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Gamasellodes

Taxonomic Position

Cohort Gamasina

    Subcohort Dermanyssiae

  Superfamily Ascoidea

Family: Ascidae Voigts & Oudemans

Subfamily: Ascinae

Gamasellodes Athias-Henriot

 

Diagnostic characters:

Ecology & Distribution.  These mites are small soil-inhabiting predators that feed on small invertebrates (e.g. nematodes, mites, springtails); reproduction is by arrhenotoky or thelytoky.

Similar taxa in key. Antennoseius Berlese, Ectoantennoseius Walter, Asca von Heyden, Protogamasellus Karg, Diseius Lindquist & Evans.

 

Key to Adult Females of Rhodacarus-like Mites
(Rhodacaridae, Ologamasidae, Digamasellidae, Ascidae)

1.  Arthrodial process simple ..... 4

-   Arthrodial process produced as a brush .... 2

2.  Basitarsus IV with 4 setae (pl4 present) .... Pararhodacarus

-   Basitarsus IV with 3 setae (pl4 absent) ... 3

3.  Tectum with single median process or dentate .... Afrogamasellus

-   Tectum with median stalk y-shaped, usually with lateral tines ......... Afrodacarellus

4.  Scleronoduli present ........... 5

-   Scleronoduli absent ........... 10

5.  Tibia I with 4 ventral setae; palp apotele 3-tined ................ 6

-   Tibia I with 3 ventral setae; palp apotele 2-tined ................. 9

6.  3 scleronoduli (median unpaired);  j1-2, z1, and s1 on anterior margin of podonotal shield ............ 7

-   4 scleronoduli (median pair +/- fused);  j1 (but not j2), z1 and s1 on anterior margin of shield ........ 8

7.  Pretarsus I absent; without presternal platelets ................. Rhodacarus (+Mediorhodacarus)

-   Pretarsus I present; with 2 pairs of presternal platelets........................ Rhodacaropsis

8.  Podonotal shield entire ...................... Rhodacarellus

-   Podonotal shield divided between setae j3-j4; tectum denticulate-trifurcate .... Minirhodacarellus

9.  Tibia I with 5 (rarely 4) dorsal setae; 2 pairs of scleronoduli; sternal shield with 4 pairs of setae; anal opening normal ................................ Dendrolaelaps (Digamasellidae)

-   Tibia I with 6 dorsal setae; 3 scleronoduli; sternal shield with 3 pairs of setae (st4 in soft cuticle); anal opening enlarged ....................................... Protogamasellus mica Group (Ascidae)

10.  Sternal seta st4 on sternal shield .............. 11

-   Sternal  seta st4 in soft cuticle ................. 15

11.  Anal opening large; tibia I with 5 dorsal setae ............. Digamasellus (Digamasellidae)

-   Anal opening normal; tibia I with 6 dorsal setae ..................... 12

12.  Sternal shield strongly sclerotized throughout; tibia I with 4 ventral setae ....... Geogamasus (Ologamasidae)

-   Anterior region of sternal shield poorly sclerotized, setae st1 in soft or granulate cuticle; tibia I with 3 ventral setae ..................... 13

13.  Palp apotele 2-tined; coxa I without dorsal spine ..... 15

-      Palpapotele 3-tined: coxa I with dorsal spine ...... 14

14.   Presternal area granulate ................................ Protogamasellopsis

-     Presternal area with paired stacks of 4 presternal platelets ..... Rhodacarella

15.  Posterior margin of podonotal (at j6) and anterior margin of opisthonotal (at J1) shields with transverse lines; genu IV with 8 setae, tibia IV with 9 setae ......... Protogamasellus hibernicus Group (Ascidae)

-   Podonotal and opisthonotal shields without transverse lines; genu IV with 9 setae, tibia IV with 10 setae .......................................... Gamasellodes (Ascidae)

 

 

Key to genera in the subfamily Ascinae

 

1.  With holodorsal shield that captures the R-series ..... 2

-   Dorsal shield divided into two subequal shields; R-series setae in soft cuticle ..... 3

2.  Seta z1 present laterad seta j1 on anterior median region of dorsal shield; femur III with 7 setae; genu I with 13 setae; tibia II with 10 setae ..... Orthadenella (Blattisociidae)

-    Seta z1 absent; femur III with 6 setae; genu I with 12 setae; tibia II with 9 setae ..... Neojordensia

3.   Opisthonotal shield with 12 pairs of setae (J3, Z2, S1 absent); podonotal shield lacking setae j2, z1, z3; adult leg setation strongly neotenous, genua I-II-III-IV with 11-8-7-7 setae, tibiae with 11-7-7-7 setae; female with anal shield ..... Diseius

-     Opisthonotal shield with 15 or more pairs of setae (J3, Z2, S1 present); podonotal shield with setae j2, z3, sometimes z1; adult leg setation not strongly neotenous, minimum number of setae on genua 12-11-8-8, on tibiae 13-10-8-9; female with anal or ventrianal shield ..... 4

