Monday 14 September 2020

Sceliscelis marshi, Scelidocteus taitave, & Hybosida machondogo: Three new species of Palp-footed Spiders from Kenya.

The Palp-footed Spiders, Palpimanidae, are a small family of araneophagous (Spider-eating) Spiders recognized by the coriaceous carapace, haplogyne genitalia, two spinnerets and especially by the first pair of legs with dorsally enlarged femora and well-developed prolateral scopula on the tibia, metatarsus and tarsus. A total of 152 species in 18 genera are distributed in tropical and subtropical zones worldwide, absent only in the Nearctic and Australia. Within Africa, the family is known to include 56 species belonging to 12 genera, although some of these species are certainly misplaced in the family. More than 800 spider species and subspecies belonging to 55 families are known from Kenya. However, Palpimanidae have not been thoroughly studied. Up to now, only three species have been described: Scelidocteus incisus, Hybosida lesserti, and Hybosida scabra

In a paper published in the journal African Invertebrates on 28 Jult 2020, Ambata Oketch of the Institute of Zoology of the Chinese Academy of Sciences, the National Museums of Kenya, and the University of the Chinese Academy of Sciences, Sergei Zonstein of the Steinhardt Museum of Natural History at Tel Aviv University, and the Department of Zoology and Centre for Invasion Biology at the University of Venda, Esther Kioko also of the National Museums of Kenya, and Shuqiang Li, also of the Institute of Zoology of the Chinese Academy of Sciences, and the University of the Chinese Academy of Sciences, describe  one new genus and three new species of Palpimanid Spiders found during the examination of Spiders collected in various protected sites in Kenya.

The first new species is placed in a new genus, Sceliscelis, which possesses some characteristics that are also found in Sarascelis and Scelidocteus, such as the dentate segments of leg I (which include at least the dorsal surface of the coxa and basal part of the femur) and the spiral embolus. The name Sceliscelis is a combination of 'Sceli' from Scelidocteus and 'Scelis' from Sarascelis. It is given the specific name Sceliscelis marshi, in honour of Brian Marsh OBE, the founder of the Marsh Christian Trust Awards for Ecologists in Africa, which Esther Kioko was awarded in 2019. The species is described from two specimens, one male and one female, both collected from Tsavo West National Park in Taita Taveta County, Kenya.

Sceliscelis marshi, male holotype (A)–(C) habitus in dorsal, ventral and lateral aspects (D)–(F) palp: (D) prolateral (E) ventral and (F) retrolateral aspects. Abbreviations: am. accompanying membrane; co, 'conductor'; cy, cymbium; ds, dorsal portion of scutum; em, embolus; hle, hook-like extension; pe, palm-like embolic extension. Scale bars are 1 mm (A)–(C), 0.1 mm (D)–(F). Oketch et al. (2020).

The male has a total body length of 3.83 mm, with a carapace 2.13 mm long, and 1.75 mm wide. The female has a total body lenght of 5.1 mm, and a carapace 3.1 mm long, and 2.2 mm wide. The is dome shaped, coarsely granulated, hairless, and medially elevated, with a longitudinal fovea (thoracic furrow), open posteriorly, in an elongated Ω-shape. Labium triangular, notched, longer than wide but broader at base. Chelicerae directed ventrally, 2 times longer than clypeus, granulate. Endites trapezoidal, about 1.5 times longer than wide. Abdomen clay yellow, oval and covered with short, gray setae in both sexes. Femur of male palp slender, longer than wide, patella shorter than 'conductor'. Cymbium with setae, pointed at tip and indented (prolateral view). Embolus spiral, with accompanying membrane and a silvery, palm-like embolic extension. 'Conductor' sword-shaped, longer than wide, slightly longer than embolus. Endogyne wavy anteriorly, forming a rigid epigastric wall.

Sceliscelis marshi, female paratype. Cephalothorax (A) dorsal and (B) ventral aspects (C), (D) endogyne, ventral and dorsal aspects, respectively. Abbreviations: Bl, book lung operculum; ch, receptive chamber; ds, dorsal portion of scutum; Gr, grape-shaped glands; Ls, late Okeral sclerite; Re, rigid extension of posterior wall of epigastric fold; sco, scopula; Sr, sac like receptacle. Scale bars are 1 mm (A), (B), and 0.2 mm (C), (D). Oketch et al. (2020).

The second new species is placed in tbe genus Scelidocteus, and given the specific name taitave, which is a is a combination of Taita and Taveta, the county from which the specimens were collected. The species is described from four specimens, two males and two females, collected from the Mbololo Forest in the Taita Hills of Taita Taveta County.

Scelidocteus taitave, male holotype (A), (B) dorsal and ventral habitus respectively (C)–(E) palp: (C) prolateral (D) ventral (E) retrolateral aspects. Abbreviations: am, accompanying membrane; cl, claw like extension; co, 'conductor'; em, embolus; cy, cymbium; rt, retrolateral thorns; sco, scopula. Scale bars are 1mm (A), (B), and 0.2mm  OkOe(C)–(E). Oketch et al. (2020).

Males of this species differ from those of other members of Scelidocteus by the uniquely spiral-shaped embolus. Females of Scelidocteus taitave differ from those of other species by the structure of the endogyne; the orientation of sac-like receptacles touching medially, with a space below them) mounted on oval, membranous receptive chambers and the outline of a rigid extension of the posterior wall of the epigastric fold.

