Alismobates galapagoensis, Pfingstl, Tobias & Schatz, Heinrich, 2017

Pfingstl, Tobias & Schatz, Heinrich, 2017, New littoral mite species (Acari, Oribatida, Fortuyniidae) from the Galápagos archipelago, with ecological and zoogeographical considerations, Zootaxa 4244 (1), pp. 39-64 : 40-49

Alismobates galapagoensis sp. nov.

Fortuyniidae gen. sp. 1 in Schatz 1998, p. 384.

Type material. Holotype: Adult male, GAL 87-702: Isabela Island, Punta García, preserved in ethanol, deposited in the collections of the Senckenberg Museum für Naturkunde Görlitz ( SMNG) (DNR 56386) , Paratypes from the same sample, 1 male, 1 female, deposited in Naturhistorisches Museum Wien / NHM Vienna ( NHMW 28545 ), additional specimens in the collections of the authors.

Etymology. The specific name refers to the archipelago of Galápagos where the species was collected.

Diagnosis. Average length 364 µm, average width 240 µm. Notogaster rounded, oval in shape. Habitus typical for the genus Alismobates . Sensillus clavate, distally spinose. Lenticulus large with irregular lateral and posterior borders. Areas flanking lenticulus conspicuously granular. Van der Hammen’s Organ well developed, typical for the genus. Fourteen pairs of notogastral setae in adults, c3 absent; fifteen pairs in nymphs, c3 present. Epimeral setation 3-1-2-2. One pair of obvious longitudinal cuticular ridges on epimeron 3.

Description of adult. Females (N=22), length: 357–391 µm (mean 376 µm), width: 234–271 µm (mean 251 µm); males (N=36), length: 342–388 µm (mean 357 µm), width: 219–259 µm (mean 234 µm).

Integument. Colour dark brown.

Prodorsum ( Fig. 1 A). Cerotegument finely granular, slightly larger granules adjacent to anterior notogastral border. Rostrum rounded in dorsal view, slightly projecting anteroventrally in lateral view; demarcated from remainder of prodorsum by conspicuous transverse ridge. Rostral seta (ro) setiform, smooth (approx. 20 µm), lamellar seta (le) thin, shorter (approx. 15 µm). Pair of two slightly converging, thickened and broad cuticular ridges in position of prodorsal lamellae, borders of these ridges shaped irregularly except for lateral aspects showing clear straight edge. Interlamellar seta (in) thin, short (approx. 8 µm), almost spiniform with sharp tip, exobothridial seta (ex) minute. Bothridium small cup-like with very narrow orifice and lateral incision. Sensillus of normal length, clavate, distally spinose.

Gnathosoma. Typical for the genus. Palp pentamerous 0-2-1-3-8 (solenidion not included). Solenidion ω on tarsus erect, not associated with eupathidium acm. Large porose area on paraxial ventral side of femur. Chelicera chelate, movable digit slightly darker sclerotized, with three small, blunt but distinct teeth, fixed digit with two teeth, all teeth interlocking. Setae cha and chb of approximately same length, both dorsally slightly pectinate. Gena well sclerotized and finely granular. Distal part of rutellum developed as thin triangular membrane, slightly curved inward with longitudinal incision. Setae a and m long (approx. 28 µm), smooth. Mentum regular, finely granular, seta h simple and of normal length (approx. 16 µm).

Gastronotic region ( Fig. 1 A). Notogaster oval in dorsal view. Cerotegument basically finely granular; larger granules flanking lenticulus laterally and irregularly shaped granules and lines posterior of lenticulus and larger but indistinct bumps on lateral and posterior face of notogaster. Lenticulus large with irregular lateral and posterior borders. Fourteen pairs of thin, simple notogastral setae (length 17-25 µm), c1-2, da, dm, dp, la, lm, lp, h1-3, p1-3; c3 absent. Five pairs of notogastral lyrifissures present; ia next to seta c2, im posterior and laterad of seta la, ih laterally, ip laterad and anterior of seta p3 and ips next to p2. Orifice of opisthonotal gland gla laterally, between seta lm and lp. Four pairs of single pores arranged in two median parallel rows. First pair posterior c1, second posterior da, third posterior dm and fourth posterior dp. Next to seta h2 series of four pores arranged in semicircular median row. No sexual dimorphism in the arrangement of these pores.

