Diplothyrus lecorrei Klompen, 2010

Klompen, H., 2010, Holothyrids And Ticks: New Insights From Larval Morphology And Dna Sequencing, With The Description Of A New Species Of Diplothyrus (Parasitiformes: Neothyridae), Acarologia 50 (2), pp. 269-285 : 272-280

Diplothyrus lecorrei Klompen

( Figures 2-6 )

Diagnosis

The new species shares with the type species of the genus Diplothyrus , D. schubarti Lehtinen , the presence of what appear to be 2 pairs of dorsolateral orifices (Thon’s organ system) connected by a distinct strip of cuticle, an epiandrum that is hardly depressed, and a palp tibial comb consisting of 5-6 thick setae. The species differs from D. schubarti primarily by the absence of a modified seta on the palp genu, and by a different structure of Thon’s organ. In D. schubarti both orifices of Thon’s organ are positioned at equal distance to the dorsal shield margin, in D. lecorrei the posterior orifice is positioned substantially closer to that margin, and the connecting strip in fact ends at the margin of the dorsal shield.

Larva

Chelicera ( Figure 2a ) poorly developed: tips of both fixed and movable digit with a broad mass of small cuticular outgrowths, but without distinct teeth. Dorsal seta and one lyrifissure present, second lyrifissure not observed.

Palp ( Figure 2b ) relatively well developed, with 5 distinct segments, although tibia and tarsus appear immovably attached. Trochanter without setae, femur with 4 (al, pd1, pd2, pl), genu with 5 (al, ad1, ad2, pd1, pl), tibia with 9, and tarsus with 14 sensilla ("sensilla" as used here includes mechanoreceptors (setae s.s.) as well as chemoreceptors etc.). Three tarsal sensilla terminating in a small round structure ( Figure 2c ). Femoral setae pd1 and pd2, genual setae ad1 and pd1, and 1 tarsal seta barbed, all other palpal sensilla smooth, setiform. Pretarsus/apotele 3-tined.

Subcapitulum ( Figure 2d ) with 2 pairs of hypostomal setae and small horn-like corniculi (inserted dorsally). Lateral lips poorly developed, labrum not

Klompen H.

observed. Deutosternal groove very weakly developed. Based on the structure of the subcapitulum and chelicera it seems unlikely that this instar feeds.

Idiosoma ( Figure 3 ). Length 377 µm, width 339 µm (measurements based on a cleared specimen in a cavity slide). Dorsal shield(s) very weakly developed, margins unclear. With very distinct muscle scars mid-dorsal, and distinct shieldlets lateral (see Figure 3a ). Dorsal setation pattern slightly hypotri-

Acarologia 50(2): 269–285 (2010)

chous. Anterior half of the dorsum with 12 pairs of setae, posterior half with another 12 pairs. Setal length varies from 70 (z5) to 7 (J2) µm. Venter with distinct remnants of legs IV (as in larval Opilioacaridae and Allothyridae ). Sternal region without obvious shields, with 3 pairs of sternal setae and 2 pairs of pores (exact nature unclear). Opisthogaster with a distinct pattern of cuticular modifications forming a V-shaped pattern originating lateral to legs IV and joining around the anus. Lateral to this "V" a series of lyrifissures. Anal plates with a single small seta each. Anus flanked by a pair of paranal setae (at mid-level of anal plates). A small, unpaired postanal seta present. Cribrum not observed. With a variety of setae both median and lateral to the "V". Tentatively all median setae are considered part of the Jv and Zv series, all lateral ones part of the Sv series.

Legs ( Figure 4 ). Length: 360, 300, and 310 µm, respectively. Leg I with an indistinct acrotarsus, and an indistinct basifemur; legs II-III with welldeveloped basitarsi and indistinct basifemora. Setation (legs I-III by segment): trochanters: 4, 5, 4; femora: 9 (2 2/1 2/0 2), 7 (1 2/1 2/0 1), 6 (1 1/2 1/1 0); genua: 8 (1 2/1 2/1 1), 8 (1 2/1 2/1 1), 8 (1 2/1 2/1 1); tibiae: 7 (1 1/1 2/1 1), 7 (1 1/1 2/1 1), 7 (1 1/1 2/1 1). Tarsus I: telotarsus: 19; acrotarsus: 16 "normal" and 5 modified sensory sensilla ( Figure 4b ). Pretarsus: 0 setae. Tarsi II-III: basitarsi: 6 (1 2/0 2/0 1), 6 (1 2/0 2/0 1); telotarsi: 14 (2 2/3 2/3 2), 14 (2 2/3 2/3 2); pretarsi: 2. With the exception of some sensory setae on acrotarsus I, all leg setae are thin and setiform. All segments for which the chaetotaxy could be scored with whorls of 6 setae.

