Aniara sepulchralis, (Fabricius, 1801) (Fabricius, 1801)

Silva, Ruan Felipe da, Brito, Rodrigo de Oliveira, Martins, Ivan Carlos Fernandes, Campos, Lourival Dias, Mello, Marcello Neiva de & Pearson, David Leander, 2023, Morphological redescription and morphometry of Aniara sepulchralis (Coleoptera: Cicindelidae) from Northeast Para, Brazil, Papéis Avulsos de Zoologia 63, pp. 1-11 : 3-10

RESULTS AND DISCUSSION

General description

The species is entirely black in color with a body length ranging from 11.3 to 12. 8 mm, and an overall fusiform shape and body proportion approximately three times longer than broad.The cuticle is heavily sclerotized with a rough elytral surface ( Figs. 14-18 ).

Head

Rectangular head, broader than long, forehead occupying almost all head space and with two frontal grooves protruding near the orbits and reaching the labral suture ( Fig. 9 ). Two supraorbital bristles on each side with distinct punctuation, the bristle being at the apex longer than the other. Flat clypeus, partially fused to the front, separated only by a weak suture, compound eyes, laterally fitted to the head ( Figs. 1-2 ).

Sub-rectangular labrum, broader than long with distal teeth with either rounded or triangular shapes and 4 bristles between the teeth ( Figs. 1-2 ).

Robust mandibles, longer than broad and concave ventrally; right mandible with molar region consisting of three sinuous teeth at the apex of the inner region, left mandible with two robust and larger teeth than the right at the apex, and two teeth at the base, one larger and another smaller than at the apex ( Figs. 1-2 ).

Unsegmented galea, with rounded apex composed of palpi and with licinia composed of thick bristles on the inner margin.

Segmented antennae with 11 antennomers; scape longer than the other segments, and with two bristles at the apex; short pedicel, rounded and without any bristles; 3-4 antennomers larger than pedicel, with antennomere 3 greater than 4, both have two bristles; 5-11 antennomers steadily smaller in size as they approach the apex, the 5 th largest of these antennomers, and all have a large number of small bristles ( Figs. 7-8 ).

Thorax

Sub-square pronotum, slightly convex, corrugated microsculpture, wider anteriorly and posteriorly, elevations on the lateral side, slightly globular slightly curved lateral margins, slightly rounded and short-bristled anterior and posterior angles, small and barely visible scutellum ( Figs. 15-18 ).

Elytra convex, with parallel lateral margins,completely rough surface, distinct punctuations on entire surface, higher concentration near pronotum, completely short and rounded humeral angle and no bristles ( Figs. 15-18 ).

Prothoracic legs large and thin, small trochanter, globose and without bristles. Large femur, largest leg joint, broader in the mid region and tapered towards the apex; longitudinally spaced bristles and in a line toward the apex. Tibia smaller than femur, homogeneously thin from base to apex, longitudinally spaced bristles and lined toward apex where they cluster; two symmetrical spurs at the apex ( Figs. 10-13 ). Proximal tarsus, with first tarsomere larger than the others, 2-3 more globous, 4 smaller than the others, 5 larger than 2-4 with dilated apex, bearing two simple claws; bristles throughout the tarsus,and tarsomeres 1-3 with agglomerated bristles on the inside.

Metathoracic and mesothoracic legs large and thicker than prothoracic legs. Subtriangular femora without bristles. Trochanter a bean-like shape with a slight depression in the convex part. Large femur, wider in the middle region; spaced bristles, fewer in number than other parts, lined vertically toward the apex. Narrow tibia, larger than femur; longitudinally spaced bristles, in four rows, towards the apex, and with two apical spurs. Proximal tarsus with first tarsomere larger than the others and with the presence of bristles; tarsomeres 2-5 practically the same size and with the presence of bristles, tarsomere 5 with dilated apex, carrying two simple claws ( Figs. 10-13 ).

Dimorphism

Sexual dimorphism within Cicindelidae and closely related Carabidae species has been widely studied. Such structures as legs, mouth and wings, distinguish the sexing of animals ( Ide, 2007; Martins et al., 2010; Moravec, 2015).

In A.sepulchralis there was no significant difference in the dorsal aspect (body shape and length) between male and female. However, some specific structures, such as the labrum and tarsi, exhibited differences ( Figs. 1-4 ).

The labrum in both sexes has dark coloration, 4 bristles and 5 teeth. However, females have have triangular-shaped teeth and rectilinear labral suture. Males, on the other hand, have a more sinuous shape in both the teeth and the labral suture ( Figs. 1-2 ). Such sexual differences have been observed in several species of Cicindelidae ( Martins et al., 2010) .

Males and females also present differences in the bristles present in tarsomeres I, II and III. In males there are adhesive bristles on the inside, which are absent in females ( Figs. 3-4 ). This dimorphism is observed in many species of Cicindelidae ( Martins et al., 2010) . It is thought that these bristles help males grip the females in copulation and subsequent mate guarding.

Morphometry

Some variables that contributed little to variance within the principal component analysis (PCA) were excluded. These non-relevant variables were head length, antenna, tibia of leg 1, thigh of leg 1, femur of leg 1, spur of leg 1 and trochanter of leg 3 ( Fig. 5 ).

