Alismobates inexpectatus, Pfingstl, Tobias & Schuster, Reinhart, 2012

Pfingstl, Tobias & Schuster, Reinhart, 2012, First record of the littoral genus Alismobates (Acari: Oribatida) from the Atlantic ocean, with a redefinition of the family Fortuyniidae based on adult and juvenile morphology, Zootaxa 3301, pp. 1-33 : 3-11

Alismobates inexpectatus sp. nov.

Type material - Holotype: female, Bermuda, Tobacco Bay, upper intertidal zone, rocks covered with mats of algae; 17/07/1981, R. Schuster leg. (Be-108=sample number in the collection R.S.). Paratypes: 4 females and 4 males, same locality as holotype. Deposition of holo- and paratypes: Senckenberg Museum für Naturkunde Görlitz, Germany (Collection Nr. 81/47300).

Etymology. About 30 years ago, when he discovered F. atlantica on Bermuda ( Krisper & Schuster 2008), Schuster also collected specimens of another unknown species. He regarded these specimens to be individuals of a new selenoribatid species but did not pay further attention to it as he focused on the sexually dimorphic F. atlantica . Decades later, when Schuster was told that he had found at that time a new Alismobates species, he was very surprised. He did not expect a further fortuyniid species to be present on the archipelago of Bermuda, therefore the name refers to the Latin word “ inexpectatus ” meaning unexpected.

Diagnosis. Dark brown sclerotized mites. Habitus typical for the genus Alismobates . Average length 366 µm, mean width 246 µm. Notogaster oval in shape. No conspicuous sexual dimorphism in notogastral setation, porose areas, anogenital region and features of the legs; there is only the common sexual dimorphism in overall body size, with females being generally slightly larger. Van der Hammen’s Organ well developed, but diverging from Fortuynia typical pattern. Sensillus clavate, spinose. One pair of large cuticular ridges in position of prodorsal lamellae. Interlamellar setae minute. Lenticulus large, variable in shape. Areas flanking lenticulus conspicuously granular. Fourteen pairs of short and simple, notogastral setae, associated with small porose areas. Four pairs of single pores medially on notogaster and one pair of four semicircular grouped pores on posterior gastronotic region. Epimeral setation 3-1-2-2. Four pairs of genital setae. One pair of aggenital setae. Three pairs of adanal setae. Two pairs of anal setae. Legs monodactylous with large claw. Porose areas on trochanters III and IV and all femora. Leg setation (chaetome, solenidia): Leg I 0- 4 -2-3-18, 1-2-2; leg II 0- 4 -2-3-15, 1-1-1; leg III 1-3-1-3-15, 1- 1-0; leg IV 1-2-2-3-12, 0-1-0. Juveniles plicate with large foveate centrodorsal plate.

Description of adult. Females (N=17), length: 360–391μm (mean 375 μm), width: 240–253 µm (mean 249 µm); males (N=21), length: 347–372 μm (mean 356 μm), width: 235–249 µm (mean 242 µm)

Integument. Colour ranging from dark brown to nearly black. Cuticle appears shiny, but finely granulate under dissecting microscope.

Prodorsum. Cerotegument finely granular, larger granules next to anterior notogastral border. Rostrum rounded in dorsal view, but slightly projecting anteroventrally in lateral view. Whole rostrum clearly demarcated from remainder of prodorsum by an obvious transverse ridge. A 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 a clear straight edge. A further single and nearly elliptic median area of thickened cuticle between lamellar setae. Rostral setae (ro) strong, simple and dorsally slightly barbed. Lamellar setae (le) simple, short and smooth. Interlamellar setae (in) minute. One pair of very short and fine exobothridial setae (ex). Bothridia cup-like with a lateral incision, strongly projecting, orifice narrow and circular. Sensilla of normal length, slightly clavate, distally spinose. An elliptic plate-like cuticular ridge dorsally adjacent to base of bothridium, covering dorsosejugal suture over a short distance.

Gnathosoma. Pedipalp ( Figure 1 A) pentamerous 0-2-1-3-9 (including solenidion), trochanter very short, femur by far longest segment, genu, tibia and tarsus of almost equal length. Solenidion ω on palptarsus erect, not associated with eupathidium acm. Chelicerae ( Figure 1 B) chelate, mobile digit slightly darker sclerotized, with three small, blunt but distinct teeth, whereas from frontal view most distal teeth split into two symmetrical teeth; fixed digit with two teeth, all teeth interlocking. Large lateral porose area from middle of chelicerae to joint of digits. Seta cha and chb of approximately the same length, both dorsally slightly pectinate. Trachea reaching into anterior part of chelicera. Gena well sclerotized but finely porose. Distal part of rutellum developed as thin triangular slightly curved inward membrane ( Figure 1 C). Seta a and m long, robust and smooth. Mentum regular, seta h simple, thin and of normal length.

