Galapa Huber 2000
Creators: name: Huber, Bernhard A.
name: Meng, Guanliang
name: García, Jimmy Cabra
name: Carvalho, Leonardo S.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Pholcidae
Galapa

description: Genus Galapa Huber, 2000
Galapa Huber, 2000: 100. Type species by original designation: Pholcophora baerti Gertsch & Peck, 1992.
Galapa — Huber & Villarreal 2020: 58.
Diagnosis. Tiny (body length ~1.0– 1.5 mm), short-legged, eight-eyed pholcids with globular abdomen (Fig. 2). Males are easily distinguished from all other known Ninetinae by modified cheliceral fangs and by absence of frontal modifications on base segment of chelicera (Figs 3, 8A, 13C). Similar chelicerae occur only in the distantly related Modisiminae genus Chibchea Huber. Further distinguished by dorsal process on procursus (Figs 7B, 14B, 21B; similar only in the southern South American genus Guaranita Huber), and by retrolateral distal process on procursus (Figs 7B, 14B, 21B). Females are externally very similar to other small New World Ninetinae such as Guaranita, Tolteca Huber, and Kambiwa Huber (in terms of body size, body shape, coloration, leg length, and simple epigynal plate); distinguished from these by internal genitalia: large membranous structure (Figs 11D, 16F, 24G) rather than pair of receptacles (Tolteca) or median receptacle (Guaranita, Kambiwa).
Description (amendments; see Huber 2000).
Male
MEASUREMENTS.Total body length~1.0–1.5.Male carapace width0.38–0.60.Distance PME-PME35–45µm; diameter PME30–45 µm;distance PME-ALE 15µm;distanceAME-AME 10–15 µm;diameterAME 15–30µm.Tibia 1 length 0.41–0.74.Tibia 1 L/d:9–10.Leg formula 4123. Diameters of leg femora 0.075–0.10, of leg tibiae:0.05–0.06.
COLOUR (in ethanol). Prosoma and legs pale ochre-yellow, carapace without pattern, legs without darker rings; abdomen ochre-grey, monochromous or with indistinct internal marks.
BODY. Ocular area not raised. Carapace without thoracic groove (Figs 6A, 20A, 27A). Clypeus either not more protruding than in females (Galapagos species) or slightly more protruding than in females and with sclerotized rim (mainland species), in G. murphyi also with cluster of sexually dimorphic hairs (Fig. 27C). Sternum slightly wider than long, with pair of indistinct anterior humps near coxae 1 (Fig. 13D; ~5–20 µm high, 20 µm diameter at basis). Abdomen globular. Gonopore either with four epiandrous spigots arranged in two pairs (G. baerti, G. bella, G. gabito; Figs 6F, 13E; see also Huber 2000: fig. 127) or without epiandrous spigots (G. spiniphila, G. murphyi; Figs 20E, 28E, F). ALS with one strongly widened spigot, one long pointed spigot, and five cylindrical spigots, of which one is much wider than the others (Figs 6C, 22A, B, 28A); PMS with two conical spigots (Figs 6C, 22A, 28A); PLS without spigots.
CHELICERAE. Chelicerae main segment unmodified (Fig. 3); with stridulatory files consisting of ~30–50 ridges, distances between ridges either constant throughout (1.5–1.6 µm) or wider proximally (2.0 µm) than distally (1.1 µm), either with or without further fine subdivision (Figs 8B, 13A, 20C, 27F). Fang with curved proximal process (Figs 8A, 13C, 27E).
PALPS. Palpal coxa unmodified. Trochanter without process or with very short ventral protrusion. Femur proximally with prolateral stridulatory pick (modified hair; Figs 8C, 20D), distally slightly widened but without modification. Femur-patella joints variably shifted towards prolateral side. Tibia oval, with two trichobothria. Tibia-tarsus joints slightly shifted towards retrolateral side. Palpal tarsal organ weakly to strongly raised (Figs 9A–C, 14E, 23D, 29E; see also Huber 2000: fig. 77), diameter 4.1–6.7 µm, diameter of opening 1.0–1.7 µm. Procursus retrolateral distal process simple (Figs 7B, 14B, 21B) or bifid (Fig. 25B, 29C); dorsal process curved towards prolateral; tip of dorsal process covered by large flap of genital bulb or lodged in pocket of genital bulb (Figs 7B, 14B, 21B). Genital bulb with distal apophysis (Figs 7B, 17B, C, 25B, C), in G. spiniphila also with retrolateral-dorsal process and pair of ventral processes (Figs 17, 21C, D); in G. gabito and G. murphyi with small prolateral distal apophysis (arrows in Figs 12B, 25A; 29D); sperm duct opening on prolateral-ventral side directly on bulb (Figs 7H, 21D, 29D).
