Litoribates caelestis, 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 : 49-58

Litoribates caelestis sp. nov.

Fortuyniidae gen. sp. 2 in Schatz, 1998, p. 384.

Type material. Holotype: Adult female, sample GAL 88-824: Santa Cruz Island, Academy Bay, Puerto Ayora , preserved in ethanol, deposited in the collections of the Senckenberg Museum für Naturkunde Görlitz ( SMNG) (DNR 56387), 2 Paratypes (1 female, 1 male) from same sample, deposited in Naturhistorisches Museum Wien / NHM Vienna ( NHMW 28546 ), additional specimens in the collections of the authors.

Etymology. The generic name is composed of the Latin word “ litus ”, which means coast or seashore and refers to the marine associated lifestyle of these animals, and the word “ oribates ”, standing for moss mite. The species name is derived from the Latin word “ caelestis ” (given as noun in apposition) meaning celestial, heavenly and refers to the notogastral surface structure, which resembles more or less a drawn star chart.

Diagnosis. Brown sclerotized mites. Average length 322 µm, average width 203 µm. Notogaster rounded, almost circular in dorsal view. Prodorsum with slender lamellar ridges. Sensillus slightly fusiform, pectinate, long (approx. 60 µm). Notogastral cerotegument with specific reticulate pattern. Sternal longitudinal ridge present, interrupted by three gaps. Legs with large sickle-shaped claw.

Description of adult. Females (N=10), length: 319–342 µm (mean 329 µm), width: 200–214 µm (mean 208 µm); males (N=10), length: 307–323 µm (mean 315 µm), width: 191–206 µm (mean 198 µm).

Integument. Colour brown.

Prodorsum ( Fig. 7 A). Cerotegument granular, smaller granules next to anterior notogastral border. Rostrum nearly triangular in dorsal view, slightly projecting anteroventrally in lateral view. Rostrum demarcated from remainder of prodorsum by obvious transverse ridge. Pair of two converging, slender lamellar ridges in slightly lateral position, reaching from bothridium to lamellar seta. Rostral seta (ro) robust, setiform, smooth (approx. 15 µm). Lamellar seta (le) simple, short and smooth (approx. 7 µm). Interlamellar seta (in) simple (approx. 12 µm), exobothridial seta (ex) minute. Sunk bothridium, i.e. not strongly protruding, borders not clearly defined; orifice narrow and circular. A semicircular depression directly anterior of bothridium. Sensillus long (approx. 60 µm), slightly fusiform and distally pectinate.

Gnathosoma. Palp ( Fig. 8 A) pentamerous 0-2-1-3-8 (solenidion not included), trochanter very short, femur by far longest segment, genu, tibia and tarsus of almost equal length. Large porose area on ventral paraxial face of femur. Solenidion ω on palptarsus not associated with eupathidium acm. Chelicera ( Fig. 8 B) chelate, mobile digit darker sclerotized; distinct teeth all interlocking. Seta cha and chb of approximately the same length (approx. 15 µm), both dorsally slightly pectinate. Gena well sclerotized. Distal part of rutellum developed as thin triangular membrane, slightly curved inward ( Fig. 8 C), with longitudinal incision. Setae a and m long (approx. 20 µm), robust and smooth. Mentum regular, seta h simple, thin (approx. 15 µm).

Gastronotic region ( Fig. 7 A). Conspicuously rounded in dorsal view, convex in lateral view; anterior notogastral margin distinct, forming a slightly overhanging bulge. Dorsal plate slightly depressed medially and laterally. Cerotegument with obvious ornamentation; central notogastral area with large granules connected randomly by small lines, resulting in more or less reticulate overall pattern (see etymology of species name) ( Fig. 9 A); lateral and posterior areas with smaller granules ( Fig. 9 B). Lenticulus nearly rectangular with slightly irregular borders. Two short irregular longitudinal ridges flanking lenticulus on anterior notogastral border on a level with bothridia, covering lyrifissure ia in dorsal view. Fourteen pairs of relatively short and setiform notogastral setae (8–23 µm), c1-2, da, dm, dp, la, lm, lp, h1-3, p1-3; seta c3 absent. Five pairs of notogastral lyrifissures present; ia next to seta c2, hidden under cuticular ridge in dorsal view; im slightly anterior and laterad of seta lm; ih laterad and anterior to h3; lyrifissures ip and ips laterally of seta p3 and p2 respectively. Orifice of opisthonotal gland (gla) not traceable due to prominent cerotegument structure.

Lateral aspect ( Fig. 7 C). Cerotegument basically finely granular, larger granules in areas surrounding acetabula. Pedotectum I small rounded, only slightly projecting. Pedotectum II absent. Discidium present, inconspicuous. Van der Hammen’s organ present; consisting of four main channels ( Fig. 10 ): (1) canal s starting at the lateral part of dorsosejugal suture, passing posterior of bothridium underneath a cuticular bulge and running ventrad to area between acetabulum II and III, where it diverges into channel e and t; (2) channel t short running to acetabulum III; (3) channel e passing acetabulum II posteriorly and curving ventrally into longitudinal part reaching ventral tip of pedotectum I where it opens in acetabulum I; (4) channel c connecting acetabulum I with camerostome. Short canal running from bothridial orifice b ventrally, fading close to channel s; not discernable if connected with channel s. The latter has small posterior internal opening leading into large sacculus sac.

