Alycus denasutus ( Grandjean, 1937 )

Alycus denasutus ( Grandjean, 1937) View in CoL

( Figs. 5A–E, 6A–C)

Pachygnathus dugesi ssp. denasutus .—Grandjean 1936: 398, comparisons between non-specific characters; Grandjean 1937: fig. 6A–C., Strasbourg, France.

Pachygnathus villosus var. denasutus View in CoL .— Thor & Willmann 1941: 137.

Alycus roseus denasutus View in CoL .—van der Hammen 1969: 193.

Alycus denasutus View in CoL .— Uusitalo 2010: 45.

Alycus sp. nr. denasutus View in CoL .— Walter & Lumley 2021: 73.

Description. Dorsum (n= 1 male and 7 females, Figs. 5A, C, 6A). Length of male 360 µm, female approximately 500 µm in length; parallel ridges on soft integument meandering, mostly continuous; neotrichous, dorsal setae ciliate, caudal setae longest with long cilia. Prodorsum: naso absent, thin strip of hard integument connecting the eye area and setae sce and exp; setae sce inserted anteriorly to anterior pair of eyes; setae exp above reduced (lensless) pair of posterior eye; narrow strip of hard integument (=crista) from nasal area up to sensillar area interrupted by ridges of soft integument (arrow); setae vi on separate microplates; setae in, sce and vi subequal in length; distance between counterparts of setae in, and sensilla ve, subequal to distance between counterparts of setae vi.

Venter ( Fig. 5B, D–E). Male: genital setae 15–16 per valve; 8 pairs of eugenital setae; anal setae 5 per valve. Female: genital setae 24–26 per valve; 1 pair of eugenital setae; anal setae 7 per valve, see Remarks.

Gnathosoma ( Fig. 5A). Rutella with broad shaft, three ventrodistal projections, and an apical point; three adoral setae on right and left side of subcapitulum, respectively; one pair of dorsal cheliceral setae; three pairs of pseudacanthoid palpal eupathidia apically.

Legs ( Fig. 5A). Solenidial formula for tarsi, tibiae, genua and femora of legs I, II, III and IV, respectively: 2-1- 0-0, 1-2-2-0, 4-2-2-1, 1\2-0-0-0, see Remarks.

Material examined. 1 male, litter back dunes, brushy area, AM, Sea pines, Hilton Head Island, Beaufort Co., South Carolina, USA, 15 August 1997, VE LaRoche: slide NA17, collection number AL5210, deposited at the Acarology Laboratory, Ohio State University .

3 females as Alycus sp. nr. denasutus , from Site 33SER, 59.64667511, -112.275978, ABMI.2009.11, Alberta, Canada, David E. Walter: slide (4) TMS: M 00016843, see Remarks; 2 females as Alycus sp. nr. denasutus from litter on dry mesa, 646m, 50°45’35.97’’N 111°31’23,77’’W, and 2 females from grass, herbs in coulee, S-slope, 642m, 50°45’38’’N 111°31’21,98’’W, Dinosaur Provincial Park, Newell Co., Alberta, Canada, 13-14 July 2010, David E. Walter: slides (5) TMS: M00016844, (6) TMS: M00016846, (7) TMS: M00016845. The material is deposited in the Royal Alberta Museum.

Differential diagnosis. Alycus denasutus is closely related to A. roseus because these species share the same setal form on the dorsum. Alycus denasutus is distinguished from the latter by being white, lacking a naso, and having dorsal ridges that are mostly long and parallel. Compared to A. utahensis , A. denasutus lacks the elongated cilia of dorsal setae.

Remarks. The crosschecked specimens from Canada and Europe are 1) described by different techniques (phase contrast vs. scanning electron microscopy) 2) belong to different sexes (male vs. female) and 3) belong to markedly unconnected gene pools (North America vs. Europe), but the identification of Alycus denasutus seems to be well founded (as already suggested in Uusitalo (2010) and see below). This rarely collected species may have a Holarctic distribution, but so far, there are no reports from Asia.

The prodorsum of the male and females corresponds well to the European A. denasutus ( Uusitalo, 2010: figs. 25–35), even the crista or strip from naso to sensillar area is interrupted by ridges of soft integument ( Figs. 5A, 6A vs. 6B, arrows).

The Canadian females ( Fig. 5C) and the European female ( Fig. 6C) are ca. 60 % larger than the male but females are bigger in this family ( Uusitalo 2010: 48). Intraspecific variation in body size of males is unknown because I have seen only one male (360 µm in length) but females are ca. 500 µm or more and the size varies a lot (460 µm with 4 eggs; 480 µm with 2 eggs; 490 µm with no eggs but 3 eggs in medium; 530 µm; 560 µm; 580 µm; and 720 µm with 11 eggs ( Fig. 5C). Typically, the soft integument is folded so that the ridges supporting the lamellae are close to each other (e.g., in Pachygnathus villosus , Fig. 6D). The folded integument become stretched for various reasons like becoming highly gravid, or through artificial pressure in the slide making process, which makes exact dimensions of specimens a poor character state in the family Alycidae .

