Identification of two Australian salt-lake chironomid species from subfossil larval head capsules

Palaeogeography, Palaeoclimatology, Palaeoecology, 54 (1986): 317--328

317

Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

IDENTIFICATION OF TWO AUSTRALIAN SALT-LAKE CHIRONOMID SPECIES FROM SUBFOSSIL LARVAL HEAD CAPSULES

MICHAEL KOKKINN

Department of Zoology, The University of Ade!aide, Adelaide, South Australia 5001 (Australia) (Received September 24, 1984; revised and accepted July 2, 1985)

ABSTRACT Kokkinn, M., 1986. Identification of two Australian salt-lake chironomid species from subfossil larval head capsules. Palaeogeogr., Palaeoclimatol., Palaeoecol., 54: 317--328. Most palaeotimnological work with chironomid larvae has used the association between certain tribes and trophic status to interpret lake palaeohistories. Such interpretations cannot apparently be made from Australian chironomid subfossils. However, these may be useful in other ways. A present difficulty is that Australian larval chironomids remain undescribed at the species level. This effectively conceals potentially valuable ecological information of use to palaeolimnologists. Yet head capsules can be separated specifically, and those of two salt-lake inhabitants, Tanytarsus barbitarsis Freeman and Tanytarsus semibarbitarsus Glover, are described using scanning electron micrographs. The occurrence of head capsules of T. barbitarsis, Australia's best-studied chironomid species, indicates: salinities between 35--100°/oo, shallow waters, eutrophy and mild climatic conditions. T. semibarbitarsus head capsules indicate salinities below 30°/°°. INTRODUCTION

In 1913, Thienemann proposed that particular chironomid taxa were indicative of lake trophic status. Most subsequent palaeolimnological work involving chironomid remains has used this proposition to trace fluctuations in lake trophic status through recent geological time (Deevey, 1942; Frey, 1955; Brundin, 1958; Stahl, 1959; Warwick, 1975; Hofmann, 1983). Other studies have been able to indicate the frequency of stratification and the variation of lake depth with time (Megard, 1964; Goulden, 1966; Roback, 1970). However, the correlation of the Tanytarsini with oligotrophy and the Chironomini with eutrophy, widely applied by palaeolimnologists on other continents, does not generally hold in Australian lacustrine environments (Timms, 1980). To date, there is but one palaeolimnological investigation using chironomid remains in an Australian lake (Paterson and Walker, 1974b). Patterns of species occurrence in the sediments of Lake Werowrap, Victoria were ex0031-0182/86/$03.50

© 1986 Elsevier Science Publishers B.V.

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plained in the light of laboratory experiments: It was suggested that Tanytarsus barbitarsis was absent from sediments of low salinity because of an inability to compete with other chironomids under those conditions. No indication was given as to how the different species were distinguished. Crisman (1978) has noted that chironomid t a x o n o m y is based upon adult characters, and that the apparent lack of intra-generic morphological diversity among the larvae hinders identification of individual species. The resulting inability to resolve a potentially ecologically diverse palaeofauna to the species level confounds t h e reconstruction of past environments based upon larval remains. Nevertheless, in North America and Europe, descriptions are available which enable resolution of many chironomid larvae to the species level (Bryce and Hobart, 1972; Mason, 1973). In Australia, available keys separate only genera (Martin, 1974, 1975) and the lack of species descriptions of Australian chironomid larvae seriously reduces their value as palaeoecological indicators. The recent general acceptance of the importance of chironomids in aquatic ecosystems highlights such deficiencies (Cadwallader et al., 1980; Hume and Pribble, 1980; Maher, 1984; Maher and Carpenter 1984). The distinguishing larval features of two species of salt-lake chironomids, Tanytarsus barbitarsis and Tanytarsus semibarbitarsus, are presented here. T. barbitarsis is Australia's best-studied chironomid (Paterson and Walker, 1974a; Edward, 1983; Kokkinn, unpublished data). In addition, it is unique among Australian chironomids in its ability to exploit saline waters (up to 140 g 1-1 in certain areas; Edward, 1983). Its ecological specialization makes it a convenient starting point for the description of the larval forms of Australian chironomids. Whilst not the only chironomid species to occur in Australian inland saline waters, it is, nevertheless, the most common. T. barbitarsis is compared here to T. semibarbitarsus, a closely related species, essentially to demonstrate that it is possible to resolve Australian chironomid larval remains to species and thereby give access to ecological information of use to limnologists and palaeolimnologists alike. M AT ER I ALS AND METHODS

