Ophiomegistus spectabilis Klompen & Austin

Klompen, Hans & Austin, Christopher C., 2007, A new species of Ophiomegistus Banks (Acari: Paramegistidae) from Papua New Guinea, Zootaxa 1387, pp. 47-57 : 48-54

Ophiomegistus spectabilis Klompen & Austin sp. nov.

( Figs. 1–5 )

Diagnosis. Female with two small setae on each latigynial shield. Ventral opisthosoma of both adults with a few very small setiform setae anterior on the ventri­anal shield and 15–22 large, translucent, leaf­like setae covering most of the posterior parts of that shield. Metapodal shields broadly fused with peritrematal shields. Marginal setae well developed, including long rod­like setae interspersed among larger numbers of distinctly shorter, rounded, and blade­like setae.

Male ( Figs. 1–4 ). Idiosomal length 741 (681–767), width 604 (568–640), N=5. Dorsum covered by a single shield with slightly crenulate patterning ( Fig. 1 ); pattern more of less striate near the margin, uniform in the center of the shield. One pair of anterior marginal setae (j1?) long (108 [90–118]) and rod­like with small barbs near the tip; other dorsal setae minute. Setal patterns are not completely regular and symmetrical, but hypertrichy appears limited; nearly all setae observed can be accommodated within the standard model for Mesostigmata ( Lindquist and Evans 1965) . With respect to other cuticular structures (glands, lyrifissures) assignment is tentative, due to the difficulty of distinguishing consistently between gland­like structures and lyrifissures (only anterior lyrifissure id1 is quite distinct). Even so, the patterns appear generally symmetrical and surprisingly regular. Specialized marginal setae (R and Rv setae?) surround the entire opisthosoma. They include two types of setae, long, rod­like ones and much shorter, blade­like setae with rounded tips. The rodlike setae are generally smooth, with a few very small barbs near the tip, the blade­like setae have rounded tips and are somewhat flattened. The total number and interspersion pattern of these setae is variable between individuals and even between the left and right side of single individuals ( Table 1 ). Lateral blade­like setae smaller than the posterior ones, with the median posterior pair longest [84 (73–90)]. Most rod­like setae of similar size, 231 (211–250) for posterior lateral ones, but the most anterior lateral pair of rod­like setae much shorter [94 (81–102)], and the pair flanking the median posterior pair of blade­like setae somewhat shorter [167 (150–184)].

Venter ( Fig. 2 ) with a distinct anterior sclerite carrying sternal setae st1 and one pair of lyrifissures (stp1). Genital opening midsternal, covered by two small shields, and including a pair of small (eu)genital setae. Sternito­ventri­anal shield with pronounced patterning anteriorly, less distinct posteriorly. In the sternal region this shield carries four pairs of small setae, two pairs of lyrifissures (stp2, stp3) and one pair of small pores; two additional pairs of small setae and one pair of pores posterior to coxae IV. Posterior portion of shield with 15– 19 pairs of large, translucent, and leaf­like setae, arranged in four rows. As with the marginal setae, patterns are variable ( Table 2 ). One pair of small preanal, and two pairs of small postanal setae surround the anus. Unpaired postanal seta absent. Metapodal areas each with well developed shields, fused broadly to peritrematal (anterior), and weakly to sternito­ventri­anal shields (antero­lateral). Each metapodal shield usually with two subulate setae ( Fig. 2 B); occasionally with one additional, setiform seta (1 of 8 sides examined), or with one subulate and 1 setiform seta (3 of 8 sides examined). Metapodal shield surface with distinct crenulated patterning near the posterior tip. Peritremes surrounded by relatively small shields, extending anteriorly to the level of coxae I. Tritosternum without subapical spines ( Goff 1979) on the tritosternal laciniae.

