New Zealand Entomologist Vol 33: 38-42 (February 2010) Container-inhabiting Monopelopia larvae (Diptera: Chironomidae: Tanypodinae) newly recorded in New Zealand TANYA J. BLAKELY1, PETER S. CRANSTON2, MICHAEL J. WINTERBOURN1 1 School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch. E-Mail: tanya.blakely@canterbury.ac.nz 2 Entomology Department, University of California, Davis CA 95616, USA ABSTRACT Worldwide, Monopelopia larvae have been found to inhabit small, boggy and often acid waters including phytotelmata, billabongs, and dystrophic lakes, pools and streams. Although Tanypodinae larvae have previously been associated with phytotelmata in Auckland and Wellington, until now Monopelopia has not been reported from New Zealand. Larvae of an undescribed chironomid species belonging to the genus Monopelopia (Tanypodinae: Pentaneurini) were the most abundant insects colonising artificial waterfilled tree-hole containers attached to red beech trees in Orikaka Ecological Area, north Westland, New Zealand. Here we describe the final-instar larva and comment on the larval diet as indicated by gut contents. In the absence of pupae and adults, larvae were attributed to Monopelopia based on the arrangement of their cephalic setae and ventral sensory pit. Gut contents of 185 final-instar larvae contained sooty mould fungi, fine detritus and animal prey items including small conspecific larvae. KEYWORDS Monopelopia, Nothofagus fusca, phytotelmata, Tanypodinae, Pentaneurini, water-filled tree holes, sooty mould fungi, New Zealand INTRODUCTION Monopelopia (Diptera: Chironomidae: Tanypodinae) was described originally by Fittkau (1962) for the European species Tanypus tenuicalcar Kieffer whose larvae develop in small, boggy and often acid waters. Into the genus, Fittkau added a Sumatran species, Pentaneura divergens Johannsen, whose larvae had been found in Sphagnum ‘moss’, and a reared but undescribed species from ponds in Java. Subsequently, two species were described by Beck & Beck (1966) from the Nearctic: M. boliekae and M. tillandsia, the first species known to inhabit phytotelmata (plantheld waters).More recently, further phytotelm species have been described from Jamaican terrestrial tank bromeliads (M. mikeschwartzi Epler, in Epler & 38 Janetzky 1999) and from Brazilian bromeliads (M. caraguata, in Mendes et al 2003). Bromeliad denizens belonging to Monopelopia are also known from Puerto Rico (Cranston 2007a) and Florida (John Epler pers. comm) where M. caraguata is reported. Although these recent records reveal diverse phytotelm taxa, larval records from Australia (billabongs, dystrophic lakes, Cranston & Dimitriadis 2004), Thailand (subcoastal pools, Cranston 2007b) and a stream in Brazil (Stur 2000) confirm and extend the presence of Monopelopia in non-plant-held water bodies. Monopelopia has not been reported previously in New Zealand, where Ablabesmyia and Zavrelimyia, each with a single species, are the only genera of Pentaneurini (Tanypodinae) currently recognized (Boothroyd & Forsyth 2003). Brief descriptions of the larva and pupa of Zavrelimyia harrisi (Freeman) (as Pentaneura harrisi) were provided by Forsyth (1971) and the larval maxillary palp of Ablabesmyia mala (Hutton) was figured by Stark (1981). In a previous study, Derraik & Heath (2005) recorded three species of Tanypodinae from phytotelmata in the Auckland and Wellington regions, but only one, Apsectrotanypus sp. (Macropelopiini) was identified to genus. Meanwhile, in a wider study of aquatic insects inhabiting artificial water-filled tree holes attached to red beech trees (Nothofagus fusca) (Blakely 2008), larvae of an undescribed chironomid species belonging to the genus Monopelopia (Tanypodinae: Pentaneurini) were the most abundant insects found. Thus, the purpose of this note is to provide an initial description of the larva of Monopelopia, with an aim to facilitate a full species description based on adults reared through from larvae at a later date. We also examine and comment on the larval diet as indicated by gut contents. MATERIALS AND METHODS We examined over 185 specimens of Monopelopia, which naturally colonised artificial water-filled treehole containers attached to red beech trees in Orikaka Ecological Area (41° 27’S 171° 25’E) Buller District, Westland, New Zealand (Blakely 2008). Specimens Container-inhabiting Monopelopia larvae were collected from the artificial tree holes by TJB from April-December 2006, immediately frozen and later preserved in 70% ethanol prior to mounting on slides in either lactophenol-PVA, Hoyers or Euparal. Voucher specimens, slide mounted in either Hoyers or Euparal, are deposited in the New Zealand Arthropod Collection, Entomology Division, Landcare Research New Zealand Ltd., Auckland, New Zealand. RESULTS Description of Monopelopia sp. inhabiting artificial water-filled tree holes Final-instar larva. Body length 5-6 mm. Head capsule (Figure 1A) length 550-630 μm, maximum width 430490 μm: cephalic index 0.71-0.78; yellow with posterior margin of head capsule outlined by narrow dark band. Cephalic setae with ventral pit (VP) almost aligned laterally with seta