After removal of non-relevant variables, the explanation of total variance was near 70% ( Fig. 6 ). The graph shows how relevant each structure is for the analysis, where the red components have the highest contribution. Each component is consistent for the high or low values. The smaller the angle between the variables, the greater the relationship between them.

Although the sample sizes were small, the p values were so significant, we consider them appropriate for cautious biological interpretation. Regarding morphological differences based on the site from which they were collected, the moist significant variables included: head width (p = 0.0014), pronotum width (p = 0.0088), distance between eyes (p = 0.0130), width from the base of the pronotum (p = 0.0176), labral length (p = 0.0214), labral width (p = 0.0273) and spur (p = 0.0858).The specimens from Igarapé-AÇu showed larger sizes than those from Belém ( Table 1 ).

Behavior and microhabitat have been associated with variation within some morphological structures of several species of beetle. Species of the genus Siagona and Carabus showed variation in the body length and in the morphology of the compound eyes ( Talarico et al., 2007; Talarico et al., 2011), and Scaphinotus petersi showed a difference in the head and pronotum ( Ober & Connolly, 2015) that were correlated with anthropogenic interferences, such as proximity to urbanized environments ( Papp et al., 2020). However, both biotic and abiotic factors need to be tested in the future to determine if individuals of A. sepulchralis from the two study areas are associated with these human influences and, if so, which ones.

The female specimens presented larger body length and morphological structures ( Table 2 ). Significant variables for sexual dimorphism were: Body length (p = 0.0024); head width (p = 0.0118), distance between eyes (p = 0.0142), pronotum length (p = 0.0415), pronotum width (p = 0.0115), labral length (p = 0.0253); and pronotum base width (p = 0.0785).

As observed in other studies, cicindelids/carabids commonly exhibit sexual dimorphism, as in spurs of the first segment of the tarsus ( Fuente et al., 2010), antenomers ( Benitez, 2013; Fuente et al., 2010) and abdominal segments ( Alibert et al., 2001).The female of A.sepulchralis is significantly larger, as in many invertebrates ( Gould, 1996). This may be due to factors such as the ability to support the male′s weight during copulation or the need to support more and heavier eggs for increased fecundity ( Adams & Funk, 1997; Tammaru et al., 2002). Possible cause(s) of this size dimorphism include a combination of environmental factors, such as humid or dry weather, and anthropogenic factors, such as soil or forest management and increased urbanization near these sites ( Benitez, 2013; Papp et al., 2020).

Figures

Figures 13-15. Habitus of Aniara sepulchralis.(13) Length of tibia,tarsus and spur of third leg pair;(14) Elytra length at the level of the elytra;pronotum junction to the elytra endpoint;elytra width at the level of the widest region of the structure;(15)Width of pronotum at apex and base level.

Figures 16-18. Habitus of Aniara sepulchralis. (16) Head width at eye level; interocular distance between the nearest points between the eyes;(17) Total length from the apex of the head to the last abdominal segmentin dorsal view;(18) Length of the pronotum at the central level of the plate region.

Figures 9-10.Head and first pair of legs.(9) Length of the head along the longitudinal line;(10) Length of the trochanter and femur of the first pair of leg.

Figures 1-4. Sexual dimorphism of the labrum and tarsus of Aniarasepulchralis.(1-2) labrum.(1) male;(2) female.(3-4) tarsus.(3) male;(4) female.

Figures 7-8.Antennas.(7) Pedicel length from base to apex;(8) Length of the antennas,from the base of the pedicel to the apex of the last antennomer.

Figures 5-6. Principal component analysis (PCA) toverify variables thatcontributed to the simple variance analysis.

Tables

Table 2. Means and analysis of variance of body measurements of Aniara sepulchralis (Carabidae:Cicindelinae)in relation to sex (maleand female) sampled in Belém and Igarapé-Açu,Pará,Brazil.

Measured variable	Male	Female	F	p
Body length	11,611	12,560	21,3011	0,0024	***
Head width	3,187	3,342	11,4260	0,0118	**
Eyes Distance	2,407	2,574	10,5020	0,0142	**
Pronotum Length	2,688	2,872	6,2074	0,0415	**
Pronotum width	3,064	3,216	11,5430	0,0115	**
Pronotum Base	2,443	2,546	4,2374	0,0785	*
Elytra Length	7,353	7,671	0,7881	0,4042
Elytra Width	4,259	4,778	3,4638	0,1050
Antenna pedicel	0,766	0,776	0,2320	0,6447
Labrum Length	0,854	0,944	8,0190	0,0253	**
Labrum Width	1,856	1,905	0,4500	0,5239
Leg I	6,924	7,056	0,0027	0,9603
Tarsus I	2,289	2,217	1,6227	0,2434
Leg III	12,360	12,624	0,0316	0,8639
Femur III	3,469	3,721	2,0307	0,1972
Tibia III	3,859	3,866	0,0832	0,7814
Tarsus III	3,967	4,033	0,0463	0,8358
Spur III	0,654	0,605	0,7834	0,4055

Significant variables for p =‘***′ 0.01‘**′ 0.05‘*′ 0.1