Gnathosoma and palps ( Fig. 3 ). Chelicera ( Fig. 3 A) with long cheliceral seta, and distinct lyrifissue i; lyrifissure id not observed. Cheliceral digits edentate, inside movable digit fimbriate. Fixed digit with one basal, movable digit with three terminal extensions; interdigital membranous extension present. Gnathotectum triangular with a smooth anterior edge and a very weakly developed, or absent, keel ( Fig. 3 B). Subcapitulum with a poorly developed deutosternal groove. Subcapitular setae (sc) and setae hyp2 short blunt spines with minute barbs, setae hyp1 long, smooth spines, and setae hyp3 small and setiform ( Fig. 3 C). Lateral lips fringed on outside, labium and paralaciniae brush­like. Designation of brushy, dorsally inserted structures as “paralaciniae” (pl in Fig 3 C) tentative. Corniculi unclear in all specimens examined, apparently largely membranous and with a shape resembling that illustrated for O. luzonensis Banks ( Voss 1966) and O. keithi Domrow (Domrow 1978) . Palp ( Fig. 3 D). Palp setation for the basal segments follows the standard pattern for Antennophorina , 2 setae on the trochanter, 5 on the femur, and 7 on the genu. Posterior lateral and posterior dorsal setae on the femur and genu thickened, rod­like and barbed. Tibia and tarsus completely fused, with a total of 24 sensilla, 1 more than listed by Domrow (1978) for O. keithi and O. luzonensis . Pretarsal claw two­tined.

Legs ( Fig. 4 ). Coxae I with small anterior spur ( Fig. 2 A). Setation pattern generally as for O. luzonensis ( Domrow 1978) , but without tibial setae pd 3 I and pv 2 IV, losses shared with O. keithi . Legs laterally flattened, most lateral setae poorly developed. Femoral seta pv 1 IV a rounded spine. Anterior dorsal setae of genua, tibiae, and (basi)tarsi III–IV blade­like with fimbriations along one side (less prominent on legs II), posterior dorsal and posterior ventral setae generally longer, rod­like with terminal barbs. Genual and tibial setae pl 1 II–III long, rod­like; genual and tibial pl 1 IV small, setiform. Tarsi II–IV with seta al3 present. setae ad1, pd1 poorly developed, very thin. Ventrodistal spurs on tarsi II–IV absent. Pretarsi I absent, pretarsi II–IV large, with vestigial claws. Chaetotactic formula’s: Coxae 2­2­2­1. Trochanters I: 2 1/2 1; II: 1 0/3 1; III: 1 1/3 0; IV: 1 1/3 0. Femora I: 2 3/3 1/2 1; II: 2 2/2 2/1 1; III: 1 2/1 2/1 0; IV: 1 2/1 2/1 1. Genua I: 2 3/1 3/1 1; II: 2 3/2 3/1 1; III: 2 3/1 2/1 1; IV: 2 3/1 2/1 0. Tibiae I: 2 2/2 2/2 2; II: 2 2/2 2/1 1; III: 2 2/1 2/1 1; IV: 2 2/1 2/1 1. Tarsi II–III with 19 setae (seta al3 present), tarsi IV with 21 (setae av4, pv4 present). Chaetotactic formula’s as noted are slightly different from those proposed by Domrow (1978) for O. luzonensis but this may an artifact of leg orientation.

Female ( Fig. 5 ). Idiosomal length 868, width 718 (N=1). Dorsum as in male. Marginal setae slightly more numerous and slightly longer than in male, but pattern very similar ( Table 1 ). Blade­like setae in posterior median pair 98 long. Anterior pair of rod­like long setae (j1) 122, anterior lateral pair 113, longest 265, and pair flanking posterior median pair of blade­like setae 197. Peritremes as in male. Metapodal areas sclerotized, shields broadly fused to peritrematal shields (anterior); each with two subulate and one setiform seta ( Fig. 5 B). Ventri­anal shield with 17–20 pairs of large leaf­like setae, arranged in 4 rows ( Table 2 ). Preanal and postanal setae as in male. Unpaired postanal seta absent. Sternal region anteriorly with two pairs of shields: anterior pair carrying one seta (st1) and one lyrifissure (stp1) each; second pair carrying three pairs of setae (st2–st4) and one lyrifissure (stp2) each. Sternogynial shield also paired, with one small lyrifissure (stp3) on each shield. Genital area with separate and well developed latigynial shields, each carrying two small setae and one small gland pore. Mesogynial shield fused posteriorly with ventri­anal shield, without setae, lyrifissures or pores. Endopodal shield remnants fused to sternal and latigynial shields. Small exopodal shieldlets between coxae II and III.

