Polypedilum (Pentapedilum) nodosum ( Johannsen, 1932 )

Tang, Hong-Qu, Cranston, Peter S., Zhao, Jian-Gang, Lok, Chan-Wa, Wong, Kai-Chin & Li, Zhi-Qiang, 2014, The immature stages of Polypedilum (Pentapedilum) nodosum (Johannsen) and Polypedilum (Tripodura) masudai (Tokunaga) (Diptera, Chironomidae, Chironominae), Zootaxa 3893 (3), pp. 416-428 : 418-423

Polypedilum (Pentapedilum) nodosum ( Johannsen, 1932)

( Figs 1–3 )

Pentapedilum nodosum Johannsen, 1932: 541 ; Sasa & Hasegawa, 1983: 325; Sasa & Suzuki, 2002: 75. Polypedilum (Pentapedilum) nodosum: Tokunaga, 1964: 597 ; Oyewo & Saether, 2008: 49; Yamamoto et al., 2012: 38. Polypedilum (Pentapedilum) ‘K1’; Cranston, 1996, 2007; Cranston & Dimitriadis, 2004.

Material examined. Le/Pe/♂, Macau, the Bay of St. Lazarus, near Taipa Houses Museum, 27. ii. 2013 (emerged 3. iii. 2013), other 20Pe in alcohol bottles (H.Q. Tang); 10Pe in alcohol bottles, the same place as above, 16. i. 2013; 3 P♂ and 4L, other 60L in alcohol bottle, same locality, 24. ix. 2013 (H.Q. Tang); 2L, Macau, Tapai Grande, 12. vi. 2013 (H.Q. Tang) (all EJNU).

Additional examined material. Holotype ♂, slide mounted, Pentapedilum nodosum Johannsen ; INDONESIA: East Java, Klakah, Lake Lamongan, October 12 (coll. Thienemann Sunda Exped) ( BMNH)

AUSTRALIA, 14L., Queensland, Atkinson Dam, artificial stream, 27°06'S 152°27'E, 8.viii.1991 (J. McLean); Northern Territory, Kakadu N.P., Le/P♀ Magela Ck., Oenepelli Crossing, 12°34'S 132°53'E, 12.iv.1989 (P.S. Cranston); 2♂, nr Jabiru, Gulungul Ck., 12°39'S 132°53'E, 11.iv.1989 (P.S. Cranston); ♂, Magela Ck., Ranger outflow, 12°40'S 132°56'E, 5.i.1989 (P. Dostine); ♂, Ranger retention pond #1, 12 °41'S 132°55'E, 31.vi.1988 (P.S. Cranston); 4Pe, Yellow Waters, 12°54'S 132°32'E, 30.v.1988; ♂, east branch West Alligator R., 2.vi.1989 (P. Dostine); ♂, 5km NNW of Cahill’s Crossing, East Alligator R., 8.vi.1973 (D.H. Colless) (all ANIC).

SINGAPORE, L, Murai Reservoir, 1°23'54''N 103°40'13''E, colonisation tray, x. 2008 (‘ NUS team’); ♂, NUS campus outside lab, xii. 2012 (Yuchen) ( RMBR)

THAILAND: L, Phang Nga, Amphur Khura Buri, Aow Keuy Beach, pond @5 Masl., 09°18'N 98°22'E, 3.i.2006, L-878; L, same except 7.vi.2006, L-924; L, Ban Nam Ken pond, 08°51'N 98°15'E 12 masl, 4.i.2006, L- 882; Amphur Takua Pa, Tumbonbang Muang, L, Ranong, Laem Son N.P., pond nr HQ, 6 Masl., 09°36'N 98°28'E, 2.viii.2005, L-837; L, same except 3.i.2006, L-875. All collected by Sites & Vitheepradit ( UMOC).

Larva (n=5). Head capsule yellow, with dark brown mental teeth and mandible teeth. Occipital margin yellow to pale brown.

Dorsal surface of head ( Fig. 1 A). Frontoclypeus present, anteriorly broadened, with a very narrow hyaline strip of 3–5 µm width.

Antenna ( Fig. 1 B) yellow, with reduced third segment and fourth segment about 2 times as long as third, the fifth segment subequal or longer than third, blade extending beyond the terminal of flagellum.

