Mecynogea buique Levi 1997
Creators: name: Martins, Pedro H.
name: Santos, Adalberto J.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Araneidae
Mecynogea
Mecynogea buique

description: Mecynogea buique Levi, 1997
Figs 9–11
Mecynogea buique Levi, 1997: 229 –230, figs 55–58, map 2A (Female holotype from between Catimbau and Buique, Pernambuco, Brazil [8°36'44.56"S, 37°12'12.3"W], 20.VIII.1982, P.F. Lins Duarte leg., in MCN 25574, examined by photograph).
Diagnosis. The male of Mecynogea buique can be distinguished from the other species of the genus, except M. ocosingo Levi, 1997, by the proximal rounded branch of the terminal apophysis, with acuminated ventral projection (Figs 10A, 11A). It differs from M. ocosingo in the shape of the internal branch of the terminal apophysis, which is scythe-shaped in M. buique (Fig. 10A). Females of M. buique resemble females of M. ocosingo, M. martiana (Archer, 1958), M. apatzingan Levi, 1997 and M. bigibba Simon, 1903, in the absence of a posterior cavity on the epigynum. It can be separated from those species by the squared epigynum apex (Figs 12C, 13B), which is trapezoidal in M. ocosingo (Levi 1997: figs 59–60) and triangular in M. martiana and M. apatzingan (Levi 1997: figs 67, 73), and curved in M. bigibba (Levi 1997: figs 4, 7).
Description. Male from Serra Talhada, Pernambuco, Brazil (UFMG 15787). Carapace orange with a narrow median line and two wider, marginal black bands (Fig. 9B). Chelicerae dark orange, endites and labium dark brown proximally and white distally. Palp and legs light orange, except for first femur, which is dark orange. All femora darker on ventral side. Sternum and coxae yellow, fourth coxae with a median, darker area. Dorsum of the opisthosoma with a pale-yellow background colour, with two white bands on the edges and two posterior black marks. Venter pale yellow with black stripes. Total length 4.31, carapace 1.92 long, 0.76 wide in the thoracic area, 1.57 wide after the posterior median eyes. Femur I length 3.4, patella 0.91, tibia 2.72, metatarsus 3.35, tarsus 1.12. Patella II 0.81, III 0.51, IV 0.81. Tibia II 2.38, III 1.1, IV 1.88. Male palp with a large terminal apophysis externally divided in two branches, the proximal one rounded and ventrally acuminated and the distal one bulbous-shaped (Figs 9C–D, 10A–B, 11A). Internal branch of terminal apophysis curved, arising from the same chamber (Figs 10A–B, 11A). Embolus originating from terminal apophysis base (Fig. 9D), hidden behind terminal apophysis proximal branch, visible only in expanded palp (Fig. 9C–D). Conductor is fused to tegulum, appearing as a small tegular projection (Figs 10A–B, 11A). Radix membranous, with a basal sclerotized lobe (Fig. 11A). Paracymbium simple, curved and apically rounded (Fig. 11B–C).
Female. Colour and measurements as in Levi (1997: 229). Epigynum (specimen from Serra Talhada, Pernambuco, Brazil, UFMG 15730) lacks the atrium and hood seen on other species of the genus. Instead it has a wrinkled median plate in posterior view (Fig. 12C). This median plate is connected directly to the apex of the epigynum (Fig. 13B). Copulatory openings located on epigynum apex (Fig. 13A). Copulatory ducts pass inside epigynum apex and through inner fold (Figs 12D, 13C–D). Spermathecae have two receptacles almost equal in size, both with several small and large pores (Figs 12D, 13D). Fertilization ducts sclerotized and posteriorly connected to spermatheca base (Figs 12B, 13D).
Variation. The embolus of the right palp of a male from Serra Talhada, Pernambuco, Brazil (UFMG 15787) is visible, appearing at the tip of the distal projection of the terminal apophysis. A male from the same locality (UFMG 15790) has four pairs of dark marks on the sternum, and another male from the same sample has only one pair of these marks on the anterior edge of the sternum. The total length of males varies from 3.75 to 4.92 (n,4).
Remarks. The male-female match proposed here is based on a sample of four males and six females collected near the type-locality in Fazenda Buenos Aires, Serra Talhada, Pernambuco, Brazil (UFMG 15730, 15787–15790, 19545, 19546). It is rare to find large samples of Mecynogea specimens, particularly with males and females collected together, as the genus is usually represented in collections by a few specimens per sample. We interpret a sample with many males and females collected together as a reliable indication of co-specificity.
Distribution. This species is known mostly from Brazilian dry physiognomies and savannas in the states of Minas Gerais, Paraíba, Pernambuco and Bahia (Fig. 17). The only habitat exception is from a southernmost record in the central-southeastern state of Minas Gerais, which is a semideciduous humid forest (UFMG 5449). The northernmost record is located in the south of the state of Paraiba.
