Simulium (Hebridosimulium) paradisium Craig., 2006

Craig, Douglas A., Currie, Douglas C., Hunter, Fiona F. & Spironello, Mike, 2006, A taxonomic revision of the southwestern Pacific subgenus Hebridosimulium (Diptera: Simuliidae: Simulium), Zootaxa 1380 (1), pp. 1-90 : 63-65

Simulium (Hebridosimulium) paradisium Craig. n. sp.

( Figs. 10a , 11g , 13h , 16h , 18h , 20h , 22b )

Types

Holotype. Larva : last instar in alcohol. Label data – “ Simulium (Hebridosimulium) paradisium , Vanuatu, Santo, upper cascade, trib. Sarakata River, S15.43224° E167.07600°, alt. 217m. 13.ix.2004. Coll. D. A. & R. Craig. HOLOTYPE. No. 16609” ( BPBM) . Paratypes. Larvae: last instars in alcohol (larvae; BPBM, DAC, LCNZ). Penultimate and earlier instars in alcohol (larvae; BPBM, DAC, ROM). Label data – as for

Holotype, but with “ PARATYPE ”.

Diagnosis

Pupa: cuticle with numerous granules; gills branched basally, petioles short; filaments thin, finely tapered. Larva. Head: evenly dark brown, head spots negative, appendages dark brown; body markedly pale, posterolateral diagonal grey stripes on sixth segment.

Description

Adult female. Unknown.

Adult male. Unknown.

Pupa (based on pharate material). Gill ( Fig. 10a ): filaments fine, gradually tapering, petioles short ((2+2) +2 +2 +2); maximum length 1.4–1.8 mm. Thorax: cuticle with numerous distinct granules.

Larva (based on numerous mature last-instar larvae). Body ( Fig. 11g ): relatively large species; total length 6.4–7.3 mm; colour: no obvious sexual dimorphism, prothorax and mesothorax completely light gray, metathorax very pale yellowish orange, abdominal segments I–III pale medially, light gray laterally, pale ventrally, segments IV & V pale, remainder of abdomen gray dorsally, laterally with 3 distinct grey diagonal bands. Head ( Fig. 13h ): overall dark brown; anterior apotome markedly pigmented, unusual pale region medial of fan stalk bases, sensilla 5 and 6 bases markedly pale; dorsal head spots negative and markedly distinct; width 0.69–0.73 mm; length 0.73–0.86 mm; distance between antennal bases 0.43–0.44 mm; ecdysial lines irregular, diverging strongly posteriorly, inflexion at maximum width broadly rounded; lateral margins of head subparallel; posterior edge of apotome slightly emarginated, postocciput not extended between cervical sclerites and apotome. Antenna: total length 0.45 mm; distal article 0.30 times as long as basal articles; longer than labral fan stalk, distal article brown, remainder light brown to pale. Labral fan: stalk moderately pigmented, anterior palatal bar noticeable, but not markedly protrusive; 57–60 dark rays, 0.75–0.84 mm in length, medial rays 0.015 mm in width, 10–12 posterolateral rays finer than others; microtrichia well developed, subequal in length to ray width, pattern distinct, with 5–7 shorter microtrichia between those longer. Postgenal cleft ( Fig. 16h ): V-shaped; 1.2 times longer than maximum width. Postgenal bridge 0.25 time as long as cleft depth; genae evenly dark brown, paler around stemmata; posteroventral elongated muscle scar markedly negative. Hypostoma ( Fig. 18h ): overall dome-shaped; ratio 4.8; median tooth markedly prominent, lateral teeth smaller but also prominent, scalloped medially, directed laterally, sublateral teeth distinct; paralateral teeth essentially absent, lateral serrations slightly developed; 11 or 12 hypostomal setae per side. Mandible ( Fig. 20h ): preapical teeth poorly developed, apical tooth and subapical teeth prominent; spinous teeth substantial, gap absent; serration and sensillum prominent, but not markedly developed; blade region smooth and slightly convex. Abdomen: thorax and anterior abdominal segments subequal in width, expanded gradually to maximum width, markedly steatopygous; posterodorsal tubercles absent. Posterior circlet ( Fig. 22b ): directed posteriorly; 208–214 rows of hooks, 34–36 hooks per row (total hooks ca. 7,300).

