Callidosoma cassiculophylla, Bernardi & Wohltmann & Ferreira, 2017

Bernardi, Leopoldo Ferreira De Oliveira, Wohltmann, Andreas & Ferreira, Rodrigo Lopes, 2017, A novel symbiotic relationship between mites and recluse spiders (Sicariidae: Loxosceles), with a description of a new Callidosoma species (Trombidiformes: Erythraeidae), Zootaxa 4338 (3), pp. 459-474 : 461-471

Callidosoma cassiculophylla sp. nov.

Diagnosis. Medium sized Callidosoma with elongated body, crista metopica with setulose sensilla and distinct posterior process. Idiosomal setae uniform, brush-like. Proximal leg segments not distinctly enlarged.

Description. Adult. Habitus as in Figure 1 and 2 . Metric data from the holotype and 11 paratypes are given in Table 3. Body elongate, ovoid, length 1400–1450, width 825–950 (mounted specimens). Colour in life reddish.

Gnathosoma. Of typical erythraeid type, with three pairs of prominent, long and smooth setae cs located dorsolaterally at the anterior tip and a pair of club shaped elcp dorsolateral at level of palp trochanter. Numerous, setulose setae ventrally. Normal, setulose setae present on palp trochanter, femur, genu and tibia ( Fig. 1D–E , Fig. 3 ). Odontus of palp tibia hook-like. Palp tarsus almost cylindrical, with the apical part overreaching the termination of odontus, 7–10 eupathidia distally, one solenidium more proximal and several setulated normal setae. Chelicera undivided, elongate, with fine teeth at the most anterior part. Paired stigmata located between chelicerae in posterior third of its length.

Idiosoma. Scutum almost reduced to crista metopica ( Fig. 4 ), widened at anterior and posterior sensillary areas. Anterior tip of crista rounded with six to eight setulose setae AL (35–60) anterior to ASens, which in turn is covered with small setules throughout its length. Rod of crista metopica widening towards the posterior sensillary area. PSens similar to ASens, but longer. Posterior process of crista distinct. Eyes, each composed of single circular lens (20–25 diameter) inserted in a rounded sclerite (33–50), located laterally at the level of posterior third of crista. Posterior dorsal setae (35–55) ( Fig. 5 ) setulose, with ventral setules arising in a 70°–90° angle from the seta stem whereas dorsal setules are almost in the same orientation as the seta stem—giving the seta a brush like appearance. Ventral setae similar to dorsal ones, but more slender. Coxae I–II and III–IV fused, each coxa strongly sclerotized along its anterior border. Coxa I with club shaped seta elc I located dorsally anterior. Genital opening (L: 265–310; W: 54–70) with inconspicuous epivalves and strongly sclerotized centrovalves; the latter bearing about 60 setae.

Anal sclerites (L: 95–110; W: 34–45) well sclerotized, bearing about 24 setae. Legs. Leg segmentation formula: 7- 7-7. Leg segments tarsus tibia lesser in height than all other segments. Normal, setulose setae of the same type present on all leg segments. Tarsi I–IV with two claws, which in turn are provided with minute fimbriae at its proximal parts. Ventral setae on tarsi I–IV shorter than lateral and dorsal ones; at other leg segments no such distinct difference. Tarsus I ( Fig. 7 ) with several smaller eupathidia in its distal and ventral part and about five longer eupathidia in dorsal or dorsolateral position, moreover dorsal and lateral with 20–30 solenidia. Tarsi II–IV with 3–5 eupathidia and 0–2 solenidia. Tibia I with 3–6 solenidia and 7–10 eupathidia, tibia IV with 4–6 solenidia and 1–4 eupathidia. Tibia II–III each with 2–3 solenidia and 1–4 eupathidia. Genu I and IV each with 4–8 solenidia and 3–6 eupathidia, on genu II–III each with 2–3 solenidia and 2–4 eupathidia. Telofemur I–IV each with 0–2 solenidia and 2–6 eupathidia. Eupathidia always with minute setules (smaller than at normal setulose setae), solenidia smooth. No specialized setae on basifemur and trochanter I–IV.

Remark. Because of the presence of a completely developed genital opening, all specimens are obviously adults. Internal sclerites as described for erythraeoid males ( Witte 1975, 1998) were not detected. Thus, all specimens are probably females.