Fourth instar larvae of T. barbitarsis were collected from the lagoons adjacent to the power station at Port Augusta. T. semibarbitarsus were collected from the Noora evaporation basin {both sites in South Australia). The identity of both species has been confirmed by Dr. D. H. D. Edward (personal communication, 1984). Several hundred specimens of T. barbitarsis were viewed. Fifty of the less abundant T. semibarbitarsus were examined. To examine head capsules, they were first critical-point dried, then m o u n t e d on stubs with double-sided adhesive tape, double-coated with carbon (i.e. 2 X 15 nm) and gold/palladium alloy (i.e. 2 X 20 nm) in a Denton Vacuum Model 502 high-vacuum evaporator. They were viewed in an ETEC Autoscan scanning electron-microscope fitted with a tungsten filament.

319 Further specimens were cleared in 4% KOH and m o u n t e d on glass slides in polyvinyl-lactophenol to which a few drops of acid fuchsin in glacial acetic acid had been added. These specimens were viewed under a microscope at 400 X and drawn with the aid of a camera lucida. DISTINGUISHING TANYTARSUS BARBITARSIS FROM TANYTARSUS SEMIBA RBITARS US Features of larval head capsules may be treated under two categories: (a) Diagnostic features, likely to be preserved in subfossils; (b) Supplementary features which m a y not preserve in subfossils. (a ) Diagnostic features (1) Antennal tubercles. In T. barbitarsis the antennal tubercles are flared outwards and as wide as long. In dorsal view a curved line separates them. (Fig.l.a). In T. semibarbitarsus they project directly forward, and are twice as long as wide. In dorsal view the tubercles are separated by a rectangular line (Fig.2.a). (2) The h y p o s t o m i u m . The outer t o o t h o f the h y p o s t o m i u m of T. barbitarsis is reflected outwards (Fig.l.c), whereas in T. semibarbitarsus it projects upwards in the same way as its neighbour (Fig.2.c). (3) Shape of the head capsule. In T. barbitarsis the head capsule is no longer than its breadth (Fig.3.a) whereas in T. semibarbitarsus it is elongated (Fig.3.b). (b ) Supplementary features (1) The central t o o t h of the hypostomium. This is c o m m o n l y ornate in T. barbitarsis (Fig.l.d), but never in T. semibarbitarsus (Fig.2.d). (2) The antenna. In T. barbitarsis, the petioles of the Lauterborn organs are roughly as long as the third antennal segment (Fig.l.b); in T. semibarbitarsus t h e y are almost as long as segments three, four and five combined (Fig.2.b). (3) The mandible. The largest t o o t h on the mandible of T. barbitarsis is bulbous (Fig.l.e), whereas in T. semibarbitarsus it is elongate (Fig.2.e). The accessory t o o t h of T. semibarbitarsus has a characteristic V-shape (Fig.2.f); in T. barbitarsis it is bulbous (Fig.l.f). (4) Range of the head capsule size. To aid identification when several instars occur in sediments, the range of head-capsule width in each of the four instars is presented for T. barbitarsis (Fig.4). Table I gives a summary of the features which distinguish the two species.

320

Fig.1. Tanytarsus barbitarsis, a. Dorsal view of head capsule showing the short, flared antennal tubercles, b. Antenna showing the petioles of the Lauterborn organs to be as long as the third antennal segment, c. The hypostomium showing outward reflection of the outer tooth, d. The central tooth of the hypostomium with elaborations, e. The mandible showing the bulbous main tooth, f. Detail of accessory tooth of the mandible. Scale bars on micrographs represent 10 #m.

