Bioacoustics of Ninetis

Diagnosis. Tiny (body length ~ 0.9–1.5 mm ), short-legged, eight-eyed pholcids with globular abdomen ( Fig. 3 ). Most known species (except N. samail sp. nov. ) with distinctive configuration of male genital bulb, with slender ventral process and partly membranous dorsal process, the latter carrying sperm duct (e.g., Figs 7F , 14F ). This bulb morphology is otherwise only found in Magana Huber, 2019 , which is distinguished by its unique curved procursus, and Nerudia Huber, 2000 , which is distinguished by longer legs (male tibia 1: 1.1–2.5, versus 0.40–0.84 in Ninetis ; tibia 1 L/d: 14–31, versus 8–15 in Ninetis ). Females of most species (except N. minuta , N. marnif sp. nov. , N. samail sp. nov. ) with median epigynal pocket ( Figs 10F , 15E , 16F ; see also fig. 331 in Huber 2000 ; fig. 11 in Huber 2002 ; fig. 27 in Huber & El-Hennawy 2007); such pockets are otherwise not known in Ninetinae . Note. In a previous diagnosis of Ninetis ( Huber 2000: 81 ) , the genus was thought to differ from Nerudia by the absence of stridulatory files on the male chelicerae. This is not the case. In both genera, males of most if not all species have stridulatory files; females do not.

Description Male MEASUREMENTS. Total body length ~0.9–1.3. Carapace width 0.38–0.56. Diameter PME 35–50 µm; diameter AME 15–30 µm. Tibia 1 length 0.40–0.84. Tibia 1 L/d: 8–15. Leg formula 4123. Diameters of leg femora (at half length) 80–90 µm, of leg tibiae 50–55 µm. COLOUR (in ethanol). Prosoma and legs pale ochre-yellow to light brown, carapace without pattern, legs without darker rings; abdomen ochre-grey to light brown, monochromous or with indistinct internal marks. BODY. Ocular area not or barely raised. Carapace without thoracic groove (e.g., Fig. 10A, B ; see also Huber 2000 : fig. 4). Clypeus either unmodified or rim more sclerotized than in female. Sternum approximately as wide as long, with or without pair of anterior humps near coxae 1 ( Fig. 24B ). Abdomen globular. Gonopore either with four epiandrous spigots arranged in two pairs ( N. subtilissima , N. namibiae , N. toliara , N. amoud sp. nov. ; Figs 10E , 16E ; see also Huber 2000 : fig. 125) or without epiandrous spigots ( N. samail sp. nov. , N. marnif sp. nov. ; Figs 24E , 31E ) (in other species not examined). ALS with one strongly widened spigot, one long pointed spigot, and five cylindrical spigots, of which one is much wider than the others (cf. Figs 10G, H , 16G, H , 24G, H , 31G, H ; see also Huber 2000 : fig. 152); PMS with two conical spigots ( Figs 10G , 16G , 24H ); PLS without spigots ( Fig. 10G ). CHELICERAE. Chelicerae usually with pair of frontal apophyses ( Figs 7G–I , 14G–I , 22H–J ), absent only in N. marnif sp. nov. ( Fig. 29G–I ); usually with stridulatory files ( Figs 10C , 16D , 24C , 31C, D ) consisting of ~15–35 ridges, distances between ridges usually 1–2 µm, in N. samail sp. nov. wider (3 µm). In some species possibly without stridulatory ridges ( N. minuta , N. namibiae ; not examined with SEM). Fangs unmodified (cf. Fig. 16C ). PALPS. Palpal coxa unmodified. Trochanter without process or with short ventral protrusion. Femur in species with stridulatory ridges with prolateral stridulatory pick proximally (modified hair; Fig. 17E ), distally slightly widened but usually without modification, only in N. amoud sp. nov. with ventral tubercles ( Figs 13 , 17A ). Femur-patella joints variably shifted towards prolateral side. Tibia roundish to oval, with two trichobothria. Tibia-tarsus joints variably shifted towards retrolateral side. Palpal tarsus with row of strong