Beitr. Biol. Pflanzen 65, (1990), 377 -383

The occurrence of crystals in a cynipid leaf gallon Quercus turbinella

Kristalle in einer Cynipiden-Galle auf Blãttern von Quercus turbinella

By G. Wilson Fernandes, Ralph W. Preszler & J. Normam Grim

Department of Biological Sciences Northern Arizona University Flaggstaff

(With 5 figures)

Received November 9. 1989

K e y w o r d s : Insect galls, Quercus turbinella, Atrusca caprone, Gall

crystals, CynipiQae

Abstract

Crystals in insect gall tissue are variable and more rare than in other types of planttissue. This is the first description of crystalline structures in Atrusca caprone(Hymenoptera: Cynipidae) leaf galls on Quercus turbinella. Crystals are only found inyoung galls which indicates that their production may have been influenced by larvalactivitv.

Zusammenfassung

Kristalle in Geweben von Insektengallen sind variabel und erheblich seltener als inanderenPflanzengeweben. Dieser Beitrag enthãlt die erste Beschreibung der Kristall-strukturen in von AtTUsca caprOne (Hymenoptera: Cynipidae) verursachten Blatt-gallen an Quercus turbinella. Kristalle finden sich nur in jungen Gallen, was daraufhindeutet, daB ihre Entstehung auf den Einflu6 der Larven zuriickgeht.

This is the first description of crystalline structures in a Atrusca caproneWeld (Hymenoptera: Cynipidae) leaf gall on Quercus turbinella Greene.Crystals have seldom been found in gall tissue (DENGG 1971, REY & MOREAU1983.

Only one to two hundred of the 16 000 types of galls in the world havebeen adequately studied (LAREW 1982). Among the insect galls the cynipidgalls are well known for their abundance, species richness, and complexmorpholof!.V. especiallvon ()uercus and Rosa (e.!!. WELD 1957.1960. BRON-

G. Wilson Fernandes. Ralph W. Preszler & J. Normam Grim

NER 1977, ROHFRITISCH & SHORTHOUSE 1982, CORNELL 1983). In spite of sev-eral studies addressing cypinid galls' natural history (e.g. SHORTHOUSE 1973,COLLINS et al. 1983), distribution (e.g. AsKEW 1961, TAPER & CASE 1987), and,anatomy (e.g. MANI 1964, LAREW 1982, MEYER 1987, and MEYER & MARES-QUELLE 1983 for reviews), the significance of the cynipid gall's complex mor-phology and anatomy are not well known (but seeC;ORNELL 1983).

Quercus turbinella is widely distributed in the chaparral vegetation ofArizona (McDOUGALL 1973). Galls were found throughout the host plant dis-tribution. They were more abundant between 1,200 and 1,500 metersaltitude (adjacent to highways I- 17, and 89A South). Galls were firstobserved in the beginning of June 1987 and by the end of September all ofthe galls were mature.

The cynipid galls occurred on the abaxialleaf surface, and were spheri-cal, glabrous, and one-chambered with only one gall making larva perchamber. Galls varied from yellow to red. Most had red vertical stripesradiating upward from the base of the gall. Mature galls, from which the gallmaker had emerged, had a mean diameter of 10.99 mm (S.E. = 0.42,n = 225),"The mean gall wall thickness was 0.62 mm (S.E. = 0.04, n = 225).

KINSEY (1930) and LAREW (1982) describe the ext~mal and internal macros-copic appeaJ;"ance of the gall, and the cytology and anatomy of a strúcturallysimilar cynipid (Besbiscus mirabilis var. mirabilis [Kinsey] Weld) leaf gallon Quercus garryana Dougl., respectively.

Young galls were solid, but the centrally located larval chamber becameseparated from the gall walls during gall development (Fig. 1). However, thelarval chamber remained attached to the gall walls by numerous radiatingstrands (Fig. 1, 2, 3). Vascular bundles ran from the leaf base to the larvalchamber and to the gall's outer shell. The mean length of the radiatingstrands was 5.66 mm (S.E. = 0.34, n = 225). Most of the strands were unicel-

lular, occasionally branching or terminating before attachment, and wereparenchymatous. Intra-cellular rosette-shaped crystals were found withinandalong these strands (Figs. 4,5).

The occurrence of crystals in plant tissue has been described as unpredict-able (FREY-WYSSLING & MfJHLETHALER 1965, see also SCHNEPF 1971, WERGIN& NEWCOMB 1970, WERGIN et al.1970). Crystals in gall tissue are variable andmore rare than in other types of tissue (e.g. DENGG 1971, KfJSTER 1930,MEYER & MARESQUELLE 1983). They ate localized in well defined regions ofthe galls, in 'general near conductive tissues (see MEYER & MARESQUELLE1983). Most of the few crystals described from galled tissue are formed bycalcium oxalate. Calcium oxalate crystals are highly insoluble in water (sol-ubility in grams per 100 ml of cold water is 0.0006713c, and 0.001495c in hotwater (HODGMAN 1948). However, the crystals of the present study werewater soluble (H. ARNOTT, pers. comm.). The presence of water soluble crys-

Cynipid gall crystals 379

i

Fig. 1 -4. Atrusciz caprone leaf gall on Quercus turbinella. 1. Cross-section of gall.2. Strands radiating out to gall wal1s. 3. Cross section of strands and vascular bundle.The vascular bundles ran from the leaf base to the gall chamber which is positioned inthe center of the gall, and to the gall walls. 4. Rosette-shaped crystals within strands.Arrow shows a well defined crystal and its radiating crystalline structures from the

crystal center.