Larva. Unknown.

Type specimens. Holotype, Female collected in Lapa do Coronel cave, municipality of Buenópolis, Minas Gerias state, Brazil, 29 March 2015, coll. L. Rabello et al, deposited at Collection of Subterranean Invertebrates (ISLA), Centro de Estudos em Biologia Subterrânea, Department of Biology , Universidade Federal de Lavras ( UFLA), Lavras, Minas Gerais state, Brazil .

Paratypes, 3 females collected in Lapa d’agua cave, municipality of Lassance, Minas Gerais state, Brazil . coords. 23K 541083 mE 8018711 mS, 19 February 2015, Coll. L Rabello et al, deposited at Collection Arachnologische Sammlung, Senckenberg Museum für Naturkunde , Goerlitz, Germany . 1 females collected in Lapa Vermelha VI cave, coords 23K 605379 mE 7830802 mS, municipality of Pedro Leopoldo, Minas Gerais state, Brazil, 13 January 2017, coll. L Andrade et al, deposited at Collection of Subterranean Invertebrates (ISLA), Centro de Estudos em Biologia Subterrânea, Department of Biology, Universidade Federal de Lavras ( UFLA) , Lavras, Minas Gerais state, Brazil . 2 females collected in Cavidade 17 cave, coords 23L 264948 mE 8299835 mS municipality of Formosa, Goiás state, Brazil, 2 December 2015, coll. F Bondezan et al, deposited at Collection of Subterranean Invertebrates (ISLA), Centro de Estudos em Biologia Subterrânea, Department of Biology, Universidade Federal de Lavras ( UFLA) , Lavras, Minas Gerais state, Brazil . 3 females collected in Gruta São José, coords 23L 584907 mE 8261256 mS, municipality of Ibiracatú, Minas Gerais state, Brazil, 21 January 2015, coll. L Rabello et al, deposited at Coleção de Acarologia ( UFMG-AC) , Departamento de Zoologia , Universidade Federal de Minas Gerais , Belo Horizonte, Minas Gerais state, Brazil . 2 females collected in Gruta São José, coords 23L 584907 mE 8261256 mS, municipality of Ibiracatú, Minas Gerais state, Brazil, 21 January 2015, coll. L Rabello et al, deposited at Mite Reference Collection, Departamento de Entomologi e Acarologia, Escola Superior de Agricultura “ Luiz de Queiroz ” ( MZLQ) , Universidade de São Paulo , Piracicaba, São Paulo state, Brazil .

Etymology. The name cassiculophylla from the Latin “ cassiculus ”, meaning spider web and “ phylla ” meaning friend. The name refers to the association of postlarval instars with spiderwebs as habitat.

Morphology remarks. Generic affiliation of the species remains difficult because of the mostly poor state of taxonomy in postlarval Callidosomatinae and Abrolophinae , with only few descriptions fitting modern standards. Affiliation of the species according to characters listed by Witte (1995) in his system of Erythraeoidea based on phylogenetic analysis remains difficult because of most characters listed (ultrastructural, behavioural, larval) have not been observable in our specimens. Applying the process of elimination our species clearly belongs to the Erythraeoidea because of the particular design of chelicerae (elongate styliforme, digitus mobilis absent). The missing retractability of the gnathosoma excludes Smarididae . Of the seven subfamilies of Erythraeidae , several are defined by autapomorphies and are easily excluded: Balustiinae (with urnulae); Phanolphinae (with uniquely modified body setae); and Myrmicotrombiinae (eyes placed in front of crista). The Erythaeinae are also excluded as these have two pairs of eyes; Leptinae are excluded because of the posterior position of the eyes and the colour and shape of the dorsal setae in the new species. The Abrolophinae are closest, but the Callidosomatinae have all of the setae on the palp femur of subequal length (at least one seta on the palp femur at least twice as long as other setae in Abrolophinae ), the form of the genital sclerites (conspicuous epivalves, centrovalves with lateral flaps in Abrolophinae ) and small lateral extension of the scutum (distinct extension of the scutum lateral of crista metopica in Abrolophinae ). Therefore we have placed our new species in the Callidosomatinae because the new species fits the definition of Southcott (1961a) with regard to postlarval instars (i.e. crista metopica present, one pair of eyes situated posterior to the middle of crista, lack of urnulae).

