Laetesia raveni, Hormiga, Gustavo & Scharff, Nikolaj, 2014

Hormiga, Gustavo & Scharff, Nikolaj, 2014, The strange case of Laetesia raveni n. sp., a green linyphiid spider from Eastern Australia with a preference for thorny plants (Araneae, Linyphiidae), Zootaxa 3811 (1), pp. 83-94 : 84-92

Laetesia raveni new species

Figs. 1–6

Material examined. Holotype. AUSTRALIA: Queensland, Lamington National Park, Binna Burra section, Border track, 28°12’14.6”S, 153°11’26.8”E, 24.iv. 2011, 850 m a.s.l., general collection, day, rainforest, G. Hormiga & N. Scharff leg., 1M (QM). Paratype. AUSTRALIA: Same data, together with male holotype, 1F (QM).

Additional material examined. AUSTRALIA: New South Wales: Dorrigo National Park, Dorrigo Rainforest Centre, along Wonga walk, 30°22’ 3.5”S, 152°43’42.4”E, 19.iii. 2010, 758 m a.s.l., general collection, night, rainforest, 9FF, 2Juv, G. Hormiga & N. Scharff leg. ( CAS); Border Ranges National Park, Brindle Creek Road, 28°22’42.2”S, 153°04’09.4”E, 22–23.iii. 2010, 713 m a.s.l., general collection, night, rainforest, 2FF, G. Hormiga & N. Scharff leg. ( GWU, MCZ). Queensland: Lamington National Park, Binna Burra section, 28°12’11”S, 153°11’20”E, 18.iv. 2002, 910 m a.s.l., general collecting, day, rainforest, 2FF, G. Hormiga, M. Kuntner & F. Alvarez leg. ( AMNH); Lamington National Park, Binna Burra section, Border track, 28°12’14.6”S, 153°11’26.8”E, 24.iv. 2011, 850 m a.s.l., general collection, day, rainforest, 11FF, 1M, G. Hormiga & N. Scharff leg. ( ZMUC); Lamington National Park, Binna Burra section, Border track, 28°12’14.6”S, 153°11’27.1”E, 24.iv. 2011, 847 m a.s.l., general collection, day, rainforest, 14FF, 1M, 2Juv, G. Hormiga & N. Scharff leg. (QM, MCZ, CAS); Lamington National Park, Green Mountains, Border track, 28°14’04.2”S, 153°8’31.1”E, 22.iv. 2011, 896 m a.s.l., general collecting, night, rainforest, 2FF, G. Hormiga & N. Scharff leg. ( MCZ).

Etymology. The species epithet is a patronym in honour of our colleague Dr. Robert Raven, of the Queensland Museum (Brisbane), who over the years has offered us unconditional help and support for our research on Australian spiders.

Diagnosis. Males of Laetesia raveni n. sp. can be differentiated from other species described in this genus by their long, setiform and highly sclerotized apophysis of the lamella characteristica. Females are separated by the broad dorsal plate of the epigynum and by the two small digitiform lobes on the ventral plate (although there is intraspecific variation in the size of these lobes, and in some specimens the lobes are hardly visible or even absent). The bright green colour of Laetesia raveni n. sp. might be diagnostic as to our knowledge no other linyphiid species has been reported to be green, although the green coloration fades quickly in ethanol.

Description. Male holotype (from Lamington National Park, Binna Burra Section, 24.iv.2011): Total length 3.40. Cephalothorax 1.60 long, 1.24 wide. Sternum 0.78 long, 0.79 wide, shield-shaped. Abdomen 2.00 long, 0.95 wide. Colour (preserved specimen): Cephalothorax, legs and abdomen yellowish white. Carapace with broad blackish margin, also surrounding cephalon. Black rings around eyes. Fovea with black Y-shaped marking. Abdomen with irregular black and white dorsal markings ( Figs. 1 A–E). Legs with distinct black annulations distally on tibiae and metatarsi ( Fig. 1 E). AME diameter 0.09. Clypeus height 4 times AME diameter. Cephalon with long strong setae in ocular area ( Fig. 4 C). Chelicerae with 4 prolateral teeth, the second distal-most with dorso-ventral fork. Chelicerae without stridulating file. Retrolateral teeth not visible on type specimen, but a subadult male from Dorrigo National Park had 3 on the right chelicera and 4 on the left. Femur I 2.84 long, 1.78 times length of cephalothorax. All femora with long strong setae ventrally and shorter strong proximal setae dorsally. Ventral setae several times longer than diameter of femora. Leg formula 1243. Trichobothrium metatarsus I = 0.18. Pedipalp ( Figs. 2 , 3 A): Tibia unmodified, with a long dorsal macroseta and one dorsal and two retrolateral trichobothria. Cymbium dorsally widest at the basal third, gradually tapering towards a blunt apex. Alveolus occupying the basal half of cymbium. Tarsal organ apicoventral. Paracymbium intersegmental, U-shaped, with broad base, tapering distally into a pointed apex. Tegular division with a pointed caudal apophysis (which in mesoventral view sits over the base of the suprategulum; Fig. 3 A) and an anteriorly projected apical lobe with a sack-like membranous process that is more sclerotized in its acutely pointed apex ( Figs. 2 B and 3A, left pointing arrow). Suprategulum projected into a long distal suprategular apophysis (DSA), with a slightly bifurcating pointed apex ( Figs. 2 B–C). Column in caudal position on the tegular division, bearing a long, membranous embolic membrane that in mesal view runs parallel to the DSA and the embolus ( Figs. 2 B–C). Lamella characteristica massive, about the same length of cymbium, highly sclerotized and with two apical processes: a conspicuous setiform sclerotized apophysis and two processes with highly serrated margins (one membranous, the other sclerotized; Fig. 2 C, left pointing arrow). Embolus arm-shaped, running parallel to the DSA and embolic membrane ( Fig. 2 C). Radix a slight engrossment of the embolus base, concealed under the lamella characteristica. A slightly sclerotized sclerite, with a linguiform process, sits anteriad to the embolus base (possibly a homolog of the terminal apophysis; Fig. 2 C). Spermduct with a kinked diameter constriction on dorsal tegular region (in mesoventral view the narrowing of the duct can be seen under the column; Fig. 3 A).

