Detachable adhesive knobs in Dactylaria

Detachable adhesive knobs in Dactylaria

Notes and Brief Articles 311 DETACHABLE ADHESIVE KNOBS IN DACTYLARIA G. L. BARRON Department of Environmental Biology, University of Guelph, Guelph...

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Notes and Brief Articles

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DETACHABLE ADHESIVE KNOBS IN DACTYLARIA G. L. BARRON

Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada Dactylaria candida (Nees) Sacco possesses both adhesive knobs and nonconstricting rings for the purpose of catching nematodes. Drechsler (1937) noted that the stalked knobs in D. candida were rarely seen to be operative and then only in the capture of the smallest and feeblest of nematodes. Enmeshment in a ring, however, always resulted in the destruction of the host regardless of whether the ring remained attached to the stalk or was broken off in the struggle. Duddington (1962) supported Drechsler's observations and noted, with respect to predaceous fungi possessing both knobs and non-constricting rings, that the knobs were usually secondary in action to the rings and that in some cases the knobs appeared to be functionless. A strain of D. candida corresponding to Drechsler's description was recovered from greenhouse soil in Canada. The strain differed from Drechsler's in that stalked adhesive knobs (PI. 42, fig . I) were produced profusely and the non-constricting rings (PI. 42, fig. 6) were relatively few in number especially in young cultures where the proportion of knobs to rings was about 1000 to I . As noted by Drechsler and Duddington very few nematodes were ever found held fast to the knobs. More critical observations on attached nematodes, however, revealed that in a few minutes and sometimes in a matter of seconds a nematode attached to a knob could break away from the hypha and swim off with the knob attached to the cuticle. Knobs seemed rather easily detached and in one case a nematode was observed held by knobs at three points along the length of its body which considerably limited its capability for violent thrashing movements. Despite this, the nematode was able to free itself in less than a minute and swim off with the three detached knobs firmly adhering to its cuticle. In all cases observed, the knobs broke off at the apex of the support stalk. Mounts of free swimming nematodes showed that many of these had detached knobs adhering to their cuticle (PI. 42, fig. 7) and sometimes more than 20 knobs could be seen attached to the body ofa victim (PI, 42, fig. 4). From such detached knobs a peg penetrated into the body cavity of the host and produced a subcuticular swelling (PI. 42, fig. 5) from which the infection hyphae originated. Subsequent development was typical and brought about the eventual destruction of the host. The rings present in this strain (PI. 42, fig. 6) were non-constricting but were never seen to catch a nematode, due perhaps to their low frequency of occurrence. Subsequently a strain of Dactylaria haptotyla Drechsler was found to behave in a similar fashion (PI. 42, figs. 1-3). D. haptotyla possesses no Trans. Br, mycol. Soc. 65 (2), (1975). Printed in Great Britain

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Transactions British Mycological Society

rings and depends entirely on knobs for capture of nematodes. Results were similar to D. candida except that the knobs were not as readily detached and as a result proportionately more nematodes were held fast to the knobs without breaking them off. Even in this species however a large number of nematodes had one or more detached knobs stuck to the cuticle as evidence of previous' escapes'. In some cases in D. haptotyla detached knobs did not penetrate the host cuticle but germinated in situ to produce a secondary knob on a short stalk (PI. 42, fig. 8). These knobs were also functional and occasionally nematodes could be seen swimming in tandem, held together by the two knobs with the stalk as a connective. It is probable that the knobs are detachable in other species of predaceous fungi. The occurrence of detachable knobs is a distinct advantage to the biological success of the parasite. A nematode can travel a significant distance on the micro scale before penetration and growth of the fungus incapacitates it. Thus the parasite is not only transported to a new site for further predation but arrives with an immediately available food source and can quickly produce additional trapping devices. Detachable knobs are obviously especially important for species which depend entirely on knobs for predation. The writer thanks the National Research Council of Canada for financial support. REFERENCES

DRECHSLER, C. (1937). Some hyphomycetes that prey on free-living terricolous nematodes. Mycologia 29, 447-552. DUDDINGTON, C. L. (1962). Predaceous fungi and the control of eelworms. Viewpoints in Biology I, 151-200. EXPLANATION OF PLATE

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Fig. I. Dactylaria haptotyla. Captured nematode filled with hyphae of parasite. Fig. 2. D. haptotyla. Freshly caught nematode held at five locations. Fig. 3. D. haptotyla. Freshly caught nematode stilI struggling but held by knob in tail region. Note number of detached knobs attached to forward part of body indicating previous' escapes'. Fig. 4. Dactylaria candida. Nematode with more than twenty detached knobs adhering to cuticle. Fig. 5. D. candida. Detached knobs have penetrated cuticle and produced subcuticular swellings. Note deterioration of oesophageal musculature in vicinity of infection bulbs. Fig. 6. D. candida. Non-constricting ring. Fig. 7. D. candida. Free-swimming nematode with detached knobs adhering to cuticle. Fig. 8. D. haptotyla. Free-swimming nematode with detached knobs germinating to produce secondary knobs.

LONG-CHAIN FATTY ACIDS IN SPORES OF PENICILLIUM R. K. DART

Department ofChemistry, University of Technology, Loughborough, Leicestershire, U.K. The Penicillia can be divided into a number of subgroups (Raper & Thorn, 1949; Pitt, 1973) all of which have small spores usually lacking any Trans. Br. mycol, Soc. 65 (2), (1975). Printed in Great Britain