Fortuynia elamellata Luxton, 1967

Pfingstl, Tobias, Minor, Maria, Schäffer, Sylvia & Shimano, Satoshi, 2023, Coastal oribatid mites (Acari) from New Zealand: new morphological, ecological, and developmental data, International Journal of Acarology 49 (7 - 8), pp. 422-439 : 427-428

Fortuynia elamellata Luxton, 1967

Luxton (1967) gave a very good and detailed description of the adult and juvenile stages of this species. Therefore, we only repeat the most important features and add very few morphological details that were not given in the original description.

Adult

Diagnosis. Dark brown to almost black mites. Body length ranges 438–488 µm and body width 270–290 µm (females slightly larger than males). Integument finely punctate. Prodorsum triangular in dorsal view, rostrum demarcated by faint transversal ridge passing in front of lamellar setae ( Figure 4d ). Rostral (ro) and lamellar seta (le) smooth, spiniform, the latter slightly shorter (ca. 20 µm vs. 15 µm). No lamellar ridges ( Figure 4a,b,d ). Interlamellar (in) and exobothridial seta (ex) vestigial. Sensillum (ss) smooth, medially incurving, with clavate head. Van der Hammen´s organ typical for the genus ( Figure 4c ); canal ce present, short, reaching bothridium, canal ci absent. Gnathosoma typical for the genus. Notogaster with anterior rectangular light spot with irregular border. Fourteen pairs of long, smooth spiniform notogastral setae (length 15–40 µm), seta da faintly serrated (difficult to observe), c 3 absent ( Figure 4a,b ). Lyrifissures and opisthonotal gland opening typical for the genus. Pedotectum I small, scale-like; pedotectum II absent. Epimeral formula 3-1-3-2, setae smooth, length ranging 15–45 µm, 1b longest, 3a shortest. Five pairs of genital setae, one pair of aggenital setae. Two pairs of anal and three pairs of thin and smooth adanal setae. Legs monodactylous, long hook-like claws with two dorsal rows of minute serration (difficult to observe) ( Figure 4e,f ). Porose areas present on all femora and on trochanter III and IV. Trochanter III and IV with distinct dorsal spur. Leg setation and solenidia: I (1-4-2-3-18) (1-2-2), II (1-4-2-3-15) (1-1-1), III (2-3-1-3-15) (1-1-0), IV (1-2-2-3-12) (0-1-0).

Remarks

The specimens investigated herein match exactly the morphological description of Fortuynia elamellata specimens in Luxton (1967) and there is no doubt that we are dealing with the same species. The supposed subspecies F. elamellata shibai was described from Japan and shows differences in the length of notogastral seta da, in the position of the aggenital setae, the development of pedotectum I and the spur on trochanter III ( Aoki 1974). A recent study (Pfingstl et al. 2019) concluded that these differences are of interspecific nature and that F. e. shibai represents a distinct species. We confirm the differences and agree that F. shibai should not be longer regarded as subspecies. Another suggested subspecies, namely F. elamellata micromorpha , was described from South African coasts ( Marshall and Pugh 2002), and also diverges from the nominate species in the length of seta da, position of aggenital seta and size of pedotectum I, but additionally shows a striking difference in body size (380–404 µm in F. micromorpha versus 438–488 µm in F. elamellata ). Altogether, this subspecies shows more differences to F. elamellata than F. shibai and thus its status as subspecies may also no longer be justified. A recent phylogeny of marine associated mites using morphological and molecular genetic data ( Pfingstl et al. 2023) indicated a close relation of the above-mentioned taxa but did not render them as direct sister species or groups of a single clade. Moreover, the three “ elamellata ” species differ in the length of the 28S gene fragment and show different substitutions in at least one base pair, which strongly supports the distinctness of each species.

Ecology

Fortuynia elamellata specimens were all collected from intertidal rock habitats ( Luxton 1967, present study) which indicates a preference for this type of environment. Furthermore, their claws are strongly curved and high (from dorsal to ventral edge), which indicates an adaptation to rocky tidal coastal environments ( Pfingstl et al. 2020).

