Maeota setastrobilaris, Garcilazo-Cruz, Uriel & Alvarez-Padilla, Fernando, 2015

Garcilazo-Cruz, Uriel & Alvarez-Padilla, Fernando, 2015, Description of a novel mating plug mechanism in spiders and the description of the new species Maeotasetastrobilaris (Araneae, Salticidae), ZooKeys 509, pp. 1-12 : 3-5

Taxon classification Animalia Araneae Salticidae

Maeota setastrobilaris sp. n. Figures 1-7, 8-15, 16-23

Type materials.

Holotype: male from Jardín Escultórico Edward James, Xilitla, San Luis Potosí, Mexico 26-30 March 2012 (Alvarez-Padilla col.). Allotype: female with the same locality data and collected 10-15 June 2012 ( Gonzáles-Contreras col.). Both specimen deposited at MZC, Harvard University.

Etymology.

The species epithet is a noun in apposition referring to the anatomy of the cymbial strobilate seta used as a mating plug, which resembles a strobilar gymnosperm cone.

Diagnosis.

Maeota setastrobilaris differs from Maeota simoni by the embolus coiled less than two times. It differs from Maeota flava and Maeota dorsalis by larger proximal tegular lobe and the finger shaped RTA extended ventrally (Fig. 13, 19). This species differs from Maeota dichrura by the shorter PLS and the absence of a lateral abdominal patch of enlarged setae in males. Unique features of Maeota setastrobilaris also include: epigynum copulatory duct openings covered by drop-shaped flaps (Fig. 23), embolus coiled 1.2 times and the cymbium dorso-basal edge with modified setae used as mating plugs.

Description.

Male total length 3.58 mm. Cephalothorax: length 1.83 mm, width 1.29 mm. Carapace dorsal surface dark-orange covered with scattered white scales and a glabrous longitudinal paler area posterior to the PLE. Carapace lateral surfaces and clypeus dark-orange with a reticulated pattern darker in color and concentrated towards the carapace edges (Fig. 18). Ocular anterior region: AME encircled with several scales, white at the center and orange at the sides. Ocular region 2/3 wider than long. PLE 0.5, PME 0.1 and ALE 0.5 times the diameter of AME. PME closer to PLE than ALE (Fig. 8). Chelicera paturon base dark-brown turning lighter distally, retromarginal tooth bifurcated. Endites pale-yellow distally, darker at their base and slightly longer than wide. Labium with same color pattern as the endites and triangular in shape. Sternum pale-yellow and longer than wide (Figs 11). Abdomen: surface background dark yellow covered with white or iridescent scales. Dorsal pattern with two brown longitudinal lines and a posterior broken pattern of dark chevrons (Fig. 8). Lateral surface almost covered by an additional dark reticulated thick line that extends towards the spinnerets. Ventral pattern with a dark gray rectangle that extends behind both sides of the epigastric furrow. Spinnerets gray and encircled with black pigmentation. PMS twice as thick as the PLS. PLS 2/3 longer than PMS with the distal segment darker in coloration and its ventral surface covered by thick black setae. Legs pale-yellow, I and II similar in size and smaller than III and IV. Leg IV the longest. Femora lighter than the other articles. Macroseta patterns based on voucher specimen JAM327. Femora with a 1-1-1 dorsal macroseta pattern. The distal spination has up to three subdorsal shorter macrosetae, two prolateral and one retrolateral. Patella with two subdorsal macrosetae, one on each side. Retrolateral tibia surfaces I to IV with six macrosetae distributed at 2-2-1-1 pattern. Tibia prolateral surfaces with the following macrosetae numbers and distributions: I, II 3-1-1-1; III-IV 3-2-1-1. Metatarsus prolateral surfaces: I 1-1-1-3; II 1-1-0-3; III-IV 2-0-0-3. Tarsi without macrosetae. Pedipalp: Tegulum with a proximal drop-shaped lobe and spermatic duct coils visible (Figs 14, 21). An additional sclerite present between the prolateral cymbial edge and the tegulum (Fig. 21 arrow). Embolus base circular, flat and attached to the embolus. Embolus heavily sclerotized, thick and coiling 1.2 times around embolus base edge (Fig. 21). Cymbium ventral surface notched distally near embolus, dorsal surface hirsute with four modified basal seta on the edge, the largest used as a mating plug (Fig. 19, stS). Female as in male except as noted. Total length 3.87 mm. Cephalotorax: length 1.62 mm, width 1.25 mm. Carapace lighter in coloration, reticular lateral pattern absent (Fig. 2). Abdomen: pattern as in male but lighter in coloration. Spinnerets: PLS 1.2 times longer than PMS. Legs: macroseta patterns based on voucher specimen JAM326. Retrolateral tibia surfaces: I-III 1-2-1-1; IV 2-1-1-1. Prolateral tibia surfaces: I, III-IV 1-2-1-1; II 1-1-1-1. Epigynum: with two comma-shaped, concentric cuticular flaps covering the genital opening entrance (Figs 6, 7, 20, 23). Spermathecae peanut-shaped with two lobes communicating by a thick channel, fertilization ducts tiny and located on the middle section of posterior lobes (Fig. 22).

