Microzetidae

Dorsal view of Cosmozetes striatissimus, from Balogh & Balogh (1992 vol. 2).

Belongs within: Holonota.
Contains: Acaroceras (Acaroceras), Microzetes (Microzetes).

The Microzetidae are a cosmopolitan group of very small pteromorph-bearing oribatid mites.

The microzetid enigma
Published 27 June 2021

The armoured mites of the Oribatida include their fair share of ornately ornamented species but perhaps the most grotesque of all are to be found under members of the family Microzetidae. These typically fairly small oribatids (the average size is about a third of a millimetre) are primarily found in soil and litter deposits around the world. They include a handful of species found in the far north but are primarily found in warmer regions with the greatest known diversity in the Neotropics (Woas 2002).

Dorsal, ventral and lateral views of Acaroceras galapagoensis, from Heinrich Schatz & Jose Palacios-Vargas.

The microzetids are primarily distinguished by elaborate outgrowths of the cuticle around the front of the body. In many oribatids, a pair of thin lamellae run down either side of the prodorsum (the part of a mite that might at first glance be taken for the ‘head’). In microzetids, these lamellae have become massively enlarged and detached from the prodorsum over much of their length. As a result, they form a kind of hood over the front of the body. They are flanked on either side by similar lateral extensions called tutoria. The prodorsum as a whole is often remarkably large compared to the rear part of the dorsum, the notogaster. Indeed, the notogaster is often as wide as or wider than it is long. A pair of wing-like extensions, pteromorphs, extend on either side of the front of the notogaster; in microzetids, the pteromorphs are typically sharply pointed. To top all these excrescences off, the insertions of the first pair of legs are also shielded by well-developed flanges called pedotecta.

What, if anything, is the purpose of all these anatomical extravagances is a question I am unable to answer: whether they are related in some way to defense or water retention, for instance. They also make it difficult to understand the position of microzetids relative to other oribatids. The presence of pteromorphs has commonly been thought characteristic of a group of oribatids that have been referred to as the Poronoticae. However, microzetids lack any sign of another distinctive feature of poronotic oribatids: the array of glandular openings on the cuticle known as the octotaxic system. Some oribatids are known to have reduced octotaxic systems, and microzetids do bear a certain resemblance to a definitely poronotic family in the Oribatellidae, so it is possible they represent poronotic mites in which the octotaxic system has been lost. However, other features of microzetids further support affinities outside the Poronoticae. In particular, nymphs of microzetids carry scalps. As they moult from one instar to the next, the shed cuticle of the notogaster is retained in place like a cap. Over successive instars, this cap becomes a stack of scalps that potentially assist in defence (a would-be predator attempting to grab onto the notogaster finds itself holding only an empty scalp). This is generally thought to be a primitive bahaviour that was lost in the ancestor of the poronotics. So are the microzetids primitive relatives of the poronotics, descended from ancestors that had acquired pteromorphs but not yet lost the scalp-carrying habit? Are they derived poronotics that eschewed the octotaxic system and taken up their scalps once more? Further research into oribatid phylogeny is needed to know.

Systematics of Microzetidae

Characters (from Balogh & Balogh 1992): Very small, length 150–250 µm, exceptionally to 460 µm. Chelicerae with small corniculi. Lamellae usually very large, lamellar system complicated. Notogaster usually broad; pteromorphae immovable, long; octotaxic system absent. Apodemata IV thickened. Six pairs of genital setae.