Scelidocteus taitave, female paratype (A), (B) habitus (C) endogyne ventral (D) same, ventral (E) same, enlarged (F) leg I. Abbreviations: ch, receptive chamber; Ft, fine threads; Gr, grape-shaped glands; Re, rigid extensions of posterior wall of epigastric fold; Sr, sac like receptacle. Scale bars are 1 mm (A), (B). Oketch et al. (2020).

The males have a total body length of  3.90 mm. Chelicerae flattened anteriorly towards the fangs, 1.60 mm long, cheliceral furrow with several peg-like teeth. Stridulatory mound absent. Clypeus approximately 2 times shorter than length of chelicerae. Sternum 1.09 mm long, 0.86 mm wide at leg II; shield shaped, rebordered, finely granulate. Endites almost D-shaped, labium notch 0.13 long, about a quarter of labium length. Leg I: coxa, patella and tibia possess dark, thorn-like outgrowths and well developed prolateral scopula on tibia and metatarsus. Tarsus I with weakly developed scopula. Abdomen oval with short, grey setae, dorsal portion of epigastric scutum very small, pedicel short, spinnerets short and unsegmented. Palp with tibia as long as wide, approximately 2.5 times wider than femur. Cymbium long and thin, tapering distally. 'Conductor' bifurcate; embolus long and spiral, obscuring some parts of tegulum. Embolus ends with a bleached, claw-like structure at apex.

Females have a total length of 4.88 mm. Carapace 2.19 mm long, 1.72 mm wide. Sternum 1.25 mm long, 1.00 mm wide, labium 0.5 mm long, 0.44 mm wide at the base, labium notch 1/3 length of labium. Vulva with fine, thread-like structures and 3 pairs of stalked, grape-shaped glands attached to a pair of relatively ovate and membranous receptive chambers.

The third new species is placed in the genus Hybosida, and given the specific name machondogo, which is a combination of two Swahili words 'macho', meaning eyes, and 'ndogo’, meaning small, referring to the indiscernible posterior median eyes of this species. The species is described from an adult male specimen from Mount Kenya National Park, and two subadult males Mount Elgon National Park.

Hybosida machondogo male holotype (A)–(C) habitus: (A) dorsal (B) ventral and (C) prolateral aspects (D)–(F) palp: (D) prolateral (E) ventral (F) retrolateral. Scale bars are 1 mm (A)–(C), and 0.2 mm (D)–(F). Abbreviations: cy, cymbium; ds, dorsal portion of scutum; em, embolus; pa, patella; Ta, tegula apophysis. Oketch et al. (2020).

Like other members of Chediminae, Hybosida machondogo possess contiguous lateral eyes and accessory structures of the male palp. It closely resembles Hybosida lesserti by having (1) a more compact carapace with the cephalic part narrowed (2) an elevated carapace with a steep posterior slope (3) a strongly convex carapace in lateral view and (4) poorly developed scopula on both the metatarsi and tarsi of legs I. However, Hybosida machondogo differs from Hybosida lesserti and other members of this genus by having (1) 8 eyes instead of 6, (2) a bulb with relatively long, sharp and less curved apophysis (vs. strongly curved in Hybosida lesserti).

Hybosida machondogo, subadult male, habitus (A) dorsal view (B) ventral (C) male holotype, ocular area, anterodorsal (D) thoracic fovea, dorsal. Scale bars are 0.5 mm (A)–(D). Oketch et al. (2020).

The adult male specimen has a total body length of 2.05 mm. The carapace, pedicel and sternum reddish orange, 1.11 mm long, 0.83 mm  wide at leg II, carapace dome-shaped and covered with white setae at the edges, finely rugose. Thoracic region higher than cephalic region, steeply sloping towards pedicel. Fovea crescent-like, bipartite, wide distally (sulci diverging). Sternum with long, gray setae. Labium deeply notched (smoothly recurved in all described palpimanids). Endites colored as sternum, depressed proximally, covered with gray setae. Legs: yellowish without spines. Femur I enlarged and longer than patella; scopula on tibia, metatarsus and tarsus weakly developed (compared to Scelidocteus). Femur II somewhat longer than femora III–IV, tarsal claws long and unidentate. Metatarsi II–IV with distal preening comb. Generally, leg integument appears rough. Abdomen: unsclerotized, uniformly yellowish, oval, narrow towards the pedicel and wide at the middle. Pedicel considerably exposed, lateral and postgastric scutum extensions absent, dorsal portion of scutum present but short. Spinnerets short yellowish and unsegmented.

Palp yellowish, femur longer than tibia, patella about 2 times shorter than femur. Tibia enlarged, almost conical in prolateral view, 1.86 times wider than patella, about 2 times wider than femur. Cymbium about 1.5 times longer than tibia, slightly shorter than apophysis. Tegular region is membranous, apophysis pointed, extends anteriorly. Embolus short, blunt and directed laterally.

This species is peculiar because it is at odds with the initial description of the type species of the genus Hybosida, which states that the number of eyes is 6. It does, however, resemble Hybosida in the shape of the carapace, the fovea and the general structure of the male palp. It is therefore treated as belonging to this genus.

See also...

Follow Sciency Thoughts on Facebook.