Berzercon ferdinandi Seeman & Baker

Seeman, Owen D. & Baker, Michelle R., 2013, A new genus and species of Discozerconidae (Acari: Mesostigmata) from carabid beetles (Coleoptera: Carabidae) in New Zealand, Zootaxa 3750 (2), pp. 130-142 : 132-140

Berzercon ferdinandi Seeman & Baker sp. nov.

Figures 1–22

Type material. Holotype: Female, New Zealand, Wairarapa, Mt Holdsworth, 11.iv.2004, A.M. Paterson, ex Megadromus sp. ( Carabidae ). Deposited in Landcare Research, Auckland, New Zealand. Paratypes: 3 males, same data as holotype; 1 female, 2 males, same data as holotype except ex Mecodema sp. ( Carabidae ), 15.xi.2002; 1 female, same data as holotype, except ex Plocamostethus sp. ( Carabidae ), 15.xi.2012. 2 females, 1 male, New Zealand, Waikato, Maungatautari (South Cell, outside CR4, transect 1, pitfall trap G), Jan–Feb 2009, C.H. Watts. 3 females, 3 males, New Zealand, Waikato, Limestone Downs (Contact Energy Waikato Wind Farm, block C, track CO15-CO13, trap D), 22 Dec 2009 – 13 Jan 2010.

Paratype deposition: 3 females, 5 males, Landcare Research, Auckland, New Zealand; 1 female, 1 male, Canterbury Museum, Christchurch, New Zealand; 2 females, 2 males, Queensland Museum, South Brisbane, Australia; 1 female, 1 male, Ohio State University, USA (OSAL0104614 (M) and OSAL0104613 (F)).

Other material: 1 female, 1 male gold-coated on SEM stub (QM). 1 females, 3 males, OSU (unmounted).

Collection notes: The sample from Maungatautari had seven species of carabid beetles: Mecodema oconnori (n = 1), Parabaris atratus (n = 10), Ctenognathus sp. (n = 2), Dicrochile sp. (n = 2), Aulacopodus calathoides (n = 1), Holcaspis mordax (n = 1) and Molopsida polita (n = 1). The sample from Limestone Downs had six species of carabid beetles: Aulacopodus calathoides (n = 1), Ctenognathus bidens (n = 8), Ctenognathus lucifugus (n = 4), Dicrochile sp. (n = 1), Holcaspis mordax (n = 4) and Mecodema crenaticolle (n = 2).

Description. Female (n = 8; Figures 1–11 )

Dorsum (see male Fig. 12 ). Dorsal idiosoma length 1500 (1150–1500), width 1350 (1010–1350), with approximately 84 loosely paired minute setae.

Venter ( Figs 1 , 8–10 ). Tritosternum length 310 (270–310), laciniae separate, length 245 (225–245). Presternal shield entire, length 70 (50–70), width 255 (200–255), reticulate. Sternal and endopodal shields fused; cuticle reticulate medially, becoming smooth laterally. Genital shield dome-shaped, fused posteriorly at level of coxa III, extends anteriorly almost to anterior margin of sternal shield; genital shield reticulate. Sternogenital shield length 665 (525–665), width 570 (475–570). Genital shield length 215 (205–235), width 310 (275–310). Four pairs of intercoxal setae: st1 lightly barbed, 65 (35–75), st2 lightly barbed 70 (35–70), st3 smooth, 75 (40–75), st5 smooth 45 (35–45); setae st1 – 3 flank genital shield; setae st5 posterior to genital shield. Two pairs of lyrifissures, stp1 anterolaterad st2, stp2 anteriad st3. Genital shield with one pair of pores. Internal genital structure present, tongueshaped, length 160 (140–165), width 35 (25–40).