321

Fig.2. Tanytarsus semibarbitarsus, a. Dorsal view o f t h e h e a d capsule s h o w i n g t h e elongate a n t e n n a l t u b e r c l e s s e p a r a t e d b y a r e c t a n g u l a r line. b. A n t e n n a s h o w i n g t h e p e t i o l e s o f t h e L a u t e r b o r n organs t o b e e q u a l in l e n g t h to s e g m e n t s three, f o u r a n d five. c. T h e h y p o s t o m i u m s h o w i n g t h e regular n a t u r e of t h e o u t e r teeth, d. T h e c e n t r a l t o o t h of t h e • h y p o s t o m i u m w i t h o u t e l a b o r a t i o n , e. T h e m a n d i b l e w i t h e l o n g a t e m a i n t o o t h , f. Access o r y t o o t h o f t h e m a n d i b l e w i t h c h a r a c t e r i s t i c V-shape. Scale bars o n m i c r o g r a p h s repres e n t 10 urn-

322

I( I

J Fig.3. Ventral view of head capsules, a. Tanytarsus barbitarsis, b. Tanytarsus semibarbitarsus. L = labrum; M = mandible; H = hypostomium; S - striated plate. ist Instar I

20-

J

2nd Instar

3rd Instor

L

~

9

o

-

-

o

6

o

6

I

I

o

o

4th Instar

I

o

_=

I0o

0.i Maximum

0.z Width

Measur ed

an the

0t~ Dorsal S u r f a c e

0:4

(ram)

Fig.4. Range of head capsule width in each of the four larval instars of Tanytarsus barbitarsis.

PALAEOLIMNOLOGICALLY RELEVANT ECOLOGY ON T A N Y T A R S U S BA RBITA RSIS

A l t h o u g h P a t e r s o n and Walker ( 1 9 7 4 b ) believed t h a t T. barbitarsis was able to survive and r e p r o d u c e in f r e s h w a t e r e n v i r o n m e n t s , its p r e s e n c e in fresh w a t e r in t h e field has n o t b e e n c o n f i r m e d . It is m o s t c o m m o n l y f o u n d in w a t e r s ranging in salinity f r o m 35% o t o 100% o. E d w a r d ( 1 9 8 3 ) has r e p o r t e d it f r o m lakes with salinities o f 140°]oo o n R o t t n e s t Island (Western Australia). It o c c u r s in large n u m b e r s in Lake W e r o w r a p (Victoria) at salinities o f 40% o ( P a t e r s o n and Walker, 1974a). A t P o r t Augusta ( S o u t h Australia), it occurs in high n u m b e r s (reaching 150 000 individuals m -2) at salinities a r o u n d 70°~o ( K o k k i n n , u n p u b l i s h e d data). It also o c c u r s in t h e s o u t h

323 TABLE I Morphologically distinctive features of Tanytarsus barbitarsis and Tanytarsus semibarbitarsus from larva] head capsules Taxonomic unit

Name

Distinguishing features

Sub-family

Chironominae

Striated plates present.

Tribe

Tanytarsini

Antenna] tubercles prominent, as long as wide or longer, first antenna] segment long and curved.

Genus

Tanytarsus

Antenna] tubercles without a spur. Petioles of Lauterborn organs shorter than last three antenna] segments.

Species

barbitarsis

The antenna Antenna] tubercles flared laterally and separated by a curved line (Fig.l.a). Petioles of Lauterborn organs roughly equal in length to third antenna] segment (Fig.l.b). The hypostomium Outer hypostomia] tooth is reflected outwards (Fig.l.c). Central hypostomial tooth may be ornate (Fig.l.d). The mandible Largest mandibular tooth rounded (Fig.l.e). Accessory mandibular tooth blunt (Fig. 1.f). The head capsule Head capsule is as wide as it is long when viewed from the ventral surface (Fig.3.a).

Species

semibarbitarsus

The antenna Antenna] tubercles prominent. Twice as long as wide, project straight forward. Separated by a rectangular line (Fig.2.a). Petioles of Lauterborn organs as long as the last three antennal segments (Fig.2.b). The hypostomium Lateral teeth even (Fig.2.c). Outer tooth not markedly reflected outwards (Fig.2.c). Central hypostomial tooth simple with three rounded denticles (Fig.2.d). The mandible Largest mandibular tooth elongate (Fig.2.e) Accessory tooth V-shaped (Fig.2.f). The head capsule Head capsule is elongated anterio-posterially (Fig.3.b).