The male of Alycus denasutus is much less setose (ca. 36 setae on C-segment, Fig. 5A) than the females of A. denasutus (ca. 45 setae on C-segment, Figs. 5B, 6C), which seems to be due to differences in body sizes. Also, the numbers of genital and anal setae per valve vary, the male having 15–16 and 4–5, respectively vs. 24–26 and 7 on the females. Neotrichous setal numbers on the valves are included in the definition of species as a concession to tradition. Due to this intraspecific variation the numbers of genital and anal setae are of minor importance in the taxonomy of Alycidae ( Uusitalo 2010: 81) .

Alycus denasutus is reported to have 2 solenidia ( Uusitalo 2010: 50) or only 1 solenidion ( Walter and Latonas 2012: 61) on femora I. Examination of all the 14 femora I of the Canadian material revealed 5 cases with 2 solenidia and 9 cases with 1 solenidion. Solenidiotaxy is also exposed to intraspecific variation.

The text on the label means that the 3 specimens were collected by ABMI (the Alberta Biodiversity Monitoring Institute), at the SE (southeast) corner of Site 33 in the year 2009. The specimens were found in the alcohol residuals (the “ R ”), i.e. ABMI only looks at the oribatid mites, so any other taxa are considered “residuals”. Public coordinates of the site 33 are 59.64667511, -112.275978. The actual site is within 5.5 km of this public geographic coordinate ( ABMI does not release the actual coordinates, to protect the site and maintain confidentiality for landowners (Dr. Lisa Lumley, in litt.). GoogleMaps

Alycus sp. from Oregon. Dr. G.W. Krantz’s imposing endeavour to treat all the acarine families led to the Manual of Acarology ( Krantz 1970, 1978). All treatments, including chosen illustrations, were designed to illustrate a general type and family characters rather than species characters. The family Pachygnathidae was treated by depicting outlines of an oval-shaped dorsum, chelate chelicera, linear palpus and four walking legs of a specimen called “ Pachygnathus sp. from Oregon ” ( Krantz 1978: fig. 57–1). The schematic picture also showed familiar character states, such as two pairs of prodorsal sensilla, hysterosomal segmentation demonstrated by some (39) dorsal setae in eight rows (without full information of the number of setae), and a few solenidia on leg segments. Some 30 years later the name of the family and specimen were changed into Alycidae and Alycus sp. in the 3rd edition ( Krantz & Walter 2009: fig. 14.3A). Dr. D.E. Walter—simply trying to represent the family more faithfully based on his experience, and without seeing an original specimen—edited the old picture by adding two pairs of eyes and a pair of setae exp on prodorsal area and several dorsal setae on segments C-, D-, E-, F-, and H- (now 48), still leaving out e.g. cheliceral setae and naso and several leg solenidia. No particular species was intended but the nasoless model now unintentionally reminds us of a holotrichous species, as if a new species to science. Two genera of the tribe Alycini have a holotrichous species (e.g., Pachygnathus nasutus — Fig. 10G, Uusitalo et al. 2020: fig. 27; and Amphialycus mayteni Uusitalo et al. 2020 : fig. 65), but no holotrichous Alycus had been described at that time, and to date no such specimen has been found in the Oregon State Arthropod Collection, Corvallis (Dr. Christopher Marshall, in litt.). However, Dr. G.W. Krantz collected widely but was especially fond of Mary’s Peak in the Coastal Ranges. That coastal area seems to have escaped glaciation and is a refugium of sorts (Dr. D.E. Walter, in litt.). Perhaps the truth is out there.

After saying all that, it seems that both Krantz and Walter had their point, where a tritonymph of an eyeless and holotrichous new species from Mexico (ca. 5700 km south of Oregon) is described below.

Genus Odontoalycus gen. nov.

Type species: Odontoalycus exoculo sp. nov.

Description. The sole species of this new genus differs from all genera of the tribe Alycini by having an eyeless prodorsum ( Figs. 7A, B, 9A, B) and clawless empodia ( Figs. 8A, B, 9E); it also differs from the genus Alycus by having a holotrichous prodorsum and ca. 20 tiny teeth (Figs: 8F, 9C, D), and from the remaining genera of the tribe by having robust and non-elongated chelicera ( Fig. 8E), Remarks.

Etymology. The name of the genus is a latinised combination of the Greek word ”δόντι” (=donti), meaning teeth, and ”alycus”, see Remarks under the genus Alycus .

Remarks. The division of the tribe Alycini into genera was based on the different structures of the chelicerae ( Uusitalo 2010), which was assumed to reflect different feeding habits and feeding sites, but the genus Alycus can tentatively be defined by plesiomorphic states only. The species with the robust, non-elongated and sparsely toothed chelicera are traditionally included in the genus Alycus , although whether this is a monophyletic group remains unsolved. The holotrichous specimen, although a tritonymph, but equipped with numerous teeth, unhooked empodia and without eyes, deserves to be placed in a new genus, especially as the shape of the chelicera can be considered plesiomorphic.