Revalidation of the spider genus Citharoceps Chamberlin, 1924 (Araneae, Segestriidae)

Abstract Citharoceps Chamberlin was diagnosed by the presence of a very distinctive stridulatory apparatus composed of two patches of ridges on the sides of the cephalic region, and a stridulatory thorn on the prolateral region of the femur I. Currently, this genus is a junior synonym of Ariadna Audouin, with the assumption that the stridulatory apparatus could constitute an exclusive feature of its unique known species, Citharoceps fidicina Chamberlin, currently senior synonym of Citharoceps californica Chamberlin & Ivie. In the present study, Citharoceps is revalidated and redescribed based on the occurrence of the stridulatory apparatus in Citharoceps fidicina and Segestria cruzana Chamberlin & Ivie, and also on the presence of distinguishable characters, such as the length of the labium-sternum junction, ventral median spine on male metatarsi I, and strong sclerotized interpulmonary fold in females, forming a conspicuous median flap. Segestria cruzana is transfered to Citharoceps, with Citharoceps californica removed from the synonym of Citharoceps fidicina, and proposed as a junior synonym of Citharoceps cruzana, due to the similarity between the additional material examined and the original description. Males of Citharoceps fidicina and Citharoceps cruzana are described for the first time.

The genus Citharoceps was described by Chamberlin (1924) to include only Citharoceps fidicina, described based on an immature holotype from Ensenada, Baja California, Mexico.He distinguished this genus from other segestriids by the presence of a stridulatory apparatus composed of two distinctive patches of grooves on both sides of the cephalic region and a stridulatory thorn located on the prolateral region of femur I. Later, Chamberlin and Ivie (1935) described a new species, Citharoceps californica, based on immatures from Laguna Beach, California, USA, distinguishing it from C. fidicina by the larger size and darker coloration.Beatty (1970) examined the holotype of C. fidicina and paratypes of C. californica, and synonymized C. californica with C. fidicina, and Citharoceps with Ariadna.After the study was submitted to publication, Beatty (1970: 485) discovered a male specimen of C. fidicina with stridulatory patches like those found on the female.To the author, this characteristic, together with other structural features, confirms his assumptions on the synonymy of Citharoceps with Ariadna.This comment was included in the publication as an addendum.
In the present study, the revalidation of the genus Citharoceps is proposed, based on the presence of the stridulatory apparatus, together with distinctive characters, such as the labium-sternum length equal or smaller than the endite-sternum junction, a ventral median spine in the metatarsi I of males, and the internal female genitalia with a strong sclerotized interpulmonary fold, forming a conspicuous median flap.The genus is redescribed with more detailed information on the morphological characters, mainly with regard to male and female genitalia.The male of C. fidicina is described for the first time.Citharoceps californica is removed from the synonym of C. fidicina and proposed as a junior synonym of Segestria cruzana Chamberlin & Ivie, 1935, together with the transfer of this species to Citharoceps, and the first description of its male.