324 TABLE

II

D e t a i l s o f l o c a l i t i e s w h e r e T. b a r b i t a r s i s a n d T. s e m i b a r b i t a r s u s h a v e b e e n c o l l e c t e d Locality

Latitude

Longitude

Environmenta

Barbi- S e m i tarsis b a r b i t a r s u s

Reference

Bolivar Coorong--south lagoon

34046 ' 36°15 '

138030 , 139°38 '

Sewage works Salt l a g o o n

+ +

Berri Blanchetown Devlln Pound Port Augusta Little Dip L a k e I C I Saltfields Port Broughton T h o m p s o n ' s Beach Middle B e a c h Waterfall Gully Ramco Milang Arkaroola Big S w a m p Kersbrook Creek H a p p y Valley I n m a n River m o u t h Bremer River, Callington Barmera-Lake Bonney Morgan Swan Reach Reedy Creek Falls--Caloote Whyana Lake Eyre South Noora

34017 ' 34021 ' 34010 ' 32030 ' 37010 ' 34048 , 33°36 ' 34°52 ' 34036 , 34048 , 34010 ' 35°24 ' 30020 ' 34039 ' 34047 , 35009 ' 35030 ' 34058 ' 34°15' 34002 , 34034 , 34058 ' 33002 ' 29013 ' 34026 '

140036 ' 139037 , 140011 ' 137046 ' 139045 ' 138°36 ' 137°56 ' 138°30 , 138025 , 138°30 ' 139057 , 138058 , 139°22 , 135°42 ' 138051 , i37°09 ' 138°31 ' 139o02 ' 140028 , 139040 ' 139036 ' 139016 ' 137035 ' 137030 , 140052 '

Glover, 1973 Kokkinn unpublished Glover, 1973 Glover, 1973 Glover, 1973 Glover, 1973 Kokkinn unpublished Kokkinn unpublished Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Glover 1973 Kokkinn unpublished Ruello, 1976 Suter, personal communication, 1984

Lake Werowrap

38°15'

143029 '

L a k e Keilambete Lake Gnotuk C h e e t h a m Saltworks R e d R o c k , Alvie

S o u t h Australia +

Salt l a k e 32°/o~ T D S Brine p o n d s Mangrove swamp Samphire swamp

Sewage works

Mangrove swamp Salt lake Evaporation basin

+ + +

54% o T D S

+

38013 , 1 4 2 0 5 3 , 38°13 ~ 1 4 3 0 0 6 '

72~/oo T D S 57 /oo T D S

+ +

37055 ' 1 4 4 0 3 5 ' 37°31 ' 1 4 4 ° 3 9 '

Brine P o n d

+ +

Victoria Paterson and Walker, 1 9 7 4 a Kokkinn unpublished B a y l y a n d Williams, 1966 Glover, 1973 Glover, 1973

N e w South Wales Bar m a h Moruya Heads

Glover, 1973 Glover, 1973

36°01 ' 1 4 4 ° 5 7 ~ 35055 ' 1 5 0 0 1 0 ,

Western Australia Rottnest Island Dampier B r e m e r Bay Tambrey Station Dalyup River Millstream Station Nedlands Needilup Creek Lake Grace Esperance Toodyay Marchagee

32000 ' 20°39 ' 34023 , 21°38 ' 33044 ' 21035 , 31°57 ' 33057 ' 33006 , 33052 ' 31°33 ' 30003 '

115°30 ' 116°43 ' 119023 ' 117°36 ' 121034 ' 117°04 ' 115051 , 118°46 ' 118028 , 121"54 ' 116°28 ' 116004 '

23024 ,

133009 '

Salt lake

+ ÷ + + + ÷ + + + +

Salt lake

÷

Freeman, 1961 Glover, 1973 F r e e m a n , 19 61 F r e e m a n , 19 61 Freeman, 1961 Freeman, 1961 Glover, 1973 Glover, 1973 Freeman, 1961 Freeman, 1961 Glover 1973 Halse, 1 9 8 1

Northern Territory M o u n t H a y Bore aWhere

no indication

of the environment

+ is g i v e n , s p e c i m e n s

have been recorded

Glover, 1973 as adults.