<==Microzetidae [Microzetoidea]
    |--Cuspitegula Hammer 1966S04
    |    `--*C. stellifer Hammer 1966S04
    |--Papuazetes Balogh 1968S04
    |    `--*P. insignis Balogh 1968S04
    |--Oxyzetes Balogh 1958S04
    |    `--*O. pectiniger Balogh 1958S04
    |--Arenozetes Krivolutsky 1971S04
    |    `--*A. christovi Krivolutsky 1971S04
    |--Mysterozetes Hammer 1961S04
    |    `--*M. scapulatus Hammer 1961S04
    |--Trichozetes Balogh & Mahunka 1980S04
    |    `--*T. neotrichus Balogh & Mahunka 1980S04
    |--Hauserozetes Mahunka 1980S04
    |    `--*H. mausiae Mahunka 1980S04
    |--Acanthozetes Balogh 1958S04
    |    `--*A. platypterus Balogh 1958S04
    |--Mirabilozetes Mahunka 1977S04
    |    `--*M. dentatus Mahunka 1977S04
    |--Schalleriella Engelbrecht 1972S04
    |    `--*S. gravouwensis Engelbrecht 1972S04
    |--Rhabdozetes Hammer 1962S04
    |    `--*R. pennatus Hammer 1962S04
    |--Calozetes Balogh & Mahunka 1969S04
    |    `--*C. monticola Balogh & Mahunka 1969S04
    |--Fusozetes Balogh 1972S04
    |    `--*F. fusiger (Balogh 1962) [=Rhopalozetes fusiger]S04
    |--Plumozetes Balogh 1972S04
    |    `--*P. plumifer (Balogh & Mahunka 1968) [=Rhopalozetes plumifer]S04
    |--Dinozetes Balogh 1962S04
    |    |--*D. mirabilis Balogh 1962S04
    |    `--D. latissimus Balogh 1962S04
    |--Mystacozetes Balogh 1962S04
    |    |--*M. ornatus Balogh 1962S04
    |    `--M. nervosus (Balogh & Mahunka 1969) [=Acaroceras nervosus]S04
    |--Christovizetes Krivolutsky 1975S04
    |    |--*C. ovatus Krivolutsky 1975S04
    |    `--C. prasadi Mahunka 1995S04
    |--Vermacarus Balogh & Mahunka 1980S04
    |    |--*V. longissimus Balogh & Mahunka 1980S04
    |    `--V. armatus Mahunka 1997S04
    |--Schizozetes Balogh 1962S04
    |    |--*S. quadrilineatus Balogh 1962S04
    |    `--S. similis Mahunka 1966S04
    |--Rugozetes Balogh 1960S04
    |    |--*R. grandjeani (Balogh 1959) [=Microzetes grandjeani]S04
    |    `--R. gladiator Balogh 1962S04
    |--Kaszabozetes Mahunka 1988 [incl. Sinozetes Mahunka 2000]S04
    |    |--*K. velatus Mahunka 1988S04
    |    `--K. botulus (Mahunka 2000) [=Sinozetes botulus]S04
    |--Sturmozetes Balogh & Balogh 1992 [=Gymnozetes Balogh 1984 non Calugar & Vasiliu 1983]S04
    |    |--*S. marginatus (Balogh 1984)S04 [=*Gymnozetes marginatusBB92]
    |    `--S. longisetus (Balogh 1989) [=Gymnozetes longisetus]S04
    |--Orthozetes Balogh 1962S04
    |    |--*O. dispar Balogh 1962S04
    |    |--O. depilatus Balogh 1968S04
    |    `--O. papuanus Balogh 1968S04
    |--Cavernozetes Mahunka 1984S04
    |    |--*C. excavatus Mahunka 1984S04
    |    |--C. interruptus Mahunka 1988S04
    |    `--C. latus Mahunka 1988S04
    |--Szentivanyella Balogh & Mahunka 1969S04
    |    |--*S. latilamellata Balogh & Mahunka 1969S04
    |    |--S. africana Mahunka 1984S04
    |    `--S. szentivanyi Hammer 1979S04
    |--Anakingia Hammer 1961S04
    |    |--*A. williamsae Hammer 1961S04
    |    |--A. borneensis Mahunka 1997S04
    |    `--A. reticulata Balogh & Mahunka 1969S04
    |--Phylacozetes Grandjean 1936S04
    |    |--*P. membranulifer Grandjean 1936S04
    |    |--P. ensifer Mahunka 1984S04
    |    `--P. quadridentatus Mahunka 1985S04
    |--Brazilozetes Balogh & Mahunka 1969S04
    |    |--*B. flagellatus Balogh & Mahunka 1969S04
    |    |--B. fusiger Balogh & Mahunka 1981S04
    |    `--B. phaseolus Balogh & Mahunka 1969S04
    |--Comorozetes Mahunka 1994S04
    |    |--*C. atavisticus Mahunka 1994S04
    |    |--C. concurvatus Mahunka 1999S04
    |    `--C. corrugatus Mahunka 1997S04
    |--Miracarus Kunst 1959S04
    |    |--*M. hurkai Kunst 1959S04
    |    |--M. discrepans Mahunka 1966S04
    |    |--M. senensis Bernini 1975S04
    |    `--M. similis Subías & Iturrondobeitia 1978 [incl. M. abeloosi Lions 1979]S04