Distribution. Fortuynia elamellata has been reported from four different locations in New Zealand: (I) from the Three Kings Islands north of Auckland, (II) from the Bay of Islands in the northern part of Auckland region, (III) from the Takatu Peninsula in North Auckland ( Luxton 1967, 1990), and (IV) from Waiheke Island close to the eastern shore of Auckland City (present study). All these occurrences are restricted to the northern parts of the North Island where warmer seawater temperatures prevail. Fortuyniid mites are known to be adapted to warmer climates (e.g. Pfingstl et al. 2021); therefore, it makes sense that F. elamellata may be restricted to the warm temperate regions of New Zealand. Although supposed subspecies of F. elamellata were found on shores of South Africa and Japan ( Aoki 1974; Marshall and Pugh 2002; Pfingstl et al. 2021), the nominate species has not been found yet outside of New Zealand and thus may represent a strictly endemic species.

Juvenile stages. Apheredermous, dark brown in colour (similar to adults). Integument plicate and soft except more sclerotized centrodorsal plate. Pattern of plication and system of tracheal pores in folds typical for the genus. Prodorsum triangular, hysterosoma oval in dorsal view. Bothridium small cup, sensillum with short stalk and smooth clavate head. Interlamellar (in) and exobothridial (ex) seta already vestigial. In larva, all notogastral setae faintly serrated, in following stages only setae c 1, c 2 and da with faint serration. Bases of notogastral setae surrounded by small pores.

Larva (N = 2). Length 225–246 µm (mean 236 µm).

428 T. PFINGSTL ET AL.

Eleven pairs of notogastral setae. Epimeral setation 2-1-2. Leg setation and solenidia: I (0-2-2-3-16) (1-1-1), II (0-2-2-2-13) (1-1-1), III (0-2-1-1-13) (1-1-0).

Protonymph (N = 2) ( Figure 5a,b ). Length 299–310 µm (mean 305 µm).

Fifteen pairs of notogastral setae. Epimeral setation 3-1-2-1. One pair of genital setae. Leg setation and solenidia: I (0-2-2-3-16) (1-1-2), II (0-2-2-2-13) (1-1-1), III (0-2-1-1-13) (1-1-0), IV (0-0-0-0-7) (0-0-0).

Deutonymph (N = 4). Length 350–369 µm (mean 363 µm).

Fifteen pairs of notogastral setae. Epimeral setation 3-1-2-2. Two pairs of genital (g), one pair of aggenital and three pairs of adanal setae (ad 1–3). Leg setation and solenidia ( Figure 6 ): I (0-3-2-3-16) (1-2-2), II (0-3-2-2-13) (1-1-1), III (1-2-1-1-13) (1-1-0), IV (0-2-2-1-12) (0-1-0).

Tritonymph (N = 8) ( Figure 5c ). Length 436–481 µm (mean 460 µm).

Fifteen pairs of notogastral setae. Epimeral setation 3-1-3-2. Four pairs of genital, one pair of aggenital, three pairs of adanal, and two pairs of anal setae (an 1–2). Leg setation and solenidia: I (0-4-2-3-18) (1-2-2), II (0-4-2-2-15) (1-1-1), III (1-3-1-2-15) (1-1-0), IV (1-2-2-2-12) (0-1-0).

Remarks

Our specimens of F. elamellata juveniles conform with the characteristics given by Luxton (1967). When comparing the juveniles of F. elamellata to immatures of the former supposed subspecies F. shibai (Pfingstl et al. 2021) , they look very similar at first glance. The habitus, developmental setal formulas and the size range of each stage are identical. But the sizes and shape of nearly all notogastral setae are significantly different. In juveniles of F. shibai most notogastral setae (c 1–3, da, dm, la, lm, h 2) are spinose and long, whereas in F. elamellata immatures all notogastral setae are relatively short (only a third of the length of the setae in F. shibai ) and only the setae c 1–2, da, dm are spinose; the rest are setiform. Juveniles of F. elamellata differ in the same way from immatures of the supposed subspecies F. e. micromorpha ( Hugo-Coetzee et al. 2022) but the latter are ca. 50 µm smaller in each stage and thus easily distinguishable.

Figures

Figure 4. Fortuynia elamellata SEM-images of adult female. (a) Lateral view. (b) Dorso-frontal view. (c) System of lateral cuticular channels in detail. (d) Prodorsum in dorso-lateral view. (e) Tarsus and tibia I, paraxial view. (f) Claw of leg I showing minute dorsal spines.

Figure 5. Fortuynia elamellata nymphs. (a) Protonymph dorsal view, legs omitted. (b) Protonymph ventral view, leg segments partially omitted. (c) Tritonymph lateral view.

Figure 6. Fortuynia elamellata legs deutonymph, antiaxial view. (a) Left leg I. (b) Left leg II. (c) Right leg III. (d) Right leg IV.