Hypogastrura ireneae ( Wray, 1953 )

Bernard, Ernest C., 2015, Redescriptions of Hypogastruridae and Onychiuridae (Collembola) described by David L. Wray, Zootaxa 3918 (3), pp. 301-338 : 313-316

Hypogastrura ireneae ( Wray, 1953)

Figs. 1 D, 8, 9

Achorutes ireneae Wray 1953: 2 .

Hypogastrura ireneae Salmon 1964: 216 ; Christiansen & Bellinger 1980: 99; 1998: 99.

Specimens examined. Lectotype female, 4 paralectotypes (1 female, 1 male, 2 juveniles) (by present designation), USA, North Carolina, Fayetteville, 11 November 1949, on mushrooms in bog, D. L. Wray, coll.; 2 females, USA, North Carolina, Raleigh, Bloomsbury Park, 9 December 1943, mushrooms on rotted log, collected with C. jondavi, G. F. Knowlton , coll.

Redescription. Body length of females 1.70, 2.03 mm, male 1.57 mm [up to 2.0 mm]. [Color pale yellow background color over which a reddish pigment is thickly speckled]. Granulation moderate, granule width 2.3–3.2 Μm; Yosii’s ‘a’ number 14–17. Most body setae similar in length, setiform, very finely serrated ( Figs. 6 A–C). Head with all dorsal setae; setae c1, c2, d1, p2, and sd1 microsetae. Seta v2 more than twice the length of v1. Lateral seta of pronotum longer than more medial setae. Thoracic and abdominal sensilliform setae much shorter than neighboring setae, except p3 on Abd. V two-thirds to equal in length to p4. On metanotum, m-row setae complete and with extra setae m2’ and m3’ between the m-seta row proper and the p-seta row; setae p1, p2 and p3 forming angle; microsensillum not observed. Metanotal chaetotaxy similar to that of mesonotum except extra m-setae not present. Seta a3 missing on abdominal tergites I–III, present on tergites IV and V. M-row setae m3 and m4 usually present on tergites I–III, m4 occasionally missing. Seta m3 present or absent on tergite IV. Seta p2 on Abd. IV slightly longer than seta p1; on Abd. V seta p1 slightly longer than p2, 4+4 anterior setae inside the p5 setae. Subcoxae I–III with 1, 2, 3 setae, respectively, the longest setae serrate. Plurichaetosis absent.

Antennal segment IV with simple apical vesicle, without prominent, finely granulated apical protrusions ( Figs. 7 D, E). Subapical organite of Ant. IV spherical, microsensillum minute, arcuate; two lateral and six dorsal sensilla, the lateral sensilla and two dorsal sensilla strongly bent; most dorsal setae sensilliform, most ventral setae setiform. Ventral sensory field with 53–58 short, thick, brush-tipped or capitate microsensilla, one sensilliform seta near center of sensory field, two longer, rounded subapical sensilla and hooked apical sensilliform seta ( Fig. 7 E). Sense organ of Ant. III ( Fig. 7 F) with two weakly lobed sensilla in shallow groove flanked by longer sensilla; peg-like microsensillum present on Ant. III. Eversible sac between Ant. III and IV not observed, represented by weak aperture at apex of Ant. III. Antennal segment I with 7 setae, Ant. II with 13 setae.

Postantennal organ width less than diameter of nearest ocelli, anterior lobes slightly longer or equal to posterior lobes, accessory tubercle not seen ( Figs. 7 A–C). Labrum not clearly seen in dorsal view; in lateral view, with granulate basal region and smooth distal region separated by curving ridge projecting dorsally ( Fig. 1 D). Maxilla with lamella 1 finely serrated and ciliated, extending past capitulum; lamellae 2 and 4 reaching capitulum teeth, lamella 5 long with double row of fine serrations ( Fig. 7 H). Outer lobe of maxilla with one sublobal hair. On labial palpus ( Fig. 7 G) lengths of sensilla A–E equal to or longer than guard setae, of which a1, b1, b2, d2, e2 and lateral papilla lp are setiform; guard setae b3, b4, d3, d4, e1, e3 and e5 foliate; guard setae d1 and e7 absent. Labial palpus with six proximal setae.

