Borralinae, Gray & Smith, 2008
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publication ID |
https://doi.org/ 10.3853/j.0067-1975.60.2008.1493 |
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persistent identifier |
https://treatment.plazi.org/id/038E4730-6E35-C146-E794-A55EFB673EEE |
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treatment provided by |
Felipe |
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scientific name |
Borralinae |
| status |
subfam. nov. |
Borralinae new subfamily
Diagnosis. Gracile cribellate spiders ( Fig. 5b,c View Fig ). All posterior eyes with grate-shaped tapeta; AME usually largest; feathery hairs present; trochanters deeply notched; male palpal tibia with VTA; cymbium with retrolateral flange; tegulum with basal to retrolateral tegular lobe; female copulatory ducts short, broad and flattened; PMS with fused paracribellar bases placed anteroectally.
The Borralinae differs from the Stiphidiinae by the presence of a GST in all posterior eyes, a palpal tegular lobe, a median apophysis and broad copulatory ducts. It differs similarly from the Kababininae —but tapetal structure in latter is unknown— and additionally by the presence of a palpal RVTA. (See comments below on relationships of Kababininae ).
Description
Cephalothorax and abdomen ( Figs 1a–f View Fig , 4a–d View Fig ). Carapace profile usually highest at fovea in males but arched to flattish in females and in both sexes of Therlinya ; carapace wider in males, caput more prominent in females; carapace either patterned with a pair of dark grey longitudinal stripes stopping short of posterior carapace margin (“striped group” genera); or unpatterned with a cover of light grey-fawn hairs ( Therlinya ). Chilum entire. Chelicerae vertical, with prominent retrobasal boss; fang groove with 2 retromarginal and 3 promarginal teeth, basal promarginal tooth extended as a strong carina; numerous sensory hairs on the lower frontal paturon, with an enlarged hair at promarginal groove apex opposite the fang base; retrolateral jaw margin with a single apical sensory hair. Cheliceral/palpal femur “stridulatory” setae present or absent ( Fig. 15a–d View Fig ). Maxillae longer than wide, lateral margins straight to weakly undulate, with a strong linear serrula. Labium slightly longer than wide, basally notched and narrowing to a weakly notched to truncate apex. Sternum cordate, posteriorly pointed to midway between coxae IV. Dorsal and ventral abdominal pattern typically as in Figs 1a View Fig , 4c,d View Fig .
Eyes ( Figs 1a,b,e,f View Fig , 4f View Fig ). Eyes in two rows; AME largest or subequal to PME; from above AER weakly recurved, PER weakly procurved; ALE with a canoe-shaped tapetum; PLE and PME with grate-shaped tapeta in the form of highly reflectile, broad, loose loops ( Fig. 4g View Fig ).
Legs. Slender; male legs longest with metatarsi I and II sometimes modified (slightly bowed and/or flattened). Femora and tibiae grey/brown banded. Trochanters deeply notched. 3–4 serrate accessory setae are placed lateral to the inferior tarsal claw ( Fig. 3j View Fig ); claw tufts and scopulae absent. Calamistrum linear, sub-proximal to central, 0.4–0.45× length of metatarsus and delimited at each end by a retrodorsal spine; weakly developed in males.
Sensillae and cuticle ( Fig. 3g –i View Fig ). Feathery hairs abundant on body and legs. Trichobothria longest distally, in single row on tarsi and metatarsi and 2 rows on tibia; present on female palpal tarsus and male cymbium ( Fig. 2d View Fig ); bothria collariform, proximal plate longitudinally ridged. Tarsal organ distal to trichobothria, capsulate with fine longitudinal ridging and pore keyhole to pyriform shaped. Cuticle sculpturing of “fingerprint” pattern ( Fig. 3h,i View Fig ).
Male palp ( Figs 2a–i View Fig , 6a,b View Fig ). Palpal cymbium with basal retrolateral flange. Tegular lobe basal to retrolateral, usually well developed ( Fig. 2a View Fig ) but sometimes reduced ( Fig. 16a View Fig ). Sperm duct clearly visible, S-shaped on basal or prolateral tegulum and partly associated with the TL ( Fig. 6a View Fig ). MA usually bipartite, if unipartite usually membraneous; bipartite MA with medial process membraneous (mMA), lateral process variably sclerotized (sMA) ( Fig. 2f,i View Fig ); MA occasionally reduced (e.g., Pillara griswoldi Gray and Smith ). Conductor varies from T or modified T-shape to stalked broad falciform (prolateral limb of T may be reduced and retrolateral limb either spiniform or thickened); antero-prolateral conductor margin simple or with flange-like processes and folded to form a groove for the embolus ( Fig. 2e,h View Fig ). Embolus basally robust or slender, spiniform to rod shaped, curved and distal part embraced within the conductor groove ( Fig. 2a,b,e,f,h View Fig ). Tegular window prolateral to retrobasal, small to large ( Fig. 6a View Fig ). Tibia with two retrolateral apophyses (RVTA+RTA or RVTA+RDTA) and 2–3 strong prolateral to dorsal bristles or spines; patella with 1 or 2 long dorsal bristles ( Figs 2c,g View Fig , 6a,b View Fig ).
