Simognathus cramerae, Rivas, Gerardo, 2006

Rivas, Gerardo, 2006, First record of Simognathus (Acari: Halacaridae) from Mexico, including the description of a new species, Zootaxa 1259, pp. 61-68 : 62-66

Simognathus cramerae sp. nov.

( Figs 1–3 )

Holotype: Female, on Laurencia sp. (Rhodophyta: Ceramiales ) in the rocky intertidal from Playa Ventura, Guerrero, Mexico, 24 September 1998, colls. G. Rivas and C. Letechipia (NMCUNAM)

Paratypes: All specimens are in the author´s collection: one deutonymph on Laurencia sp. from Playa Ventura, Guerrero, México, 24 September 1998, colls. G. Rivas and C. Letechipia; one female, two males, two deutonymphs, and one larva on Tayloriella dictyurus (Rhodophyta: Ceramiales ), Jania sp. (Rhodophyta: Corallinales), and Laurencia sp. from Punta Maldonado, Guerrero, México, 23 September 1998, colls. G. Rivas and C. Letechipia; one female and one male on Sargassum liebmanii (Phaeophyta: Fucales ) and Jania sp. from Bahía Chamela, Jalisco, México, 10 April 1998, colls. G. Rivas and C. Letechipia.

Female: Idiosoma 282 m long and 140 m wide. Dorsal plates with circular and oval foveae with dense porosity ( Fig. 1 A). AD almost rectangular, 200 m long, 150 m wide. OC more or less triangular 35 m long, 12 m wide with a small terminal projection, with the posterior end drawn out into a sharp point. PD 119 m long, 69 m wide, anterior margin almost rounded. Setae ds­1 and ds­3 inserted on AD, ds­2 outside of OC, and ds­4 and ds­5 on the PD. Adanal setae inserted on anal papilla. AE 130 m long, slightly porose, and lateral areas with foveae.

Epimeral process large; vesicles large and elliptical ( Fig. 1 B). Posterior AE rounded. GA 109 m long, 76 m wide. Anterior portion of GA with fine porosity, remainder of the plate foveate. GO surrounded by 11 pgs.

Gnathosoma 88 m long, 71 m wide. Dorsal gnathosoma with a small spine on the anterior margin. Second pedipalpal segment without a knob (ventral apophysis), and with a large seta ( Fig. 3 B). Third pedipalpal segment short, half of the second segment’s length. Telofemora foveate. Tibia and telofemur of all legs almost equal in length; length­width ratio in tibia and telofemur I 1.6 and 1.4, respectively ( Fig. 1 C). Telofemur II about as long as tibia II ( Fig. 1 D). Tarsus II twice as long as wide. Tibia I, III, and IV (figs. 1 E–F) about 1.8 times longer than wide. Telofemora I, II, III, and IV about 1.3 times longer than wide. Trochanters II, III, and IV almost as long as telofemora of respective legs.

Leg chaetotaxy: leg I: 1, 2, 2, 4, 5, 6; leg II: 1, 2, 3, 4, 5, 6; leg III: 1, 1, 2, 3, 5, 5; leg IV: 1, 1, 2, 3, 5, 5. Ventral spine of tibia I long and tapering. Spine on tibia II bipectinate. Median claw on tarsus I large. Lateral claws on posterior legs long, with a palmate accessory process with 6–8 minute teeth ( Fig. 3 C). Pecten absent from the margins of shaft claws. Tarsus I with a tapering ventral spine, a pair of long parambulacral setae and three dorsal setae, tarsus II with two parambulacral setae. Ventral setae of tibia II nearly pectinate, ventral setae of tibiae III and IV smooth.

Male: Idiosoma 242 m long, 145 m wide. Dorsal plates similar in outline though slightly longer than in female. AD 123 m long, 71 m wide; OC 35 m long, 12 m wide. PD 119 m long, 69 m wide. Ventral idiosoma: GA 109 m long, 76 m wide. Two pairs of outlying setae on GA and 9–10 pairs of pgs closely surrounding GO ( Fig. 3 A). Leg chaetotaxy: leg I: 1, 2, 2, 4, 5, 6; leg II: 1, 2, 3, 4, 5, 6; leg III: 1, 1, 2, 3, 5, 5; leg IV: 1, 1, 2, 3, 5, 5.

