Ceratoppia Berlese, 1908

Lindo, Zoë, 2018, Diversity of Peloppiidae (Oribatida) in North America, Acarologia 58 (8), pp. 91-97 : 92-93

Ceratoppia Berlese

Ceratoppia is the most common and species-rich genus of Peloppiidae and is restricted to the northern hemisphere. Several species are Holarctic ( Schatz 2006) and a total of nine (plus two subspecies) are known from North America ( Lindo 2011). The main character states defining Ceratoppia among the Peloppiidae are chelate-dentate chelicerae, a conspicuous and straight sejugal apodeme, tridactyl pretarsus, and long lamellar cusps and bothridial setae. The main character states differentiating North American species of Ceratoppia are the number of hypostomal setae on the subcapitular mentum, and the number and expression of posterior notogastral setae; other diagnostic characters include the length of the lamellae and shape of the rostrum.

Of the North American species, the Holarctic C. bipilis (Hermann) , and C. quadridentata

(Haller) are best known. Both species are additionally represented by subspecies within their

North American range: C. bipilis spinipes (Banks) (also C. bipilis brevicuspis (Jacot) —

later synonymised with C. bipilis by Jacot (1936) — and C. quadridentata arctica Hammer ,

respectively ( Marshall et al. 1987). In North America C. quadridentata arctica is more commonly reported than the nominate C. quadridentata , which is recorded only from Alaska

( Bohnsack 1973); the latter record is likely C. quadridentata arctica as there is considerable variation reported within C. quadridentata ( Aoki 1969) , and C. quadridentata arctica is common in Alaska ( Hammer 1955). Both C. bipilis and C. quadridentata arctica are widespread in arctic, subarctic, boreal and temperate areas, and overlap in the western subarctic and arctic areas (Alaska, Yukon, Northwest Territories, and Nunuvut) with C. sexpilosa Willmann , and C.

sphaerica (L. Koch) . The subspecies C. bipilis spinipes is recorded from eastern North America including Ontario, Connecticut, Maine, Maryland, New Hampshire, Virginia and West Virginia

( Marshall et al. 1987). The validity of both subspecies C. quadridentata arctica and C. bipilis spinipes requires confirmation as both C. bipilis and C. quadridentata arctica display a wide variety of body size across their North American distributional range. Observed specimens of

C. bipilis spinipes also display considerable variation in body size.

Lindo (2011) recently described five new species of Ceratoppia from Pacific coastal

North America with overlapping distributions but differing in habitat preference. Three of these species were described primarily or solely from arboreal habitats C (. longicuspis, C.

tofinoensis , C. valerieae ), one species was collected solely from bark habitats ( C. offarostrata ),

and one species collected solely from forest floor soils ( C. indentata ). Distributions of C.

indentata, C. longicupsis , and C. valerieae span the North American Pacific coastline from north-central British Columbia, Canada, to north-central California State. It was noted that

C. indentata has increasing morphological variation in the southern extent of its distribution.

Ceratoppia valerieae has the most expansive distribution longitudinally, being found in arboreal habitats near the coast and dry ground habitats in interior Washington State and southern British

Columbia. Ceratoppia tofinoensis is less commonly sampled and appears to be restricted to coastal Oregon and Washington, and the west coast of Vancouver Island, British Columbia.

The fifth species from western North America, C. offarostrata , named for a large ‘hump’ on the rostrum, is known only from a few locations on Vancouver Island and Haida Gwaii, British Columbia. Morphological variation in C. offarostrata on Haida Gwaii needs to be compared with that of C. sphaerica ; the distributional patterns of C. sphaerica suggest this species is limited to arctic and subarctic areas in western Canada, however, C. offarostrata shares several character states, and may be a southern variant subspecies of C. sphaerica .