Bryobia gigas, Auger, Philippe, Arabuli, Tea & Migeon, Alain, 2015

Auger, Philippe, Arabuli, Tea & Migeon, Alain, 2015, Two new species of Bryobia (Acarina, Prostigmata, Tetranychidae) from South France, ZooKeys 480, pp. 21-39 : 28-30

Taxon classification Animalia Prostigmata Tetranychidae

Bryobia gigas sp. n. Figures 6, 7, 8, 9, 10

Type material.

Holotype (female), 9 female and 2 larvae paratypes on 12 microscopic preparations from Bituminaria bituminosa (L.) C.H. Stirt. ( Leguminosae ), Four de la caux (43°35.2241N, 3°44.9143E, alt. 90 m), Pignan, Hérault (34), France, 23.XII.2012, leg. P. Auger. All the material deposited in the collection of the CBGP, coll. Auger-Migeon N°1827 for holotype, 1828-1838 for paratypes.

Diagnosis.

Body and leg I large, anterior dorsal propodosomal projections over gnathosoma well developed, inner lobes with fused base, candle like-shaped distally, incision between inner vertical setae (v1) wide, bottom rounded. Dorsal body setae short, spatulate, serrate, inserted on small bulges, subequal in length on hysterosoma, f1 and f2 setae marginal not contiguous. Empodia I with a pair of tenent hairs, others with two rows of tenent hairs.

Description.

FEMALE. Holotype 880 long (including gnathosoma), width 593. 7 paratypes measured, 860-916 long, width 574-628.

Dorsum. Prodorsum with four pairs of setae, anterior propodosomal lobes well developed (Figs 6A, 7 A–B). Lobes with basal width about 125 (122-134), outer propodosomal lobes 66 (61-74) high (excluding setae), teat-like shaped, extending about three quarters of inner lobes; inner lobes longer than broad, 73 (63-76) high, 51 (49-56) wide, with fused base about half their length, well separated by deep, wide and bottom rounded incision 27 (27-33) in depth (measured from the bottom of the incision between the inner lobes to their tip, excluding setae). Incision between median and outer lobes deep and narrow. The imaginary transverse line passing to the top of the outer lobes crosses inner near or just above the bottom of the incision. The line joining tips of second pair of propodosomal stae (v2) located on the outer lobes generally passes just above the bases of the first pair (v1). Distance between v1 and v2 setae insertions 29 (19-29) and 86 (86-103), respectively, v1 and v2 setae subequal in length, v1 and v2 subspatulate to spatulate, v2 wider. Dorsal body setae spatulate, palmate, rough, serrate, inserted on small bulge-like structures, subequal in length, sc1 the shortest (Fig. 6 A–B). Dorsocentral setae (c1, d1 and e1) shorter than distances between consecutive setae (length of holotype and variations of 7 paratypes): v1 28 (24-30); v2 30 (29-31); sc1 24 (21-24); sc2 24 (20-26); c1 28 (24-29); c2 29 (22-30); c3 24 (21-27); d1 26 (23-29); d2 28 (22-31); d3 26 (22-30); e1 29 (25-30); e2 27 (25-28); e3 28 (23-30); f1 27 (23-27); f2 27 (23-28); h1 26 (23-26). Distances between setae: c1-c1 88 (83-98), d1-d1 67 (67-79), e1-e1 68 (63-74), c1-d1 145 (125-149), d1-e1 111 (11-127). Sacral setae (f1 and f2) in marginal position, not contiguous. Dorsal integument on propodosoma with irregularly rounded reticulated granulated pattern medially more elongated laterally and oblique. Folds on hysterosoma mostly transverse, irregularly arched in the caudal part. Two pairs of more or less oval-shaped shallow dimples present between d1-d3, and e1-e3 setae and one present posteriorly.

Gnathosoma. Stylophore longer than wide. Tibial claw of palpus bidentate. Palptarsus subequal in length to tibial claw, about 28 (27-29) long with three tactile setae, three eupathidia and one solenidion (Fig. 7D). Eupathidia ul’ζ, ul’’ ζ shorter than solenidion, suζ longer than solenidion. Peritreme anastomosed distally in a relatively long and slender enlargement, 62 (52-71) long (Fig. 7E).

Venter. Striation transverse between 1st (1a) and 2nd (3a) pairs of setae, between 2nd and 3rd (4a) irregular longitudinal striation medially more or less oblique or arched laterally, transverse above and between 4a and the area anterior to aggenital (ag) setae, longitudinal between members of ag setae, area immediately anterior to genital flap with irregular longitudinal striation. Sacculus of spermatheca elongated, length 22.5, width 5.5 (Fig. 7C). Three pairs of pseudanal setae (ps1-3) and two pairs of ventrocaudal (h2-3) setae present.