Materials and methods
The specimens examined are deposited in the American Museum of Natural History, New York (AMNH; L. Prendini), California Academy of Sciences, San Francisco (CAS; C. E. Griswold), Collection of the Cabrillo National Monument Park, San Diego (CNMP; K. Lombardo), Darrel Ubick collection, San Francisco (CDU), Instituto Butantan, São Paulo (IBSP; A. D. Brescovit), and Queensland Museum, Brisbane (QM; R. Raven).The morphological examinations and descriptions follow Grismado (2008) and were made under Leica MZ6 and MZ12 stereomicroscope.Spine notation was modified from Grismado (2008) with the absence of the term "apical" (ap), and description of the leg IV spination.Measurements are in millimeters.The male genitalia was divided into bulb and embolus by the narrowing of the spermatic duct, where it has a less sclerotized region (Figs 6A-B, 8A-C; see Lipke et al. 2014, fig. 10).The investigation of the internal female genitalia followed three steps: (I) dissection of the ventral anterior region of the abdomen; (II) digestion of the dissected material with Ultrazime® contact lenses cleaner enzyme in 1 tablet/5 ml distilled water for 24 hours; (III) posterior treatment with heated KOH for 20 minutes, according to Platnick et al. (1999).Spigot nomenclature followed Platnick et al. (1991) and Griswold et al. (2005).Illustrations were made under a Zeiss Axioscop 20, with a camera lucida attached.Photographs were taken with a Leica DFC 500 digital camera attached to a Leica MZ16A stereomicroscope.Extended focal range photos were composed with Leica Application Suite 3.3.For scanning electron microscopy (SEM) images, the body parts were dehydrated through a series of graded ethanol (80% to 100%), dried by critical-point drying method, mounted on metal stubs using adhesive copper tape and nail polish for fixation, and sputter coated with gold.SEM photographs were taken with a FEI Quanta 250 scanning electron microscope from the Laboratório de Biologia Celular of the Instituto Butantan, São Paulo.Abbreviations: AC-aciniform gland spigot; ALS-anterior lateral spinnerets; AR-anterior receptaculum; B-bulb; d-dorsal; DL-dorsal lobe; E-embolus; GD-glandular ducts plate; IF-interpumonary fold; LS-less sclerotized portion of the sperm duct; mAP-minor ampulate gland spigot; MAP-major ampulate gland spigot; p-prolateral; PI-piriform gland spigot; PLS-posterior lateral spinnerets; PMS-posterior median spinnerets; PR-posterior receptaculum; r-retrolateral; T-tracheal trunk; UE-uterus externus; v-ventral; VL-ventral lobe; vp-ventroprolateral; vr-ventroretrolateral.Geographical coordinates were obtained with Google Earth (Lat/Lon-WGS84).
Trichobothria on the dorsal subdistal region of metatarsi I-IV, dorsal subproximal and subdistal region of tibia I-IV, and dorsal region of the male and female palpal tibia; trichobothrial bases with a transverse ridge, curved inwards; trichobothrial shaft filiform (Fig. 2F).Legs with three tarsal claws, paired claws pectinated, and unpaired one with only a small tooth (Fig. 2D); chemosensory setae on the distal ventral region of tarsi I-II in males (Fig. 2D, G; according to Foelix and Chu-Wang 1973: figs 17a-b).Preening comb of metatarsi IV with 5-7 spines (Fig. 2H).Abdomen uniformly hairy, longer than wider (Figs 5A-B, F-G; 7A-B, F-G).Spinnerets: ALS with three segments, the basal segment crossed by a diagonal membranous stripe (Fig. 3A), and one MAP spigot with 8 PI (Fig. 3D); PMS with just one mAP spigot (Fig. 3C); PLS with 4 AC spigots (Fig. 3B).Colulus triangular and pilose (Fig. 3E).Internal female genitalia: anterior receptaculum bilobated with a hyaline external cuticle, a short dorsal lobe, and a small plate of glandular ducts restricted to the ventral and lateral region of the dorsal lobe; posterior receptaculum membranous, with pores (Figs 4D-G; 6C-D; 8C-D).Chamberlin, 1924, comb Diagnosis.Males of Citharoceps fidicina differ from those of C. cruzana by the slightly shorter and thicker embolus (Fig. 6A-B) and by a straight metatarsus I (Fig. 5C-E).Females differ from C. cruzana by the anterior receptaculum with both dorsal and ventral lobes well delimited, the ventral lobe projected and laterally expanded (Figs 4D-F, 6C-D).
Distribution.South of California, USA and Baja California, Mexico (Fig. 11).
Remarks.We feel that species attribution is unproblematic.The immature specimen collected in Baja California del Norte by Craig and Dailey in 1962, matches perfectly with the type material of C. fidicina.In addition, that immature was collected with two females that match perfectly with the females collected in San Diego.(Chamberlin & Ivie, 1935) Diagnosis.Males of Citharoceps cruzana differ from those of C. fidicina by the presence of a relatively longer and slender embolus (Fig. 8A-B), and a slightly prolaterally bent metatarsus I (Fig. 7C-E).Females differ from C. fidicina by the darker coloration, and anterior receptaculum with both dorsal and ventral lobes with similar length, the ventral lobe not expanded (Figs 4G, 8C-D).
Remarks.One male of Citharoceps was found from the type locality of S. cruzana.After the examination of the immature holotype of S. cruzana, it was detected that it possessed the stridulatory apparatus exclusive for Citharoceps, not detected by Chamberlin and Ivie (1935), thus we transferred this species to this genus.In addition, in the additional material, females of Citharoceps were found from the middle coast of California that resemble those described by Chamberlin and Ivie (1935) as C. californica, together with a male, from the same region, that is similar to the one from Santa Cruz Island.Thus, C. californica is removed from its synonym with C. fidicina, due to its greater size and darker coloration, and placed as junior synonym of C. cruzana.

Discussion
The distribution of the genus Citharoceps Chamberlin, 1924 comprises only coastal regions of the state of California, USA, and Baja California, Mexico (Fig. 11).The Baja California peninsula has a tectonical origin and is well known to harbor a great diversity and endemic species of fauna and flora, mainly because of climate and topography divergences (Murphy 1983, Grismer 1994).Under this scenario, the diagnostic features presented by Citharoceps are rather distinct based on the other two segestriid genera occurring in this region e.g.Ariadna and Segestria.Although those characters are putative synapomorphies, the stridulatory apparatus, once thought by Beatty (1970) to be exclusive of C. fidicina, is also present in C. cruzana, contradicting his assumption.In addition, the labium-sternum junction length, the presence of a ventral median spine on metatarsi I of males, and the morphology of the interpulmonary fold are very distinctive characters from Segestria (Fig. 9D; Giroti and Brescovit 2011, figs 19-20, 23), Ariadna (Figs 9A, 10A;Grismado 2008, figs 1A, 4D, 6H) and Gippsicola (Figs 9B, 10B).Under these circumstances, it seems reasonable that Citharoceps is a different genus and must be treated as a valid taxon.