Nymphs

The collection included two nymphs of quite different size. Their overall color, as for the larva, is whitish. Unlike nymphal Allothyridae ( Walter 2009) , these nymphs have distinct dorsal and ventral shields, but these do not cover the entire idiosoma. On the dorsum they carry a narrow anteromarginal shield, an extensive dorsal shield (more similar to the dorsal shield in larval Argasidae than to dorsal shields in any other parasitiform taxon), and a pair of small, lateral shieldlets with mammillate patterning, similar in position to the shieldlets of the larva or the mammillate zones near Thon’s organ of the adults. Both shields and soft cuticle carry numerous medium long setae. Venter with a small sternal shield adjoining a large expanded ventral shield. Anus not incorporated into the ventral shield. Thon’s organ(s) present in same position and general shape as in adult (closely associated with posterior edge of shieldlets).

Adults

Gnathosoma. Observations and measurements based on a single dissected female.

Chelicera ( Figure 5a ) well-developed. They appear to consist of 4 parts, movable and fixed digit, and 2 basal segments. Total length 1410 µm; basal-1 415 µm, basal-2 500 µm, fixed digit 495 µm, movable digit 260 µm. Movable digit with two large, and numerous very small, teeth; fixed digit with a single, median large tooth, a subterminal spine-like structure, and numerous small teeth in between (latter as for movable digit). With a single dorsal seta (17 µm) on the fixed digit, no other cheliceral setae observed. One lyrifissure (id?) dorsal near the base of the fixed digit, lyrifissure iα not observed. Chelicera with a single, complex branched outgrowth (120 µm), inserted antiaxial on the fixed digit at the articulation with the movable digit. Basal segments without setae. The fixed digit includes what appears to be the next instars’ chelicera, suggesting adults in this species molt. The possibility that the most basal segment may represent the basal segment of the "new" chelicera (squeezed out during slide mounting) cannot be ruled out completely.

Palps ( Figure 5b ). Total length 1290 µm, individual segments 180, 410, 250, 390, and 70 µm, respectively. Trochanter with 2 spinose, pointed setae, one lightly barbed. Femur with 15-16 setae; av and 3-4 al setae spinose finely barbed; distal av seta with a blunt tip, all others pointed. Genu with 17- 18 setae, av and 1 al seta spinose, finely barbed; av seta with blunt tip and dense, fine barbs. Long specialized seta listed by Lehtinen (1999) not observed. Tibia with approximately 70 setae; 5 av and 1 al setae spinose with blunt tips and dense, fine barbs (the av setae make up the "palpal comb"); 5-6 other ventral (v) setae strong, smooth, pointed spines. Tarsus distinct, but with limited independent movement; with numerous sensilla (most not figured), including a long sensillum with a expanded tip (figured). Pretarsus/apotele well-developed, 3-tined.

Subcapitulum ( Figure 5c ). Width 1030 µm, height (hypostome to base) 630 µm. Deutosternum poorly developed, with no visible teeth. Cuticular patterning limited to mammillate zones on each side of the deutosternum. Subcapitulum with about 9 relatively short setae, hypostomal lobes each with 3 longer (160-190 µm) setae. Cornicula (140 µm) horn-like, inserted dorsally. Lateral lips well developed, with numerous small, short projections; labrum appears poorly developed (but could be damaged in the dissected specimen). Gnathotectum very poorly developed or absent (unclear in dissected specimen).

Idiosoma. Generally well-sclerotized, light brown in color. Length (including gnathosoma) and width in female 2060 x 1530 µm, in male 1980 x 1520 µm, suggesting no major size difference between the sexes.

Dorsum. Highly domed, with numerous relatively long (100-120 µm) setae. Almost completely encased in well sclerotized shields. Dorsal shield cuticle with light reticulate patterning interrupted by numerous shallow, round indentations. Lateral, especially between peritremes and Thon’s organ, with patches of mammillate cuticle ( Figure 6c, d ) in the same position as the lateral shieldlets in the immatures. Peritremes well-developed, at lateral edge of dorsal shield; stigmata at level of coxae III; peritremes extending anterior from stigma beyond coxa I and posteriorly to the posterior edge of coxae IV. Two pairs of orifices dorsolateral on the shield, connected by a distinct cuticular strip running postero-ventral towards the edge of the shield ( Figures 6c, d ). The more posteroventral of the two orifices is probably the true Thon’s organ. It is connected internally by a membranous funnel to grapelike structures, strongly resembling the structure of Thon’s organ in Sternothyrus braueri (Thon) ( TravØ 1983). The nature of the second (more anterodorsal) structure in unknown. It shows a small dorsal rim, but no distinct internal structures.

