Yarrhpelopia acorona Cranston & Krosch, 2021

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 : 7-11

Yarrhpelopia acorona Cranston & Krosch sp. n.

( Fig. 3 )

urn:lsid:zoobank.org:act:B234D3F2-4FB4-43A9-B5B4-796B5D665DCA

[‘? Telmatopelopia ’ (part) Cranston 1996]

Type material. Holotype P ♂, slide-mounted in Euparal, AUSTRALIA: New South Wales, New England, Cathedral Rock N.P., Sphagnum pool, 30°26’18”S 152°17’9”E, 13.iii.2017 (Cranston) ANIC, MV: NSWNE17.3.1 . Paratypes (collected Cranston unless stated otherwise, deposited ANIC). 3 Pe, Queensland, Mt. Lewis N.P., Churchill Ck., 420 m. asl, 16°34’S 145°20’E, 6–7.iv.1997 ; P ♂, P ♀, 9 Pe, Herberton, Carrington Falls , 17°34’S 145°20’E, 9–10.iv.1997 ; P ♂, 3 Pe, Cardwell , 5 Mile Ck., 18°20’S 146°03’E, 1–4.iv.1997 [P ♂ to ZSM]; Pe, Fitch Hatton Gorge, 21°05’S 148°37’E, 200 m. asl, 22.iii.1998.

Northern Territory, Pe, Arnhem Land, ‘ Podocarpus canyon’, 12°39’S 133°26’E, 18–19.v.1992; Kakadu N.P., Pe, U. Magela Ck., below Bowerbird Billabong , 12°47’S 133°03’E, 28.v.1988; Rockhole Mine Ck., 13°30’S 132°30’E (M. Smith); 2 Pe, 22.iv.1993, Pe, P (♀), 29.iv.1993 [Pe to ZSM], Pe, P (♀), 6.v.1993, Pe, P (♀) 20.v.1993, 3P(♀), 27.v.1993 (all M. Smith) [P ♀ to ZSM]; Pe, same location, 25.iv.1992, 2Pe, 3.vi.1992 (Hardwick) .

Unassociated larvae: 3L, as above, Rockhole Mine Ck., 13°30’S 132°30’E,. v.1993 (M. Smith). L, New South Wales: nr Tallong, Barber’s Ck. (Sydney Water), viewed previously, now unavailable.

Description. Adult male (n=4, pharate/dissected).

Teneral body length ~ 3 mm, abdomen 2 mm, wing length ~ 2 mm. Thorax yellow-brown, scutal vittae midbrown, scutellum darker brown; antennal plume and legs pale yellow.

Head. Antenna with terminal flagellomere 50 long, with tapered or rounded apex, 2.5–3 × as long as broad, with terminal seta 50–60 long ( Fig. 3A ); penultimate flagellomere 4.5–6× terminal flagellomere; A.R. 3.4–3.5. Eye bare, with dorsomedial extension of 6 ommatidia. Temporal setae 11–14 aligned continuous with inner verticals, none dorso–laterally. Clypeal setae 13–16. Palp (2–4) 30, 64, 85, 116. Pedicel with 4 aligned setae.

Thorax. Antepronotal setae 1–3; acrostichals ~15–24, unevenly uni-biserial between vittae ending in anterior prescutellar field; dorsocentrals ~24–42, arising with cluster in anterior humeral field, multiserial in humeral area, =/- uni-biserial between vittae, expanded nearer to scutellum; supraalars 0; prealars 14–15 bi/multiserial, extending anteriorly more than usual; scutellars 12–14, scattered.

Wing. Membrane unpatterned, densely setose in all cells and all veins. Continuous row of near hyaline, bluntended 40 long setae ( Fig. 3B ) running from base of vein R to apex of R 1 observed in 1 intact wing, not in other abraded wings. Venation and VR not determinable on teneral uninflated wing. Anal lobe not determined. Squamal setae 18.

Legs. All teneral/pharate, only P 1 lengths and ratios calculated: 350, 360, 330, 210, 160, 120, 100; LR 1 0.91, BV 1 2.06, SV 1 2.15. Tibial spurs sinuous, each with 2–5 short lateral teeth and 0–several denticles ( Fig. 3C ): lengths; P 1 35–40; P 2 28–30, 28–30; P 3 52–63, 35. Without tibial comb. Claws very slender, sinuous curved, distally pointed, simple. Pulvilli absent.

Hypopygium ( Fig. 3D ). Tergite IX setose, dorsally with paired clusters, ventrally with median and lateral clusters; “anal point” present, hyaline, not illustrated. Gonocoxite 75–85 long, cylindrical, beset with dense setae on dorsal and lateral surface, extending only slightly beyond base of gonostylus; proximal dorso-medial surface with demarcated oval area of dense, mid-lengthed, medially-directed setae; posterior and lateral to this area, dense long setae are directed postero-laterally/medially. Gonostylus 60–70 long, with swollen base, strongly tapering, microtrichiose without longer setae, megaseta 8–12 long. Phallapodeme slender 50 long, sternapodeme slender, inverted V-shaped.

