): BRAZIL, Serra da Canastra , São Francisco river histori- cal springs (-20.2442, -46.4468), 08–iii–2018, Guillermo-Ferreira leg. , 2 ♂♂ and 1 ♀♀ F0 (reared in laboratory).

Head. Roughly trapezoidal, 1.88 as wide as long measured from the occipital bar to labrum convex cephalic lobes, with few punctuations, without setae. Ventral margin of the eyes at mandibles level. Antennae 7-jointed, third antennomere the longest. Distal half of antennomeres 1 and 2 and antennomeres 6 and 7 ochre, 3–5 yellow; length of antennomeres: 0.15 [0.16–0.13], 0.24 [0.26–0.22], 0.32 [0.33–0.32], 0.20 [0.19–0.20], 0.13 [0.13–0.14], 0.07[.06– 0.07], 0.06 [0.06–0.07]. Prementum 0.70 as wide as long. Dorsal surface of the prementum with 4–5 setae on each side, the inner one the smallest. Ligula prominent with crenulated distal margin. Labial palp with one tooth smaller than the movable hook. Five small teeth between movable hook and distal tooth. Five or six palpal setae with no spines at base. Among male individuals, one had five palpal setae, and four setae on each side of prementum, while the other male had six setae on labial palps and five on prementum. Mandibles with molar teeth but without molar crest, with the formula: L 1+2345 y ab (1<3<4<5<2)/ R 1+2345 y a (1<3<2<4<5) ( Fig. 4 ).

Thorax. Pronotum trapezoidal with a lobed lateral expansion at the posterior margin, bearing no setae. Wing pads yellow, extending up to S4. Legs yellow; femur crenulated with small setae.

Abdomen. Mostly pale, with dark spots all over the abdomen. Cerci conoidal; distal margin rounded in lateral view, pointed forwards; S8–9 with 2–3 small setae; ♂ gonapophyses blunt; not reaching S10; ♀ gonapophyses surpassing S10 (~ 1.36mm). Gills (sensu Novelo-Gutiérrez 1992) laminar narrow at base, lanceolate with acuminate tips; granulated color pattern; median lamella shorter than lateral lamellae; tracheae ochraceous.

Measurements. Total length without appendages: 10.63 [10.03–11.47]. Total length of head: 1.43 [1.34–1.56]; max. width: 2.29 [2.16–2.26]. Prementum length: 1.47 [1.45–1.51]; max. width: 1.04 [1.01-1.05]. Total length of la- bial palp: 0.73; max. width: 0.24. Femur I: 0.99 [0.91–1.07]; II: 1.28 [1.17–1.45]; III: 1.67 [1.56–1.88]. Tibia I: 1.18 [1.16–1.23]; II: 1.35 [1.11–1.69]; III: 1.73 [1.54–1.95]. Inner wing pads: 2.85 [2.96–2.75]; external wing pads: 2.73 [2.66–2.86]. Medial caudal lamellae: 4.11 [4.21–4.02]; lateral caudal lamellae: 4.59 [3.92–5.15]. The ♀ antenna was broken and was not added to the measurements.

Habitat and Ecology: The final instar larvae of F. longispinum were collected in the São Francisco river historical springs, on roots of the aquatic vegetation. The soil is permanently wet, defined as a Vereda wetland (a unique Neotropical savannah environment with typical hydrosoil and vegetation) ( Vilela et al. 2016). The species seems to be endemic and restricted to these springs.

Remarks. Differential diagnosis. The characters discussed here were based on the identification key for Coenagrionoidae by Lozano et al. (2018, p. 475–494), and do not reflect phylogenetic relationships. Furthermore, based on preliminary data from a recent molecular analysis (Vilela et al. unpub. data), Franciscagrion seems to be related to Acanthagrion , Homeoura , Argentagrion and/or Franciscobasis . However, since further analyses are needed to infer phylogenetic relationships, here we discuss morphologically similar genera.

The larvae of Franciscagrion do not present the lateral carina in the abdomen, which is present in the larvae of Ischnura and Argentagrion . Argentagrion larvae are also smaller (~ 6mm) than Franciscagrion (~ 10mm). Homeoura larvae do not have unique diagnostic characters, however, they can be distinguished from Franciscagrion by presenting the medial margin of the labial palp crenulated; while Franciscagrion presents smooth medial margins of the labial palp. The larvae of Acanthagrion and Franciscagrion can be differentiated by the size of the caudal lamellae, which are as long as the abdomen in Acanthagrion , while in Franciscagrion , the abdomen is 1.50 times longer than the mean length of the caudal lamellae. For more comparisons about larval traits, please see Table 1.

Figures

FIGURES 1–4. Franciscagrion longispinum. 1a. F0 exuvia habitus; 2. antenna; 3. prementum: 3a. detail of labial palp, 3b. lateral row of setae; 4. right and left mandibles.

FIGURES. 5a–c. Franciscagrion longispinum. 5a. posterior view of F0 exuvia cerci, 5b. dorsal view of cercus, 5c. ventral view of F0 exuvia S9 and S10 ♂ gonapophyses.

FIGURE. 6. Franciscagrion longispinum. Median and lateral lamellar of exuvia.