Within the Callidosomatinae , the cylindrical form of the palp tarsus ( Southcott 1961b) excludes Charletonia and the absence of a greatly enlarged telofemur and genu of leg IV ( Beron 2000) does not fit Cecidopus . The absence of distinctly different postdorsal body setae excludes Neoabrolophus (Khot 1965) and the form of the dorsal body setae and the absence of different types of normal leg setae ( Beron 2000; Southcott 1961a, b) do not fit Caeculisoma . The presence of tubercles on tibiae I–IV were described for some other postlarval Callidosoma ; and was even used as causal reasoning for the Callidosomatini including Callidosoma and Caeculisoma ( Southcott 1961b) . However, later descriptions ( Sharma et al. 1983, Treat 1985) showed that tubercles may be absent in other species of Callidosoma . In a comment, Southcott (1996) accepted the missing support for Callidosomatini and expected a better resolution of relationships within Callidosomatinae from future correlation of genera only known from the larval stage with their postlarval instars. We tentatively assign the new species to Callidosoma based on the general appearance and the special form of dorsal setae, which have are similar to for C. metzi Sharma et al. 1983 . Callidosoma cassiculophylla sp. nov. differs from the other five species of Callidosoma known from the postlarval instar ( Mąkol & Wohltmann 2012) by the absence of tubercles on tibia I–IV ( C. ripicolum (Womersley,1934) , C. dasypodiae (Womersley, 1934) , C. womersleyi Southcott,1946 ) and by the smaller size of the palp tarsus and chelicera ( C. metzi , C. apollo Southcott, 1972 ).

Treat (1985) already commented on the problem that the causal reasoning for Callidosoma is not convincing and needs revision. As stated by Southcott (1996) we expect some progress in understanding Callidosoma relationships from the correlation of postlarval to larval instars, although some closely related genera are still proposed based on larvae solely (e.g. Neomomorangia Fain & Santiago-Blay,1993 ; Iraniella Iravanlou, Kamali & Talebi, 2002 ; Iguatonia Haitlinger, 2004 ; Nagoricanella Haitlinger, 2009 ).

Biology remarks. This research describes for the first time the symbiotic and (apparently) permanent relationship between adults of a species of Erythraeidae , and spiders of the genus Loxosceles in Brazilian caves.

The first observations on their behavior were made in 2007 during fieldwork in the Lapa Nova cave (17°58'59.82"S 46°53'27.06"W), located in Vazante municipality, in the northwestern region of Minas Gerais state, Brazil. At that time, the unusual association between spiders and mites was observed near the entrance of the cave. Hypotheses were made and experiments were undertaken only after recurrent observations of the same pattern were made in other caves in several other municipalities of Minas Gerais state (Confins, Cordisburgo, Lagoa Santa, Pains, Arcos, Lassance, Matozinhos, Paracatu and Varzelândia), aiming to better understand the observed behavior ( Figure 8 ).

An only casual association of C. cassiculophylla sp. nov. with spiders of the genus Loxosceles can be discarded, since the adult mites were only found in spider webs and not on other substrates inside the caves. However, the benefits gained by the mite were still unclear. Based on our field observations, we hypothesized that mites benefit from the association with Loxoceles by eating the prey caught in the web spiders.

To better understand the symbiosis, in 2010, behavioral experiments were performed in four caves located in Vazante municipality, to test the relationship between mites and spiders. To conduct the experiment, we captured specimens of the cave moth Hypena sp. Schrank, 1802 ( Lepidoptera : Noctuidae ), that are potential prey for Loxosceles . They were placed alive in the spider webs, allowing us to observe the mites’ behavior (a total of 24 webs in 4 different caves). The spiders quickly attacked and killed the moths as soon as they were placed in the web. However, mite movement towards the prey did not occur immediately after the adhesion of the prey to the web. After the prey was placed in the web, mites took between 5 to 40 minutes to reach them. Despite arriving later, mites and spiders consumed the prey simultaneously. Interestingly, spiders showed no aggressive behavior or expulsion of the mites (Figures 9, 10). In addition, the mites were never observed eating invertebrate carcasses, including those in an advanced state of decomposition. Erythraeid mites were observed eating freshly killed individuals only. The usual diet of erythraeid mites is small invertebrates and their eggs ( Clark 2004; Southcott 1961b).