Lateral aspect ( Fig. 1 C). Cerotegument finely granular, larger granules on pedotectum I and in acetabular regions. Tutorium (tut) present, anterior part ventrad curved bulge, posterior part fused with prodorsal lateral ridge. Pedotectum I present, round, small. Cuticular canals of van der Hammen’s organ typical for genus Alismobates (see Pfingstl & Schuster 2012).

Ventral region of idiosoma ( Fig. 1 B). Cerotegument finely granular in sternal region, larger granules laterally next to acetabula. Epimeral setation 3-1-2-2, all setae thin, smooth (approx. 15 µm). Conspicuous longitudinal ridge on epimeron III close to acetabulum 3 ( Fig. 16 A). Apophyse b well visible as dark dot. Four pairs of fine genital setae, 1 pair of aggenital setae, all of same length (approx. 12 µm). Anal valves nearly triangular, 2 pairs of anal setae an1-2 (approx. 15 µm). Outer part of preanal organ triangular, inner part shaped like broad transverse bar. Three pairs of simple adanal setae an1-3 (approx. 15 µm). Lyrifissure iad orientated longitudinally, flanking posterior third of anal orifice. Genital and anal opening closely adjacent, both surrounded by strongly sclerotized cuticle. Laterad of genital opening large circular area of thickened cuticle.

Legs ( Fig. 2 ). Monodactylous. Long hook-like claws. Cerotegument granular, conspicuously larger granules on femora. Cuticle heterogeneous, trochanters dark, proximal third of femur I and II light, remainder dark, femora III and IV dark, all genua dark, all tibiae light and proximal part of all tarsi only slightly darker than distal part.

Femora with small ventral carinae. Large porose areas on paraxial aspect of femora I and II, femora III and IV with narrow, elongate porose areas on paraxial dorsal side. Kidney-shaped porose area on dorsal paraxial face of trochanter III and IV. All tarsi with proximal lyrifissure. Most setae slightly serrate. Chaetome and solenidia as shown in Table 1.

Sexual dimorphism. Females of A. galapagoensis sp. nov. slightly larger, most of them bearing one or two large eggs. Apart from adult size, no external sexual dimorphism could be observed.

Common features of juvenile stages. Apheredermous. Colour brown. Integument plicate and soft, except for centrodorsal plate. Habitus typical for the genus (see Pfingstl & Schuster 2012). Prodorsum triangular, anterior part finely granular, rostrum rounded. Rostral (ro) and lamellar setae (le) short. Interlamellar seta (in) very short, exobothridial seta (ex) minute. Sensillus clavate, distally spinose. Bothridium cup-like, laterally opened. Hysterosoma slightly convex. Large, slightly foveate and stronger sclerotized centrodorsal plate. In nymphal stages posterior median area of this plate lesser sclerotized resembling an inverted Y. Small circular or elliptic porose areas associated with bases of all notogastral setae. Cerotegument of ventral aspect basically finely granular, larger granules in acetabular regions and ventral furrows. Ventral furrows typical for genus. In nymphal stages no distinct genital sclerites developed, genital opening thin longitudinal slit, inner margins showing small granules. Respiratory system typical for genus. Legs monodactylous. Porose areas present in all immature stages showing same relative size and positions as in adults. Development of leg chaetome shown in Table 1.

Larva. Length (N=2): 172–188 µm (mean 180 µm).

Gastronotic region ( Fig. 3 A). Eleven pairs of notogastral setae; c1-3, da, dm, dp, la, lm, lp, h1-2; h3 absent; dm, dp and h1 slightly thickened and serrate. Transverse ridge on centrodorsal plate passing posterior line of setae dm and lm.

Ventral region of idiosoma ( Fig. 3 B). Epimeral setation 3-1-2, epimeral setae of normal length, thin and simple, except for seta 1c minute, valve-like protecting Claparède’s organ cla.

Protonymph. Length (N=4): 225–237 µm (mean 233 µm).