Adult female (n=6, all pharate/dissected). Body length ~ 2.5 mm, abdomen ~ 1.5 mm, wing length ~ 1.6 mm. Yellow-brown, scutal vittae and scutellum mid-brown. Antennal plume and legs pale yellow.

Head.Antenna with 4 setae on scape, 6–8 on pedicel; with 11 flagellomeres, terminal flagellomere 90–115 long, abruptly tapered to narrow blunt apex, with terminal seta 0–30% longer than terminal flagellomere; A.R. 0.29–0.31; eyes bare, separated medially by 2–3 ommatidia. Temporal setae 10–12 continuous with uniserial 5–7 inner verticals. Clypeal setae 9–13. Palp segment lengths (2–5): 30–37, 60–75, 85–105, 125–160.

Thorax. Some thoracic setae (esp. scutellars) stout and long, up to ~200. Antepronotal setae 3; acrostichals 29–34, uni-biserial between the vittae ending in anterior prescutellar field; dorsocentrals 32–42, anteriorly commencing with cluster in anteriormost humeral field, multiserial from humeral area, =/- uni-biserial in broader area towards scutellum; supraalars 0; prealars bi/multiserial 9–15; scutellars 22–26 multiserial.

Wing. Membrane unpatterned, densely setose with long setae in all cells and all veins (without distinctive setae on R veins). Anal lobe not determined. Squamal setae 16–18.

Legs. All teneral/pharate, lengths and ratios incalculable. Tibial spurs sinuous, each with 2–5 lateral fine teeth exemplified on P 1 ( Fig 3 , left) and few small fine hairs, lengths; P 1 45–50; P 2 29–43, 25–27; P 3 43–47, 25–27. Without tibial comb. Claws fine, slender, curved, distally pointed, simple; pulvilli absent.

Genitalia. Gonocoxapodeme VIII pale-brown, gently curved. Gonapophysis VIII triangular with a tapering distally rounded microtrichiose lobe. Gonotergite IX without setae. Notum thin, 110–132 long, 3x seminal capsule length, free part of rami pale. Tergite IX thin, non-setose. Postgenital plate large bearing small globular cerci, 30 x 30. Three ovoid / globular seminal capsules, 40 long, 30 wide; spermathecal ducts bare, ending separately.

Pupa (n=10, including some pharate). Length 5.2–6.8 mm, colour varying from mid yellow to darker golden yellow, transverse apophyses distinct, mid-yellow to darker.

Thoracic horn ( Fig. 3E, F ) tubular, of variable shape: holotype 360 long, 100 wide, near parallel-sided to slightly broadening distally, plastron plate ovoid 160 long, 45% length of horn, respiratory atrium 50–60% width of stem ( Fig. 3E ); Rockhole Mine Ck shorter, 250–270 long, less broadened distally, 45 wide at base, 55 at widest (subapex); plastron plate ovoid, 75–88 x 55–60, ~30% length of horn ( Fig. 3F ); corona absent, externally with dense well developed spines, separated or with fused bases in tropical specimens; respiratory atrium lacking internal structuring, occupying ~70–80% of horn width, tubular until constricted at connection to plastron plate. Thoracic comb of ~12 small blunt tubercles varying in size, in single uneven row.

Abdomen ( Fig. 3G ) with somewhat squat segments, with strong scar on I, distinct apophyses, and prominent dense, strong, simple spinules ( Fig. 3H ), with posterior transverse band of stronger darker spinules on a darkened background in tropical specimens, fainter in temperate specimens. Anal lobe triangular 245–280 long, 140–160 wide at base, distally a slightly but distinctly offset triangular point; setae of anal lobe rather narrow, inserted at ~40 and 55% of length respectively; mediolaterally with simple spinules, some extending to margin ( Fig. 3I ). Genital sacs triangular in male, 75–80% length of anal lobe, in female rounded and very small, ~30–40% of lobe length.

Larva (n=1). Head length 600; tapering, cephalic ratio (l:w) 77%, pale yellow with occipital margin deeper yellow. Cephalic setation ( Fig. 3O ) dorsally conventional for Yarrhpelopia with S7, S8, and DP near aligned at ~90° to A–P axis, S5 slightly anterior to alignment; ventrally with S9, S10 and VP proximate in triangular arrangement, SSm posteriormost, significantly distant from remainder.

Antenna ( Fig. 3J ). ~50% head length, 3× mandible length, segment lengths: 260: 55: 6: 4; A.R. 3.8, ring organ at mid–point; basal segment ~10× as long as basal width; blade bifid, inner narrow branch 60, outer dilate branch 64. Style very small 2–3; Lauterborn organ slender extending beyond antennal apex.

Mandible ( Fig. 3K ) gently curved, 110 long, with bluntly tapering apical tooth, short, barely projecting inner tooth, and weakly protruding rounded mola from which seta subdentalis arises.

Ligula ( Fig. 3L ) with 5 teeth in concave row, apices of middle teeth directed slightly laterally; ligula gently broadened from midpoint; darkened apical teeth to 33% of ligula, area of muscle attachment occupying basal 20– 25%. Paraligula bifid, with outer branch 50% length of ligula, inner shorter. Pecten hypopharyngis ( Fig. 3M ) with 16 distinct teeth, transversely orientated in gentle arc with innermost tooth longest and directed medially.