Epigynum ( Figs 6c,d View Fig , 13d,g View Fig ). Without lateral lobes or teeth; epigynal fossa paired or unpaired with anterolateral copulatory openings; copulatory ducts short, broad and flattened; paired spermathecae medium to large sized, globular to ovoid.
Spinnerets ( Figs 3a–f View Fig , 4e View Fig ). Cribellum bipartite, spinning fields widely separated in female (seam c. 0.3–0.4× a field width); seam and posterior plate margin strongly sclerotized, latter medially indented; in male, similar shape but narrower and non-functional. PLS slightly longer than ALS; PMS shortest. ALS: broad truncate cone, bases separated by about half a base width, apical segment very short with wide margins; PMS adjacent, spigot field longer than wide; PLS slender, bases separated by twice a base width, apical segment tapering distally and almost as long as basal segment. Spigots (female): ALS: 2 MAP, 28–80 piriform; PMS: 1 mAP, 5–13 aciniform, multiple paracribellar on 2–6 fused bases placed anteroectally, 1 cylindrical; PLS: 11–35 aciniform, 1 modified PLS spigot, 3 free paracribellar, 2 cylindrical. Spigots (male): ALS: 1 MAP + 1 nubbin, piriform; PMS: 1 mAP + fused paracribellar nubbins, aciniform; PLS: aciniform + modified PLS spigot and paracribellar nubbins.
Tracheal system. Simple with 4 unbranched tubes confined to abdomen. Spiracle just anterior to cribellum and about 0.4× as wide as cribellum plate.
Included genera. Therlinya Gray & Smith, 2002 ; Borrala Gray & Smith, 2004 ; Pillara Gray & Smith, 2004 ; Jamberoo n.gen.; Couranga n.gen.; Asmea n.gen.; Karriella n.gen.; and Elleguna n.gen.
Biology. Borraline spiders are common in forest habitats in southern and eastern Australia and highland Papua New Guinea. They occupy simple, lacy, cribellate sheet webs associated with logs, rocks, hanging bark and stable soil banks ( Fig. 5a View Fig ). The webs are planar to arched sheets from 15 to 35 cm in extent with more or less irregularly scalloped margins depending on the position of guying points. The arched basal area tapers back into a short funnel-like entrance vestibule of stronger silk that leads into a shallow, sparsely silked retreat hole, crevice or cavity. The spiders run inverted under the sheet.
Mating behaviour—epigynal mutilation. In many spider species matings of males with mated females may be thwarted by the presence of epigynal mating plugs—either a hardened male secretion or detached parts of the male palp blocking the female copulatory ducts ( Suhm et al., 1996, Fromhage & Schneider, 2006). Secretory mating plugs are often seen in borraline spiders. However, another mechanism observed here that also may have a paternity assurance function is female genital mutilation. Several borraline species have unusual epigynal structures—prominent “knobs” ( Jamberoo spp. , Fig. 9c,d View Fig ; Karriella spp. , Fig. 13d,e View Fig ; Pillara griswoldi , in Gray & Smith, 2004, fig. 11c,d) and thin marginal flanges ( Elleguna major n.sp, Fig. 16c View Fig )—as well as the slender median epigynal septa seen in most Jamberoo spp. , E. minor n.sp. ( Fig. 17c View Fig ) and Asmea spp. ( Fig. 19c View Fig ). Interestingly, these structures have been observed to be partly or completely broken away from the epigynum. The most notable mutilations were seen on the epigyna of Jamberoo spp. ( Fig. 9e,f View Fig ), Karriella spp. ( Fig. 13f View Fig ) and Elleguna spp. ( Fig. 16d View Fig )—sometimes making them almost unrecognizable taxonomically. It seems possible that the damage is associated with movements of the male palp during mating—perhaps inflicted by the robust apophyses on the palpal tibia and bulb or the cymbial flange. In some cases the epigynum may be both mutilated and plugged ( Figs 9e View Fig , 13f View Fig ).