Gastronotic region ( Figure 2A ). Conspicuously rounded, anterior notogastral margin distinct. Cerotegument mainly finely granular, but showing conspicuously larger granules in areas flanking median light spot. Lenticulus developed as large anterior median light spot with irregular borders. Shape of lenticulus highly variable, from rectangular to square. Fourteen pairs of relatively short and simple notogastral setae, c1-2, da, dm, dp, la, lm, lp, h1-3, p1- 3; seta c3 absent. Small circular porose areas associated with bases of all notogastral setae. Additionally 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 a series of four pores arranged in a semicircular median row. No difference in the arrangement of these pores between the sexes. Five pairs of notogastral lyrifissures present; ia next to seta c2 close and rectangular to anterior notogastral border; im slightly anterior and laterad of seta lm; ih between seta h2 and h1; lyrifissures ip and ips laterally of seta p3 and p2 respectively. Orifice of opisthonotal gland (gla) laterally between setae lm and lp.

Lateral aspect ( Figure 2 B). Cerotegument generally finely granular, larger granules in areas surrounding acetabula. Tutorium present, anterior part a ventrad curved bulge, posterior part fused with prodorsal lateral ridge. Pedotectum I weakly developed, only slightly projecting. Pedotectum II a minute plate-like ridge. Discidium not conspicuously expressed. Van der Hammen’s Organ modified, consisting of a system of four combined parts (Figure 3A): First and major part (1), a large canal connected with the outside only by a small slit, starts at the lateral part of dorsosejugal suture, passes posterior of bothridium and runs ventrad to area between acetabulum II and III, where it diverges into an anterior and posterior branch. Second and smallest part (2) consisting of a short channel connecting lateral incision of bothridium with the above mentioned main canal. Third part (3) is the anterior lateroventral branch passing acetabulum II posteriorly and curving on the ventral side anteriorly into a distinct longitudinal canal reaching ventral tip of pedotectum I where it opens in acetabulum I. Fourth part (4) is the posterior branch, represented by a deepened broad groove running caudad passing dorsally acetabulum III and ending at acetabulum IV. Stigma of acetabular trachea III situated in ramification of part one, three and four ( Figure 4 ).

Ventral region of idiosoma ( Figure 2 C). Cerotegument in sternal region finely granular, larger granules laterally next to acetabula and on most posterior part of ventral plate. Epimeral setation 3-1-2-2, all setae simple and smooth. Seta 1b about a third longer than other setae. Seta 1c close to pedotectum I, laterad of ventral longitudinal channel of van der Hammen’s Organ. Internal borders of all epimera well visible, sternal apodemes II, III and IV well developed. Genital and anal opening closely adjacent, both surrounded by strongly sclerotized cuticle. Rounded genital plates with four pairs of fine and simple genital setae. First and longest pair near medial margin of valves, second and fourth pair median on plates and third pair close to lateral margin of valves. Laterad of genital opening a circular spot of thickened cuticle. One pair of simple aggenital setae ag. Anal valves nearly triangular, median margins slightly overlapping. Outer part of preanal organ triangular with rounded edges, inner part shaped like a broad transverse bar. Two pairs of short and simple anal setae, an1-2, arranged in a longitudinal row. Three pairs of short and simple adanal setae, ad3 laterad of anterior third of anal plates, ad2 near posterior third of anal valves and ad1 posterior of anal opening. Lyrifissure iad orientated longitudinally and flanking posterior third of anal plates. Thickened cuticle on posterior part of ventral plate, clearly delimitated from anterior thinner cuticle by two concave symmetric arches next to anal opening.

Legs ( Figure 5 ). Monodactylous. Long, strong hook-like claws. 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 without ventral carina. Cerotegument generally finely granular, larger granules only on distal third of all femora. All tarsi with proximal lyrifissure. Large irregularly shaped porose areas on ventral paraxial side of femur I and II, porose areas on proximal part of femora III and IV divided in a large dorsal and a smaller ventral part, kidney-shaped porose areas on paraxial dorsal aspect of trochanters III and IV. Dorsal seta d on all femora slightly thickened and dorsally serrate. Lateral setae of all genua short, broadened and slightly serrate. Ventral setae of all tibiae and tarsi, long and ventrally strongly serrate. Solenidia ϕ 1-2 on tibia I borne on small apophysis. Chaetome and solenidia see table 1.