Gastronotic region ( Fig. 3 C). Fifteen pairs of notogastral setae; c1-3, da, dm, dp, la, lm, lp, h1-3 and p1-3, all setae simple and thin from this stage.

Ventral region of idiosoma ( Fig. 3 D). Epimeral setation 3-1-2-1. Seta 1c next to trochanter I, seta 4a close to trochanter IV. One pair of short genital setae. Aggenital setae absent.

Deutonymph. Length (N=4): 277–303 µm (mean 287 µm).

TABLE]. Alismobates galapagoensis sp. nov. Leg setation from larva to ađult. First đevelopment of setae characterizeđ by letters. () = pairs of setae, - = no change with regarđ preceđing stage.

Instars Trochanter Femur Genu Tibia Tarsus Chaetome Soleniđia

I larva - d, bv´´(l), σ (l), v´, φ1 (pl), (pv), s, (a), (u), (p), (tc), (ft), ε, ω1 θ-2-2- 3-ı 6 ı-ı-ı protonymph - l´ - - ω2 θ-3-2- 3-ı 6 ı-ı-2 ađult - - - l ´, v´´- ı-2-2 - 3-ı 2 θ-ı-θ

Gastronotic region ( Fig. 4 A). Fifteen pairs of notogastral setae, same positions and shapes as in protonymph. Ventral region of idiosoma ( Fig. 4 B). Epimeral setation 3-1-2-1. Two pairs of short genital setae arranged in longitudinal row. One pair of setiform and short aggenital setae ag. Three pairs of adanal setae ad1-3 flanking anal valves. Vestiges of anal setae present on anal valves.

Tritonymph. Length (N=5): 325–350 µm (mean 341 µm).

Gastronotic region ( Figs 4 C, 5). Fifteen pairs of notogastral setae, no difference to deutonymph.

Ventral region of idiosoma ( Fig. 4 D). Epimeral setation 3-1-2-2, seta 4b median on epimeral plate IV.

Three pairs of short genital setae in longitudinal row. One pair aggenital setae ag. Three pairs of adanal setae ad1-3. Two pairs of anal setae an1-2.

Legs are shown in Fig. 6 .

Records on the Galápagos Islands: Alismobates galapagoensis sp. nov. is known from 262 adult and 107 juvenile specimens collected on six islands of the Galápagos archipelago. Specific collection data: GAL 85-137: 3 ad., GAL 85-138: 122 ad., 24 juv., GAL 87-413: 1 juv., GAL 87-424: 4 ad., GAL 87-431: 6 ad., 5 juv., GAL 87- 432: 3 ad., 3 juv., GAL 87-476: 55 ad., 15 juv., GAL 87-477: 1 ad., GAL 87-701: 2 ad., GAL 87-702: 66 ad., 58 juv., GAL 88-810: 1 juv., GAL 88-840: 1 ad.

Figures

FIGURE 1. Alismobates galapagoensis sp. nov. adult. A—dorsal view; B—ventral view, distal segments of legs omitted; Clateral view.

FIGURE 2. Alismobates galapagoensis sp. nov. adult. A—right leg I, slightly oblique, antiaxial view; B—left leg II, paraxial view; C—left leg III, antiaxial view; D—left leg IV, antiaxial view.

FIGURE 3. Alismobates galapagoensis sp. nov. juveniles. A—larva, dorsal view; B—larva, ventral view; C—protonymph, dorsal view; D—protonymph, ventral view.

FIGURE 4. Alismobates galapagoensis sp. nov. juveniles. A—deutonymph, dorsal view; B—deutonymph, ventral view; Ctritonymph, dorsal view; D—tritonymph, ventral view.

FIGURE 6. Alismobates galapagoensis sp. nov. tritonymph, legs antiaxial view. A—right leg I; B—right leg II; C—left leg III; D—left leg IV.

FIGURE 16. Photographs of left ventral epimeral region of adults showing the most distinctive feature for species delineation. A— Alismobates galapagoensis sp. nov.; B— Alismobates inexpectatus. Arrow pointing to short longitudinal ridge only present in A. galapagoensis sp. nov.; g = genital valve; scale bars 60 µm.