Female paratype (together with holotype): Total length 5.27. Cephalothorax 1.98 long, 1.44 wide. Sternum 1.04 long, 0.98 wide, shield-shaped. Abdomen 3.32 long, 1.79 wide. Colour (preserved specimen): As male holotype. AME diameter 0.08. Clypeus height 0.42, 5.25 times AME diameter. Chelicerae with 3 prolateral and 4 retrolateral teeth. Chelicerae without stridulating file. Femur I 3.59 long, 1.81 times length of cephalothorax. All femora with long strong setae ventrally and shorter strong proximal setae dorsally. Ventral setae several times longer than diameter of femora. Leg formula 1243. Pedipalp long and slender (1.4 times the length of cephalothorax) and provided with long spines on tibia and tarsus. Trichobothrium metatarsus I = 0.17. Epigynum ( Figs. 3 B–D, 4A–B): Epigynal region bulging in lateral view. Dorsal plate broad, with a sclerotized basal stalk on midventral surface, projected into a long scape bearing an apicoventral socket with darker pigmentation. Posterior margin of ventral plate (VP) cleaved, forming two semicircular lobes. Atrium flanked by two small digitiform processes on VP, caudally oriented. Copulatory openings in mid epigynal region, at the base of the dorsal plate (DP) stalk, in atrium (under VP). Copulatory ducts (CD) make long loops towards the lateral margins. Spermathecae darkly pigmented, curved as an extension of CD, visible by transparency through the epigynal cuticle on both sides of the VP lobes. Fertilization duct located dorsally at the DP margin, caudolaterally oriented ( Fig. 3 C), then curving anteriad. Tracheae (Binna Burra, 2010 specimens) can be seen in life specimens by transparency through the abdominal cuticle. The tracheal trunks are very superficial, consisting of two simple, unbranched pairs (haplotracheate system). Lateral pair seen as thin white lines running anteriorly from atrium and then dorsally on abdomen; median pair can be seen too, not as superficial as lateral.

Life coloration. Female ( Figs. 1 A–E): Carapace green, margins dark green (wider marks in posterior half), cephalic region darker, Y-shaped, extending into fovea. Black rings around eyes. Sternum uniformly green. All leg segments translucent light green; leg tibiae and metatarsi darker, more brownish, distally suffused with dark/ blackish pigment. Abdomen bright green, with a longitudinal median band, brown and black with a few yellow marks, delineated by white guanine spots. Ventrally uniformly green, with dark brown spots in front of epigastric furrow (copulatory ducts and spermatheca). Males (n = 3) of similar colour, green tint not as bright as in females.

Variation. Colour (in preserved specimens): Blackish markings on carapace vary from a faint band along carapace margin to almost total coverage in certain individuals. Dorsal abdominal markings may be more or less pronounced and some female individuals are a little darker, overall. Epigynum: Lateral digitiform processes on VP vary in length, even in specimens from same locality, and can be absent. Measurements: Male total length ranges from 3.37 to 3.40 (n = 2). Female total length varies from 3.36 to 5.27 (n = 20). Male cephalothorax ranges from 1.57 to 1.60 (n = 3). Female cephalothorax length ranges from 1.31 to 1.98 (n = 20).

