Collembola of Rapa Nui (Easter Island) with descriptions of five endemic cave-restricted species Author Bernard, Ernest C. Author Soto-Adames, Felipe N. Author Wynne, J. Judson text Zootaxa 2015 3949 2 239 267 journal article 10.11646/zootaxa.3949.2.6 a552157a-8bfc-43e7-b509-601638f4f152 1175-5326 231733 F678EF65-50F2-4B30-BDFD-A1DF3295D144 Coecobrya aitorererere Bernard, Soto-Adames & Wynne , n. sp. Figures 4‒6 , 7 B Material examined. CHILE , Rapa Nui, Maunga Hiva Hiva region, holotype female and 7 paratypes ( 3 females , 2 males , two juveniles), all on slides, Cave Q15-071, hand collection in west passage, 12 July 2009 , J. Wynne, coll. Additional paratypes : 3 specimens , one female on slide, two of undetermined sex in ethanol, same data as holotype except collected at fig tree in entrance; 3 specimens , one on slide, two in ethanol, sex undetermined, from Cave Q15-076/078, direct search within fern-moss gardens in entrance 3, 0 4 July 2009 , J. Wynne, coll.; 2 specimens , sex undetermined, from Cave Q15-127, opportune collection within entrance, 0 2 July 2009 , J. Wynne, coll. Description. Length up to 1.4 mm . Body white ( Fig. 7 B), sometimes with sparse clusters of minute reddish dots; all appendages white. Eyes absent. Macrosetae blunt or weakly truncate. Antennal segment I dorsally with 3 small, smooth microsetae near the base, other setae of this segment ciliate with three much smaller than the others ( Fig. 4 H); Ant. II ( Figs. 4 H, I) with a macroseta and several strong mesosetae on outer side, about 12 smooth, pointed setae distributed mostly in distal half and 13 sensillum-like setae of various lengths distributed primarily ventrally and laterally; ventromedially Ant. II with about 9 very small, ciliate mesosetae. Ant. III ( Figs. 4 H, I) clothed mostly with ciliate mesosetae but also with about 23 sensilla and six pointed, smooth setae: sensilla of sense organ paddle-like, exposed; 5 lunate sensilla along the lateral edges; remaining 16 sensilla typical but of varying lengths. Apical bulb absent on Ant. IV ( Fig. 4 J); this segment with several subapical to apical smooth, pointed setae without distinct sockets but with one or two ring-like expansions near their bases, numerous arched sensilla that are minutely punctuate on their convex sides, typical sensilla with rounded apices, and smooth, straight, socketed setae subapically and on the exterior face. Prelabral setae smooth. Prelabrum and labrum ( Fig. 4 G) with 4-/5-5-4 setae, all setae smooth; bases of distal two rows of setae elevated. Left mandible with four teeth, right mandible with five teeth. Outer lobe of maxillary palp with three sublobal setae ( Fig. 4 F). Labial palp ( Fig. 4 D) with guard seta a1 stout, pointed, half the length of b1; b2 on separate stalk, reaching tip of sensillum B; d4 shorter than other d-guard setae; lateral process stout, rounded apically, reaching or slightly surpassing base of sensillum E; guard seta e1 short, tapering. Labial triangle setae smooth, formula MrEL1L2A1‒5 ( Fig. 4 B). Six pairs of ventromedial setae along ventral groove, fifth pair finely serrated, others smooth ( Fig. 4 C); arrangement of smooth and serrate postlabial setae varying between specimens; setae x1 and x2 minute ( Figs. 4 B, C). Dorsal head seta A1 absent ( Fig. 4 A); 3 macrosetae in zone H1, setae An1 a mesoseta; H2 with one macroseta (A5); M-row with 3 macrosetae, M3 a mesoseta; S0 posterior to S1 setae; zone H4 with three macrosetae and a mesoseta (S 4i ); H5 with two macrosetae. Group I with alternating meso- and macrosetae, Group II with 5 macrosetae. Cephalic bothriotricha short. Hind trochanter ( Fig. 5 E) with 13 short, pointed microsetae in trochanteral organ and three longer setae, the most proximal seta smooth and pointed. Hind tibiotarsus ( Fig. 5 F) with zig-zag row of seven smooth setae in distal half, proximally with 1‒2 macrosetae and two long, stout mesosetae; one small ciliate seta basally and one minute smooth microseta at level of macrosetae; other ciliate tibiotarsal setae of similar appearance. Foot complex ( Fig. 5 G) similar on all legs; tenent hair pointed; inner unguis edge with three teeth, paired basal teeth unequal, one tooth large, wing-like, two small inner teeth about midway along edge; unguiculus weakly to clearly truncate ( Figs. 6 B‒D), with large outer wing-like tooth more than half the unguicular length. Ventral tube ( Fig. 5 H) with 4+4 slender ciliate anterior setae, 3+3 short, smooth posterior setae, and 7+7 short, smooth lateral setae. Tenaculum arms with 4 teeth each, corpus with one seta. Manubrium with two rows of smooth setae ( Fig. 5 I), manubrial plaque with 2 pseudopores and two setae on each side. Dens with two smooth basal setae, other setae ciliate. Spine of mucro ( Fig. 5 J) usually slightly bent, nearly reaching mucronal