Appl. Phys. A 68, 379–385 (1999) / DOI 10.1007/s003399900012
Applied Physics A
Materials
Science & Processing
Springer-Verlag 1999
Invited paper
UV-laserablationof sensorycells inlivinginsects
G. Fuhr
1
, B. Ronacher
1
,R.Krahe
1
,S.Fest
1
, S.G. Shirley
1
, S. Rogaschewski
2
1
Humboldt-Universität zu Berlin, Institut für Biologie, Invalidenstr. 42, 10115 Berlin, Germany
(Fax: +49-30/2093-8635, E-mail: fuhr@rz.hu-berlin.de)
2
Humboldt-Universität zu Berlin, Institut für Physik, Chausseestr. 110, 10115 Berlin, Germany
Received: 10 Dezember 1998/Accepted: 15 December 1998/Published online: 24 February 1999
Abstract. An experimental set-up for applying pulsed UV-
laser ablation to the integument of insects and the high preci-
sion of ablation is demonstrated. In order to test for possible
detrimental effects on physiologicalresponses, this technique
was applied to the ears of migratory locust (Locusta migra-
toria L.). The handling of living insects, the survival, and
physiological response after treatment are described. We se-
lectively interrupted the d-receptor of the tympanal organ,
which is the receptor system responsible for the locust’s sen-
sitivity in the high-frequency range (> 10 kHz). The effects
of the laser treatment were tested by determining hearing
thresholdsin electrophysiologicalrecordingsfrom the tympa-
nal nerves. In agreement with the literature, the interruption
of the d-receptors led to a significant shift towards higher
values of the thresholds in the high-frequency range. Future
perspectives and biological applications of UV-laser ablation
are discussed.
PACS: 43; 89; 42.55.Gp; 42.62.Be; 43.64.+r; 81.15.Fg
Lasers have found widespread applications in technology,
medicine, and biotechnology. They can be used for measur-
ing purposes and also as surgical instruments, for example in
opthalmology to re-fix parts of the retina or to coagulate tis-
sues (for review see [1–4]).The accuracy of the treatment de-
pends on the quality of the focus and the manipulation of the
laser beam. Pulsed UV-laser ablation has been successfully
applied as a precise tool in structuring surfaces of metals [5–
7], semiconductors and oxides [8–10], and polymers ([11],
overview in [12]). By using short laser pulses (subpicosecond
range) the thermal influences upon neighbouring areas are
further reduced compared with long-pulse applications [13].
In the field of live sciences, UV-laser ablation has been used
for several years to correct corneae in human eyes, to open
the zona pellucida of eggs for in vitro fertilisation and to clean
teeth [2,4,14]. However, up to now laser ablation was rarely
applied to arthropods.
In insects, UV-laser treatment should be able to change
the properties of sensory systems (for example, optical,
acoustical) or of mechanical resonance systems in a def-
inite way. Still, the thermal loading of the border region
around the illuminated area may be critical and should be
minimised. This can be achieved by using pulsed UV lasers,
i.e. with pulse lengths shorter than the thermal conduction in
the substrate. Chitin, the main component of insect cuticle
is comparable to polymers exhibiting relatively low thermal
conductivities, and, therefore, should be a suitable material to
test the precision of laser techniques.
The aim of this work was to test the applicability of such
an excimerlaser system to reduction of chitinousstructuresof
living insects, with the main focus upon exploring the preci-
sion and lower limits of thermal loading that can be attained.
To achieve this goal, we wanted to have a system in which the
possible limitations imposed by thermal loading and pressure
pulsescouldbe tested physiologically.We therefore chose the
tympanal organ of locusts, since this sensory structure allows
a rather easy physiological test of the possible detrimental
effects of laser treatment to the neighbouring structures. In
addition, its topography is demanding. It is located in a cav-
ity and partly occluded by a chitin plate (Fig. 1a). Therefore,
it is a good example for showing the capacities of the “laser-
writing” technique.
1 Material and methods
1.1 Animals
Experimental animals were adult locusts (Locusta migrato-
ria L.) of both sexes that were obtained from a commercial
supplier. The ears of the locust are located at the sides of
the first abdominal segment, as shown in Fig. 2b. The tym-
panal membrane is composed of connected chitin plates (the
so-called thin and thick membranes) and additional cuticular
structures located at the junction of both “membranes” which
confer to the tympanum a complicated frequency-dependent
pattern of vibration modes (for details see [15–19]). Viewed
from the inner side of the tympanum (Fig. 1b), about 70–100
receptor cells are attached to the tympanum in four distinct
groups, called the a-, b-, c-, and d-cells (as the so-called
Müller’s organ) [15,16]. As has been determined by means
of microelectrode recordings [16,20], the four groups exhibit
different frequency tuning: a-, b-, and c-cells being most sen-
sitive in the low-frequency range around 3–6kHz, whereas
the d-cell receptors are tuned to the high-frequency range