Metarhombognathus Newell, 1947

Bartsch, Ilse, 2015, The genital area of Halacaridae (Acari), life stages and development of morphological characters and implication on the classification, Zootaxa 3919 (2), pp. 201-259 : 223-224

Metarhombognathus Newell, 1947

( Fig. 64 )

Type species. Rhombognathus armatus Lohmann, 1893 .

Adults. In female GP reduced in size, separated from AP. GP only slightly larger than GO, anterior pair of pgs on or in margin of GP, two following pairs in striated integument. Genital sclerites lack sgs. Anterior-most of three pairs of internal gac more slender than following pairs and adjacent or fused to second pair ( Bartsch 1975a: fig.

14a, 2003c: fig. 6M); that anterior pair may be obscured in ventral aspect. Pairs of gac at and posterior to the level of middle of GO, posterior pair internally extending posteriad beyond GO. Ovipositor short, both at rest and everted. Genital spines with numerous delicate spicules included in a membrane. Everted ovipositor with four pairs of genital spines. Two antero-apical pairs and one of postero-apical pair recognizable when ovipositor at rest ( Bartsch 1975a: fig. 14a). In male GP and AP fused. Length of male GO similar to that of female. GA with 30–40 pairs of bristle-like, smooth pgs, genital sclerites with three pairs of small, rather spiniform sgs. Acetabula internal, situated adjacent in posterior part of GO ( Fig. 64 ); gac somewhat smaller than in female. As in female, anterior pair of acetabula more narrow and fused with second pair ( Bartsch 1972: fig. 10, 2003c: fig. 6I). Adults without epimeral pores.

Juveniles. With one larva and two nymphs. Genital and anal plate fused in both deutonymph and protonymph. Deutonymph with two pairs of internal gac, two pairs of pgs, no sgs ( Bartsch 2003c: fig. 6G). Protonymph with single pair of gac; pgs and sgs not developed ( Bartsch 2003c: fig. 6F). Larva with pair of tube-like epimeral pores ( Bartsch 1974b: fig. 1c).

Remarks. Two species have been described, both are common in tidal green algal belts of the northern Atlantic and Arctic Sea ( Bartsch 2009a).

Figures

FIGURE 64. Metarhombognathus nudus (Viets, 1928), genital opening, male. FIGURES 65 – 66. Mictognathus werthelloides Newell, 1984, 65. genital opening, female; 66. genital plate, deutonymph. FIGURE 67. Phacacarus flavellus Bartsch, 1992, genitoanal plate, female. FIGURE 68. Rhombognathides spinipes (Viets, 1933), genital opening, female. FIGURES 69 – 70. Scaptognathides hawaiiensis Bartsch, 1988, female, 69. posterior part of genitoanal plate; 70. left AE with epimeral pore. FIGURES 71 – 72. Simognathus maculatus Bartsch, 1994, 71. posterior part of genitoanal plate, female; 72. posterior idiosoma with genital plate, protonymph. FIGURE 73. Simognathus fuscus Viets, 1936, posterior idiosoma with genital plate, deutonymph. FIGURE 74. Simognathus sp., genital plate, deutonymph. FIGURE 75. Simognathus actius Otto, 2000, posterior idiosoma with genital plate, protonymph. (ep, epimeral tube; gac, genital acetabula) Scale = 50 µm