    |--Kalyptrazetes Balogh 1972 [incl. Allozetes Higgins 1965 non Berlese 1913]S04
    |    |--*K. harpezus (Higgins 1965) [=Allozetes harpezus]S04
    |    |--K. americanus Mahunka 1995S04
    |    |--K. desaussurei Mahunka 1983S04
    |    `--K. lupitae Mahunka & Palacios-Vargas 1996S04
    |--Afrozetes Engelbrecht 1972S04
    |    |--*A. magoebaensis Engelbrecht 1972S04
    |    |    |--A. m. magoebaensisS04
    |    |    `--A. m. capensis Engelbrecht 1972S04
    |    |--A. champaignensis Engelbrecht 1972S04
    |    `--A. natalensis Engelbrecht 1972S04
    |--Hymenozetes Balogh 1962S04
    |    |--*H. mirabilis Balogh 1962S04
    |    |--H. quadricornutus Mahunka 1993S04
    |    |--H. reticulatus Mahunka 1996S04
    |    |--H. stellifer Mahunka 1999S04
    |    `--H. verticillatus Mahunka 1997S04
    |--Acaroceras Grandjean 1936S04
    |    |--A. (Acaroceras)S04
    |    |--A. (Malgoceras Mahunka 1993)S04
    |    |    `--A. (*M.) helleri Mahunka 1993S04
    |    `--A. (Trichacaroceras Mahunka 1991)S04
    |         `--A. (*T.) africanus Mahunka 1991S04
    |--Protozetes Balogh 1962S04
    |    |--*P. capitulum Balogh 1962S04
    |    |--P. clavatus Mahunka & Palacios-Vargas 1996S04
    |    |--P. digitifer Mahunka 1985S04
    |    |    |--P. d. digitiferS04
    |    |    `--P. d. alticola Balogh 1989S04
    |    `--P. longicornis Balogh 1989S04
    |--Caucasiozetes Shtanchaeva 1984 [incl. Teraja Mahunka 1995]S04
    |    |--*C. lamellatus Shtancheva 1984S04
    |    |--C. asymmetricus (Mahunka 2001) [=Teraja asymmetrica]S04
    |    |--C. fimbriatus (Mahunka 1988) [=Microzetes fimbriatus]S04
    |    |--C. flagellifer (Mahunka 1989) (see below for synonymy)S04
    |    |--C. sungai (Mahunka 1997) [=Teraja sungai]S04
    |    |--C. tuberculatus (Mahunka 1987)S04 [=Microzetes tuberculatusS04, Teraja tuberculataM01]
    |    `--C. wongi (Mahunka 1995) [=Teraja wongi]S04
    |--Licnozetes Balogh & Mahunka 1969S04
    |    |--L. (Licnozetes)S04
    |    |    |--*L. (L.) flabellatus Balogh & Mahunka 1969S04
    |    |    `--L. (L.) multiareolatus Balogh & Mahunka 1969S04
    |    `--L. (Undulozetes Balogh & Mahunka 1969)S04
    |         |--L. (*U.) granulatus (Balogh & Mahunka 1969) [=*Undulozetes granulatus]S04
    |         |--L. (U.) marginatus (Balogh & Mahunka 1969) [=Undulozetes marginatus]S04
    |         `--L. (U.) topali (Balogh & Csiszár 1963) [=Rhopalozetes topali]S04
    |--Rhopalozetes Balogh 1962 [incl. Austrozetes Balogh & Mahunka 1969]S04
    |    |--*R. milloti Balogh 1962S04
    |    |--R. brazilianus (Balogh & Mahunka 1969)S04 [=*Austrozetes brazilianusBB92, S04]
    |    |--R. canagaratnami Balogh 1970S04
    |    |--R. capensis Mahunka 1985S04
    |    |--R. georgensis Engelbrecht 1972S04
    |    |--R. lokobensis Mahunka 1993S04
    |    |--R. madecassus Mahunka 1993S04
    |    |--R. maximus (Pérez-Íñigo & Baggio 1994) [=Austrozetes maximus]S04
    |    |--R. panabokkei Balogh 1970S04
    |    `--R. witfonteinensis Engelbrecht 1972S04
    |--Schalleria Balogh 1962S04
    |    |--*S. sexcornuta Balogh 1962S04
    |    |--S. bacillifera Balogh 1962S04
    |    |--S. cruciata Balogh & Mahunka 1969S04
    |    |--S. forceps Balogh & Mahunka 1980S04
    |    |--S. incurvata Balogh & Mahunka 1969S04
    |    |--S. latilamellata Balogh & Mahunka 1980S04
    |    |--S. martii Balogh & Mahunka 1974S04
    |    |--S. mexicana Mahunka & Palacios-Vargas 1996S04
    |    |--S. monoceros Balogh 1962S04
    |    |--S. ramosa Balogh & Mahunka 1969S04
    |    `--S. trifurcata Balogh & Mahunka 1979S04
    |--Microzetes Berlese 1913S04
    |    |--M. (Microzetes)S04
    |    |--M. (Megazetes Balogh 1959)S04
    |    |    |--M. (*M.) micropterus (Balogh 1959) [=*Megazetes micropterus]S04
    |    |    |--M. (M.) eckeri (Mahunka 1982) [=Megazetes eckeri]S04