Labrum. SI and SII plumose on both sides. Pecten epipharyngis with 3 scales, the lateral with 4 teeth and the median with 3 teeth. Premandible with 2 apical teeth and 1 inner tooth.

Mandible ( Fig. 1 C) with 1 apical, 1 dorsal and 3 distinct inner teeth. Mola area pale yellow. Seta subdentalis reaching the apical part of most proximal inner teeth.

Mentum ( Fig. 1 D) with two median teeth, first lateral mental teeth depressed to medians. Width of ventromentum less than the mentum, with the medially-directed pointed apex or slightly anteriorly directed.

Body. Anterior claws pale golden, and posterior claws a little brown, both simple and dense. Procercus and apical setae yellowish brown. Mensural features as in Table 1 .

Pupa (n=8). Exuviae yellow, apophyses brown. Cephalic tubercles absent ( Fig. 2 A). Thorax with conspicuously large granules near suture. Apex of wing pad with obvious nose ( Fig. 2 B).

Length of hook row II 0.36–0.50, 0.42 times width of corresponding tergite. Tergites as in Fig. 2 C & D, II–VI with obvious anterior transverse bands of spinules stronger than those of median and posterior patches. Median and posterior patch of tergites III–VI consist of 4 separated sub-patches. Median patch of tergite VII absent, only one trans-anterior band and 2 posterior bands remain. Tergite VIII without trace of spinulation. Median patch usually reduced on tergite II and VI ( Fig. 3 A, B & C), and sometimes two sub-median patches fused in the middle of tergite III–V. Conjunctives present in tergite III/IV and IV/V, with points about the same size as the points of those of the anterior transverse bands. Comb of segment VIII composed of 3–4 slender small teeth ( Fig. 3 D). Lateral taeniae of segments IV–VIII: 0, 3, 3, 4, 4. Mensural features as in Table 2 .

Remarks. Larvae of P. nodosum are similar to those of P. cultellatum in the shape of the mentum and in the distinct antennal blade extending beyond the apex of the flagellum. These two species live together in the Macau ponds, but the latter appears to differ clearly in antennal and mandibular features, with antennal segment 3 distinctly more than half the length of the 4th segment and with 2 inner mandible teeth, in contrast to P. nodosum segment 3 which is about half the length of the fourth segment, and the mandible has distinctly 3 inner teeth. The less developed third antennal segment (relative to the fourth segment, not reduced as in Tripodura ) also occurs in some species of Uresipedilum (e.g., P. aviceps Townes 1945 and P. flavum (Johannsen 1905)) ( Epler 2001) , but the latter differ significantly in well-developed ventromentum posterior lobes. We noted some characters in dorsal sclerites, such as frontoclypeus with a distinct anterior hyaline band and the S3 insertion to the posterior of lateral lobes, which resembles P. australotropicus Cranston 2000 , but the latter appears to differ clearly in the mental teeth, with protruding median teeth and well separated 1st laterals. In contrast in P. nodosum , the median teeth of the mentum are constricted basally, with small 1st laterals appressed to the medians. Among all described Polypedilum larvae, this is one of the Polypedilum larva that can be identified with confidence – it is the only one with 3 clear inner mandibular teeth, plus the interesting arrangement of the median and first lateral teeth. The three well-developed complete mandibular inner teeth with the presence of dorsal teeth is totally different from most with 2 inner teeth plus a dark-brown mola area, except few head capsules in subfossil P. nubeculosum (Meigen 1804) and P. u nc i na t u m (Goetghebuer 1921) with developing 3 inner mandible teeth which perhaps represents the eroding mola area. (H.Q. Tang pers. obs.). Such a characteristic is unique in this genus. The depressed first mental laterals to medians also seems to be unique in Polypedilum : a similar arrangement can be found in Chironomus ‘ type I’ for central mental teeth ( Webb & Scholl 1985). Some Polypedilum species may have basally constricted median teeth, but the first laterals are relatively independent, not appressed to medians.