apex. FIGURE 4. Coecobrya aitorererere n. sp. A) Dorsal head chaetotaxy. B, C) Anterior ventral head chaetotaxy. D) Labial palpus. E) Labial papilla E. F) Setae of maxillary palpus. G) Labrum. H) Ant. I–III, dorsal view, and enlargement of crescentiform sensillum. I) Ant II–III, ventral view, and enlargement of sense rod in Ant. III apical organ. J) Apex of Ant. IV, and enlargements of pointed seta with double basal ring and curved sensillum with punctate convex surface. FIGURE 5. Coecobrya aitorererere n. sp. A) Dorsal chaetotaxy: Th. II‒Abd. IV, left side, Abd. IV, right side without mesosetal marks. B) Abd. V‒VI, left side, Question marks indicate mesosetae of uncertain affinity. C) Abd. II, bothriotrichal region. D) Abd. III, bothriotrichal region. E) Hind trochanter. F) Hind tibiotarsus. G) Hind foot complex. H) Ventral tube; as, anterior setae; ls, lateral setae; ps, posterior setae. I) Furcula, subdorsal view of left side, filled dots represent fringed mesosetae. J) Mucro. Setal labels for Abd. IV and V after Zhang et al . (2011). FIGURE 6. Coecobrya aitorererere n. sp. A) Mesothorax, anterior lateral region; mi: microsensillum; ms: microseta. Dashed arrow points anteriorly. B‒D) Images of unguiculi showing truncate distal region. Scales = 10 Μm. Macroseta formula 21, 20/5, 4, 3, 4+0+3, 6, 3 ( Fig. 5 A). Mesonotal macrosetae excluding collar setae arranged as follows: Group I (corresponding with Zone T1) with 3 setae; Group II (Zone T2), 2; Group III, 3; Group IV, 2; Group V, 9; Group VI, 2. One microseta dorsolaterally; laterally, relative positions of mesonotal microsensillum and microseta ( Fig. 6 A) variable, microseta sometimes in more lateral position. Metanotal macroseta arrangement: Group I, 8; Group II, 8; Group III, 2; Group IV, 2. Metanotum with two sensilla, one lateral to Group III, the other in Group IV. Abd. I with five macrosetae and two sensilla; Abd. II with 3+1 macrosetae (m3, m3e, m3ep, m5) and two microsetae ( Figs. 5 A, C); Abd. III with 1+2 macrosetae (m3, pm6, p6) and two microsetae ( Figs. 5 A, D). Abd. IV ( Fig. 5 A) with four inner (I, M, A6, B5) and three outer macrosetae (E2‒4); approximately 15+15 sensilliform setae, two outermost setae shorter than others; two transverse rows of four sensilliform setae anterior to I macrosetae. Abd. V dorsally with 6+6 macrosetae (m2, m3, m5, p1, p3, p5), p4 a large, pointed mesoseta; 3+3 sensilla (as, ms, ls); extra mesosetae near m3 and a5. Abd. VI with 3+3 macrosetae ( Fig. 5 B). Etymology. The species name is a combination of two Rapanui terms, aito and rererere . Aito is “jumper” and rererere is translated as “skillful”; when combined this translates to “skillful jumper.” Remarks. Coecobrya aitorererere n. sp. is similar to C. tenebricosa (Folsom, 1902) and will key to that species in Chen & Christiansen (1997) , Zhang et al. (2009) and Jordana (2012) . The two species may be separated by the arrangement and number of macrosetae and sensillum-like setae. The metanotum of C. aitorererere n. sp. has eight macrosetae in Group I and eight in Group II, while C. tenebricosa has 9‒13 in Group I and 9‒10 in Group II ( Chen & Christiansen 1997 , Zhang et al. 2009 ). On Abd. IV C. aitorererere n. sp. has two transverse rows of four sensillum-like setae each anterior to the A3 macrosetae, whereas C. tenebricosa has a single row of six ( Zhang et al. 2009 ). The arrangement of Ant. III sensilla on C. aitorererere n. sp. also appears to differ markedly from that of C. tenebricosa ( Chen & Christiansen 1997 ) and other species figured by Zhang et al. (2009) ; however, these sensilla can be difficult to see through the dense, ciliate mesosetae. Coecobrya aitorererere n. sp. differs from the other Rapa Nui species, C. kennethi , in having two macrosetae in cephalic Group I (three in C. kennethi ); two macrosetae in mesothoracic Group IV rather than 3 as in C. kennethi ; 8 macrosetae in metathoracic Group I rather than 5; 3 outer macrosetae on Abd. IV rather than 6; ventral side of hind tibiotarsus with a zig-zag row of 7 smooth, pointed setae (one distal smooth seta in C. kennethi ). Zhang et al . (2011) reported that the chaetotaxy of Abd. V was useful in separation of the Coecobrya spp. they studied. In the current paper the designations of macro- or mesosetae on the abdomen were determined by examination of specimens with setae still attached to their sockets; large, serrated, truncated setae ( Fig. 5 A) were called macrosetae, and serrated, pointed setae were considered mesosetae. The m-macrosetae always originated from large sockets, but in some specimens the sockets of the p-macrosetae (p1, p3, p5) were no larger than those of the mesosetae, even though the attached setae clearly were macrosetae. Designations of relative setal size based on socket size needs to be approached with caution.