Prey detection by the mites may have occurred by chance since mites are constantly moving in the webs. Web vibration at the moment of prey capture could be used as an alternative alert, guiding the mites towards the prey. However, this experiment did not confirm unequivocally whether mites used web vibration to locate food sources in the web. In Loxosceles webs where no prey was recently captured, individuals of C. cassiculophylla sp. nov. were evenly dispersed without any visible perceived aggregation (Figures 9, 10).

Spider webs of Loxosceles are usually positioned near the substrate, generally on the ground or on walls. The webs cover the entire surface; the filaments are disposed irregularly, forming a shapeless mesh over the substrate. Besides, in some cases, the webs of different Loxosceles specimens are interconnected with no visible distinction between them. The direct contact between the web and the substrate provides conditions in which the mites move on the web and the substrate (Figures 9 and 10).

Holotype (range min-max) PALP pa tr (L) 37 (34–50)

pa tr (W) 60 (50–62)

pa fe (L) 175 (165–185)

pa fe (W) 67 (65–79)

pa ge (L) 120 (100–121)

pa ge (W) 42 (35–44)

pa ti (L) 77 (70–86)

pa ti (W) 27 (24–32)

odontus (L) 37 (32–40)

pa ta (L) 47 (45–68)

pa ta (W) 12 (11–16)

LEG I ta I (L) 290 (280–350)

ta I (H) 85 (70–90)

ti I (L) 410 (360–455)

ge I (L) 405 (375–470)

tfe I (L) 380 (360–440)

bfe I (L) 357 (290–385)

tr I (L) 137 (110–165)

cx I (L) 175 (160–190) LEG II ta II (L) 187 (180–220)

ta II (H) 50 (40–60)

ti II (L) 292 (275–345)

ge II (L) 287 (255–305)

tfe II (L) 242 (200–250)

bfe II (L) 185 (140–210)

tr II (L) 102 (100–125)

cx II (L) 200 (200–235) LEG III ta III (L) 187 (180–225)

ta III (H) 50 (45–55)

ti III (L) 350 (285–395)

ge III (L) 300 (265–310)

tfe III (L) 252 (225–295)

bfe III (L) 197 (155–235)

tr III (L) 112 (85–120)

cx III (L) 190 (190–210)

...... continued on the next page Holotype (range min-max)

LEG IV ta IV (L) 245 (245–275) ta IV (H) 37 (37–70) ti IV (L) 460 (385–480) ge IV (L) 425 (380–450) tfe IV (L) 325 (310–355) bfe IV (L) 240 (200–325) tr IV (L) 130 (110–140) cx IV (L) 325 (300–340)

SCUTUM CML 500 (430–500) CMW 55 (45–70) SBp-post end of scutum 85 (70–100) pPr (posterior process) 67 (50–90) Asens 75 (75–95) SBa 18 (20–20) Psens 117 (117–131) SBp 20 (20–21) ISD 387 (340–390)

Mite-spider associations are frequently observed, but such associations often involve direct contact between the mite and the host’s body. Parasitism of spiders occurs in certain Laelapidae (Mesostigmata) and larvae of Parasitengona ( Fain 1991; Mąkol et al. 2012; Mąkol & Felska 2011; Masan et al. 2012; Welbourn & Young 1988) and phoretic associations are also common, as is the case of some Scutacaridae (Trombidiformes) associated with Mygalomorphae ( Araneae ) ( Ebermann & Goloboff 2002). Another type of association between mites and spiders occurs indirectly, when some species use the spider webs as habitat. Species of the families Rhodacaridae , Phytoseiidae and Aceosejidae have been observed in nests of spiders ( Agelena nr. leucopyffa Pavesi) ( Evans 1958). However, in this case the nests were full of leaves and stems, which could provide a propitious environment for such mites. The observation of mites walking and living in spider webs is reported for Laelapidae species, as well as associations within web-lined funnels of Hexathelidae spiders, where mites spend all their life cycle ( Strong 1995). In the case of Parasitengona, the only association regarding spider webs was reported for a Smarididae species ( Wohltmann 2010), but in this case no observation of any interaction between mites and host was made; this association may be casual.