Tibiotarsi I, II, and III with 19, 19, 18 setae, respectively. Clavate tenent hairs absent. Unguis ( Figs. 7 I–K) with basal pairs of small lateral and dorsolateral teeth, median dorsal tooth in middle third of unguis, and pair of distal lateral teeth; larger ventral tooth present. Unguiculus with strong basal lobe and terminal spine extending slightly past ventral tooth.

Ventral tube with 4+4 setae. Tenaculum with 4+4 teeth, without setae. Dens about twice length of mucro, strongly tuberculate dorsally, with seven smooth, slender setae, proximal and distal outer setae longer than others ( Fig. 7 L). Mucro tapering to rounded apex, with strong outer lamella ( Figs. 7 L, M). Anal spines short, conoid, nearly straight, less than half the length of inner edge of hind unguis.

Remarks. Wray’s illustration of the PAO ( Wray 1953) is quite misleading. The organ itself was drawn in proportion but much too large, nearly twice the width of the nearest ocellus. Specimens tentatively assigned to this species by Christiansen & Bellinger (1980, 1998) clearly are a different species on the basis of PAO size. In addition, their illustration of Abd. IV and Abd. V chaetotaxy shows the presence of seta m2 on Abd. IV, which is absent in type specimens of H. ireneae .

Hypogastrura ireneae is a member of the H. trybomi group and keys to H. oregonensis Yosii, 1960 in Babenko (1994) and Thibaud et al. (2004); it also traces to H. oregonensis in Christiansen & Bellinger (1998) due to the erroneously stated size of the PAO. These two species are very similar and may be synonyms. Comparison of type material is necessary to determine the limits of these species.

Figures

FIGURE 6. Hypogastrura gravesi. A) Paratype (juvenile), dorsal chaetotaxy. B) Adult specimen from Ravensford, Swain County, North Carolina, dorsal chaetotaxy. C) Labrum, holotype. D) Maxilla, Ravensford specimen. E) Maxillary palpus, Ravensford specimen. F) Labial palpus, Ravensford specimen. G) Labial palpus, holotype. H) Anal spines, holotype. I) Anal spines, paratype. J) Macrochaetae of posterior abdominal segments.

FIGURE 7. Hypogastrura gravesi. A) Left and right postantennal organs (PAO) and anterior eyes of specimen from Ravensford, Swain County, North Carolina. B) Left-side PAO and anterior eyes of holotype. C) Ventral view of fourth antennal segment, Ravensford specimen. D) Dorsal view of third and fourth antennal segments, Ravensford specimen. E) Partial third and fourth antennal segments, holotype; in Figs. C ‒ E typical pointed setae black, sensilliform setae with rounded tips outlined, sensilla stippled. F) Terminal protuberances of fourth antennal segment, specimen from Waterrock Knob, Swain County, North Carolina. G ‒ I, Ravensford specimen. G) Fore tibiotarsus. H) Middle tibiotarsus and apex of femur. I) Hind tibiotarsus. J) Foot complex, holotype. K, L) Dentes and mucrones. K) Ravensford specimen. L) Holotype.

FIGURE 1. A) Ceratophysella hermosa, dorsal habitus of ethanol-preserved specimen from Jackson, County, North Carolina. B) Hypogastrura gravesi, dorsal habitus of ethanol-preserved specimen from Sevier County, Tennessee. C) C. hermosa, upright dorsal cephalic spines (d 5, sd 5). D) H. ireneae, labrum in lateral view. A: antenna; M: mandible. Arrow indicates labrum base. Scale bars: A, B = 500 µm; C = 100 µm; D = 20 µm.