    |    |    |--M. (M.) flagellifer (Mahunka 1988) [=Megazetes flagellifer]S04
    |    |    |--M. (M.) pocsi (Mahunka 1998) [=Megazetes pocsi]S04
    |    |    |--M. (M.) rugosus (Mahunka 1986) [=Megazetes rugosus]S04
    |    |    |--M. (M.) scriptus (Mahunka 1988) [=Megazetes scriptus]S04
    |    |    `--M. (M.) tanzicus (Mahunka 1983) [=Megazetes tanzicus]S04
    |    `--M. (Stylozetes Balogh & Mahunka 1969)S04
    |         |--M. (*S.) physoseta (Balogh & Mahunka 1969) [=*Stylozetes physoseta]S04
    |         |--M. (S.) discrepans (Balogh 1962) [=Nellacarus discrepans]S04
    |         |--M. (S.) processus (Balogh & Mahunka 1977) [=Stylozetes processus]S04
    |         `--M. (S.) spinosus (Balogh & Mahunka 1981) [=Stylozetes spinosus]S04
    |--Berlesezetes Mahunka 1980S04
    |    |--B. ornatissimus (Berlese 1913) (see below for synonymy)S04
    |    |    |--B. o. ornatissimusS04
    |    |    |--B. o. appalachicola (Jacot 1938) [=Microzetes auxiliaris appalachicola]S04
    |    |    |--B. o. mirus (Mihelčič 1956) [=Microzetes mirus]S04
    |    |    `--B. o. orkneyensis (Engelbrecht 1972) [=Microzetes auxiliaris orkneyensis]S04
    |    |--B. aegypticus (Bayoumi 1977) [=Microzetes aegypticus]S04
    |    |--B. alces (Piffl 1961) [=Microzetes alces]S04
    |    |--B. arenarius (Krivolutsky 1966) [=Microzetes arenarius]S04
    |    |--B. brazilozetoides Balogh & Mahunka 1981S04
    |    |--B. brevis (Warburton 1912) [=Oribata brevis]S04
    |    |--B. cuspidatus Mahunka 1982S04
    |    |--B. glaber Mahunka 1982S04
    |    |--B. ‘grandjeani’ (Mahunka 1977) [=Microzetes grandjeani non Balogh 1959]S04
    |    |--B. kingi Bayoumi & Al-Khalifa 1986S04
    |    `--B. peruensis (Hammer 1961) [=Microzetes peruensis]S04
    `--Cosmozetes Balogh & Mahunka 1969S04
         |--C. (Cosmozetes)S04
         |    |--*C. (C.) striatissimus Balogh & Mahunka 1969S04
         |    |--C. (C.) cubanus Balogh & Mahunka 1974S04
         |    |--C. (C.) ecuadoriensis Balogh 1989S04
         |    |--C. (C.) jaccoudi Mahunka 1998S04
         |    |--C. (C.) negroi Balogh & Mahunka 1977S04
         |    |--C. (C.) rohri Balogh & Mahunka 1969S04
         |    `--C. (C.) vermiculatus (Balogh & Mahunka 1980) [=Rhopalozetes vermiculatus]S04
         `--C. (Magoebazetes Engelbrecht 1973)S04
              |--C. (*M.) magoebaensis (Engelbrecht 1973) [=*Magoebazetes magoebaensis]S04
              |--C. (M.) cornutus (Mahunka 1999) [=Magoebazetes cornutus]S04
              |--C. (M.) engelbrechti (Mahunka 1985) [=Magoebazetes engelbrechti]S04
              |--C. (M.) natalensis (Engelbrecht 1973) [=Magoebazetes natalensis]S04
              |--C. (M.) nosybe (Mahunka 1993) [=Megazetes nosybe]S04
              |--C. (M.) pentasetarum (Engelbrecht 1973) [=Magoebazetes pentasetarum]S04
              `--C. (M.) reticulatus (Balogh 1962) [=Rhopalozetes reticulatus]S04

Berlesezetes ornatissimus (Berlese 1913) [=Microzetes ornatissimus; incl. M. africanus Balogh 1958, M. auxiliaris Grandjean 1936, *Berlesezetes auxiliaris, M. auxiliaris pachyseta Hammer 1971]S04

Caucasiozetes flagellifer (Mahunka 1989) [=Microzetes flagellifer non Megazetes flagellifer Mahunka 1988 (not preoc. if in dif. gen.)]S04

*Type species of generic name indicated

References

[BB92] Balogh, J., & P. Balogh. 1992. The Oribatid Mites Genera of the World vol. 1. Hungarian Natural History Museum: Budapest.

[M01] Mahunka, S. 2001. Oribatids from Brunei III (Acari: Oribatida). (Acarologica Genavensia XCI). Revue Suisse de Zoologie 108 (2): 317–349.

[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.

Woas, S. 2002. Acari: Oribatida. In: Adis, J. (ed.) Amazonian Arachnida and Myriapoda: Identification keys to all classes, orders, families, some genera, and lists of known terrestrial species pp. 21–291. Pensoft: Sofia.

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