When intact, the epigynal structures noted above may play a significant role during mating as guides or anchor points for facilitating male palpal insertion. If this is so, their damage or loss could be expected to seriously compromise or negate subsequent male mating success.
Only one other example of possible paternity assurance via female genital mutilation is known to us. This is the breakage of the elongate epigynal scapes present in some araneid genera, notably Eriophora Simon. Broken scapes have been observed in females of both Australian (pers. obs.) and American ( Levi, 1970) species of Eriophora . Levi (1970) noted that the scape was missing in about 50% of E. ravilla and E. fulginea specimens examined.
Notes on characters
The grate-shaped tapetum in borraline spiders and Stiphidion (see also notes in Gray & Smith, 2004). In recent analyses of entelegyne spider relationships ( Griswold et al., 2005) the genera Stiphidion Simon and Pillara are both scored as having eyes with a grate-shaped tapetum (GST). In Pillara and the other borraline spiders examined, a GST in the form of several wide reflectile loops ( Fig. 4g View Fig ) is present in both the PME and PLE, while the ALE has a canoe-shaped tapetum (CST). The GST has been observed in representatives of the five borraline genera for which fresh material was available— Therlinya , Pillara , Borrala , Couranga and Jamberoo —and it is presumed to be present in the remaining three genera. Homann (1971) records the presence of a GST in the PME and CST in the PLE and ALE of “ Stiphidium spec. ”. Examination of the eyes of Stiphidion facetum Simon shows a strongly reflecting CST in the ALE ( Fig. 4h View Fig ) but not in the PLE. In both the PLE and PME the tapetum appears as a moderately bright, flocculent, greyish-white layer. This layer may be either relatively uniform or differentiated, appearing either as a field of more or less bright fuzzy spots ( Fig. 4i View Fig , PME) or as variable flocculent bands ( Fig. 4j View Fig ), the latter usually seen in the PLE. By contrast, the grate tapeta in many lycosoid and the borraline spider eyes consist of highly reflectile loops ( Fig. 4g View Fig ) that are readily visible using the observational methods described here. In their study of zoropsid spiders, Raven and Stumkat (2005) note that they were “unable to confirm that Stiphidion has a grate-shaped tapetum”. Taken together, the present evidence warrants the rejection of the presence of a GST in Stiphidion .
Serrate accessory claw setae. Although serrate setae are most strongly developed in the araneoid spiders ( Griswold et al., 2005), similar setae are also present in some stiphidiid spiders. Three to four of these “toothed” setae are placed at each side of the inferior tarsal claw in Jamberoo johnnoblei n.sp. ( Fig. 3j View Fig ) and Borrala dorrigo (fig. 2c,d in Gray & Smith, 2004). In these genera the “teeth” are in a single row but this may be doubled basally. Serrate setae are also present in Stiphidion facetum but the “teeth” are in a long double row ( Fig. 3k View Fig ). Griswold et al. (2005) score these setae as absent in Pillara and Stiphidion .
Retrolateral tibial apophyses. In Therlinya , Borrala and Pillara the decidedly more ventrally placed of the two retrolateral apophyses present was termed the RVTA, while the laterally placed apophysis was the RTA. However, in the genera described here the “RTA” is usually more dorsally placed and is termed the RDTA; whether all of these RDTA’s are RTA homologues is probable but uncertain. The term RVTA is retained for the more ventral apophysis, although in the new genera its position is often somewhat more retrolateral than in the three previously described genera. However, their homology is suggested by their basic structural similarity.
Median apophysis. An MA is present in all borraline genera. A single, membraneous MA is present in Therlinya , Pillara and Elleguna ( Fig. 17a View Fig ). In the other genera the MA is a bipartite apophysis—the medial process is always membraneous, while the lateral process is weakly to strongly sclerotized ( Fig. 2f,i View Fig ). The unipartite membraneous MA may be homologous with the medial process of the bipartite MA.
Legs. Male metatarsi I and II are long and slender but in Jamberoo , Couranga , Asmea , Karriella and Elleguna they are also gently bowed and may be flattened as well.
Stridulatory setae. Modified setae are present on adjacent surfaces of the lateral paturon and the prolateral palpal femur in Elleguna and Karriella ( Fig. 15a–d View Fig ). Their position suggests a stridulatory function. In Karriella treenensis n.sp. the setae may be absent in some populations.
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