submentum (SSm); SSm, S9, S10 forming a slightly curved alignment medial to lateral (Figure 1B); dorsal setae S7, S8 and S5 well separated, near linearly (transversely) aligned, without dorsal pit (Figure 1C). Antenna 275-300 μm, 4-segmented, lengths 225230; 62-70; 2-3, 4-5; Antennal ratio 2.9-3.1; basal segment slightly curved with ring organ distal to midlength (c. 60%), pale distal blade subequal to length of segment 2; Lauterborn organ distally on segment 2 forms apical complex with a ‘tuning fork’ appearance (Figure 1D). Mandible (Figure 1E) 180-210 μm with long apical tooth, short inner tooth, and expanded mola (‘basal tooth’) bearing seta subdentalis extending to middle of apical tooth. Ligula (Figure 1F) 160-180 μm slightly ‘waisted’, with 5 teeth ending in straight line, middle 3 teeth subequal in size, ending in rounded points directed anteriorly; paraligula bifid with short and narrow inner branch; pecten hypopharyngis (Figure 1G) with 7-8 narrow teeth. Maxillary palp (Figure 2A) on pale base, basal segment undivided, 3.5 times as long as wide, ringorgan located in apical 1/3, beyond mid-length; terminal segments very short and surrounded by ‘crown’ of setae and sensilla of unequal length and shape. Submentum (Figure 2B) evenly microgranular, without differentiated banding. Dorsomentum without teeth; M appendage developed with 2 small teeth laterally, vesicles rounded. Pseudoradula 15-18 wide, densely granulose without clear alignment into rows. Abdomen: Lacking any setal fringe; procercus (Figure 2C) pale, slightly darkened posteriorly, 95-105 Figure 1. Monopelopia sp. larva. A, Ventral whole head; B, Ventral cephalic setae and pit; C, Dorsal cephalic setae; D, Antennal apex; E, Mandible; F, Ligula; G, Pecten hypopharyngis. Figure 2. Monopelopia sp. larva A-D, pupa (pharate in larva) E & F. A, Maxillary palp; B, Submentum; C, Procerci; D, Posterior parapod claws; E & F, Pupal thoracic horn. 39 New Zealand Entomologist Vol 33: 38-42 (February 2010) μm by 22-25 μm wide; posterior prolegs bearing claws with variable degrees of pigmentation but including one dark claw with 3 or sometimes 4 small spines on the inner margin (Figure 2D). Pupa (pharate in larva). Thoracic horns (Figures 2E, 2F) narrow, tubular, with somewhat elongate plastron plate and no obvious corona; surface spinose all over, more densely so apically. Food of larvae Gut contents of 185 final-instar larvae mounted on slides in lactophenol-PVA were examined microscopically at 50 and 200 times magnification. Except for 28 prepupae all larvae contained ingested material and in all instances this included fragments of sooty mould fungi and fine detritus of indeterminate origin. Animal prey items were found in 27 guts (17% of larvae containing food), the most frequently occurring being very small con-specific tanypod larvae (Table 1). In only five guts was more than one prey item present: two, two and three tanypod larvae in three individuals, four copepods in one individual, and chironomid eggs and a mite in another gut. All chironomid and tipulid larvae that had been ingested were very small relative to the predator. Thus, head capsule widths of measurable individuals were all 90 μm, about 0.2 of the width of the tanypods that had eaten them. Partially ingested pupae or adults of the endemic culicid Maorigoeldia argyropus (Walker) were identified by the presence in Monopelopia guts of their characteristic wing scales. DISCUSSION Species of Monopelopia are found nearly globally, living either in container habitats or within small ponds and pools. The Palaearctic M. tenuicalcar shows a preference for moss within stagnant bodies of water in eastern Siberia (Kravtsova 2000) and for bog-pools, polyhumic lakes and reservoirs in Finland (Paasivirta et al. 1988). Similar small and acidic non-phytotelm habitats are used in south-east Asia and Australia (Cranston & Dimitriadis 2004, Cranston 2007b). Water in the container habitat of the New Zealand larvae was also often acidic (pH range: 3.3-6.9) and strongly “tannin-stained” by organic acids leached from enclosed beech leaves (Blakely 2008). Although a continuum could be envisaged between such containers (or phytotelms) and small sphagnum pools and acidic ponds, as yet, no phytotelm species have been found living outside their preferred container habitats, or viceversa. Taxonomy Larval Tanypodinae have been difficult to identify with confidence in the absence of the more distinctive pupae and adults. Reliance on what have proved to be somewhat variable features of colour and ratios of antennal proportions and head shape, and uncertainty about applicability of definitions based on northern hemisphere studies (e.g., Fittkau & Roback 1983), has prevented confident identification, especially within the tribe Pentaneurini. However, discovery of the identificatory significance of variation in the locations of cephalic setae and sensory pits by Kowalyk (1984), validated across a range of tanypodines (Rieradevall & Brooks 2001), including for austral taxa (e.g., Cranston 2000), provides invaluable evidence for identity. Thus, the combination of ventral setae and pit (Figure 1B) combined with the almost evenly-spaced and linearly aligned dorso-lateral / dorsal setae S7, S8 and S5, without a dorsal pit (Figure 1C), is unique to Monopelopia. The genus Monopelopia is now recognised as more diverse than was understood by Fittkau & Roback (1983) and certain key larval characters appear invalid – thus the ligula teeth may be level with each other and with a regularly sized mid-tooth, and the ventromentum need not have longitudinal folds. In the larva, variation in ligula shape, cephalic setal arrangements, and number Table 1. Frequency of occurrence of prey items in the guts of 27 final instar Monopelopia (Diptera: Chironomidae: Tanypodinae) larvae containing animal remains. Prey items Chironomidae Frequency Monopelopia (Tanypodinae) larvae 11 Limnophyes (Orthocladiinae) larvae 1 Eggs 1 Culicidae Maorigoeldia argyropus pupae / adults 6 Tipulidae unidentified larvae 1 Acari 3 Copepoda 1 Unidentified arthropod fragments 3 40 Container-inhabiting Monopelopia larvae of, and toothedness of posterior parapod claws provide characters that allow species discrimination (Mendes et al. 2003). phytotelm-dwelling Monopelopia from Brazil indicated that all larvae that he reared from phytotelmata fed on detritus, and some drops of detritus provided sufficient food for second instar larvae to develop to adults. Feeding habits Late larval instars of Tanypodinae are typically predators that either engulf prey whole or in part, or pierce the prey organism and “suck out” body contents (McKie & Pearson 2006, PS Cranston pers. obs.). The actively hunting tanypod Australopelopia prionoptera Cranston detects prey mainly by movement and will invade chironomid tubes after being attracted by the ventilatory movements of larvae (McKie & Pearson 2006). A wide range of prey taxa were recorded by Roback (1969) in the guts of 14 tanypod species, including oligochaetes, small crustaceans and insects, of which chironomid larvae were by far the most abundant. Roback (1969) also found that detritus and algae, especially diatoms, occurred widely in digestive tracts. In contrast, Baker & McLachlan (1979) found no animal remains in the gut contents of three species at four sites in the United Kingdom and noted that fine detritus was invariably the dominant material present. However, gut content analysis can only discern the hard parts of ingested prey, and any prey body contents obtained by sucking would not have been visible. Surprisingly, survival and growth of Procladius choreus (Meigen) larvae in laboratory trials was almost equally good when fed Tubificidae (Oligochaeta), detritus or larval Chironominae (Baker & McLachlan 1979), despite detritus being a much poorer quality food than invertebrates for most aquatic insects (Cummins & Klug 1979). Fungi do not appear to have been documented as a significant component of larval Tanypodinae gut contents, although Roback (1987) found that two larvae of Monopelopia tillandsia Beck and Beck contained fungal spores in addition to general detritus and fragments of mosquito larvae. Sooty mould fungi (Ascomycota), the most frequently occurring and abundant materials on slides of our Monopelopia larvae, grow on the surfaces of leaves, which were present in the containers sampled and are readily removed by grazing larvae. The larval gut contents of four stonefly (Plecoptera) and three mayfly (Ephemeroptera) species from West Coast forest streams also commonly contained sooty mould fungi (Collier 1990), which were hypothesised to be a potentially important food resource for detritivorous aquatic invertebrates. Animal prey items were very small and occurred singly in most tanypodine guts, and therefore it is likely they were ingested incidentally while grazing on detritus and fungi. However, some Monopelopia larvae may have been more predatory than was apparent if they had been sucking body contents from prey without ingesting them. Nonetheless, observations by Mendes (2002) on a ACKNOWLEDGEMENTS We thank Raphael Didham and Nick Etheridge, School of Biological Sciences, University of Canterbury, for their assistance. Raphael Didham, Jon Harding and two anonymous reviewers made constructive comments on earlier versions of the manuscript. This research was supported by the Brian Mason Science and Technical Trust, the Royal Forest and Bird Society Protection Society of New Zealand (Canterbury Branch) and a University of Canterbury Doctoral Scholarship awarded to TJB. Forest canopy work in Orikaka Ecological Area was conducted under Department of Conservation National Permit no. 11/536. REFERENCES Baker AS, McLachlan AJ. 1979. Food preferences of Tanypodinae larvae (Diptera: Chironomidae). Hydrobiologia 62: 283–288. Beck WM, Beck EC. 1966. Chironomidae (Diptera) of Florida: 1. Pentaneurini (Tanypodinae). Bulletin of the Florida State Museum 10: 305–379. Blakely TJ. 2008. Tree holes as habitat for aquatic and terrestrial invertebrates in New Zealand. Unpublished Ph.D. thesis, University of Canterbury, New Zealand. Boothroyd I, Forsyth D. 2003. Checklist of New Zealand Chironomidae (Diptera). 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