Macrocheles similis Krantz and Filipponi, 1964: 37

Özbek, Hasan Hüseyin & Durucan, Furkan, 2024, Two new records of the genus Macrocheles (Acari: Macrochelidae) from Türkiye, with redescription of M. similis Krantz and Filipponi, Acarological Studies 6 (1), pp. 44-51 : 45-49

Macrocheles similis Krantz and Filipponi, 1964: 37 .

Macrocheles similis – Rodriguez and Ibarra, 1967: 809; Tenorio et al., 1985: 301; Halliday, 1990: 422; 2000: 311; Manning and Halliday, 1994: 91; Saito and Takaku, 2013: 37; Ji et al., 2023: 79 (misidentification).

Diagnosis. Dorsal shield less than 1000, with 28 pairs of setae; z1, j5, j6, z5, z6, and J2 smooth, other setae more or less pilose, sometimes knife-like; linea media transversa distinct, linea obliquae anterior connected with linea arcuate, distinct linea angulate; ventrianal shield broader, length/width =0.92-0.99, deutosternal furrow with 4-6 rows of denticles; anterior tips of peritremes extend beyond bases of setae z1; thelytokous parthenogenesis; phoretic in beetles.

Description.

Dorsum ( Fig. 4 ). Dorsal shield elongate, 800–900 long, 490–580 wide at widest point (n=9), reticulate with polygonal punctation pattern ( Fig. 12 ), with 28 pairs of setae; setae j5, j6, z1, z5, z6, and J2 smooth and pointed, j1 and Z4 distinctly pilose and brush-like, other dorsal setae mostly distally on slightly pilose or knife-like, especially marginally situated setae pilosity more distinct and reduced pilosity toward paraxial position, distally a few denticles or entirely knife-like ( Figs 5 , 18, 19 ); setae j1 42–46, z1 20–25, j6 35–42, J5 25–30, other setae length 40–65.

Venter ( Figs 6 , 13 ). Sternal shield 180-210 long, 150-190 wide in middle of coxae II; surface sculptured with reticulate pattern and punctation and provided with three pairs of needle-like setae and two pairs of pores; st1 and st2 almost equal in length (54–58), st3 40-46 long; its surface with distinct linea media transversa, line obliquae anterior connected with linea arcuate, distinct linea angulate; area between st2 and st3 ornamented with wellsculpted large oval patterns. Metasternal shields free, elliptical, each with a pore and a smooth seta st4 (34–40). Epigynal shield 160–180 long, 165–195 wide, helmetshaped, ornamented with punctate reticulation, with a pair of smooth setae st5 (42-48). Ventrianal shield wider than long, 260–310 long, 280–325 greatest width (L/W =0.92–0.99), ornamented with polygonal punctate pattern, with three pairs of smooth pre-anal setae (40- 48), one pair of long para-anal setae, and one postanal seta. Anterolateral extensions of cribrum not reaching bases of para-anal setae. Anterior tips of peritremes reaching beyond bases of setae z1.

Spermathecal structure. As in Figure 7 . Gnathosoma . Setae h3 longest, h2 almost subequal in length to pc, h1 longer than h2. Corniculi long and hornlike. Deutosternal furrow with six rows of denticles, row between setae h1 separated into two parts ( Fig. 8 ). Epistome with a pair of lateral processes distally, a median process deeply bifurcated distally, with long spines on its stem ( Fig. 9 ). Chelicerae well developed, movable digit about 97 long, with two median teeth and unidentate terminal hook, fixed digit about 75 long to level of base of dorsal seta, with one distinct median tooth, one distal tooth near unidentate terminal hook, distinct pilus dentilis and a smooth dorsal seta. Two arthrodial brushes are present, one very short and another more than half as long as movable digit ( Figs 10 , 16, 17 ).

Legs. Chaetotaxy typical for the genus and family ( Evans, 1963). All coxae with smooth and pointed setae. Tarsus II as in Figure 11 .

