Tegeocranellus alas, copyright B. Eamer.

Belongs within: Poronoticae.
Contains: Halozetes.

The Ameronothroidea are a group of mostly semi-aquatic oribatid mites, inhabiting locations such as ephemeral rock pools or intertidal littoral zones. Gas exchange may be facilitated during immersion by a cerotegumental plastron and/or taenidia and tecta in the pleural region. Some species of Ameronothridae are noteworthy for being found in extreme environments in the Arctic or Antarctic. Tegeocranellus differs from other Ameronothroidea in the presence of well-developed lamellae on the prodorsum (Norton & Behan-Pelletier 2009). Members of the genera Antarcticola and Pseudantarcticola have fewer setae on the notogaster than other genera of Ameronothridae, with only ten or eleven pairs versus the twelve or more pairs of the latter (Balogh & Balogh 1992).

Mites by the sea shore
Published 6 October 2022

Look very carefully around the shores of Europe and you may happen upon colonies of Ameronothrus maculatus. This moderately-sized oribatid (about half a millimetre in length) inhabits rocks around the high tide mark where it grazes on lichens. It is just one of a number of mite species specialised for life in the littoral zone.

Ameronothrus maculatus, copyright Centre for Biodiversity Genomics.

Ameronothrus maculatus is one of about fifteen species of Ameronothrus known from temperate and boreal coastlines of the Northern Hemisphere. It is distinguished from other members of the genus by the combination of a single pair of anal setae, dorsal setae on the leg tibiae, no primilateral seta on the tarsi, and granular integument on the femora (Pfingstl et al. 2022). Ameronothrus has been treated as part of the Ameronothroidea, an assemblage of leathery-skinned oribatids associated with semi-aquatic habitats. However, this assemblage may be undercut by molecular phylogenetic studies. Though such studies for oribatids are still in their infancy, they raise the possibility that the shared features of ‘ameronothroids’ may be convergent adaptations to their lifestyle.

Ameronothrus clustered in a crevice, copyright D. Sikes.

Living at the water’s edge does come with challenges. Individuals of Ameronothrus maculatus are not active underwater but they are tolerant of submersion. A sculpted layer of hydrophobic wax over the mite’s cuticle captures air bubbles through which gases can diffuse out of the surrounding water. Individuals may survive in this way for more than 100 days underwater (Pfingstl & Krisper 2014). As such, an inundated A. maculatus can easily wait for the tides to recede. Other Ameronothrus species may occupy spots even lower on the shoreline, withstanding more prolonged and regular submersions (Pugh & King 1985). Ameronothrus maculatus can tolerate exposure to both salt and fresh water and may be found alongside streams and lakes as well as on the coast. It may also be found well above the tide mark when conditions suit. Interestingly, the likelihood of A. maculatus to enter terrestrial habitats correlates with temperature (Marshall & Convey 2004). In warmer parts of its range, it keeps strictly to the water’s edge. But as the temperature grows increasingly chilly, it emerges to wander across the frozen rocks.

Systematics of Ameronothroidea

Characters (from Norton & Behan-Pelletier 2009):  Adults with integument often weakly sclerotised and easily deformed. Prodorsum with or without lamellae, adjacent medially or separated, and lamellar cusps. Tutorium and translamella present or absent. Genal notch absent. Bothridial seta normally developed or extremely small, or absent. Chelicerae chelate-dentate; palpal eupathidium acm separate from solenidion; subcapitular mentum without tectum. Axillary saccule of subcapitulum absent. Dorsophragmata and pleurophragmata present or absent. Discidium present or absent, custodium absent. Pedotectum I large, extending to base of bothridium, subdivided, or absent. Pedotectum II present or absent. With or without tecta laterally to maintain plastron around sejugal region and acetabulum III. Coxisternal setation various (3-1-3-2, 3-1-2-2, 3-1-3-2, 2-1-2-3, or 1-1-1-1). Genital setation 3, 5, or 6 pairs. Ovipositor and sperrnntopositor with 11–12 setae. Notogaster overhanging ventral plate. Lenticulus present or absent. Immatures apheredermous, plicate, opisthonotum often smooth and convex centrodorsally; unideficient or bideficient; prodorsal, adanal, and latero-hysterosomal porose regions (or their saccule homologues) present or absent. Seta d variably present on tibiae and genua when respective solenidion is present.