LEGS. Without spines and curved hairs. Without slender metatarsal hairs (as described in Huber et al. 2023c). Sexually dimorphic short vertical hairs present on tibiae 1 and 2 (Figs 8E–H, 15A, B, 23A, B, 30A), barely visible in dissecting microscope, length ~15–17 µm, diameter at basis 1.0–1.2 µm. Chemoreceptive hairs similar in size (length ~10–14 µm, diameter at basis 1.3–1.7 µm) but with side branch (Fig. 30B, C) and mostly near leg tips. Retrolateral trichobothrium of tibia 1 at 52–66%. Prolateral trichobothrium absent on tibia 1. Base of trichobothria either evenly rounded (Fig. 10D) or with proximal ridge (Figs 15C, 30D, E). Legs with round cuticular plates (Figs 10A, B, 15D, 23F, 30E, 31F; diameter 4–7 µm) and rimmed pores (Figs 10A–C, 15E, 23G, 31F; outer diameter 3.0–3.7 µm, diameter of opening 0.2–0.4 µm) apparently on all leg segments. Tarsus 1 with five pseudosegments, fairly distinct. Leg tarsal organs capsulate (Figs 9D–F, 31A–E; diameter 2.0–4.5 µm, diameter of opening 0.7–1.4 µm). Main tarsal claws with ~9–11 tines (Figs 10F, 22F, 30F). Claws of tarsus 4 different from others (tines more directed towards distal; Fig. 10G).
Female
In general, similar to males but sternum without pair of anterior humps, chelicerae without stridulatory files (Figs 8D, 13B, 27G), cheliceral fangs unmodified, clypeus never strongly protruding (Fig. 27D) and without sclerotized rim, and palpal tarsal organ less strongly raised (Figs 14F, 29F; see also fig. 76 in Huber 2000) and slightly smaller (diameter 4.0–4.3 µm, diameter of opening 1.0–1.2 µm). Legs slightly shorter than in males (male / female tibia 1 length: ~1.0–1.2); tibia 1 length 0.37 – 0.74. Spinnerets as in male (Figs 6B, 13F, 22C, D, 28C). Epigynum with simple semicircular anterior plate, weakly protruding, posteriorly straight or indented medially (Figs 6E, 20F, 28D); posterior plate short and simple, with or without indistinct median division. Internal genitalia (Figs 11, 16, 24, 32) very simple, apparently without pore plates; with large membranous structure (with or without median membranous process), either directed towards posterior and covered by posterior epigynal plate or directed towards anterior and covered by anterior epigynal plate.
Relationships. Molecular (UCE) data (G. Meng, L. Podsiadlowski, B.A. Huber, unpubl. data) suggest that the closest known relative of Galapa is an undescribed species from Brazil, Piauí, Parque Nacional da Serra da Capivara. That species is known from a single male specimen that does not share any of the diagnostic genital characters of Galapa listed above. Together, these two clades are sister to Kambiwa + Pemona, two further South American genera. All of these together are sister of the southern South American genus Guaranita. Thus, Galapa is deeply nested within South American Ninetinae.
Even though a NJ tree (Fig. 1) is not supposed to reliably reflect phylogeny, it shows two splits worth mentioning. First, within Galapa, G. bella (Galapagos) is sister to the mainland species. Several morphological characters support this split: (1) Mainland species share a proximal ridge on the basis of the leg trichobothria; in G. bella, these bases are round, which is likely the plesiomorphic condition; (2) in mainland species, the male palpal tarsal organ has moved to the procursus, while in G. bella it has the plesiomorphic position on the tarsus; (3) in mainland species, the female internal genitalia are directed towards posterior, while in G. bella they are directed towards anterior, which is probably the plesiomorphic condition; (4) finally, body size and leg length are smaller in mainland species than in species from Galapagos (carapace width: ~0.4 vs. ~0.5; tibia 1 length:>0.60 versus <0.55); the plesiomorphic condition is unknown.
Second, the Central American (Costa Rican) G. murphyi is nested within a group of mainland South American species. This position is supported by the loss of epiandrous spigots in G. murphyi and G. spiniphila, while G. bella and G. gabito share the plesiomorphic presence of four epiandrous spigots.
Distribution. The genus is known from Galápagos, northern Colombia, northeastern Venezuela, and Costa Rica (Fig. 4). The distribution map of these tiny and poorly collected spiders suggests a wide range, but the ecological conditions (semi-arid, exposed habitats; see below) are not common in this region, so the suitable habitats may actually be quite limited. This is supported by our biogeographic analysis (see below).
Natural history. Representatives of the genus Galapa appear restricted to semi-arid and sun-exposed habitats where they occupy the leaf litter, spaces under stones, and dead cacti and dry branches lying on the ground and hollowed by termites (Fig. 5). We never found them in neighboring, more forested, shaded, and humid sites. When disturbed, they ran rapidly. In glass vials, both males and females built small webs on which they were seen resting a few hours after being captured (Fig. 2D). Egg-sacs are flat (a single layer of eggs) and contain up to six eggs that are wrapped by a few barely visible silk lines; egg diameters range from 0.38 to 0.43 mm. For further information, see individual natural history sections below.
Composition. The genus now includes six nominal species: three on the Galápagos, one in Costa Rica (with a dubious record in Colombia), and two in northern South America.
description: Published as part of Huber, Bernhard A., Meng, Guanliang, García, Jimmy Cabra & Carvalho, Leonardo S., 2024, Thriving in dry conditions: on the Neotropical spider genus Galapa (Araneae: Pholcidae), pp. 301-347 in Zootaxa 5419 (3) on pages 307-311, DOI: 10.11646/zootaxa.5419.3.1, http://zenodo.org/record/10791767