Specimens examined. 21 ♀♀, Aziz Sancar Park , Antalya, Türkiye, 18 May 2018, phoretic on a dung beetle. Following specimens from Erzincan Ekşisu Marsh, Türkiye 1150 m a.s.l. : one ♀, 39°43'31.91"N 39°37'20.64"E, 13 April 2013, in moss; 4 ♀♀, 39°42'38.65"N 39°36'5.18"E, 13 May 2013, dung and moss in Juncus heldreichianus ; 4 ♀♀, 39°43'53.4"N 39°37'02.8"E, 16 June 2013, soil and moss; one ♀, 39°43'41.1"N 39°37'30.2"E, 04 July 2013, dung and moss; 7 ♀♀, 39°43'53.4"N 39°37'03.0"E, 02 August 2013, dung and moss; one ♀, 39°43'59.7"N 39°37'15.3"E, 25 October 2013, in dung; 4 ♀♀, 39°43'34"N 39°37'24"E, 11 November 2013, in moss.

Notes. Macrochles similis was first described by Krantz and Filipponi (1964) and illustrated by a single female specimen in the Australian region. Later, Rodriguez and Ibarra (1967) mentioned the species in an ecological study of mites on sheep and cattle pastures in Kentucky, USA, and Tenorio et al. (1985) reported the occurrence of this species in the Hawaiian Islands, and Halliday (1990) redescribed the mature and immature stages of numerous Australian specimens and provided further details on morphology and biology. Saito and Takaku (2013) investigated the degree of predatory ability of this species on Tyrophagus similis Volgin in Japan. Finally, Ji et al. (2023) reported this species from Korea, but it is not a specimen of M. similis as it is shown in the photo of the ventral side.

Macrochles similis morphologically most resembles M. muscaedomesticae, Krantz and Filipponi (1964) distinguished it based on some characters such as the pilosity of the dorsal setae, the dimension of the body shields, and the number of rows on the deutosternal furrow of the gnathosoma, but their study revealed only single specimens, later Halliday (1990) updated all characters based on the many specimens. Halliday (1990) shows that these separating characters are unreliable, except for the dimensions of the body part. We here confirmed the statement made by Halliday (1990) based on the Turkish specimens. Krantz and Filloponi (1964) state that setae j2, j3, z2, z4, r3, s4, r4, s2, s5, s6, S1, S2, Z1 are simple, but Halliday (1990) reported that most of them may have pilosity, especially r3, S1, S2 and Z1 may be more pronounced. Specimens in Türkiye, setae j5, j6, z1, z5, z6, and J2 smooth, j1 and Z4 strongly pilose and brushy ( Fig. 18 ), other dorsal setae mostly distal on slightly pilose or knife-like, especially marginally situated setae more distinctly pilose. Krantz and Filopponi (1964) state that the deuterosternal furrow has four rows of denticles, Halliday (1990) states that it has five rows of denticles, except for one specimen which has four, a female specimen which has six rows of denticles. All specimens examined in the current study have are six rows of denticles, the row between setae h1 is divided into two parts. The body size and the ornamentation on the sternal shield (surface of the sternal shield in M. muscaedomesticae as in Figure 14 and in M. similis as in Figure 15 ) are the most reliable differences between M. muscaedomesticae and M. similis . The length of dorsal shield of M. similis is 750-881 in Australian specimens (Krantz and Fillipponi, 1964; Halliday, 1990), 800-900 in Turkish specimens. Özbek et al. (2015) also report a length of more than 1000 for M. muscaedomesticae , which was found in the dung of one specimen.

In addition, Halliday (1990) notes that non-morphological differences between M. similis and M. muscaedomesticae , such as the fact that M. muscaedomesticae is almost associated with flies as phoretic, are not observed in M. similis . In addition, M. muscaedomesticae reproduces by arrhenotokous parthenogenesis, whereas M. similis appears to be thelytokous. Furthermore, despite many specimens collected in Türkiye, no males of M. similis were found. Therefore, Turkish specimens of M. similis are also thelythokous as reported by Halliday (1990).

Figures

Figures 4-6. Macrocheles similis (female). 4. Dorsal shield, 5. Variations of dorsal setae, 6. Ventral shields.

Figures 12-13. Macrocheles similis (female). 12. Dorsal view, 13. Ventral view.

Figures 14-19. Macrocheles spp. (females). 14. Surface of sternal shield of M. muscaedomesticae. 15-19. M. similis. 15. Surface of sternal shield, 16-17. Chelicera, 18. Seta Z4, 19. Some setae on dorsal shield.

Figures 7-11. Macrocheles similis (female). 7. Spermathecal structure, 8. Gnathosoma, 9. Epistome, 10. Chelicera, 11. Tarsus II.