Opisthogaster with one pair of large suckers ( Figs 1 , 10 ), length 380 (275–380), width 280 (235–280). Four pairs of lightly barbed setae anterior to suckers, in soft cuticle, most medial setae length 65 (35–65), other setae 95– 105 (70–95). One pair of medial post-sternal setae, in soft cuticle, length 80 (45–80). Ventrianal shield elongate, finely reticulate, length 265 (245–325), width 170 (135–170), cribrum present. Anterior ventrianal setae with barbed tip, 65 (50–65); para-anal setae lightly barbed, 115 (80–115); postanal seta lightly barbed, 45 (35–45). Paired ventral shields posteriad suckers, reticulate, one pair of pores in anterolaterad margin, length 110 (95–110), width 275 (195–290). Metapodal shields reticulate, bearing three pairs of smooth to lightly barbed setae 115–135 (90–135) and two pairs of pores laterad setae; anteriorly fused to exopodal shield. Ventral marginal shield present, bearing short flattened marginal setae. All areas of soft cuticle with faint reticulation.

Exopodal, post-stigmatal, peritrematal and lateral marginal shields fused, but with lines of fusion present; shields reticulate, becoming weaker anteriorly. Stigmata at posterior level of coxa III, peritreme short, length 175 (150–180), extending to posterior level of coxa II. Porose areas posterolaterad stigmata, laterad peritreme, anteriad peritreme, and anterior to coxa I.

Marginal setae r2 – R2 long, barbed, with flattened serrate tips, r2 245 (185–245), r3 140 (110–140), r4> 160 (180–200), r5 325 (270–335), r6 195 (135–195), R1> 335 (325–360), R2 320 (265–320). Marginal setae posterior to R2 hypertrichous, 35–46 setae; all setae broad, flattened, with 3-pointed tips; 5–6 longer setae (90–110 long) interspersed amongst shorter setae (60–75 long).

Gnathosoma ( Figs 2 , 11 ). Gnathotectum tripartite (see male Fig. 15 ), length 345 (295–345), middle process longest; weak keel present, extending to tip of middle process. Hypostomal setae h1 thick, barbed at tip, length 120 (105–135); setae h2 barbed, length 110 (95–110); setae h3 smooth, length 55 (40–55). Palpcoxal setae barbed, length 105 (80–110). Deutosternum reticulate, with ca. 13 rows of denticles laterad gutter; deutosternal gutter with ca. 8 irregular rows of denticles. Corniculi large, curved, horn-like, length 175 (170–190). Internal malae long, divided mid-way into a ribbon-like process and a thicker process with one edge ciliated. Palps four-segmented, tibia and tarsus fused. Palp apotele two-pronged. Setal counts 2-5-6-20. Most adaxial setae barbed. Trochanter with small distal adaxial process. Femur with large abaxial area of darker, densely porose cuticle; seta al short, thickened. Genu with three smooth, thin setae clustered. Tibiotarsus tip with six blunt-tipped sensory setae.

Chelicerae ( Fig. 3 ). Fixed digit length 400 (315–400), with 13–18 small and two larger teeth; pilus dentilus blade-like, length 12 (10–12); cheliceral seta arises laterally, smooth, length 45–55. Moveable digit length 230 (190–230), with 6–10 small teeth, proximal tooth largest; single smooth excrescence arises ca. one-third distance from base of moveable digit, excrescence length 55 (40–55). Interdigital membrane (sensu Fain 1989) arising adaxially at base of digits, length 45–55.

Legs ( Figs. 4–7 ). Tarsus I with acrotarsus. Pretarsi without claws, membranous. Tarsal tips with small membranous flanges. Setal counts: coxae 2-2-2-1; trochanters 6-5-5-5; femora 11-11-8-7; genua 12-9-10-11; tibiae 12-10-10-10; tarsi 43-18-18-18. Setal formulae for femora: I 2,2/1,3/1,2; II 1,2/2,3/2,1; III 1,2/1,2/2,0; IV 1,2/1,2/ 1,0. Setal formulae for genua: I 2,3/1,3/1,2; II 2,2/1,2/0,2; III 2,3/1,2/0,2; IV 2, 3/1, 3/0, 2. Setal formulae for tibiae: I 2,3/1,3/1,2; II–IV 2,2/1,2/1,2. Chaetotaxy presented on figures. Tarsus I with acrotarsus bearing ca. 17 setae; dense cluster of setae on dorsal side of tarsal tip and acrotarsus (see male Fig. 21 ); legs with some setae thickened, but most noticeably FeI av1 and TaI av3; tarsi II–IV ad1, pd1 with spatulate tips (see male Fig. 22 ).