Gnathosoma and palps. Gnathotectum triangular with a smooth anterior edge. Chelicera as in male. Subcapitulum, corniculi, subcapitular and hypostomal setae as in male. Palp with tibia and tarsus completely fused; pretarsal claw two­tined. Palp setation (number, position, and shape) as in male.

Legs. Leg shape and chaetotaxy as in male.

Material examined. PAPUA NEW GUINEA: Manus, Rambutyo Island, NE of Penchal Village, Elev 100–150 m, 02°20'26"S 147°47'40"E, coll. Austin, C. C., 3 IX 2001, ex Sphenomorphus pratti (Scincidae) , host coll. no. LSUMZ 89480, specimens numbers OSAL 004135­338 (3M, 1F); same collection data, ex Sphenomorphus pratti , host coll. no. LSUMZ 89481, spec. no. OSAL 013822 (1M); PAPUA NEW GUINEA: Manus, Penchal Village, 02°19'42"S 147°46'00"E, coll. Austin, C. C., 1 IX 2001, ex Sphenomorphus pratti (Scincidae) , host coll. no. LSUMZ 89479, spec. no. OSAL 004586 (2M on one slide).

Deposition of types. Holotype male in Ohio State Acarology Collection ( OSAL) ( OSAL 4135), paratypes in Australian National Insect Collection ( ANIC), Canberra (2M, OSAL 004137­38), and OSAL (1F, OSAL 004136, 3M, OSAL 004586, 013822).

Etymology. The specific name, spectabilis or showy, refers to the striking pattern of marginal setae in this species.

Systematic affinities. Generic assignment of this species to Ophiomegistus is based on the combination of presence of a longitudinally split sternal shield and stout subulate setae on the posterior end of the metapodal shields. It is also consistent with host association, as all known Ophiomegistus are associated with squamates (snakes or skinks). The one record of O. luzonensis from a host other than a squamate, in this case a rat in New Guinea ( Gunther 1942), is almost certainly an artifact. In this assignment we noticed a flaw in the latest key to the genera of Paramegistidae ( Kim and Klompen 2002) . The couplet in that key separating Ophiomegistus from Neomegistus uses the number of setae on each latigynial shield as the primary distinction, with Neomegistus females carrying only two setae per shield, while Ophiomegistus females carry three or more. However, females of O. brachymeleus Voss, 1966 , O. mabuyae Voss, 1966 , and O. keithi Domrow, 1978 , as well as the female of O. spectabilis carry only two setae on each latigynial shield.

That being said, Ophiomegistus can be distinguished from Neomegistus by the presence of foliate setae on the venter (absent in Neomegistus ), the lack of fusion of the latigynial and ventri­anal shields (partially fused in Neomegistus ) and the presence of subulate setae on the metapodal shields (absent in Neomegistus ) (Cheol­ Min Kim, pers. comm.). The above emphasizes that Ophiomegistus and Neomegistus are quite similar, despite being associated with phylogenetically unrelated host groups. This close relationship of squamate ( Ophiomegistus ) and millipede ( Neomegistus ) associated taxa mirrors the situation in the family Heterozerconidae , which also includes squamate ( Amheterozercon ) and millipede (all other genera) associates.

The new species differs from O. brachymeleus , O. mabuyae , and O. keithi by having the foliate setae restricted to the posterior half of the ventri­anal shield (rather than covering nearly all of the ventri­anal shield). In addition, the striking dimorphism in shape of the marginal setae far exceeds that found in any other described Ophiomegistus species.