4.   Hypostome with corniculi bifid apically; anterior rostral setae thickened, spinelike; dorsal shield setae z1 absent  ..... Anephiasca

-    Hypostome with corniculi entire apically; anterior rostral setae of similar thickness to other hypostomal setae; dorsal shield setae z1 present or absent ..... 5

5.   Female with epigynial shield strongly rounded posteriorly and with small subtriangular ventrianal or anal shield bearing 3-5 setae; male with ventrianal shield united to peritrematal shields; soft body cuticle often with microtuberculate striae ..... 6

-     Female with epigynial shield truncate posteriorly and usually with well developed ventrianal shield (rarely anal shield) bearing 3-9 setae (including circumanal setae); male with ventrianal shield separate from peritrematal shields; soft body cuticle striae without microtubercles ..... 8

6.   Palps elongated, at least half as long as leg I; palp trochanter longer than femur; palp tibia almost 3 times as long as tarsus ..... Anystipalpus

-     Palps of normal length, about one-third as long as leg I; palp trochanter slightly shorter than femur; palp tibia twice as long as tarsus ... 7

7.   Legs I with ambulacra and claws ..... Antennoseius (Vitzthumia)

-     Legs I with out ambulacra and claws ..... Antennoseius (Antennoseius)

8.    Opisthonotal shield with setae Z4 & S5 usually approximate and inserted together on pair of prominent posterolateral tubercles; podonotal shield lacking setae z1,  j2 well behind level of j1; peritrematal shields of adults broad, truncate posteriorly; genu I with 12 setae (av2 absent) ..... Asca

-     Opisthonotal shield with setae Z4, S5 well separated, not borne on pair of strong tubercles; podonotal shield with setae z1 present; j2 tending to be displaced anteriorly, often in approximately transverse row with z1 and j1; peritrematal shields of adults narrow or of moderate width, tapering posteriorly; genu I with 13 setae (av2 present) ..... 9

9.      Podonotal shield with transverse line extending across surface at level of setae z6, opisthonotal shield with similar line at level of setae J1; paranal setae inserted close to anterior margin of anus; genu IV with 8 setae (pl1 absent); tibia IV with 9 setae (pl2 absent) ..... Protogamasellus

-        Dorsal shields without transverse lines extending completely across surface; paranal setae inserted closer to posterior margin of anus than to anterior margin; genu IV with 9 setae (pl1 present); tibia IV with 10 setae (pl2 present) ..... 10

10.      Sternal pore 3 in soft cuticle; setae r3 and Z5 club-shaped, densely plumose; gnathotectum denticulate; movable digit of chelicerae serrate ..... Ectoantennoseius

-        Sternal pore 3 on sternal shield; setae r3 and Z5 setiform, smooth to barbed; gnathotectum more or less smoothly trifurcate; movable digit of chelicerae usually with 4-6 teeth, not serrate ..... Gamasellodes

 

References

Evans GO & Till WM.  1979.  Mesostigmatic mites of Britain and Ireland (Chelicerata: Acari-Parasitiformes).  An introduction to their external morphology and classification.  Transactions of the Zoological Society of London 35 (2): 145-270.

Halliday RB, Walter DE & Lindquist EE.  1998.  Revision of the Australian Ascidae (Acarina: Mesostigmata).  Invertebrate Taxonomy 12: 1-54.

Hurlbutt HW. 1970. Gamasellodes bicolor (Berlese, 1918) (Acarina : Ascidae) and its relatives. Acarologia 12: 474-8.

Karg W. 1993. Acari (Acarina), Milben. Parasitiformes (Anactinochaeta). Cohors Gamasina Leach. Raubmilben. (Second Edition). Die Tierwelt Deutschlands 59: 1-523.

Walter DE.  1987.  Life history, trophic behavior and description of Gamasellodes vermivorax n. sp. (Mesostigmata: Ascidae) a predator of nematodes and arthropods in semiarid grasslands.  Canadian Journal of Zoology 65: 1689-1695.

Walter DE.  2003.  The genus Gamasellodes (Acari: Mesostigmata: Ascidae): New Australian and North American species.  Systematic & Applied Acarology Special Publications 15: 1-10.

Gwaiazdowicz DJ & Walter, DE.  2005.  Gamasellodes tatricus sp. nov. (Acari: Ascidae) from Poland.  Systematic & Applied Acarology 10: 61-66.

Walter DE & Ikonen EK.  1989.  Species, guilds and functional groups: Taxonomy and behavior in nematophagous arthropods.  Journal of Nematology 21: 315-327.

Walter DE. & Lindquist EE.  1995.  The distribution of asexual ascid mites (Acari: Parasitiformes) does not support the biotic uncertainty hypothesis.  Experimental & Applied Acarology 19: 423-442.