Phylogenetic placement. No explicitly phylogenetic (i.e., synapomorphy based) circumscription exists for the genus Laetesia . Simon (1908) originally described Laetesia to group two new species from Western Australia. Van Helsdingen (1972) provided the first modern definition of the genus, based on overall similarity. Millidge (1988) similarly defined the genus upon further study of the New Zealand fauna. The morphology of Laetesia raveni n. sp. suggests that it is congeneric with L. mollita , the type species. We hypothesize here two potential synapomorphies of Laetesia : the distally forked distal suprategular apophysis and the long, straight and narrow embolic membrane, both traits being shared by all the Laetesia species illustrated by van Helsdingen (1972) and Millidge (1988). Other distinctive characters of Laetesia may be symplesiomorphic, e.g., the presence of two latero-ventral scapes or processes in Laetesia species is also shared by several Dunedinia species (e.g., D. denticulata Millidge 1988 : fig. 203). The membranous and apically pointed tegular process of some Laetesia species (e.g., Laetesia raveni n. sp., Fig. 3 A, left pointing arrow; L. aucklandensis (Forster) , Millidge 1988: fig. 146) is also found in some Laperousea (e.g., Laperousea cupidinea (Simon) , van Helsdingen 1972: fig. 5) and Diploplecta species (e.g., D. communis Millidge 1988 : fig. 221).

Distribution. Eastern Australia. Known from Dorrigo National Park and Border Ranges National Park in north eastern New South Wales and Lamington National Park in south eastern Queensland.

Natural history. Laetesia raveni n. sp. builds dome-shaped sheet webs on vegetation ( Figs. 5 , 6 ). The spider sits upside-down under the apex of the dome, under a leaf that is usually positioned at the centre of the sheet. All webs have relatively dense upper scaffolding, although the density of silk lines in this mesh is variable. An eggsac, presumably of this species, was observed attached under a leaflet at edge of web (photos GH 2823–2828 / 19.iii.2010; Fig. 5 B, F). When disturbed, the spider flattens the body against the leaf surface. In two webs we have observed early instars with the adult female. Except in two cases, the webs of all the 48 specimens of Laetesia raveni n. sp. that we have collected were built exclusively on two plant species (both of them distinctively thorny): wait-a-while vines, also commonly known as southern lawyer cane ( Calamus muelleri Wendland , Arecaceae ; Figs. 5 A–B, E–F, 6) or on Gin's Whiskers ( Solanum inaequilaterum Domin , Solanaceae ; Figs. 5 C–D). Most webs were found in the first plant species. Only in two instances, in Binna Burra (Lamington National Park), were their webs built on other plant species, and in these two latter cases these plants were adjacent (in physical contact) to one of these two aforementioned species.

Figures

FIGURE 1. Laetesia raveni n. sp., female Dorrigo National Park, NSW (photographed on a different plant species than where it was collected). Photo voucher numbers as follows (all 10. iii. 2010). A, NS 3136. B, NS 3142. C, GH 2927. D, GH 2981. E, GH 2950.

FIGURE 2. Laetesia raveni n. sp., pedipalp of male from Lamington National Park (Binna Burra), Queensland. A, Ectal (right pointing arrow, setiform process of lamella characteristica, also in B and C). B, Mesal (left pointing arrow, membranous tegular process). C, Suprategulum and embolic division, ventral (left pointing arrow, membranous and sclerotized processes of lamella characteristica). Scale bars, 0.5 mm.

FIGURE 3. Laetesia raveni n. sp. A, Tegular division (suprategulum and embolic division dissected out, see Fig. 2 C) of male from Lamington National Park (Binna Burra), Queensland (left pointing arrow, membranous tegular process). B – D, Epigynum of specimen from Dorrigo National Park, NSW. D, ventral. C, Dorsal, cleared. D, Ventral, cleared. Scale bars, 0.5 mm.

FIGURE 4. Laetesia raveni n. sp. A, Epigynum, from Dorrigo National Park, NSW. B, Epigynum, from Lamington National Park (Binna Burra). C, Prosoma of male from Lamington National Park (Binna Burra), Queensland, lateral. Arrows denote epigynal digitiform processes (B) and absence of (A). Scale bars, A, B, 0.2 mm; C, 1.0 mm.

FIGURE 5. Webs of Laetesia raveni n. sp., from Dorrigo National Park, NSW. Webs in A, E, B, F are on Calamus muelleri (Arecaceae); webs in C, D on Solanum inaequilaterum (Solanaceae). Photo voucher numbers as follows (A, E, 18. iii. 2010, rest 19. iii. 2010). A, GH 2804. B, GH 2828 (detail of F). C, GH 2834. D, GH 2838. E, GH 2808 (detail of A). F, GH 2824 (notice eggsac under second leaflet to the left of stem).

FIGURE 6. Webs of Laetesia raveni n. sp., from Lamington National Park (Binna Burra), Queensland, on Calamus muelleri (Arecaceae). Photo voucher numbers as follows (A – C, 18. iv. 2002). A, GH 020418 _ R 05 _ 33. B, GH 020418 _ R 06 _ 05. C, GH 020418 _ R 06 _ 07 (detail of B).