325

lagoon of The Coorong (South Australia), where salinities approximate 50°/°°, as well as in tidal pools near Whyalla (South Australia) at 40%° (Kokkinn, unpublished data). Refer to Table II for the above localities. I am n o t aware of any specimens from fresh water. The larvae build tubes within the b o t t o m muds and are rarely found more than I cm below the mud--water interface, particularly in eutrophic lakes where sediments are anoxic below this level. In this situation, if sedimentation rates are low, larval remains are subject to considerable bioturbation. It is likely that larvae may eat the remains of conspecifics. In addition, under shallow conditions, larval remains are vulnerable to mechanical damage from turbulence during windy conditions. As a counter to factors which act against preservation, the occupation of tubes within sediments enhances the possibility of larval subfossilization. The larvae are reputedly detritivorous (Paterson and Walker, 1974a), but appear to ingest large numbers of diatoms (Kokkinn, unpublished data). At the end of each of four larval instar stages, moulting occurs, leaving the head capsule intact as part of the exuviae and thus available for sediment entrapment. Figure 5.a and Table II indicate where T. barbitarsis has been collected in Australia. This is not a true reflection of the actual distribution, as collecting to date has not been comprehensive. However, the lack of records from the east coast may be significant because suitable coastal habitats are abundant there. Records from as far north as Dampier (Western Australia) indicate a range extending into tropical areas. Since the adult stage is winged, it is distributed widely after emergence. Adults, although weak fliers, are commonly dispersed great distances by winds where they can exploit temporary as well as permanent water bodies. Although T. barbitarsis has not been intensively studied from a wide variety of localities, indications are that, where it occurs in large numbers, the localities in question are eutrophic (Paterson and Walker, 1974a;

(o)

(b)

Fig.5. Sites w h e r e a. Tanytarsus barbitarsis h a s b e e n c o l l e c t e d a n d w h e r e b. Tanytarsus semibarbitarsus h a s b e e n collected.

326

Kokkinn, unpublished data). Such sediments are anoxic a short distance below the mud--water interface. It is surprising, then, to find that T. barbitarsis is unable to tolerate even short periods of anoxia (Kokkinn, unpublished data). In fact, T. barbitarsis is usually confined to shallow, wellaerated water bodies. Apart from salt lakes, it also occurs in shallow, hypersaline intertidal pools such as those in the gulfs of South Australia (Kokkinn, unpublished data). PALAEOLIMNOLOGICALLY R E L E V A N T ECOLOGY ON T A N Y T A R S U S S E M I B A R B I T A R S US

There are no published studies of the life history or ecology of T. semi° barbitarsis. However, P. S. Surer (personal communication, 1984) has observed T. semibarbitarsus where it occurs in large numbers in the evaporation basins aear Noora (South Australia) which are shallow, eutrophic water bodies. He reports that it is able to exploit waters up to 25°/°0 in salinity. The work currently being conducted at Noora will contribute greatly to the value of this species as a palaeoenvironmental indicator. Figure 5.b and Table II indicate sites where T. semibarbitarsus has been collected in Australia. P A L A E O E N V I R O N M E N T A L IMPLICATIONS