Venter ( Figures 6a, b ) almost completely covered by a holoventral shield; ventral shield adjoining, but not connected to, dorsal shield. Shield surface finely granulate; with some indistinct reticulate patterning in posterior sternal region, and the round indentations noted for the dorsum. Otherwise without patterning. Sternal lyrifissures (if present) not observed. Entire ventral shield with many short setae. Anus relatively small (145 x 140 µm in female; 130 x 125 µm in male), with 3-4 setae on each valve. Female genital region ( Figures 5d , 6b ) with a very well developed mesogynal (480 x 630 µm), and a much smaller sternogynal shield. Possible remnants of latigynal shields (arrow) small, largely obscured by expanded mesogynal shield. Genital shields with numerous small setae and small pores (grey circles in Figure 5d ), cuticle finely granulate, without distinct patterning of any kind. Male genital region ( Figure 6a ) consisting of two subequal sized plates (130 x 200 µm) positioned between coxae IV. Anterior plate with numerous setae, posterior one nude or with very few setae. Epiandrum indistinct.

Legs. Length legs I-IV (female): 1800, 1400, 1440, and 2190 µm. All femora with a distinct basifemur. Tarsus I without acro- or basitarsus; tarsi II-IV with distinct basitarsi, each with 2-3 whorls of setae. Leg setation on all segments based on whorls of 8 or 9 setae each. Tarsus I with dense cluster of sensilla set in depression, but without internalized sensilla (as in the capsule of the tick Haller’s organ). Pretarsus I with almost sessile claws; pretarsi II-IV ( Figure 5e ) with an ambulacral stalk carrying 1 pair of small setae, well developed claws, and a large empodium.

Deposition types

The holotype female ( OSAL106890-106894 ; 5 slides, specimen dissected), and paratypes (1 male ( OSAL84992 ), 2 nymphs ( OSAL84991 , 84990 ), 1 larva ( OSAL106889 ) deposited at Ohio State University Acarology Laboratory ( OSAL), Columbus, U.S.A.

Collection information

French Guyana: Kaw Mountain, Amazone Nature Lodge, "monkey site", elev. 306 m, 04°33’27"N 052°12’29"W, collector Klompen, H., 2 Aug 2008, ex litter in forest, moderately wet, coll. no. AL013589 (holotype female, nymphs and larva). Same general area, "buttress site", elev. 299 m, 04°33’46"N 052°12’13"W, coll. Klompen, H., 5 Aug 2008, ex litter near buttress tree, AL013606 (male)

Etymology

This species is named in honor of FrØderic LeCorre, our host at Amazone Nature Lodge, for his strong support during our stay.

Figures

FIGURE 2: Diplothyrus lecorrei n. sp. Larva, gnathosoma. (a) – chelicera; (b) – palp, anterolateral view; (c) – palp tarsus, detail, anterolat- eral view; (d) – subcapitulum. Scale for a, b, d identical, scale bar = 100 µm; scale bar for c = 50 µm.

FIGURE 3: Diplothyrus lecorrei n. sp. Larva, idiosoma, reconstructed. (a) – dorsal view; (b) – ventral view. Scale bar = 100 µm.

FIGURE 4: Diplothyrus lecorrei n. sp. Larva, legs. (a) – leg I; (b) – detail tarsus I; (c) – leg II; (d) – leg III. Scale bar for a, c, d = 100 µm.

FIGURE 5: Diplothyrus lecorrei n. sp. Female. (a) – chelicera (details of whole chelicera and membranous outgrowth); (b) – palp, anterolateral (left) and posterolateral (right) views (setae drawn in dashed lines not consistently present); (c) – subcapitulum; (d) – genital area (arrow indicates presumed latigynal shield), open circles: setal bases, filled grey circles: pores; (e) – pretarsus II. Scale bars = 200 µm.

FIGURE 6: Diplothyrus lecorrei n. sp. Adult, idiosoma. (a) – male, ventral view; (b) – female, ventral view; (c) – male, Thon’s organ; (d) – female, Thon’s organ, detail view. Scale bars for a, b = 500 µm; scale bars for c, d = 200 µm.