Remarks. We also studied two additional females from skinks collected in Milne Bay province ( PAPUA NEW GUINEA: Milne Bay, Saga AHO River, Bush Camp, Cloudy Mountains, Elev 65 m, 10°32'39"S 150°06'55"E, coll. Austin, C. C., 18 X 2001, ex Sphenomorphus pratti , host coll. no. LSUMZ 89483, spec. no. OSAL004134 (1F); same collection data, ex Sphenomorphus jobiensis , host coll. no. LSUMZ 89482, spec. no. OSAL004133 (1F)). While superficially similar to O. spectabilis in the relative size and arrangement of the marginal and opisthogastral setae, these two females are slightly larger, and differ by having (1) only 3 (not 4) rows of opisthogastral setae, (2) bifid tips on the long rod­like marginal setae (rounded in O. spectabilis ), (3) metapodal shields that are distinctly pointed posteriorly, (4) the coxal IV seta shaped as a thick, blunt spine, and (5) having setae hyp2, hyp3, and the subcapitular setae of similar shape (distinctly different sizes in O. spectabilis ). Given the small number of available specimens from that locality, and the lack of males, it is not possible to establish whether these differences are local variations or whether the specimens represent another new species.

A single male recovered at the same locality but from a different host species ( PAPUA NEW GUINEA: Milne Bay, Saga AHO River, Bush Camp, Cloudy Mountains, Elev 65 m, 10°32'39"S 150°06'55"E, coll. Austin, C. C., 18 X 2001, ex Sphenomorphus mulleri , host coll. no. LSUMZ 89484, spec. no. OSAL004132), does not match O. spectabilis or the females from Milne Bay. Instead it closely resembles O. kaii Goff, 1979 .

Figures

FIGURE 1. Ophiomegistus spectabilis sp. nov. (male). Dorsum. Open circles: presumed glands; filled circles: presumed lyrifissures.

FIGURE 2. Ophiomegistus spectabilis sp. nov. (male). A, venter; B, detail metapodal area.

FIGURE 3. Ophiomegistus spectabilis sp. nov. (male). A, chelicera; B, gnathotectum; C, subcapitulum; D, palp, dorsal view. Scale for A, B and D identical. Abbreviations: co, corniculus; pl, paralacinia.

FIGURE 4. Ophiomegistus spectabilis sp. nov. (male). Legs, anterolateral view; A, leg I (setae of distal sensory complex omitted); B, leg II; C, leg III; D, leg IV.

FIGURE 5. Ophiomegistus spectabilis sp. nov. (female). A, dorsum; B, detail metapodal area.

Tables

TABLE 1. Individual variability in pattern of marginal setae for Ophiomegistus spectabilis sp. nov. Format: number of short, blade­like setae between long, rod­like setae; listing following margin starting anterior left side to right side; posterior median group in brackets.

Individual	pattern	total blade­like	total rod­like.
Male
OSAL4135	1­2­3­3­2­3­2­3­2­3­(3)­2­3­2­2­3­3­3­3­2­1	51	23
OSAL4137	1­2­2­3­2­3­1­1­3­1­3­(2)­2­2­2­2­2­2­4­2­2­1	45	24
OSAL4138	1­2­2­3­2­2­2­1­2­2­2­(1)­2­2­2­2­2­2­3­2­3­2­1	45	25
OSAL4586a	1­2­2­3­2­2­2­2­2­2­(2)­2­2­2­2­3­4­3­2­1	43	22
Female
OSAL4136	1­2­3­3­3­3­2­2­2­3­2­(2)­2­2­2­1­2­3­4­4­1­1	50	23

TABLE 2. Individual variability in pattern of opisthogastral leaf­like setae for Ophiomegistus spectabilis sp. nov. Format: row 1 (most anterior), row 2, row 3, row 4.

Individual	right	left
Male
OSAL4135	1­3­5­6	1­3­5­6
OSAL4137	1­2(3)­5­6	1­4­6­6
OSAL4138	1­3­5­6	1­3­5­6
OSAL4586a	1­3­5­6	1­3­5­6
OSAL4586b	1­3­6­6	1­4­5­5
Female
OSAL4136	1­4­7­8	1­5­6­7