The apparent absence of a relationship between certain chironomid taxa and trophic conditions in Australia (Timms, 1980) is probably due to the dominance of the continent b y shallow, unstratified lakes in recent geological time (Williams, 1983). T. barbitarsis, a member of the tribe which has been used to indicate oligotrophy, is indeed sensitive to anoxic conditions, as noted, b u t it most c o m m o n l y occupies eutrophic salt lakes which are shallow and well-aerated. Similar conditions are found in Dead Man Lake, Nevada (Megard 1964). Although the value of chironomids as indicators of past trophic conditions is clearly much reduced in Australia, there are, nevertheless, several examples from elsewhere where chironomids have been used to deduce a variety of palaeoconditions such as salinity (Konstantinov, 1951), climate (Anderson, 1943; H o f m a n n , 1983) and cultural influences (l~oback, 1970; Warwick, 1975; Deevey, 1955). In a recent study (Walker et al., 1985) the focus has fallen u p o n chironomid faunal assemblages which are indicative of acidity in lakes. At present, the major obstacle to the use of chironomid remains in this way in Australia is the fact that the larvae remain largely undescribed and unstudied, despite their dominance in the benthos of inland waters. T. barbitarsis, a unique exception, is well-studied and, since the emphasis of palaeolimnological research in Australia has been undertaken in saline lakes, it will be of value to indicate the following conditions of its usual occurrence: Salinities between 35°/°° and 100°/oo -- Eutrophic conditions -- Shallow water (less than 5 m in depth) -

-

327

--Temperate conditions (i.e. some mitigating physical factors which would serve to maintain water salinity in the appropriate range (35--100°/oo) long enough for a large population to develop. Such conditions may include high precipitation or a coastal situation.) T. semibarbitarsus in this discussion has largely served a comparative function; it has been used to illustrate that closely related chironomid larvae can be distinguished from one another on the basis of material likely to be preserved as subfossils. Present knowledge of its ecology is rudimentary and it therefore has very limited use as a palaeoenvironmental indicator. For the time being it can be used only as an indicator of salinities below 30°/°° (Dr. P. Suter, personal communication, 1984). ACKNOWLEDGEMENTS

I thank Professor W. D. Williams for comment. Dr. P. Suter of the Engineering and Water Supply of South Australia is thanked for advice on T. semibarbitarsus and the supply of larval material. REFERENCES Anderson, F. S., 1943. Dryadotanytarsus edentulus n.g. et. sp. (Dipt. Chiron) from the late glacial period in Denmark. Eutomol. Medd., 23: 174--178. Bayly, I. A. E. and Williams, W. D., 1966. Chemical and biological studies on some saline lakes of south-east Australia. Aust. J. Mar. Freshwater Res., 17: 177--228. Brundin, L., 1958. The bottom faunistical lake type system and its application to the southern hemisphere. Moreover a theory of glacial erosion as a factor of productivity in lakes and oceans. Verh. Int. Ver. Limnol., 13: 288--297. Bryce, D. and Hobart, A., 1972. The biology and identification of the larvae of the Chironomidae (Diptera). Entomol. Gaz., 23: 175--217. Cadwallader, P. L., Eden, A. K. and Hook, R. A., 1980. Role of streamside vegetation as a food source for Galaxias olidus Giinther (Pisces: Galaxiidae). Aust. J. Mar. Freshwater Res., 31: 257--262. Crisman, T. L,, 1978. Reconstruction of past lacustrine environments based on the remains of aquatic invertebrates. In: D. Walker and J. C. Guppy (Editors), Biology of Quaternary Environments. Australian Academy of Science, Canberra, pp. 69--101. Deevey, E. S., 1942. Studies on Connecticut lake sediments III. The biostratonomy of Linsley Pond. Am. J. Sci., 240: 233--264. Deevey, E. S., 1955. Paleolimnology of the upper swamp deposit, Pyramid Valley. Rec. Canterbury (N.Z.)Mus., 6: 291--344. Edward, D. H. D., 1983. Inland waters of Rottnest Island. J. R. Soc. West Aust., 66: 41--46. Freeman, P., 1961. The Chironomidae (Diptera) of Australia. Aust. J. Zool., 9: 611--737. Frey, D. G., 1955. L~ngsee: A history of meromixis. Mem. 1st. Ital. Idrobiol. Marchi, suppl., 8: 141--164. Glover, B., 1973. The Tanytarsini (Diptera: Chironomidae) of Australia. Aust. J. Zool., Suppl. Ser., 23: 403--478. Goulden, C. E., 1966. The animal microfossils of Laguna de Petenxil, Guatemala. Mere. Conn. Acad. Arts Sci., 17: 84--120. Halse, S.A., 1981. Faunal assemblages of some saline lakes near Marchagee, Western Australia. Aust. J. Mar. Freshwater Res., 32: 133--142.