45–50, width 165–205. Sternal and endopodal shields fused; cuticle reticulate medially, becoming smooth laterally. Genital opening just behind margin of sternal shield, length 85–105, width 90–130. Sternal shield length 500–670, width 425–590. Four pairs of intercoxal setae: st1 lightly barbed, 35–65, st2 smooth, 40–60, st3 smooth, 35–65, st5 smooth 35–50. Two pairs of lyrifissures, stp1 anterolaterad st2, stp2 anteriad st3. Marginal setae r2 140–195, r3 75–140, r4 145–205, r5 255–350, r6 115–165, R1 270–330, R2 225–270.

Opisthogaster similar to female. Sucker length 250–325, width 235–295. Four pairs of lightly barbed setae anterior to suckers, in soft cuticle, most medial setae length 35–55, other setae 70–90. One pair of medial poststernal setae, in soft cuticle, length 50–60. Ventrianal shield elongate, finely reticulate, length 235–295, width 130– 170, cribrum present. Anterior ventrianal setae smooth, 45–65; para-anal setae lightly barbed, 80–100; postanal seta lightly barbed, 30–50. Metapodal setae lightly barbed 90–130.

Gnathosoma ( Figs 14–15 ). Gnathotectum tripartite, length 260–340, middle process longest; weak keel present, extending to tip of middle process. Hypostomal setae h1 modified, tip shaped like a fish-tail, base with medial process, length of seta 75–115; setae h2 smooth, 55–65; setae h3 bulbous, length 15–21, width 8–12. Palpcoxal setae barbed, length 105–125. Deutosternum, corniculi, internal malae similar to female. Palps similar to female.

Chelicerae ( Fig. 16 ). Similar to female. Fixed digit length 295–355, with 10–14 small and two larger teeth. Moveable digit length 180–220, excrescence length 45–58.

Legs ( Figs 21–22 ). Similar to female, no spurs or stronger setae.

Etymology. This new species is named for Ferdinand the Bull, the main character of Munro Leaf’s 1936 book, and loosely refers to the mite’s large curved horn-like corniculi.

Remarks. We have treated all the material as the same species because we lack strong morphological evidence to separate them. However, the specimens exhibited a large size range, with the largest mites being from Mt Holdsworth (female 1420–1500; male 1260–1460) and the smallest from Limestone Downs (female 1150–1280; male 1110–1260). Apart from these ambiguous size differences, no other features separated collections from different host species and sites. Additionally, each of the three collection sites, confined to the North Island, are distant to one another: Limestone Downs (northwest coastal) and Maungatautari (central north) are somewhat close together, but Mt Holdsworth is in the central-south. Consequently it seems surprising that these mites, whose hosts are flightless carabid beetles and occur in isolated habitats, seem to represent the same species.

A noteworthy feature of B. ferdinandi is the presence of a keel on the gnathotectum, typically present only in the trigynaspid cohort Antennophorina . The keeled gnathotectum is expressed strongly in some antennophorine superfamilies (e.g., Megisthanoidea, Celaenopsoidea) but weakly in others and is sometimes absent (e.g., most Parantennulidae ) (Kim 2004). The keel of B. ferdinandi is weak, visible as a long thin line, as seen in Fedrizzioidea, Aenictequoidea, Antennophoroidea and some Paramegistidae .

The presence of a keel may represent convergence, as a similar keel-like structure occurs in Pyriphis (Ologamasidae) (pers. obs.). However, a trigynaspid-heterozerconine sister-group relationship was suggested by Norton et al. (1993). Within the Trigynaspida, members of the Paramegistidae are associated with millipedes, lizards and snakes (e.g. Kim & Klompen 2002; Klompen & Austin 2007; Baker & Seeman 2008) and share at least a strikingly superficial resemblance. Many paramegistids are discoid, have smooth dorsal shields with numerous marginal setae, and extensive ventral shields, but these are probably independent adaptations to living on similar hosts. More curious are similarities between the chelicerae of the Paramegistidae and Heterozerconidae (and Discomegistus ): both have a moveable digit with a fine row of cilia-like teeth and two interdigital membranes (one truly interdigital, the other on the fixed digit). Again, this probably reflects convergence in feeding habits on the same host taxon, but the likelihood of this being so is harder to dismiss due to the complex morphology of the chelicerae.