Deutonymph: Idiosoma 244 m long, 164 m wide. AD 102 m long, 69 m wide. PD 59 m long, 52 m wide. OC 23 m long, 9 m wide. GA 28 m long, 35 m wide. OC without ds­2, and ds­3 outside of AD ( Fig. 2 A). Tibia I narrower than that of female. Leg chaetotaxy ( Figs. 2 D–G): leg I: 1, 2, 2, 4, 5, 6; leg II: 1, 2, 3, 4, 5, 6; leg III: 1, 1, 2, 3, 5, 5; leg IV: 1, 1, 2, 3, 5, 5.

Larva: Idiosoma 113 m long, 68 m wide. Plates less developed than in adults, with similar but smaller ornamentation ( Fig 3 D). AD length twice that of PD, ds­2 outside of OC. AE large, more than half as long as idiosoma. Leg chaetotaxy: leg I: 1, 3, 4, 5, 6; leg II: 1, 5, 4, 5, 6; leg III: 1, 3, 3, 5, 5.

Etymology: Named for Dr. Cristina Cramer of the National Autonomous University of Mexico in recognition of her research on the aquatic mite fauna of Mexico.

Remarks: Simognathus cramerae resembles S. similis from the Galapagos Islands more closely than any other species. Most of the morphological structures of the new Mexican species are similar to this South American species. These features include the ocular plates, as well as the ornamentation on plates and leg telofemur. Notable differences include the setae which lie outside the ocular plate in S. cramerae , and on it in S. similis . Likewise, ds­3 is located on the AD plate in S. cramerae , and outside of this plate in S. similis . P2 of the new species has a ventral bristle similar to that of S. similis and S. areolatus from Chile, but without being borne on a knob (the ventral apophysis). The setal pattern of the Mexican species is shared with S. areolatus , but the ornamentation of the latter is quite distinctive, differing from that of S. cramerae with the P2.

Newell (1984) designated six species ( S. obtusus , S. subobtusus , S. areolatus , S. magellanicus , S. hulingsi , and S. pectinatus ) from South America as “group 1” based on a shared suite of features. The Mexican species described here shares several of these characters, specially with S. hulingsi , in which only the location of ds­2, the number of the minute teeth on claw processes, the size of the idiosoma, and the form of the anterior margin of PD are different. The ornamentation with foveae on the telofemur of S. cramerae is very similar to that of S. coreensis Chatterjee & Young Chang, 2004 from Korea. However, the two species differ in the position of ds­2, the width of AD and PD, and the number of minute teeth on the claw processes.

Also S. cramerae sp. nov. is closely with S. fuscus Viets and S. euphractus Pepato & Gonçalvez­Tiago , both cited from American Atlantic. These three species have the ds­2 outside of OC and similar ornamentation of dorsal plates, however S. fuscus and S. euphractus have a knob (ventral apophysis) on P2, which S. cramerae does not have. S. euphractus has two ventral setae on tarsus IV and S. cramerae only has one; S. fuscus has OC rounded in the terminal portion and in S. cramerae it is pointed, the tibia and tarsus are narrower in S. fuscus than in S. cramerae , and the number of minute teeth of claws in S cramerae (6–8) is smaller than in S. fuscus (10–14).

Figures

FIGURE 1. Simognathus cramerae sp. nov.: A, Idiosoma of female, dorsal view. B, Idiosoma of female, ventral view. C, gnathosoma. D, Leg I of female. E, Leg II of female. F, Leg III of female. G, Leg IV of female. Scale bars: 50 m.

FIGURE 2. Simognathus cramerae sp. nov. A, Idiosoma of deutonymph, dorsal view. B, Idiosoma of deutonymph, ventral view. C, Gnathosoma of deutonymph. D, Leg I of deutonymph. E, Leg II of deutonymph. F, Leg III of deutonymph. G, Leg IV of deutonymph. Scale bars: 50 m.

FIGURE 3. Simognathus cramerae sp. nov.: A, Genitoanal plate of male. B, Pedipalp of male, lateral view. C, Tarsus III of male. D, Idiosoma of larva, dorsal view. Scale bars: 50 m.