Ventral region of idiosoma ( Fig. 7 B). Cerotegument in sternal region finely granular, larger granules laterally next to acetabula and in areas surrounding genital and anal opening. Epimeral setation 3-1-2-2, all setae setiform and smooth. Setae 1b and 3a longest (22–27 µm), others shorter (7–10 µm). Internal borders of all epimera well visible. Sternal apodemes forming strongly sclerotized longitudinal protruding ridge, which is interrupted at each transition from one epimeral segment to other; first gap between epimeron I and II, second between epimeron II and III and third between epimeron III and IV ( Fig. 9 C). Slightly round and stronger sclerotized bulge posterior to acetabulum III. Genital and anal opening closely adjacent, both surrounded by slightly darker cuticle. Rounded genital plates with four pairs of fine filiform setae (approx. 7 µm). First pair near medial margin of plates, second and fourth pairs median on plates and third pair close to lateral margin of plates. Apophyse b well visible as dark dot laterad of genital orifice. One pair of setiform aggenital setae ag. Anal valves triangular. Outer part of preanal organ rectangular with rounded edges, inner part shaped as transverse bar. Two pairs of short anal setae, an1-2 (approx. 5 µm), in a longitudinal row. Three pairs of short adanal setae, ad1-3 (approx. 5 µm). Lyrifissure iad oblique, flanking posterior third of anal plates.

Legs ( Fig. 11 ). Monodactylous. Long, strong hook-like claws. Trochanter III and IV with obvious dorsal spur. Femoral carinae on legs I and II absent. All genua with ventral transversal ridge. Cerotegument generally finely granular, larger granules only on distal third of all femora. All tarsi with proximal lyrifissure. Large irregularly shaped porose area on ventral paraxial side of femur I and II, elongated proximal porose area on paraxial dorsal face of femur III and IV, kidney-shaped porose areas on paraxial dorsal face of trochanter III and IV. Dorsal seta d on all femora slightly thickened and dorsally serrate. Lateral setae of genu I and II short, broadened and slightly serrate. Ventral setae of all tibiae and tarsi, long and ventrally strongly serrate. Solenidia j1-2 on tibia I borne on small apophysis. For setation and solenidia, see Table 2 .

Sexual dimorphism. Females of L. caelestis 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 family. Prodorsum triangular, anterior part finely granular, rostrum rounded. Rostral (ro) and lamellar seta (le) short. Interlamellar seta (in) very short, exobothridial seta (ex) minute. Sensillus fusiform, distally pectinate. Bothridium small cup-like, laterally opened. Hysterosomal edges slightly convex. Centrodorsal plate large with uneven surface and semicircular median depression in posterior part. Larger cerotegumental granules in ventral furrows. Ventral furrows typical for the family (same pattern as in Fortuynia and Alismobates , e.g. Pfingstl & Schuster 2012). Epimeral seta 3a conspicuously longer than other setae in all immature stages. In nymphal stages no distinct genital sclerites developed, genital opening only a thin longitudinal slit, inner margins showing small granules. Respiratory system typical for the family ( Pfingstl & Krisper 2014). Legs monodactylous. Porose areas present in all immature stages showing same positions as in adults. For setation and solenidia, see Table 2 .

Larva. Length (N=4): 166–197 µm (mean 182 µm).

Gastronotic region ( Fig. 12 A). Eleven pairs of notogastral setae; c1-3, da, dm, dp, la, lm, lp, h1-2; h3 absent; lm, lp, 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. 12 B). Epimeral setation 3-1-2, epimeral setae of normal length, except for seta 1c minute, valve-like protecting Claparède’s organ cla.

Protonymph. Length (N=7): 215–231 µm (mean 222 µm).

Gastronotic region ( Fig. 12 C). Fifteen pairs of notogastral setae; c1-3, da, dm, dp, la, lm, lp, h1-3 and p1-3, all setae setiform and thin from this stage.

Instars Trochanter Femur Genu Tibia Tarsus Chaetome Soleniđia

Leg 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 Ventral region of idiosoma ( Fig. 12 D). Epimeral setation 3-1-2-1. Seta 1c developed normal, setiform, next to trochanter I, seta 4a close to trochanter IV. One pair of short genital setae. Aggenital setae absent.

Deutonymph. Length (N=6): 255–271 µm (mean 263 µm).

Gastronotic region ( Figs 13 A and 14). Fifteen pairs of notogastral setae, same positions and shapes as in protonymph.

Ventral region of idiosoma ( Fig. 13 B). Epimeral setation 3-1-2-1. Two pairs of short genital setae arranged in a longitudinal row. One pair of setiform short aggenital setae ag. Three pairs of adanal setae ad1-3 flanking anal valves.

Legs shown in Fig. 15 .