The pupa of P. nodosum resembles that of many members of subgenus Pentapedilum , with dominant anterior transverse bands and a prominent hook row. In the key of Oyewo and Saether (2008), the pupa of P. nodosum will key to P. (Pe.) K1 Cranston if the spinulation of tergite II is ignored or P. (Pe.) uncinatum if not considering tergite VII, but this can be separated from the above two taxa by the tergite VII with anterior and paired posterior patches spinules, and a wing pad with a distinct nose. The occurrence of a nose on the wing pad, seemingly unique in Polypedilum , usually is a typical feature to distinguish many Tanytarsini from others, and seldom is seen in Chironomini .

Cranston (1996) described P. (P e.) K1, noting only a small difference from our present description, including the median spinulation of tergite II and tergite VIII. Oyewo and Saether (2008) also suspected P. (P e.) K1 to be the true P. nodosum . After having reexamined the original material, it appeared that the tergite VIII is bare, with no trace of any anteromedian patch of spinules (P.S. Cranston pers. obs.). Thus we concluded that all those previously described as P. (P e.) K1 should be assigned to P. nodosum .

Distribution. Indonesia (Sumatra), Palau, Marianas Islands, Caroline Island, Australia, Singapore, Thailand, Japan, China ( Macau).

Figures

FIGURE 1. Larva of Polypedilum nodosum (Johannsen, 1932). A. Anterior frontoclypeus. B. Antenna. C. Mandible. D. Mentum (scale: A 50 µm, B – C 25 µm, D 30 µm).

FIGURE 2. Pupa of Polypedilum nodosum (Johannsen, 1932). A. Frontal apotome. B. Thorax. C – D. Tergites I – VIII (scale: A 50 µm, B 200 µm, C – D 100 µm).

FIGURE 3. Pupa of Polypedilum nodosum (Johannsen, 1932). A. Spinulation of tergite II (another specimen). B – C. Variation spinulation of tergite VI. D. Segment VIII and anal lobe (scale: D 50 µm, others 100 µm).

Tables

TABLE 1. Mensural features of P. nodosum and P. masudai larvae. Abbreviations as in text.

	P. nodosum	P. masudai
n	5	4
B.l.	3.70–4.10, 3.87	4.85–5.60, 5.16
H.I.	355–365, 357	300–345, 325
PM	142.5–150, 147.5	120.0–150.0, 131.7
SSm-SSm	62.5–70.0, 65.8	55.0–70.0, 61.7
HCR	2.14–2.40, 2.25	2.08–2.18, 2.14.
Ant 1	48.0–52.5, 50.3	42.5–55.0, 49.2
Ant 2	15.0–17.5, 15.6	16.5–22.5, 19.7
Ant 3	3.0–5.0, 4.5	2.5
Ant 4	8.8–10.0, 9.4	12.5–15.0, 13.5
Ant 5	5.0	3.0–3.5, 3.2
AR	1.06–1.25, 1.15	1.10–1.33, 1.20
A1R	3.3–4.0, 3.6	2.75–3.00, 2.86
ROR	0.15–0.17, 0.16	0.33
Bl	45–50, 47.5	50.0–60.0, 57.5
BlR	1.13–1.67, 1.33	1.25–1.48, 1.39
Pmd	50.0–65.0, 57.5	65.0–75, 69.3
Md	100–120, 115	90.5–105.0, 98
M.w.	75.0–87.5, 83.5	82.5–100.5, 90.8
Mmw	12.5–15.0, 14.2	17.5–18.0, 17.8
V.w.	65.0–67.5, 66.1	107.5–130.0, 116.7
VmPR	2.17–2.25, 2.19	1.25–1.30, 1.28
IPD	42.5–50.0, 45.8	17.5–20.0, 18.5
Striae	22–26, 24	ca. 40
AS	350–420, 390	350–420, 380
SAS	180–220, 205	200–240, 220

TABLE 2. Mensural features of P. nodosum and P. masudai pupae. Abbreviations as in text.

	P. nodosum	P. masudai
n	8	5
t.l.	2.80–3.30, 3.05	4.05–4.50, 4.28
b.l.	1.95–2.70, 2.26	2.75–4.35, 3.60
fs.l.	42.5–50.0, 46.4	55–80, 65
hk.	32–42, 36	60–80, 68
hr.l.	160–200, 175	260–410, 332
a.l.	24–30, 27	26–42, 33
a.l.r	1.25–2.14, 1.80	1.67–1.90, 1.78