328 Hofmann, W., 1983. Stratigraphy of cladocera and chironomidae in a core from a shallow North German lake. Hydrobiologia, 103: 235--239. Hume, D . J . and Pribble, H . J . , 1980. The biology and behaviour of Carp (Cyprinus carpio L.): A brief review. Carp Prog. Rep. No. 5. Fisheries and Wildlife Division, Victoria State Government, 30 pp. Konstantinov, A . S . , 1951. Istoriya fauny khironomid n e k o t o r y k h ozer sapovednika " B o r o v o y e " (Severniy Kazakhstan). Tr. Lab. Sapropel. Otlozh., 5: 97--107. (Quoted in: Stahl, J . B . , 1969. The uses of chironomids and other midges interpreting lake histories. Mitt. Int. Ver. Limnol., 17: 111--125.) Maher, M., 1984. Benthic studies o f waterfowl breeding habitat in southwestern New South Wales. I. The fauna. Aust. J. Mar. Freshwater Res., 35: 85--96. Maher, M. and Carpenter, S. M., 1984. Benthic studies of waterfowl breeding habitat in southwestern New South Wales. II. Chironomid populations. Aust. J. Mar. Freshwater Res., 35: 97--110. Martin, J., 1974. Key to the genera of Australian Tanypodinae larvae (Diptera: Chironomidae). Aust. Soc. Limnol. Newsl., 12(2): 12--13. Martin, J., 1975. Key to the larvae of Australian genera of Chironomini (Diptera: Chironomidae). Aust. Soc. Limnol. Newsl., 13(1): 21--23. Mason, W.T., 1973. An introduction to the identification of chironomid larvae. Analytical Control Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio (2nd Ed.), pp. 115. Megard, R . O . , 1964. The biostratigraphic history of Dead Man Lake, Chuska Mountains, New Mexico. Ecology, 45: 529--546. Paterson, C. G. and Walker, K. F., 1974a. Seasonal dynamics and productivity of Tanytarsus barbitarsis Freeman (Diptera: Chironomidae) in the benthos of a shallow, saline Lake. Aust. J. Mar. Freshwater Res., 25: 151--165. Paterson, C.G. and Walker, K . F . , 1974b. Recent history of Tanytarsus barbitarsis Freeman (Diptera: Chironomidae) in the sediments of a shallow, saline lake. Aust. J. Mar. Freshwater Res., 25: 315--325. Roback, S.S., 1970. The Chironomidae. In: G . E . Hutchinson (Editor), Ianula: an account of the history and development of the Lago di Monterosi, Latium, Italy. Trans. Am. Phil. Soc., 60: 150--162. Ruello, N. V., 1976. Observations on some massive fish kills in Lake Eyre. Aust. J. Mar. Freshwater Res., 27: 667--672. Stahl, J. B., 1959. The developmental history of the chironomid and Chaoborus faunas of Myers Lake. Invest. Ind. Lakes Streams, 5: 47--102. Thienemann, A., 1913. Der Zusammenhang zwischen dem Sauerstoffgehalt des Tiefenwassers und der Zusammensetzung der Tierfauna unsere Seen. Int. Rev. Hydrobiol., 6: 243--249. Timms, B. V., 1980. The benthos of Australian Lakes. In: W. D. Williams. (Editor), An Ecological Basis for Water Resource Management. Aust. Nat. Univ. Press, Canberra, pp. 23--39. Warwick, W. F., 1975. The impact of man on the Bay of Quinte, Lake Ontario, as shown by the subfossil chironomid succession (Chironomidae, Diptera). Verh. Int. Ver. Limnol., 19: 3134--3141. Walker, I. R., Fernando, C. H. and Paterson, C. G., 1985. Associations of Chironomidae (Diptera) of shallow, acid, humic lakes and bog pools in Atlantic Canada, and a comparison with an earlier paleoecological investigation. Hydrobiologia, 120: 11--22. Williams, W. D., 1983. Life in Inland Waters. Blackwells, Melbourne and Oxford, 252 pp.