Common features of juvenile stages. Apheredermous. Colour dark brown. Integument plicate and soft, except for centrodorsal plate ( Figure 6 ). Prodorsum triangular, anterior part finely granular, rostrum rounded. Rostral (ro) and lamellar setae (le) short and simple. One pair of short exobothridial setae (ex) and minute interlamellar setae (in). Sensilla of normal length clavate and distally spinose. Bothridia cup-like, laterally opened. Medially on posterior border of prodorsum groups of distinct pores leading into fine tracheal tubes ( Figure 7 A); these structures are difficult to detect as in dorsal view they are hidden beneath anterior folds of gastronotic region. Gnathosoma no obvious differences to adult stage. Hysterosoma slightly convex. Hysterosomal cupules not traceable in any stage. Large, foveate and stronger sclerotized centrodorsal plate bearing all notogastral setae, except for c 1-3 in all stages and seta h 2 in the larval stage. Lateral borders of plate straight, anterior border slightly convex, posterior border strongly convex. In nymphal stages posterior part of this plate showing a median lesser sclerotized and slightly concave conspicuous area without foveae resembling an inverted Y. Two parallel longitudinal rows of slightly darker pigmented spots on centrodorsal plate, whereas these spots are hardly discernable in most of the specimens. Large folds framing centrodorsal plate completely, showing fine granular surface. Within the lateral folds at least four hardly discernable pores on a level with acetabulum III and a series of further pores (number is hard to determine) aligned longitudinally. Orifice of opisthonotal gland (gla) located in posterior third of lateral folds. Small circular or elliptic porose areas associated with bases of all notogastral setae. Ventral sejugal suture developed as distinct furrow, posterior border medially opened over a short distance. Integument surrounding anal area folded. In nymphal stages no distinct genital sclerites developed, genital opening only a thin longitudinal slit, inner margins showing small granules. Anterior to genital area a slightly rostrad arched large furrow showing conspicuous granules. Nymphs with two distinct slightly curved furrows posterior of genital area, reaching from acetabulum IV to anterior end of anal opening, where they pass into distinct folds framing anal orifice. Within these furrows posterior of genital opening, fine cuticular pores. Anal area conspicuously finely granular. Legs monodactylous. Dorsal setae of tibiae and genua absent when respective solenidion present. Solenidia on tibia I borne on small apophysis. Large porose areas on ventral paraxial side of femora I and II and on dorsal paraxial side on femora III and IV. Circular porose areas on paraxial dorsal side of trochanters III and IV.

Instars Trochanter Femur Genu Tibia Tarsus Chaetome Solenidia

Leg I larva - d, bv´´(l), σ (l), v´,ϕ1 (pl), (pv), s, (a), (u), (p), (tc), (ft),?, ω1 0-2-2-3- 16 1-1-1 protonymph - l ´- - ω2 0-3-2-3- 16 1-1-2 deutonymph - l ´´ - ϕ2 - 0-4-2-3- 16 1-2-2 tritonymph - - - - (it) 0-4-2-3- 18 1-2- 2 adult - - - - - 0-4-2-3- 18 1-2-2

Leg II larva - d, bv´´(l), σ l´, v´, ϕ (pv), s, (a), (u), (p), (tc), (ft), ω 0-2-2-2- 13 1-1-1 protonymph - l ´- - - 0-3-2-2- 13 1-1-1 deutonymph - l ´´ - - - 0-4-2-2- 13 1-1-1 tritonymph - - - l ´´ (it) 0-4-2-3- 15 1-1- 1 adult - - - - - 0-4-2-3- 15 1-1-1

Leg III larva - d, ev´l´, σ v´, ϕ (pv), s, (a), (u), (p), (tc), (ft) 0-2- 1-1-13 1 -1-0 protonymph - - - - - 0-2- 1-1-13 1 -1-0 deutonymph v ´- - - - 1-2- 1-1-13 1 -1-0 tritonymph - - - - (it) 1-2- 1-1-15 1 -1-0 adult - l ´- (l) - 1-3- 1-3-15 1-1 -0