Notes on the stridulatory apparatus of Citharoceps
The occurrence of a stridulatory apparatus in spiders has been reported in at least 25 spider families (Legendre 1963, Rovner 1980, Uetz and Stratton 1982, Starck 1985, Maddison 1987, Wunderlich 1995, Ramírez et al. 2001, Jocqué 2005), and also phylogenetically tested in Haplogynae (Labarque and Ramírez 2012) and Entelegynae (Griswold et al. 2005, Ramírez 2014).Legendre (1963) was the first to classify these apparatus (types a-g), and Starck (1985) provided a complete list of known stridulatory apparatus in spiders, also discussing their structures and evolutionary context.The stridulatory apparatus found in Citharoceps can be classified as belonging to the "type l", with ridges or grooves (pars stridens) in the carapace; and thorns (plectron) in the femur I.This type was also described by Maddison (1987) for seven salticid genera.
The function of the stridulatory apparatus in Citharoceps is unknown, but considering that it occurs in males, females and immatures, it seems unlikely that it has a courtship function.Maddison (1987) reported a personal comment of M. J. Moody having heard a sub-adult male of C. fidicina making a loud buzzing sound while rubbing the carapace ridges.Considering this information, the function of the stridulatory apparatus in Citharoceps could involve defensive buzzing sounds, as described by Uetz and Stratton (1982) for Micrathena gracilis (Walckenaer, 1805), but future ethological studies are needed to corroborate this hypothesis.

Figure 1 .
Figure 1.SEM images of Citharoceps fidicina, female from La Jolla, San Diego (CAS 9039517).A cephalothorax, frontal view B cephalothorax, frontal-lateral view, showing the right stridulatory patch, white arrow indicates the lateral proximal depression C stridulatory patch cuticle in detail D cheliceral lateral basal transverse ridge E cheliceral retromarginal tooth F endites and labium, ventral view G distal region of the right chelicerae, ventro-lateral view, showing the fang and the cheliceral teeth.

Figure 3 .
Figure 3. SEM images of Citharoceps fidicina, female from La Jolla, San Diego (CAS 9039517).A Spinnerets, ventro-posterior view, white arrows indicate the ALS basal segment transverse membrane B right PLS, posterior view C left PMS, posterior view D left ALS, posterior view E colulus in ventral view.

Figure 4 .
Figure 4. Male and female genitalia of Citharoceps species.Citharoceps fidicina, male from Cabrillo N. M., San Diego (CNMP) (A-C) female from La Jolla, San Diego (CAS 9039517) (D-E) and from Baja California, Mexico (CAS 9039518) (F) Citharoceps cruzana, female from Arroyo Seco, California (CDU) (G).A right palp, retrolateral view B embolus tip, prolateral view C cymbium, dorsal view, white arrow indicates distal notch, asterisk indicates a chemosensory setae and circle indicates a tactile setae D internal genitalia, apical view, and E lateral view, white asterisks indicates the median flap F-G anterior receptaculum, ventral view, black arrows indicate the hyaline cuticle.

Figure 5 .
Figure 5. Citharoceps fidicina.Male from Cabrillo N. M., San Diego (CNMP) (A-E) female from La Jolla, San Diego (CAS 9039517) (F-I).A, F habitus, dorsal view B, G habitus, ventral view C right leg I, prolateral view D same, retrolateral view E right metatarsus and tarsus I, ventral view, black arrow indicates the ventral median spine H left leg I, prolateral view I same, retrolateral view; white arrows indicate the stridulatory thorn.Scale bars: 1 mm.

Figure 6 .
Figure 6.Citharoceps fidicina.Male from Cabrillo N. M., San Diego (CNMP) (A-B) female from Baja California, Mexico (CAS 9039518) (C-D).A left palp, prolateral view B same, retrolateral view, white dashed line indicates the narrowing of the sperm duct C internal female genitalia, lateral view, and D ventral view.White scale bars: 1 mm.

Figure 7 .
Figure 7. Citharoceps cruzana.Male from Santa Cruz Island, California (CAS 9046542) (A-E) female from Coast Ridge Trail, California (CDU) (F-I).A, F habitus, dorsal view B, G habitus, ventral view C right leg I, prolateral view D same, retrolateral view E right metatarsus and tarsus I, ventral view, black arrow indicates the ventral median spine H left leg I, prolateral view I same, retrolateral view; white arrows indicate the stridulatory thorn.Scale bars: 1 mm.

Figure 8 .
Figure 8. Citharoceps cruzana.Male from Santa Cruz Island, California (CAS 9046542) (A-B) male from Indians Road, Arroyo Seco Camping, California (CDU) (C) female from Arroyo Seco Camping, California (CDU) (D-E).A left palp, prolateral view B same, retrolateral view, white dashed line indicates the narrowing of the sperm duct C left palp, postero-retrolateral view, detail indicating the less sclerotized portion of the sperm duct D internal female genitalia, lateral view, and E ventral view.White scale bars: 1 mm.

Figure 11 .
Figure 11.Locality of the specimens of Citharoceps examined in the present study.