Tritonymph. Length (N=4): 292–319 µm (mean 305 µm)

Gastronotic region ( Fig. 13 C). Fifteen pairs of notogastral setae, no difference to deutonymph.

Ventral region of idiosoma ( Fig. 13 D). Epimeral setation 3-1-2-2, seta 4b median on epimeral plate IV.

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

Legs. Chaetome and solenidia see Table 2 .

Records on the Galápagos Islands: Litoribates caelestis sp. nov. is known from 425 adult and 186 juvenile specimens collected on two islands of the Galápagos archipelago. Specific collection data: GAL 85-137 : 2 ad., GAL 87-424: 31 ad., 1 juv., GAL 87-434: 189 ad, 59 juv., GAL 87-435: 1 ad., GAL 87-743: 1 ad., GAL 88-815: 3 ad., GAL 88-816: 2 ad., 3 juv., GAL 88-817: 1 juv., GAL 88-818: 1 juv., GAL 88-820: 29 ad., 24 juv., GAL 88- 821: 8 ad., 5 juv., GAL 88-822: 73 ad., 64 juv., GAL 88-823: 8 ad., 7 juv., GAL 88-824: 53 ad., 6 juv., GAL 88- G082: 23 ad. 16 juv.

Figures

FIGURE 7. Litoribates caelestis sp. nov. adult. A—dorsal view; B—ventral view, distal segments of legs omitted; C—lateral view.

FIGURE 8. Litoribates caelestis sp. nov. mouthparts. A—right pedipalp, antiaxial view; B—right chelicera, antiaxial view; C—right rutellum, ventral view.

FIGURE 9. Litoribates caelestis sp. nov. Adult, SEM-micrographs. A—cerotegument structure in central notogastral area; B—cerotegument structure in lateral notogastral regions; C—lateral view on acetabular and epimeral region, highlighting the grooved structure of median sternal area; arrowheads pointing to sternal gaps.

FIGURE 10. Litoribates caelestis sp. nov. adult, schematic depiction of “ Van der Hammen´s Organ ” in lateral view showing configuration of cuticular channels. b—bothridial channel, s—sejugal channel, e—epimeral channel, t—channel to acetabulum III, c—channel to camerostome, sac—sacculus, 1 — trachea I and 3 — trachea III.

FIGURE 11. Litoribates caelestis sp. nov. adult, legs antiaxial view. A—right leg I; B—right leg II; C—left leg III; D – left leg IV.

FIGURE 12. Litoribates caelestis sp. nov. juveniles. A—larva, dorsal view; B—larva, ventral view (legs III broken off); Cprotonymph, dorsal view; D—protonymph, ventral view.

FIGURE 13. Litoribates caelestis sp. nov. juveniles. A—deutonymph, dorsal view; B—deutonymph, ventral view; Ctritonymph, dorsal view; D—tritonymph, ventral view.

FIGURE 15. Litoribates caelestis sp. nov. deutonymph, legs. A—right leg I, antiaxial view; B—left leg II, paraxial view; Cleft leg III, antiaxial view; D – left leg IV, antiaxial view.

Tables

TABLE 2. Litoribates caelestis sp. nov. Chaetome anđ soleniđia from larva to ađult. First đevelopment of setae characterizeđ by letters. () = pairs of setae, - = no change with regarđ to preceđing stage.

	đeutonymph tritonymph ađult	- - -	l´´- -	- - -	φ2 - -	- (it) -	θ-4-2-3-ı6 θ-4-2-3-ı8 θ-4-2-3-ı8	ı-2-2 ı-2-2 ı-2-2
Leg II	larva protonymph đeutonymph tritonymph ađult	- - - - -	d, bv´´l´l´´- -	(l), σ - - - -	l´, v´, φ - - - l´´	(pv), s, (a), (u), (p), (tc), (ft), ω - - (it) -	θ-2-2-2-ı3 θ-3-2-2-ı3 θ-4-2-2-ı3 θ-4-2-2-ıƽ θ-4-2-3-ıƽ	ı-ı-ı ı-ı-ı ı-ı-ı ı-ı-ı ı-ı-ı
Leg III	larva protonymph đeutonymph tritonymph ađult	- - - v´-	d, ev´ - - - l´	l´, σ - - - -	v´, φ - - - l´, v´´	(pv), s, (a), (u), (p), (tc), (ft) - - (it) -	θ-2-ı-ı-ı3 θ-2-ı-ı-ı3 θ-2-ı-ı-ı3 ı-2-ı-ı-ıƽ ı-3-ı-3-ıƽ	ı-ı-θ ı-ı-θ ı-ı-θ ı-ı-θ ı-ı-θ
Leg IV	protonymph đeutonymph tritonymph ađult	- - v´-	- d, ev´ - -	- d, l´- -	- v´, φ - l´	(pv), (u), (p), ft´´s, (a), (tc) - -	θ-θ-θ-θ-7 θ-2-2-ı-ı2 ı-2-2-ı-ı2 ı-2-2-2-ı2	θ-θ-θ θ-ı-θ θ-ı-θ θ-ı-θ