dorsal hairs ( Fig. 17F ), with tarsal organ weakly to strongly raised ( Figs 11E , 17F , 25E , 32C ), diameter 4.6–6.7 µm, diameter of opening 0.8–1.1 µm. Procursus simple, in N. samail sp. nov. with unique strong spine (arrow in Fig. 22C ). Genital bulb with two processes: relatively complex dorsal process consisting of membranous and sclerotized elements, presumably carrying sperm duct (confirmed in N. minuta : Huber 2000 , fig. 321); and simple, pointed, and weakly sclerotized ventral process (e.g., Figs 7F , 14F ); in N. samail sp. nov. dorsal process with distinctive sclerite set with scales, and ventral process more complex and sclerotized ( Fig. 22F ). LEGS. Without spines and curved hairs. With slender metatarsal hairs (as first described in Huber et al. 2023a ) on metatarsus 3 (only one in very proximal position) and metatarsus 4 (one to four, in proximal position) ( Figs 12A, B , 18E, F , 26E, F , 32F–H ). Sexually dimorphic short vertical hairs present on tibia 1 only or on tibiae 1 and 2 ( Figs 12D , 18G, H , 26C , 32E ), barely visible in dissecting microscope, length ~17–22 µm, diameter at basis ~1.0–1.2 µm. Chemoreceptive hairs similar in size (length ~12–14 µm) but wider (diameter at basis 1.4–1.6 µm) and with side branch ( Figs 12C , 18D ) and mostly near leg tips. Retrolateral trichobothrium of tibia 1 at 58–67% of tibia length. Prolateral trichobothrium absent on tibia 1, present on tibiae 2–4. Base of trichobothria evenly rounded, without proximal ridge ( Figs 11H , 18B , 26B , 33H ). Legs with roundish cuticular plates ( Figs 11F , 18G, H , 26C, D ; diameter 4–7 µm) and rimmed pores ( Figs 11G , 18C , 26D ; outer diameter 2.5–3.0 µm, diameter of opening 0.2–0.3 µm) apparently on all leg segments. Tarsus 1 with three to five pseudosegments, variably distinct. Leg tarsal organs capsulate ( Figs 12E, F , 19A–C , 27A–C , 33A, B ; diameter 2.5–4.5 µm, diameter of opening 0.6–1.0 µm), but tarsal organs of posterior legs (legs 3 and 4 or legs 4 only) apparently reduced and non-functional ( Figs 19D , 27D , 33C, D ). Tarsus 4 with one comb-hair on prolateral side ( Figs 19H , 27H ). Main tarsal claws with ~10–13 teeth ( Figs 12G, H , 19E–H , 27E–H , 33E–G ). Claws of tarsus 4 slightly different from others (distal teeth more directed towards distal). Female In general, similar to males but sternum without anterior humps, chelicerae without stridulatory files ( Figs 10D , 16B , 24D , 31B ), clypeus without sclerotized rim, and palpal tarsal organ weakly raised ( Figs 18A , 26A , 32D ) and slightly smaller (diameter 3.6–4.5 µm, diameter of opening 0.7–1.1 µm). Legs either shorter than in males (male / female tibia 1 length: ~1.0–1.3, but sample sizes mostly very small except in N. marnif sp. nov. : 1.10) or equal to slightly longer than in males (reasonable sample sizes only in N. subtilissima , N. amoud sp. nov. , and N. samail sp. nov. : 0.95–0.98); tibia 1 length 0.36 – 0.83. Spinnerets, slender metatarsal hairs, chemoreceptive hairs, trichobothria, cuticular plates, rimmed pores, comb-hairs, leg tarsal organs, and claws as in male. Epigynum with simple semicircular to trapezoidal anterior plate, weakly protruding, in some species with distinct median pocket ( Figs 10F , 15E , 16F ) (or glandular duct?—bottom of pocket not sclerotized and difficult to resolve); posterior plate short and simple. Internal genitalia ( Figs 8 , 9 , 15 , 23 , 30 ) with pair of transversal posterior sclerites and complex median structures of unknown function, apparently without pore plates; in N. samail sp. nov. with pair of large membranous elements.