Additional material examined. BRAZIL: Bahia: Itapetinga, Parque Municipal da Matinha [15°15'6.48"S, 40°14'56.22"W], 286 m, III–IV.2003, J.P.S. Alves leg., 1♀ (IBSP 66 476); Minas Gerais: Belo Horizonte, Estação Ecológica da UFMG [19°52'38"S, 43°58'16"W], 845 m, III.2000, E.S.S. Álvares et al. leg., 1♀ (UFMG 5449); Itacarambi, Distrito de Fabião II (15°10'19"S, 44°10'49"W), 541 m, 5–7.V.2012, G.F.B.P. Ferreira et al. leg., 1♀ (UFMG 19487); Itaobim (16°31'58.6"S, 41°30'37.5"W), 464 m, 25.XI.2011, I.L.F. Magalhães et al. leg., 1♂ (UFMG 10095); Santana do Riacho, Parque Nacional da Serra do Cipó [19°20'57"S, 43°37'10.16"W], 822 m, 16.XI.2007, A.J. Santos leg., 1♂ (UFMG 5423); Paraíba: São José dos Cordeiros, RPPN Fazenda Almas [7°28'17.14"S, 36°53'44.43"W], 649 m, 16–24.V.2016, P.S. Souza leg., 1♀ 2juv. (UFPB-AR 909); Pernambuco: Buíque, Parque Nacional do Catimbau [8°36'0"S, 37°9'0"W], 821 m, 2–4.VI.2007, M.C. Carvalho leg. 1♀ (UFMG 4850), Parnamirim [8°5'29.99"S, 39°34'44.33"W], 396 m, 23.III.2012, A. Costa leg., 1♂ 1♀ (UFPB-AR 97); Serra Talhada, Fazenda Buenos Aires [7°58'45"S, 38°23'2.3"W], 459 m, III– IV.2010, M. Carvalho leg., 2♀ (UFMG 15730); 1♂ (UFMG 15787); 1♀ (UFMG 15788); 1♀ (UFMG 15789); 3♂ (UFMG 15790); 1♀ (UFMG 19545); 1♀ (UFMG19546); Serra Talhada, Fazenda Saco, Mata da Pimenteira (7°53'0"S, 38°18'0"W), 563 m, 12. II.2010, M.C. Carvalho & A. Brito leg., 2♂ (UFMG 14173).
Discussion – male palp sclerites in Cyrtophorinae
The first attempt to propose palp sclerite homology in Cyrtophorinae was made by Exline (1949), who described a highly sclerotized process fused to the tegulum of M. lemniscata as homologous to the araneid median apophysis. She also identified a finger-shaped, poorly sclerotized conductor in the same species. The latter sclerite is particularly difficult to see in the unexpanded palp, because it is covered by the terminal portion of the bulb above and by the tegulum below (Exline 1949: fig. 10).
Levi (1980) disagreed with Exline’s (1949) homology hypothesis, though acknowledging how challenging could it be to homologize Mecynogea palp sclerites with those of other araneids. He proposed that the structure referred by Exline as a homolog of the median apophysis should be considered as a conductor. Additionally, he stated that M. lemniscata lacks a median apophysis, a feature shared with species of Cyrtophora Simon, 1864. However, although he illustrated an expanded male palp, he did not present an alternative homology proposition for the sclerite considered as a conductor by Exline (1949).
The interpretation of the male palp sclerites in the subfamily became a bit more complicated after Levi’s (1997) revision of the Neotropical Cyrtophorinae genera. In that study, Levi stated that the median apophysis was lost in the species of Mecynogea whose females have a hood-like epigynum, implicitly assuming that it should be present in other species of the genus. The presence of a sclerite homologous to the araneid median apophysis in Cyrtophorinae seemed to be debatable for him since, although he repeatedly refers to a median apophysis along the text, he indicated the structure with a question mark (“M?”) in the homology scheme of an expanded male palp of Mecynogea bigibba (Levi 1997: figs 23–25).
In our initial analyses of the male palp of Mecyngea infelix we have found a sclerite that could be homologous to the supposed median apophysis indicated in Levi (1997). However, examining expanded palps using SEM we noticed that the sclerite originates from the terminal portion of the bulb. This position would discard the possibility of homologizing that sclerite with the araneid median apophysis, which is usually attached to the tegulum, near the base of the radix (see illustrations and discussion in Coddington 1990). Instead, this structure seems to be a branch of the terminal apophysis. Since it originates internally compared to other (proximal and distal) terminal apophysis branches, we decide to call it internal branch of the terminal apophysis (Fig. 14A–B). We find that this structure in all species of the genus, appearing in two different forms: exposed externally as in M. buique, M. ocosingo, M. martiana, and M. apatzingan, or hidden by the proximal and distal branches of terminal apophysis in M. infelix, M. lemniscata, M. bigibba, M. erythromela (Holmberg, 1876) and M. sucre Levi, 1997. The presence of a hidden internal branch of the terminal apophysis in the latter species, which females present a hood-shaped epigynum, explains Levi’s statement about the absence of a “median apophysis” in some species of Mecynogea. The only exception is M. bigibba, a species that have the internal branch of the terminal apophysis hidden by the external branches and do not have a hood-like epigynum.
To verify the taxonomic distribution of this feature, we analysed exemplars of all the Neotropical genera of Cyrtophorinae: Cyrtophora, Manogea Levi, 1997 and Kapogea Levi, 1997 (Fig. 15A–F). We discovered that the structure named by Levi (1997) as a “median apophysis” in those genera is in fact homologous to the internal branch of the terminal apophysis we have found in Mecynogea. Additionally, we have found that the other two terminal apophysis branches are also present in those genera (Fig. 15A–F). It thus seems clear to us that Cyrtophorinae genera lack the median apophysis, which is a potential synapomorphy of the subfamily. Additionally, we noted that the conductor is highly sclerotized and fused to the tegulum in all genera of the subfamily (Figs 14A–D, 15A–F), another putative synapomorphy of the Cyrtophorinae.
description: Published as part of Martins, Pedro H. & Santos, Adalberto J., 2018, Morphology and taxonomy of the orb-weaving spider genus Mecynogea, and a peculiar species of Argiope (Araneae, Araneidae), pp. 423-451 in Zootaxa 4415 (3) on pages 433-436, DOI: 10.11646/zootaxa.4415.3.2, http://zenodo.org/record/1242066