Legs. Leg I subequal in length to body length, other legs inferior to body length. Leg I 926 (825-947) long (measured from trochanter to tarsus), leg II 392 (345-392), leg III 353 (352-373), leg IV 470 (412-470). Length of segments of leg I as follows: trochanter 50 (41-69), femur 360 (300-360), genu 90 (84-102), tibia 260 (227-274), tarsus 168 (155-180). Leg setal counts as follows (Figs 8 A–C, 9 A–B):

I 2 − 1 - 25[23-24] − 8[7] - 15[16] + (1) - 20[19] + (5)[(6)] + 2 duplexes;

II 1 − 1 - 11[10] - 6[5] - 9[8] - 15 + (2) + 1 duplex;

III 1 − 1 - 5[4] - 6[5-7] − 9[8] - 13 + 1 duplex;

IV 1 − 1 − 5 - 6[5] − 9[8] - 13 + 1 duplex.

True claws uncinate, claw and empodium I with one pair of tenent hairs, other claws with several pairs of tenent hairs, other empodial pads each provided with two rows of tenent hairs (Figs 8D, 9C). Coxisternal seta 1b slender 41 (40-50), coxisternal seta 1c shorter 17 (17-20), serrate, stout (Fig. 8 E–F). Tarsi III and IV associated setae serrate and approximate with solenidion forming duplex, the tactile member shorter (about ¾ the length of solenidion) and proximal (Fig. 9 D–E).

LARVAE: two larvae measured, 366-370 long (including gnathosoma), width 246-255.

Dorsum. Prodorsal lobes absent (Fig. 10 A–B). Prodorsal setae serrate, subspatulate except v1 short, elongated. v1 setae inserted without tubercle, v2 inserted on small bulges. Other dorsal setae inserted on tiny bulges more obvious posteriorly. Hysterosomal setae serrate, wider caudally, subspatulate to spatulate, e3 and f1 wider, f2 and h1 longer. Setae f1 in normal position.

Lengths of dorsal setae: v1 13; v2 18-20; sc1 16-18; sc2 15; c1 15-16; c2 16; c3 16; d1 19-17; d2 16-17; d3 15-16; e1 18-21; e2 16-18; e3 19; f1 18-21; f2 22-23; h1 22-23.

Legs. Length inferior to body length, leg I 235-248 long. Leg setal counts as follows:

I 1 − 0 − 3 − 4 − 5 + (1) - 7 + 1 duplex;

II 0 − 0 - 3 − 4 − 5 - 7 + 1 duplex;

III 0 − 0 - 2 - 2 − 5 - 6.

True claws uncinate with one pair of tenent hairs, empodia with two rows of tenent hairs. On femur I, internal seta smooth, dorsal seta serrate.

Remarks.

Bryobia gigas is morphologically close to three species, that belong to a species-group characterized by: 1) prodorsal inner and outer lobes very well developed, outer teat like not triangular, anteromedian well separated; 2) associated setae forming a duplex on tarsus IV, tactile member shorter than solenidion; 3) similar setal counts especially on leg I with 29 and 16 setae on tarsus and tibia, respectively, and on leg II with 19 and 9 setae on tarsus and tibia, respectively; 4) a pair of tenent hairs on the empodium of the foreleg and two rows of tenent hairs on the other empodia. These species are Bryobia osterloffi Reck, 1947, Bryobia vasiljevi Reck, 1953 and Bryobia lagodechiana Reck, 1953.

Among this species-group Bryobia gigas and Bryobia lagodechiana have a similar large body size. Bryobia gigas is mainly distinctive from Bryobia lagodechiana by the shape of the inner incision between the anteromedian prodorsal lobes which is wide and bottom rounded in the former whereas narrow in the latter. In addition, the line that passes to the tips of v2 setae does not reach the bases of v1 setae in Bryobia lagodechiana . They also have a different setal count on genu I with 7-8 and 4-5 setae present in Bryobia gigas and Bryobia lagodechiana , respectively.

Bryobia gigas can be easily distinguished from Bryobia osterloffi and Bryobia vasiljevi by its body and leg sizes which are far smaller in the latters. Moreover, in Bryobia osterloffi , the incision between the inner prodorsal lobes is wide but less deep than in Bryobia gigas (the line that passes to the top of the outer lobes does not reach the bottom of the incision between inner lobes), it is not bottom-rounded but with a flat bottom and the distal part of the peritreme is less elongated. Bryobia gigas also differs from Bryobia vasiljevi by the incision between the inner prodorsal lobes which is narrow. According to Livshits and Mitrofanov (1971), 6 setae are present on the femora III and IV of Bryobia vasiljevi whereas 5 are present in Bryobia gigas . However, type’s examination of Bryobia vasiljevi in Reck’s collection gave conflicting data because 5 setae only are present on femora III and IV of the 21 type specimens. As a consequence, this morphological criterion cannot be used to distinguish between the two species.

Etymology.

The specific epithet gigas, name given to “Giants” in Greek mythology, refers to the quite unusual large body and legs sizes of this species.