Additional material examined Penultimate and earlier larvae. Same label data as Types (larvae; DAC) .

Etymology Named for the paradise-like beauty of the type locality.

Distribution VANUATU: Santo, Millennium Cave area.

Comments

Known so far only from the Millennium Cave area (Sarakata River watershed) on Santo, the larvae of S. paradisium are habitat specialists of fast, shallow water. They were taken in moderately large numbers from smooth travertine substrate in fast flow (1.5 m /s), along with low numbers of larvae of S. steatopygium and S. callipygium . Larvae show steatopygous modification to the abdomen in addition to possessing, by far, the largest number of hooks comprising the posterior circlet of any Vanuatu simuliid — both structural attributes known as adaptations to fast-flowing water ( Palmer and Craig 2000, Craig 2003). Larvae of S. paradisium notably do not twist the body to place the labral fans into the mainstream flow –– again, a known adaptation to thin films of fast water (Crosskey 1990, Craig 1997).

Of all the Vanuatu simuliids, S. paradisium has perhaps the most colourful larvae, with multiple colours of the head spots set off against a dark brown background and with a pale body. The spectacular colouration of the larva seems appropriate, given the stunning beauty of its type locality, a true jungle paradise ( Fig. 24b ).

Figures

FIGURE 10. Pupal gill filaments of Hebridosimulium species (continued). Scale bar = 0.2 mm.

FIGURE 11. Left lateral views of Hebridosimulium species larvae. Last-instar larvae, except l & n, which are penultimate. Arrowheads indicate dorsal tubercles. Scale bar = 1.0 mm.

FIGURE 13. Dorsal views of larval heads of Hebridosimulium species. a–e. callipygium species group, f–h. part of steatopygium species group. Last instars, except f & h, which are penultimate instars. Arrows (b & e) indicate anterior palatal bar. Scale bar = 0.2 mm.

FIGURE 16. Postgenal clefts and hypostoma of larvae of Hebridosimulium species. a–e callipygium species group, d–h steatopygium species group. Last instar, except b, which is penultimate. Scale bar = 0.1 mm.

FIGURE 18. Hypostomal teeth of larvae of Hebridosimulium species. Last instar. Scale bar = 0.05 mm.

FIGURE 20. Mandibular teeth of larvae of Hebridosimulium species. a–e callipygium species group, f–h steatopygium species group. Last instar, except b, which is penultimate. Arrow (e) indicates the blade region; asterisk the spinous teeth gap. Scale bar = 0.025 mm.

FIGURE 22. Anal sclerite and circlet of hooks of larvae of Hebridosimulium species. Last instar. Ca. 2800 and 7300 hooks, respectively. Scale bar = 0.2 mm.

FIGURE 24. Habitats of larvae of Hebridosimulium species. a–e. Vanuatu.a. Santo, Adsone River. Type locality of S. adsonense. b. Santo, upper cascade, tributary of Sarakata River. Type locality of S. paradisium. c. Efate, Mele Cascade. Type locality of S. steatopygium. Note travertine terraces. d. South Pentecost, Warbot River. Type locality of S. supercilium. e. Santo, small stream, Millennium Cave region. Typical locality of S. subparadisium. f–i. Fiji. Habitats of S. laciniatum larvae. f. Viti Levu, Abaca Village, above Vereni Falls. Type region. g. Taveuni, Wairiki, Devo Peak, looking down water slide. h. Kadavu, Kadavacoro Village, Wailea Waterfall. i. Vanu Levu, Waisala Rain Forest Reserve, Ravini River.