Coronapelopia quadridentata Cranston & Krosch
Cranston, Peter S., Krosch, Matt & Baker, Andrew M., 2021, Molecular evidence for deeper diversity in Australian Tanypodinae (Chironomidae): Yarrhpelopia and related new taxa, Zootaxa 4949 (1), pp. 1-23: 18-19
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|Coronapelopia quadridentata Cranston & Krosch|
[ Pentaneurini genus E Cranston 1996, 2000, 2010, 2019c]
Material examined. Holotype, slide-mounted in Euparal, Le/Pe/ ♀, AUSTRALIA: Western Australia, Shannon River N.P., mid-Shannon River, 34°39’E 116°22’E, 23–24.xi.1994 (Cranston) ANIC.
Paratypes (collector Cranston, deposited ANIC, unless indicated otherwise). As holotype, Le/Pe/ ♀, P ♀, 20 Pe; south-western Western Australia, Shannon River N.P., Shannon R., 34°39’E 116°22’E, 23–24.xi.1994 [P ♀, 6 Pe to ZSM]; 2L, Fish Ck., 34°40’E 116°23’E, 24.xi.1994 .
Description. Male unknown.
Female (n=2, +/- pharate). Total length c. 2.0 mm, wing length 2.1 mm. Antenna: scape and pedicel each with 5–7 setae ventrally in semicircle on each ( Fig. 4E View FIG ); with 10 flagellomeres, A.R. 0.26, terminal flagellomere 80 µm long, tapering, apex without seta. Dorsomedial extension of eye 5–6 ommatidia wide. Temporal setae 13, linear uniserial. Clypeal setae 27. Palp lengths 2–5: 35, 75, 108, 175, lacking any sensilla. Thoracic setation: antepronotal seta 1; acrostichals (ac) 29–32, multiserial, starting far anterior ending just short of scutellum; dorsocentrals (dc) 38, broadly scattered in humeral area, then biserial to just anterior to scutellum (ac and dc setae bimodal in size); supraalars 0; prealars irregularly biserial, 18–20; scutellars biserial, 15–16. Squama 5. Leg ratios (n=1) LR 1 0.64, BV 1 2.50, SV 1 2.93; LR 2 0.58, BV 2 2.77, SV 2 3.55; LR 3 0.64, BV 3 2.62, SV 3 2.82. Single tibial spur similar on all legs, slightly sinuous, 7–8 long, bare or with few very fine, hair-like side teeth.
Genitalia ( Fig. 4E, F View FIG ). Gonocoxapodeme VIII pale (teneral) gently curved. Gonapophysis VIII a single distally rounded lobe. Gonotergite IX protruding with 5–7 strong setae. Notum thin, pale. Tergite IX thin, non-setose. Postgenital plate narrow, with small pediform cerci. Three small globular seminal capsules of diameter 70–75, spermathecal ducts bare, ending separately.
Pupa (n=10). Body length 5.2–6.0 mm. Cephalothorax and abdomen golden-brown; wing sheaths, scar, posterolateral areas of each segment and apophyses contrastingly darker.
Cephalothorax. Thoracic horn ( Fig. 5B View FIG ) cylindrical, flattened in antero-ventral plane, curved in lateral view, dilate and rounded apically, 275 long, maximum length 2.5× maximum width, external membrane with spines nearly united into irregular mesh. Horn sac tubular, occupying c. 90% of horn, bilobed each side of connection to plastron at 80% length. Corona wide, occupying c. 30–40% length of thoracic horn, plastron plate ovoid, 50% width of corona, angled to long axis. Basal lobe tubercular, c 35 long. Thoracic comb comprising 7–8 squat, near contiguous tubercles,10 long. Thorax smooth; without scutal or postnotal tubercle. Thoracic setae difficult to discern: only 1 weak precorneal seta; dorsal setae 1 and 2 present, simple, 2 displaced laterally close to anterior wing sheath base, dcs 4 in supraalar position.
Abdomen ( Fig. 5E View FIG ). Tergite I with scar, lateral muscle marks very weak. Abdominal spinulation (shagreen) ( Fig. 5F View FIG ) aggregated into short rows, larger and denser and in triplets medially or aligned laterally especially on more posterior segments. L setae taeniate only on segments VII (4, clustered in posterior half) and segment VIII (all 5, evenly spaced). D setae: 3 on I, 4 on II, 5 on III–VII, absent on VIII; O-setae: 1 pair dorsal, 1 ventral, situated mid-curve of apophyses. Anal lobe ~1.5× as long as broad, bare, neither border with strong spinules ( Fig. 5E,H View FIG ), terminating in sclerotised point ( Fig. 5H View FIG ). Anterior seta of anal lobe half width at base (c. 8 µm) of the posterior (distal) (~ 15 µm). (Anal macrosetae adhesive. Genital sheath of female very short; of male smooth, extending c. 95% length of anal lobe,
Larva (n=2–3). Body length 4.1–4.2 mm, head capsule length 400–430, width 300–315, golden-yellow, darkened posteriorly ( Fig. 6B View FIG ), mandible golden, apical tooth variably darkened ligula golden brown grading to darker brown distal 1/3 ( Fig. 6H View FIG ), anterior parapod claws fine and pale, posterior claws broader, simple, pale yellow. Capsule elongate-oval, cephalic index 0.7–0.75. Cephalic setation ( Fig. 6B, J View FIG ): S10, S9 and SSm forming a triangle with VP between S10 and SSm, dorsal pit absent, S7 close to S8, S5 strongly retracted, aligned with extension of S7 and S8.