Variation: Male size: total length 2.76-3.58 mm, carapace 1.29-1.61 mm. Females total length 2.75-4.29 mm, carapace 1.20-1.70 mm. Spermathecal lobes vary considerably in orientation and the length of the channel. Several specimens presented asymmetric spermathecae. Flaps covering the copulatory ducts also vary in shape and in orientation relative to the middle longitudinal axis of the genital plate (Fig. 20). Specimen coloration varies from pale-yellow to dark-brown (Figs 1-5, 8-11).

Distribution.

Mexico from the Eastern Cordillera to the Southwestern States. (Fig. 16).

Records: N = 139. Mexico: Campeche: Chicana ruins ca. 8 km W of Xpujil 18°32'N, 89°31'W 270 m. Jul. 14, 1983, W. Maddison col., 1♀, MCZ. Chiapas; 76 km S on road from Palenque to Ocosingo 17°01'N, 92°02'W 1377 m. Jul. 26-29, 1983, W. Maddison col., 1♀, 1♂, MCZ; Palenque ruins 17°29'N, 92°01'W 118 m. Jun. 02-11, 1983, W. Maddison & R.S. Anderson col., 4♀, 3♂, MCZ (paratypes); Jul. 31, 1983, W. Maddison col., 2♀, MCZ. Nuevo León: 29 E Linares along highway km 60 24°08'N, 99°08'W 197 m. Jun. 03-05, 1983, W. Maddison col., 1♂, MCZ. Oaxaca: 2 km S El Tule 17°02'N, 96°40'W 1868 m. 1983, W. Maddison & R.S. Anderson col., 1♀, MCZ. Quintana Roo: 31 NE Felipe Carrillo Puerto on highway km 307 19°48'N, 87°52'W 13 m. Jul. 17, 1983, W. Maddison & R.S. Anderson col., 1♂, MCZ. San Luis Potosí: Xilitla, Cueva de Salitre 21°23'N, 98°59'W 576 m. Jun. 13, 1983, W. Maddison col., 2♂, MCZ; Las Pozas ( Jardín escultórico de Edward James) 21°23'50.9"N 98°59'38.2"W 626 m. Arachnology team col. Aug. 27-31, 2011, 13♀, 7♂; N. 14-18, 2011, 27♀, 11♂; Mar. 26-30, 2012, 25♀, 12♂; Jun. 10-15, 2012, 13♀, 12♂, Spider collection Arachnology Lab. Facultad de Ciencias. Supplementary images for paratypes deposited at CASC available at http://www.unamfcaracnolab.com with voucher and collection code numbers: N. 14-18, 2011, 1♀, JAM326 and CASENT 9051538; 1♂, JAM327 and CASENT 9051537. Additional specimens at CASC 1♀, 1♂, CASENT 9051536; 1♀, CASENT 9051539; 2♀, CASENT 9051540; 1♀, CASENT 9051541. Tabasco: 2.4 km. E Teapa, Grutas de Corona 17°33'N, 92°56'W 55 m. Jul. 7, 1983, W. Maddison col., 1♂, MCZ. Veracruz: Estacion Biología Tropical Los Tuxtlas near La Palma N of Catemaco 18°36'N, 95°07'W 366 m. 1983, W. Maddison & R.S. Anderson col., 1♀, MCZ.

Behavioral notes.

The dorsal base of cymbium presents a cluster of modified setae on its edge used during copulation as a mating plug. They are located over a pit between the membrane joining tibia-tarsus articles (Fig. 25: M). Inside the pit are three to four strobilate setae, the largest used as a mating plug while the others remain attached to the tibia-tarsus joint (Fig. 25). The largest of these strobilate setae is detached in several specimens and was found blocking the copulatory ducts entrance (Figs 24, 29: stS; 27, 28: CO). Evidence supporting the use of this strobilate seta as a mating plug lies in their rupture from a basal breakage disc (Fig. 28: BD) attached to weak setal basis (Figs 27, 30: B) and the texture that makes it difficult to mechanically extract the setae from the genital openings. The function of the smaller setae is unknown, but they could work either as pressure indicators controlling the detachment of the larger seta, or guiding it throughout the mating plug function. Total sample consisted of 127 specimens (Table 1) where 62% were females. Almost 50% of these females had the seta at least in one of their genital openings, while 60% of the males lost at least one seta from both pedipalps. Absence of both setae in males was higher than the presence of two setae in females with a ratio of 10:1. Accidental loss of setae from specimens after preservation is unlikely: exemplars collected 30 years ago that were examined in MCZ presented the structures in the same proportions as exemplars captured in 2011, suggesting that handling does not lead to accidental loss of these setae. The low proportion of females with both copulatory ducts plugged suggests a negative response to the insertion of a second seta.