    |--Tegeocranellus Berlese 1913NB-P09, S04 [=TegeogranellusH98; Tegeocranellidae]
    |    |--*T. laevis (Berlese 1905) [=Tegeocranus laevis]S04
    |    |--T. alas Behan-Pelletier 1997S04
    |    |--T. barbarae Behan-Pelletier 1997S04
    |    |--T. bolivianus Balogh & Mahunka 1969S04
    |    |--T. bosniae (Frank 1961) [=Carabodes bosniae]S04
    |    |--T. concavus Balogh & Balogh 1983S04
    |    |--T. convexus Balogh & Balogh 1983S04
    |    |--T. kethleyi Behan-Pelletier 1997S04
    |    |--T. knysnaensis Kok 1968 [incl. T. africanus Mahunka 1985]S04
    |    |--T. mediolamellatus Behan-Pelletier 1997S04
    |    |--T. mississippii Behan-Pelletier 1997S04
    |    |--T. muscorum Behan-Pelletier 1997S04
    |    |--T. opcus Tseng 1982S04
    |    `--T. sacchareus Kok 1968S04
    |    |--Thalassozetes Schuster 1963S04
    |    |    `--*T. riparius Schuster 1963S04
    |    |--Psednobates Luxton 1992S04
    |    |    `--*P. uncunguis Luxton 1992S04
    |    |--Arotrobates Luxton 1992S04
    |    |    |--*A. lanceolatus Luxton 1992S04
    |    |    `--A. granulatus Luxton 1992S04
    |    |--Selenoribates Strenzke 1961S04
    |    |    |--*S. foveiventris Strenzke 1961S04
    |    |    |--S. ghardaqensis Abdel-Hamid 1973S04
    |    |    `--S. mediterraneus Grandjean 1966S04
    |    `--Schusteria Grandjean 1968S04
    |         |--*S. littorea Grandjean 1968S04
    |         |--S. melanomerus Marshall & Pugh 2000S04
    |         `--S. ugraseni Marshall & Pugh 2000S04
    |    |--Circellobates Luxton 1992S04
    |    |    `--*C. venustus Luxton 1992S04
    |    |--Alismobates Luxton 1992S04
    |    |    |--*A. reticulatus Luxton 1992S04
    |    |    `--A. rotundus Luxton 1992S04
    |    `--Fortuynia Hammen 1960S04
    |         |--*F. marina Hammen 1960S04
    |         |--F. elamellata Luxton 1967S04
    |         |    |--F. e. elamellataS04
    |         |    |--F. e. micromorpha Marshall & Pugh 2002S04
    |         |    `--F. e. shibai Aoki 1974S04
    |         |--F. inhambanensis Marshall & Pugh 2002S04
    |         |--F. maculata Luxton 1986S04
    |         |--F. rotunda Marshall & Pugh 2002S04
    |         |--F. sinensis Luxton 1992S04
    |         `--F. yunkeri Hammen 1963S04
         |--Aquanothrus Engelbrecht 1975 [Aquanothridae]S04
         |    `--*A. montanus Engelbrecht 1975S04
         |--Capillibates Hammer 1966S04
         |    `--*C. stagaardi Hammer 1966S04
         |--Chudalupia Wallwork 1981S04
         |    `--*C. meridionalis Wallwork 1981S04
         |--Pseudantarcticola Balogh 1970S04
         |    `--*P. tropica Balogh 1970S04
         |--Antarcticola Wallwork 1967 [incl. Petrozetes Sitnikova 1968]S04
         |    |--*A. meyeri Wallwork 1967 [incl. Petrozetes oblongus Sitnikova 1968]S04
         |    `--A. georgiae Wallwork 1970S04
         |--Alaskozetes Hammer 1955S04
         |    |--*A. coriaceus Hammer 1955S04
         |    |--A. antarcticus (Michael 1903)S04 [=Notaspis antarcticaS04, Halozetes antarcticaCH98]
         |    |    |--A. a. antarcticusS04
         |    |    |--A. a. grandjeani (Dalenius 1958)S04 [=Halozetes antarctica grandjeaniCH98]
         |    |    `--A. a. intermedius Wallork 1967S04
         |    `--A. bouvetoyaensis Pletzen & Kok 1971S04
         `--Ameronothrus Berlese 1896 [incl. Hygroribates Jacot 1934]S04
              |--*A. lineatus (Thorell 1871)S04 (see below for synonymy)
              |--A. bilineatus (Michael 1888)S04 [=Scutovertex bilineatusS04, Hygroribates bilineatusL87]
              |--A. dubinini Sitnikova 1975S04
              |--A. harioti (Michael 1891) (n. d.) [=Scutovertex harioti]S04
              |--A. lapponicus Dalenius 1963S04
              |--A. maculatus (Michael 1882)S04 (see below for synonymy)
              |--A. marinus (Banks 1896)S04 (see below for synonymy)
              |--A. nidicola Sitnikova 1975S04
              |--A. nigrofemoratus (Koch 1879)S04 (see below for synonymy)
              |--A. oblongus Sitnikova 1975S04
              |--A. schneideri (Oudemans 1905)S04 [=Scutovertex schneideriS04, Hygroribates schneideriL96]
              |--A. schubarti Weigmann & Schulte 1975S04
              `--A. schusteri Schubart 1970S04