The modified hypostomal setae h1 of B. ferdinandi are also found in some sejid and trigynaspid taxa. In the Sejida setae h1 are often small and scale-like (e.g., Fig. 12.7D in Lindquist et al. 2009) but are not sexually dimorphic and bear little resemblance to the strong thick h1 setae of B. ferdinandi . In the Trigynaspida, Promegistus (Parantennuloidea: Promegistidae ) have strikingly modified setae h1, being large and membranous in both sexes (pers. obs.), and many Ophiomegistus (Paramegistidae) and Antennophoridae have h1 much stronger than other hypostomal setae (e.g., Goff 1980; Wisniewski & Hirschmann 1992). Sexual dimorphism occurs in the hypostome and hypostomal setae of some Trigynaspida, most spectacularly in the Celaenopsidae , Euzerconidae , Schizogyniidae and Megacelaenopsidae (e.g., Kinn 1970; Funk 1974, 1980; Rosario 1988), but also less impressively in the Fedrizziidae (Seeman 2007) . However these taxa are unlikely sister-groups of the Heterozerconina, being within well-established superfamilies (Celaenopsoidea and Fedrizzioidea, respectively). Instead, these partly illustrate the diversity of independently derived modifications found in male trigynaspid mites, presumably for transferring the spermatophore to the female’s genital opening. Other examples are the Asternoseiidae (modified sternal setae, see Karg & Schorlemmer 2011, erroneously placed in Fedrizziidae ), Saltiseiidae (modified gnathotecta; Walter 2000), Antennophoridae and Diplogyniidae (modified chelicerae; e.g., Wisniewski & Hirschmann 1992; Seeman 2012), and Fedrizziidae and Klinckowstroemiidae (modified presternal shields; e.g., Rosario 1988; Seeman 2007). Therefore, although the modified hypostomal setae of B. ferdinandi might provide a link with either the Sejida or Trigynaspida, the sexual dimorphism observed in these setae is likely to have evolved independently.

Figures

FIGURE 1. Berzercon ferdinandi sp. nov., adult female, ventral idiosoma.

FIGURES 2 – 3. Berzercon ferdinandi sp. nov., adult female. 2, ventral gnathosoma; 3, chelicera.

FIGURES 4 – 7. Berzercon ferdinandi sp. nov., adult female. 4, leg I; 5, leg II; 6, leg III; 7, leg IV. Leg setae are partially labelled to aid orientation; see description for formulae.

FIGURES 8 – 11. Berzercon ferdinandi sp. nov., adult female, scanning electron micrographs. 8, venter (scale bar = 500 µm); 9, sternogenital shield (scale bar = 200 µm); 10, opisthogaster (scale bar = 300 µm); 11, ventral gnathosoma (scale bar = 200 µm).

FIGURE 12. Berzercon ferdinandi sp. nov., adult male, dorsal idiosoma.

FIGURE 13. Berzercon ferdinandi sp. nov., adult male, venter.

FIGURES 14 – 16. Berzercon ferdinandi sp. nov., adult male, 14, ventral gnathosoma; 15, gnathotectum; 16, chelicera.

FIGURES 17 – 22. Berzercon ferdinandi sp. nov., adult male, scanning electron micrographs. 17, venter (scale bar = 1000 µm); 18, sternogenital shield (scale bar = 200 µm); 19, opisthogaster (scale bar = 200 µm); 20, hypostome, right hand side (scale bar = 30 µm); 21, acrotarsus and pretarsus I (scale bar = 50 µm); 22, tarsus IV, arrows point to spatulate setae (scale bar = 100 µm).