Unlike the previously mentioned cases, C. cassiculophylla sp. nov. has a distinct association in relation to other known life styles. Although C. cassiculophylla sp. nov. cannot be considered as scavenger since the prey is freshly killed, the common feeding on the same prey individual by C. cassiculophylla sp. nov. and Loxosceles spp. is unique and atypical among arachnids. Moreover, almost all Parasitengona display an exclusively predatory lifestyle of the postlarval active instars, with some Balaustium species feeding on pollen (Grandjean 1946; Childers & Rock 1981) being the only exception.

Although larval stages of Erythraeidae species have been reported by several authors as parasites of spiders and other arachnids (e.g. Baker & Selden 1997; Southcott 1961b), more than 100 specimens of Loxosceles were collected and observed under the stereomicroscope none of them presented a parasitic species of mite attached to their bodies. The larva of C. cassiculophylla sp. nov. is probably a parasite of other invertebrates present in the caves, and its association with Loxosceles sp. may be restricted to the postlarval active instars of the mite.

Considering the facts obtained through field observations, we believe that the relationship between Loxosceles and C. cassiculophylla sp. nov. can be considered as a case of kleptoparasitism This mite-spider kleptoparasitic association is novel, but kleptoparasites in spider webs are well-known in several other invertebrate groups. Among them are spiders of at least 11 families, which scrounge prey captured by other species, and some of these kleptoparasites can cohabit the webs of their hosts, such as species of the genus Argyrodes ( Theridiidae : Araneae ) ( Kerr 2005; Silveira & Japyassú 2012). In addition to arachnids, this behavior is also found in insects, such as species of the family Emesinae ( Reduviidae : Heteroptera ), inhabiting and feeding on prey captured by spider webs ( Resende et al. 2016; Wygodzinsky 1966), or among some species of dipterans in Cecidomyiidae and Milichiidae ( Sivinski et al. 1999; Sivinski & Stowe 1980). Giraldeau and Caraco (2000) categorized kleptoparasites by three types of behavior: “aggressive”, if it is accomplished with threat or aggression; “stealth”, when the kleptoparasite takes food away while avoiding the host’s perception; and “scramble”, if the food item is simultaneously exploited by the host and one or more kleptoparasites with little or no aggressive behavior. In this respect, C. cassiculophylla sp. nov. is a "scramble" kleptoparasite because it consumes the prey with the host that captured it, without displaying any aggressive behavior.

Figures

FIGURE 1. Details of a Callidosoma cassiculophylla sp. nov., adult, associated with webs of Loxosceles spiders in Brazilian caves. A: Dorsal aspect; B: Details of the frontal region of the crista metopica; C: Details of the front dorsal region of the podosoma; D: Details of the ventral setae of idiosoma; E: Details of the dorsal setae of idiosoma.

FIGURE 2. Callidosoma cassiculophylla sp. nov., adult, habitus dorsal view. ap = anal opening, ch = chelicera, cm = crista metopica, gp = genital opening.

FIGURE 3. Callidosoma cassiculophylla sp. nov., adult. A: Ventral view of palp tarsus; B: Dorsal view of palp; C: Crista metopica. AL = anterior setae, ASens = anterior sensilla, PSens = posterior sensilla; D; Dorsal body setae. L = lateral view, D = dorsal view, V = ventral view.

FIGURE 4. Callidosoma cassiculophylla sp. nov., adult, scanning electron micrographs. Dorsal body setae (A) and ventral body setae (B).

FIGURE 5. Callidosoma cassiculophylla sp. nov., adult. Lateral view of tarsus I. Only specialized setae shown, DS = normal dorsal seta, VS = normal ventral seta.

FIGURE 7. Callidosoma cassiculophylla sp. nov., adult (A – D). Mites associated with Loxosceles sp. webs in caves of Varzelândia, Minas Gerais, Brazil.

FIGURE 8. Callidosoma cassiculophylla sp. nov., adult. Mites associated with webs of Loxosceles variegata, Lapa Dágua cave, in Lassance, Minas Gerais, Brazil. A: Mites found dispersed throughout the web; B, C and D: Callidosoma cassiculophylla sp. nov. feeding on Hypena sp. beside a spider after the capture of its prey, Cazanga Cave (Arcos, Minas Gerais, Brazil).