*Ameronothrus lineatus (Thorell 1871)S04 [=Eremaeus lineatusS04, Scutovertex lineatusT05; incl. S. corrugatus Michael 1888S04, Ameronothrus corrugatusM98, Trombidium fuscum Brady 1875T05, Scutovertex occidentalis Hull 1918S04, A. occidentalisL87]

Ameronothrus maculatus (Michael 1882)S04 [=Scutovertex maculatusS04; incl. S. maculatus groenlandicus Trägardh 1904S04, S. pseudomaculatus insularis Hull 1914S04, Ameronothrus maculatus insularisL87, S. pseudomaculatus Hull 1914S04, A. maculatus pseudomaculatusL87, S. maculatus var. pseudomaculatusL87]

Ameronothrus marinus (Banks 1896)S04 [=Nothrus marinusS04, *Hygroribates marinusB65; incl. A. fucicolum Brady 1875S04, Trombidium fucicolumT05, Scutovertex spoofi Oudemans 1900S04, A. spoofiG32, S. bilineatus var. spoofiL87]

Ameronothrus nigrofemoratus (Koch 1879)S04 [=Nothrus nigrofemoratusS04, Damaeus nigrofemoratusM98, Scutovertex lineatus var. nigrofemorataT05; incl. Ameronothrus lineatus brevipes Willmann 1937S04]

*Type species of generic name indicated


[B65] Balogh, J. 1965. A synopsis of the world oribatid (Acari) genera. Acta Zoologica Academiae Scientiarum Hungaricae 11 (1–2): 5–99.

[CH98] Colloff, M. J., & R. B. Halliday. 1998. Oribatid Mites: A catalogue of Australian genera and species. CSIRO Publishing: Collingwood.

[G32] Grandjean, F. 1932. Observations sur les oribates (3e série). Bulletin du Muséum, 2e série, 4 (3): 292–306.

[H98] Halliday, R. B. 1998. Mites of Australia: A checklist and bibliography. CSIRO Publishing: Collingwood.

[L87] Luxton, M. 1987. The oribatid mites (Acari: Cryptostigmata) of J. E. Hull. Journal of Natural History 21: 1273–1291.

[L96] Luxton, M. 1996. Oribatid mites of the British Isles: a check-list and notes on biogeography (Acari: Oribatida). Journal of Natural History 30 (6): 803–822.

Marshall, D. J., & P. Convey. 2004. Latitudinal variation in habitat specificity of ameronothrid mites (Oribatida). Experimental and Applied Acarology 34: 21–35.

[M98] Michael, A. D. 1898. Oribatidae. In: H. Lohmann (ed.) Das Tierreich. Eine Zusammenstellung und Kennzeichnung der rezenten Tierformen vol. 3. Acarina pp. 1–93. R. Friedländer und Sohn: Berlin.

[NB-P09] Norton, R. A., & V. M. Behan-Pelletier. 2009. Suborder Oribatida. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 430–564. Texas Tech University Press.

Pfingstl, T., S. F. Hiruta, I. Bardel-Kahr, Y. Obae & S. Shimano. 2022. Another mite species discovered via social media—Ameronothrus retweet sp. nov. (Acari, Oribatida) from Japanese coasts, exhibiting an interesting sexual dimorphism. International Journal of Acarology 48 (4–5): 348–358.

Pfingstl, T., & G. Krisper. 2014. Plastron respiration in marine intertidal oribatid mites (Acari, Fortuyniidae and Selenoribatidae). Zoomorphology 133: 359–378.

Pugh, P. J. A., & P. E. King. 1985. The vertical distribution of the British intertidal Acari—the non halacarid fauna (Arachnida: Acari). Journal of Zoology (A) 207: 21–33.

[SK10] Schäffer, S., S. Koblmüller, T. Pfingstl, C. Sturmbauer & G. Krisper. 2010. Ancestral state reconstruction reveals multiple independent evolution of diagnostic morphological characters in the “Higher Oribatida” (Acari), conflicting with current classification. BMC Evolutionary Biology 10: 246.

[S04] Subías, L. S. 2004. Listado sistemático, sinonímico y biogeográfico de los ácaros oribátidos (Acariformes, Oribatida) del mundo (1758–2002). Graellsia 60 (número extraordinario): 3–305.

[T05] Trägårdh, I. 1905. Monographie der arktischen Acariden. In: Römer, F., & F. Schaudinn (eds) Fauna Arctica. Eine Zusammenstellun der arktischen Tierformen, mit besonder Berücksichtigung des Spitzbergen-Gebietes auf Grund der Ergebnisse der Deutschen Expedition in das Nördliche Eismeer im Jahre 1898 vol. 4 pp. 1–78. Gustav Fischer: Jena.

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