Maxillary palp ( Fig. 3N ) with distinct basal section, 25 long, flexible membranous at connection to main segment 50 long; ring organ at c 50–55% from base; crown 20 long with short setae and sensilla including 2–segmented b-seta with unequal sections.

Submentum ( Fig. 3O ) anteriorly with ‘creases’ of lighter sclerotisation. Dorsomentum, M appendage and vesicles very reduced or indistinguishable. Pseudoradula very broad, 50 wide, densely micro-granulose non-aligned posteriorly without contact to ventral hypopharyngeal apodemes.

Abdomen. Body without fringe of swim setae. Anterior parapod claws simple, pale. Anal tubules not distinguishable. Procercus pale, unicoloured, ~4.5× as long as wide (140 × 25–28), with 8 mostly broken anal setae, max length 400. Subbasal seta of posterior parapod simple, ~270 long. Posterior parapods yellow, all conventionally simple, except the shortest that is a strong flattened hook.

Etymology (Derivatio nominis). The specific epithet acorona refers to the diagnostic lack of any corona in the pupal thoracic horn. To be treated as a noun in apposition.

Remarks. The first specimens found were coded as ‘nr Telmatopelopia ’, and came from an acidic mine-affected creek in Kakadu N.P., Northern Territory. The taxon was keyed in larval and pupal stages by Cranston (1996). Tentative identification as ‘nr Telmatopelopia ’ was based on a pupal resemblance to this so-far monotypic northern hemisphere genus, notably the large ovate plastron plate lacking any surrounding corona on a tubular, spinose thoracic horn. Placement of this taxon within an expanded Yarrhpelopia derives from robust molecular evidence that it is sister to Y. norrisi ( Fig. 1 ). The adults resemble the type species Y. norrisi , as does the larva (below) although the pupa differs in the thoracic horn, spinosity of the abdomen and the terminal segment.

This taxon, listed in Smith & Cranston (1995, Appendix) as ‘nr Telmatopelopia ’, was one of 5 species based on pupal exuvial evidence that increased in abundance at the entry of the polluted Rockhole Mine adit into the creek ( Cranston et al. 1997).

Larval association has been problematic, with only one definite association from Rockhole Mine Creek and none from elsewhere. No potential larva was found amongst the sympatric specimens at the holotype location of NSWNE17.3, where larvae sampled for molecular study from that site (17.3.6,7,8 & 11) belong to Coronapelopia quadridentata (described below) and others (17.3, 4 & 9) to Yarrhpelopia norrisi . Larval specimens 17.3.2 and 10 provisionally allocated to ‘ST1’, now fall within the variation of Y. norrisi .

Initial identification as ‘near to’ Telmatopelopia is refuted by a different larval morphology including S9-S10, VP and SSm forming a curved line, with the DP absent ( Rieradevall & Brooks 2001), plus the serrate anterior parapod claws ( Cranston & Epler 2013). Although the pupa and adult male resemble Telmatopelopia , and although we lack molecular material, it is unlikely on the evidence at hand that this western European genus occurs in Australia.

Yarrhpelopia acorona is eastern Australian, apparently abundant only in the acidic polluted sections of Rockhole Mine Creek in Kakadu National Park; otherwise several locations in north Queensland (from 16°S) and a drain from a Sphagnum bog in Cathedral Rock N. P., New England (N.S.W.). Many sites are, or are surmised to be, acidified from mine wastes, with ferric flocculence, or in naturally acidic seeps or faster flowing waters.

Figures

FIG. 3. Yarrhpelopia acorona sp. n. Adult male.A, Antennal apex; B, Setae of wing veins R, R1; C, Spurs on tibial apex, (Left) P1 (♀), (Right) inner and outer P3 (♂); D, Hypopygium, left, dorsal (overlying ‘anal point’ omitted), right, stylised semi-ventral. Pupa. E, Thoracic horn (holotype); F, Thoracic horn, comb (Rockhole Mine Ck.); G, Dorsal abdomen; H, Tergite IV spinulation (‘shagreen’), detail; I, Anal lobe. Larva. J, Antenna, blade, apex; K., Mandible, L, Ligula, paraligulae; M, Pecten hypopharyngis; N, Maxillary palp; O, Mentum, submentum, ventral, right side dorsal. Abbreviations: S5–S10 cephalic setae, DP – dorsal pit, VP – ventral pit.

FIG. 1. Phylogenetic tree from Bayesian inference for Yarrhpelopia Cranston and associated taxa (Table 1) based on concatenated gene fragments. Posterior probabilities (PP) and Bootstrap support (BS from Maximum Likelihood analysis) are indicated above branches only for nodes with PP> 0.95 or BS> 70. Maximal supported nodes are indicated with an asterisk. Likelihood bootstrap support (BS), located to the right of a PP value, are cited only if>~70%, considered as supporting that node.A dash (–) for either PP or BS indicates a value below the threshold for support; unlabeled nodes are unsupported under either criterion.