380 G. Wilson Fernandes, Ralph W. Preszler & J. Nonnam Grim

c

B

Fig. 5. Composite line drawing showing the A. caprone gall internal morphology. A.Opened gall showing the larval chamber suspended by the parenchymatous strands.B. Strands enlarged to show the presence of numerous rosette-shaped crystals inside

them. C. A crystal further enlarged to show its radiating crystalline structures.

tals inside vacuoles of living cells is an apparent paradox due to the presenceof water in the vacuoles. However, crystal formation and growth is also gov-erned by the pH of the media. Thus, we suggest that t~e presence of thewater-soluble crystals in aqueous cell media is due to cell pH. Crystals may,however, be dissolved during normal preparation techniques, in which AFA(Alcohol-Formalin-Acetic Acid) is frequently used. This probably explainswhy the crystals in question have not been previously reported.

REY & MOREAU (1983) studied the presence of paracrystal1ine inclusions inthe nutritive cells of Diplolepis rosae Linnaeus (Cynipidae) galls on Rosacanina Linnaeus. Ultrafine enzymatic digestion bioassays indicated that theintra-cytoplasmatic paracrystals were of proteic nature. They stated thatthe paracrystals were probably related to the larval action which stimulatesprotein svnthesis in the cells surrounding the consumed ones.

Cynipid gall crystals 31!1

We found crystals only in immature galls. This was the stage of galldevelopment during which the larvae were actively feeding. This suggeststhat crystal production may have been influenced by larval activity.

Theimportance of these crystals to the galling insect and/or plant is stillunknown. Plant nutrients are concentrated in gall tissue (e.g. MANI 1964,LAREW 1982, ROHFRITISCH & SHORTHOUSE 1982). This may attract several gallherbivores, including predators and inquilines (FERNANDES et al. 1987) of thegall. Because gall makers and their galls are apparent and predictableresources for their natural enemies (PRICE et al. 1980, FERNANDES et al. 1987),insect galls support a diverse community of parasitoids (e.g. AsKEW 1975,PRICE et al. 1987), inquilines (e.g. SHORTHOUSE 1973), predators (e.g. MANI19U4, FERNANDES et al. 1987), and successori organisms (e.g. FERNANDES etal. 1989). In addition, predation or competition with other herbivores (sensuFERNANDES et al. 1987) to feed on the nutrient-rich and allelochemical-freenutritive gall tissue results in death of the gallÍng insect by habitat modifi-cation and/or direct killing by the competitor herbivore (FERNANDES et al.1987). Thus, it is not surprisÍng that many gall defenses have been describedÍncluding glandular trichomes, high levels of phenolics, resins, and fast lig-"nification of some tissue layers on the outer gall tissues (see MANI 1964,MEYER & MARESQUELLE 1983, MEYER 1987). Crystals are also important asdeterrent and anti-feedÍng structures agaÍnst herbivores (FRANCESCHI &HORNER 1980, McNAUGHTON & TARRANTS 1983). For example, KIMMERER &PATTER (1987) argued that the major constraÍnts which limit the success of aleafminer on shade leaves of Ilex opaca are the presence of crystal-contaÍningcells. However, crystals are also involved Ín a multitude of functions withinplants. Various functions have been attributed to plant crystals, for Ínstanceionic balance, storage, or structural support (see FRANCESCHI & HORNER 1980for a review). Thus, the significance of A. caprone gall crystals can only beunderstood after detailed studies on their chemical composition, physiologi-cal function, and ecolol!ical role have been carried out.

Acknowledgments

We would like to thank H. L. Mogensen, and J. States, and two anonymous review-ers for their encouragement and help. We also would like to thank H. Arnott for hisanalysis of the crystals and H. v. Cornell for the cynipid identification. In addition, wewould like to thank Angela Fernandes for helping in the field and laboratory work, R.Helt for help with the translation of the abstract into German, and T. Theimer forhelping with ~igure 5. Research funds were provided by the Conselho Nacional dePesauisas (CNPn-200274/R4-~-?:m "nrl Nnrt.hprn Ar;7nn" TTn;upr~it.u

G. Wilson Fernandes, Ralph W. Preszler & J. Normam Grim382

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Authors address:

G. WtLSON FERNANDEs

Departamento de Biologia GeralCP 2486ICB / Universidade Federal de Minas Gerais30161 Belo Horizonte MGBRAZIL

26 Beitr. Biol. Pf!anzen 65/3