Myrmozercon beardae, Shaw, Matthew D. & Seeman, Owen D., 2009

Shaw, Matthew D. & Seeman, Owen D., 2009, Two new species of Myrmozercon (Acari: Laelapidae) from Australian ants (Hymenoptera: Formicidae), Zootaxa 2025, pp. 43-55 : 48-50

Myrmozercon beardae sp. nov.

( Fig. 4 )

Material examined. Female holotype SAMA J11549 , “with ants”, Lucindale, South Australia, Lea Collection; female paratype SAMA J11550 gnathosoma only, same data (in SAMA).

Dorsum: Broad oval shield extends to end of idiosoma, measurements 890 x 615. Unarmed cuticle protrudes laterally in this compressed specimen giving a subcircular outline. Shield covered in scale-like reticulations, with 12–13 setae on each side of podonotum and 11–12 setae on each side of opisthonotum, medial unpaired setae absent. Setae J2 laterad J1, J1 apparently shifted posteriorly. All setae smooth, including Z5. Representative setal lengths are j2 38, J2 49. Dorsal shield with smooth even edge, sharply demarcated from unarmed striate cuticle.

Ve n te r: Tritosternum with broad, squat base 23 long to suture. Broad strap-like, smooth-edged laciniae, 154 long, branching 17 above suture. Edges of sternal shield lightly sclerotised, anterior and posterior edges of sternal shield obscure. Shield bearing at least st1–2 and two pairs of lyrifissures. Setae st1 48, st2 51, st3 46. Setae st3 inserted in glabrous and essentially desclerotised cuticle; their placement on or off the sternal shield is not clear. Setae st4 and st5 absent. Oval-shaped crater-like recess off shield on one side may represent vestigial st5. Genito-ventral shield maximum width 154. Shield with two distinct zones: an anterolateral zone featuring extended longitudinal striae, which project laterally and impart a characteristic lobed outline to the genito-ventral shield; and a posterior zone featuring a few transverse striae. All ventral setae smooth, without barbs. Setae in R series absent. Area of opisthogaster anterior to anal shield with seven pairs of setae, four of which are spinose. Metapodal shields absent. Endopodal shield not fused to other shields, shape thin, following contours of coxa III and IV. Peritremes extending to mid coxae II. On one side the peritreme is interrupted leaving a circular islet of isolated peritreme at level of mid coxa II. Post-stigmatal plates absent. Pores associated with these plates not detectable. Anal shield with strong anterolateral humera, anterior edge somewhat irregular, 192 across. Shield 172 long, 185 wide at level of cribral pores. Anal opening situated close to posterior margin and completely posterior to the cribral pores. Para-anal setae 35, post-anal seta 59. Circum-anal setae smooth, 5–6 thick at base; thicker than adjacent opisthogastric setae. Posterior margin bears a narrow zone of cribral spicules which also extend along lateral shield margin to a level just anterior of paraanal setae.

Gnathosoma: Tectum a smooth lobe. Hypostomal area anterior to h1 reduced and membranous. Corniculi interpreted as the pair of distally-notched hyaline structures flanking each side, appearing to be strongly produced laterally. Internal malae not visible. Deutosternum with 13 (specimen J11549 ) or 16 (specimen J11550 ) rows of ca. 25 denticles. Hypostomal setae h 1 29–31, h2 34–37, h3 42; palp coxal setae 47–52. Palp trochanter with two setae, palp femur with five setae; both specimens have palp genu with five setae on one side and four on the other. Palp apotele 2-tined. Dorsodistal edge of palp femur with a distinct low swelling. Chelicerae hyaline, edentate. Pilus dentilis absent, cheliceral seta 17 long, positioned dorsally. Movable digit 76–77, arthrodial corona bearing very short tines. Fixed digit with rounded tip and parallel sides. First cheliceral segment indistinct; second cheliceral segment 185–194 long to end of fixed digit.

Legs: Surface of legs smooth, lacking striations or corrugations. Leg setae essentially smooth although femur I ad1 on one side has barbs. All ambulacra with well–developed pulvilli, claws very thin. Pre-tarsal opercula with 3–4 tines. Chaetotaxy: Coxa 2-2-2-2. Trochanters 6-5-5-5. Leg I femur 2, 5/4, 2, genu 2, 3/2,3/ 1, 2, tibia 2, 3/2,3/1, 2. Leg II femur 2, 5/1, 2, genu 2, 3/1,2/1, 2, tibia 2, 2/1, 2/1, 2. Leg III femur 1, 3/0, 1, genu 2, 2/1,2/1, 2, tibia 2, 1/1,2/1, 2. Leg IV femur 1, 1/1, 1/1, 2, genu 2, 2/1,3/1, 2, tibia 2, 1/1,3/1, 2. The following leg setae are moderately thickened: trochanter I d; femur I ad1, pd2; femur II ad1, pd2; trochanter III d; femur III ad1 and ad2; trochanter IV d; femur IV ad1, ad2. Leg segment lengths as in Table 2.

I II III IV Femur 138 124 156 200 Genu 158 120 133 170 Tibia 157 104 112 150 Tarsus 220 153 168 225 Etymology. This new species is named for Dr Jennifer Beard who recollected Myrmozercon iainkayi .

Remarks. This species is easily distinguished from known Myrmozercon species in having two setae on coxa IV and in having both dorsal and ventral hypotrichy. It is similar to Myrmozercon burwelli in general appearance, but it can be easily distinguished since it has an extensive region of the anal shield anterior of the opening, four pairs of spinose opisthogastric setae, and smooth dorsal and circum-anal setae. There are also several other differences in leg setation, for example, M. beardae has fewer setae on femur I-III than M. burwelli . The chaetotaxy of M. beardae is normal ( Evans & Till 1965) with the following exceptions: coxa IV has two setae; femur II presents as 2, 5/1, 2 with only one ventral seta and both pl setae in their typical positions; femur III has only five setae (as in Myrmozercon rotundiscutum Rosario & Hunter, 1988 ); femur IV is variable, with the standard six setae on one side, and seven setae including both pv and av setae present on the other; genu III has two pl setae; genu III has two al setae; genu IV has 11 setae with both pl setae and pv 1 present, and tibia III has 2 pl setae. Note that SAMA J11549 and J11550 represent two separate individual mites. The collection date for these specimens is unknown, but A.M. Lea was collecting ant-associated mites for Nathan Banks several years prior to 1916 ( Banks 1916) and Lea died in 1932.

Figures

FIGURE 4. Myrmozercon beardae sp. nov., female: (a) dorsum; (b) venter; (c) ventral gnathosoma; (d) tectum. Scale bars = 100 μm