Leg IV protonymph - - - - (pv), (u), (p), ft´´0-0-0-0-7 0-0-0 deutonymph - d, ev´d, l´v´, ϕ s, (a), (tc) 0- 2 -2-1-12 0-1-0 tritonymph v ´- - - - 1-2-2-1-12 0-1-0 adult - - - (l) - 1-2-2-3-12 0-1-0 Larva. Length (N=10): 160–197 μm (mean 176 μm)

Gastronotic region ( Figure 8A ). Eleven pairs of slightly thickened and slightly serrate notogastral setae; c1-3, da, dm, dp, la, lm, lp, h1-2; h3 absent. Conspicuous transverse ridge on centrodorsal plate passing posterior line of setae dm and lm.

Ventral region of idiosoma ( Figure 8 B). Epimeral setation 3-1-2, epimeral setae of normal length, thin and simple, except for seta 1c shaped valve-like protecting Claparède organ. Cuticle framing the latter anteromedially thickened and slightly projecting. Integument posterior of ventral sejugal furrow with a few inconspicuous transversal folds.

Legs. Setation and solenidia see table 1.

Protonymph. Length (N=24): 200–262 μm (mean 237 μm)

Gastronotic region ( Figures 8 C, 9). Fifteen pairs of notogastral setae; c1-3, da, dm, dp, la, lm, lp, h1-3 and p1-3, all setae lesser thickened from this stage. Transverse ridge on centrodorsal plate passing posterior line of setae dm and lm absent from this stage.

Ventral region of idiosoma ( Figure 8 D). Epimeral setation 3-1-2-1. Seta 1c developed as normal seta, next to trochanter I, seta 4a close to trochanter IV. One pair of short genital setae. Aggenital setae absent. Legs ( Figure 10 ). Chaetome and solenidia see table 1.

Deutonymph. Length (N=31): 262–311 μm (mean 287 μm).

Gastronotic region ( Figure 11A ). Fifteen pairs of notogastral setae, same positions and shapes as in protonymph.

Ventral region of idiosoma ( Figure 11 B). Epimeral setation 3-1-2-1. Two pairs of short genital setae arranged in a longitudinal row. One pair of simple and short aggenital setae ag. Three pairs of adanal setae ad1-3 flanking anal valves.

Legs ( Figure 12 ). Chaetome and solenidia see table 1.

Tritonymph. Length (N=16): 329–386 μm (mean 363 μm)

Gastronotic region ( Figure 11 C). Fifteen pairs of notogastral setae, no difference to deutonymph.

Ventral region of idiosoma ( Figure 11 D). Epimeral setation 3-1-2-2, seta 4b median on epimeral plate IV. Three pairs of short genital setae in a longitudinal row. One pair aggenital setae ag. Three pairs of adanal setae ad1- 3. Two pairs of anal setae an1-2, sometimes asymmetrical variation with three setae developed on only one valve (as shown in Figure 11 D).

Legs. Chaetome and solenidia see table 1.

Figures

FIGURE 1. Alismobates inexpectatus adult. A) right pedipalp paraxial view. B) right chelicera paraxial view. C) right rutellum ventral view.

FIGURE 7. Prodorsal pores in fortuyniid immatures. A) Alismobates inexpectatus. B) Fortuynia atlantica.

FIGURE 2. A. inexpectatus adult. A) dorsal view. B) lateral view. C) ventral view.

FIGURE 4. A. inexpectatus micrograph showing origin of acetabular trachea III. Latin numbers refer to leg segments.

FIGURE 5. A. inexpectatus adult legs antiaxial view. A) right leg I. B) left leg II. C) left leg III. D) left leg IV.

FIGURE 6. A. inexpectatus LM-micrographs. Scale bar: 50 µm. A) deutonymph dorsal view, layered from 19 images. B) deutonymph ventral view, layered from 7 images. C) protonymph lateral view, layered from 21 images.

FIGURE 8. A. inexpectatus. A) larva dorsal view. B) larva ventral view. C) protonymph dorsal view. D) protonymph ventral view.

FIGURE 10. A. inexpectatus protonymph left legs antiaxial view. A) leg I. B) leg II. C) leg III. D) leg IV.

FIGURE 11. A. inexpectatus. A) deutonymph dorsal view. B) deutonymph ventral view. C) tritonymph dorsal view. D) tritonymph ventral view.

FIGURE 12. A. inexpectatus deutonymph legs antiaxial view. A) left leg I. B) left leg II. C) right leg III. D) left leg IV.