Antenna ( Fig. 6B, D View FIG ) ~50% head length, segment lengths: 137–142: 44–45: 6, 3, A.R. 2.1–2.2; basal segment ~8× as long as basal width, ring organ distal to mid-point (66%); blade bifid, broad outer branch 48, inner branch thin, both ending at apex of antenna. Lauterborn organs swollen, 10, reaching apex of antenna ( Fig. 6D View FIG ).
Mandible ( Fig. 6H View FIG ) gently curved, with tapering apical tooth, 54–57 long; short, rounded inner tooth not projecting, long seta subdentalis arises from projecting tooth-like distal mola.
Ligula ( Fig. 6F View FIG ) 48–50 long, with 4 teeth in level row, with all teeth directed anteriorly, ligula constricted medially; narrow rectangular area of muscle attachment occupying basal 8–10%. Paraligula bifid, with outer branch ~ 50% length of ligula, inner much shorter. Pecten hypopharyngis ( Fig. 6K View FIG ) with 6–8 teeth, homogenous in size or diminishing slightly laterad.
Maxillary palp with basal segment 30 long; ring organ situated at 10% length from base; crown with well-developed setae and sensilla including 2-segmented b-seta with sections subequal in length.
Submentum ( Fig. 6J View FIG ) anteriorly with only very weak transverse ‘creases’ of lighter sclerotisation. Dorsomentum and pseudoradula indistinct, faint.
Abdomen. Anterior parapods short, claws simple, pale. Anal tubules slender, pointed, 60 long. Procercus slightly darkened posteriorly, ~2.5× as long as wide (50–52 × 20–22), with 7–8 anal setae, 250–280. Subbasal seta of posterior parapod long, simple. Posterior parapods 300 long, claws subtended on parapod by few fine spinules. Two mid-sized claws are ‘folded’ ( Fig. 6L View FIG ) as noted for WA specimens by Leung et al. (2011), confirmed here also for eastern Australia in individuals with distinct.claws visible.
Etymology (Derivatio nominis). The species epithet quadridentata refers to the four-toothed larval ligula, unusual and diagnostic in Australian pentaneurine tanypods.
Remarks. As with other taxa treated using codes in Cranston (1996), ‘ Pentaneurini genus E’ was segregated based on immature stage characters (larvae and usually also pupae) of which corresponded to no northern hemisphere taxa. Formal taxonomy with diagnoses and species descriptions awaited full life stage associations and especially insights anticipated from molecular data. Although disappointingly few additional life histories have been made, pharate adults are now available from collections made in the appropriate habitats seeking material (successfully) for molecular studies. However, for ‘genus E’ all adults are pharate females and generally description of novel taxa without the adult male is to be avoided. Molecular analyses ( Fig. 1 View FIG ) reveal the taxon as sister to, and thus indicated as congeneric, with the taxon treated here as Coronapelopia valedon . The morphology of the immature stages can be reconciled with this, although the female adult is unknown for the genotype C. valedon , and the male is unknown for C. quadridentata .
The larva of C. quadridentata was segregated (as ‘ Pentaneurini genus E’ Cranston 1996) by the narrow, elongate four-toothed ligula ( Fig. 6F View FIG ). Although a tooth number of the conventional five can occur due to developmental abnormality, in this species it is unlikely given a ventral setal arrangement with S10, ventral pit and SSm transversely aligned in a pattern unknown in any previously recognised larva with an aberrant four-toothed ligula. All larvae from several localities in south-western Western Australia possessed this characteristic ligula, although some material from eastern Australia rarely may have a 5-toothed ligula, but be otherwise identical in every detail.
The species appears acidophilic in Western Australia where the Shannon River and the tributary Fish Creek naturally are acidic with low conductivity and nutrient levels, in a catchment entirely within the Shannon River National Park. The species is reported as both lotic and lentic in the south west of Western Australia by Leung et al (2011).
Several eastern Australian localities where this taxon had previously been recorded are named as swamps (e.g., Basket Swamp and Tin Swamp Creek) amongst Sydney Water monitoring sites. However, further locality details were not provided nor are specimens available for morphological study. The location from which molecular material was obtained was at elevation (~ 1360 m. asl) in a large sphagnum swamp amongst snow gums, including in a small stream draining the bog.
The sole site in Tasmania is a small pond (Jewels Pond #2) also at elevation (1185 m. asl) in cushion plant heathland.
Australian National Insect Collection
Departamento de Geologia, Universidad de Chile
University of Montana Museum
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