Invertebrate Zoology
SURVIVAL OF THE BARNACLE
SEMIBALANUS BALANOIDES AFTER ICE
SCOUR: THE IMPORTANCE OF REFUGE
QUALITY.
LJ. Walters*, E. Bourget and P.E. Sacks. Univ. of
Central Florida, Orlando and University Laval,
Quebec. [email protected]£edu
Each spring, sheets of ice scour the intertidal
zone in the Gulf of St. Lawrence. To understand
what constitutes a refuge from ice scour for
Semibalanus balanoides, we examined potential
refuge locations for newly-settled and adult
barnacles as well as barnacle mimics at three size
scales for two years. First, large-scale refuge
locations were determined in replicate transects
along three rock units parallel to the shore and
each other. Second, intermediate-scale refuges
were determined from the relative location of each
barnacle on each rock unit (base, middle and top
of rock, seaward vs landward sides). Third, smallscale refuges were considered to be crevices > the
height of adult barnacles. Survival significantly
increased with increased distance from shore,
toward the bases of rocks, and in crevices. Most
recruits were found in these locations, suggesting
that larvae discriminate at the time of settlement
and preferentially settle in high-quality refuges.
556
558
SALINITY TOLERANCE OF GAMETES AND
DEVELOPING EMBRYOS OF
POTAMOCORBULA AMURENSIS, THE ASIAN
CLAM.
M. H. Garcia. Univ. of CA., Berkeley.
[email protected].
The adults of bivalve Potamocorbula amurensis
have been collected in San Francisco Bay in
salinities ranging from 0.1 to 30 psu. The focus of
this study was to evaluate the extent of embryo
distribution throughout the Bay. Clams were
spawned at 15 psu, 15 °C. Sperm and eggs, 2 hr-old
embryos (2 to 3 cell divisions) and 23 hr-old
ciliated blastula were transferred to a salinity
exposure array of 2,10,15,20 and 30 psu. Results
of these salinity exposures demonstrated that P.
amurensis, develops the ability to osmoconform to
a wider salinity range with each stage in
development By ciliated blastula, 23 hours old,
the embryos appear to have the same euryhaline
tolerance as the adults and develop equally well at 2
psu and 30 psu. The development of early
planktonic osmoregulation of P. amurensis helps to
explain their ubiquitous distribution in the lower
reaches of the San Joaquin/Sacramento River Delta
and in North and South San Francisco Bays.
162A
557
WIND CHILL EFFECTS ON ALASKAN
TANNER CRABS.
T.C. Shirley* and L. Mcnutt. Univ. of Alaska
Fairbanks
The commercial fishery for Tanner crabs in Alaskan
waters occurs during winter months, beginning in
January. Crabs smaller than legal-size and females
are returned to the sea, but are commonly exposed
to freezing temperatures and high winds. A lab
experiment examined the effects of a 5 minute
exposure of a combination of 4 wind speeds (0,4, 8
and 16 m/s) and 3 temperatures (-2.5, -5.0 and -7.5
C), plus unexposed controls, on mortality, limb
autotomy and righting response of juvenile male
crabs. Wind chill was useful in explaining the
significant relationships occurring between wind
speed/temperature combinations and mortality, limb
loss and autotomy of the crabs. Alaskan winter
conditions common during harvest may result in a
large mortality of crabs returned to the sea. Funded
by Alaska Dept. of Fish and Game.
559
EFFECTS OF UVB EXPOSURE ON THE EARLY
DEVELOPMENT OF ANTARCTIC INVERTE-BRATES
DURING
SPRINGTIME
DEPLETION
OF
STRATOSPHERIC OZONE
I. Bosch and D. Karentz. S.U.N.Y. Geneseo and University of
San Francisco.
Annual springtime losses of stratospheric ozone over the
Antarctic during the past two decades have resulted in
increased levels of biologically-harmful UVB radiation
reaching the ocean. This phenomenon occurs at a time when
embryos and larvae of the sea urchin Sterechinus neumayeri
and the sea star Psilasler charcoli are developing in surface
waters. Eggs and embryos of these species were exposed to
ambient sunlight in outdoor tanks and in the water column
(from surface to 7 m) under normal and depleted ozone
conditions (i.e., low and high UV fluences) during spring of
1996 and 1997. Increased exposure to UVB caused increases
in cellular damage, abnormal cleavage, mortality and total
development time. Under non-depleted ozone conditions,
UVB effect"! on embryos were detected to a maximum depth
of 3 m. Under a depleted ozone column, detectable damage
occurred to depths of 5-7 m. Overall, the success of
development to a normal blastula stage was inversely related
to the total ambient UVB exposure, which in turn, was
inversely correlated to ozone levels. The reproductive success
of S. neumayeri and P. charcoli may be affected by the
recurring springtime losses of ozone over Antarctica. Detailed
information is needed on the timing of spawning and the
residence times of eggs and embryos in surface waters before
the magnitude of this stress can be fully determined.
SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
Invertebrate Zoology
560
SOLUBLE AND SURFACE-BOUND BACTERIAL
CUES FOR SETTLEMENT OF THE POLYCHAETE
HYDROIDES ELEGANS.
C.R.C. Unabia, S. Huang and M.G. Hadfield. University
of Hawaii.
Natural bacterial biofilms and films from isolated
bacterial strains induce settlement and metamorphosis of
the serpulid tubeworm Hydroides elegans. Larvae
respond to both soluble and surface-bound bacterial
products. Attachment to biofihned substrata follows an
exploratory phase during which larvae swim in spirals
maintaining proximity to and repeatedly contacting the
substratum with head and ventral body surfaces,
crawling for short intervals and tethering by a mucous
thread. Soluble, low molecular weight bacterial
products stimulate surface-directed movement and
exploratory behavior, but metamorphosis requires longer
exposure to threshold concentrations. Isolated surface
peptides and LPS from Hawaiian Vibrio fischeri strain
ESI 14 induce larval settlement. Digesting biofilm
peptides with trypsin reduces induction if new bacterial
protein synthesis is inhibited during settlement assays.
Larval response to cultured biofilms varies with strain,
incubation time, medium and surface. Manipulating
these differences allows characterization of bacterial
cues and investigation of the hypothesis that larval
settlement decisions are influenced by ecological
information signalled by resident bacterial biofilms.
CHEMICAL DEFENSE, PHYSICAL DEFENSE,
AND MUTUALISM IN ANTARCTIC
MACROALGAE, URCHINS, AND
ANEMONES.
CD. Amsler, J.B. McClintock *, and B. J. Baker.
Univ. of Alabama at Birmingham and Florida Inst.
of Technology, Melbourne, [email protected]
A unique relationship between macroalgae
(Phyllophora antarctica and Iridaea cordata), the
sea urchin Sterechinus neumayeri, and the sea
anemone Isotealia antarctica is described. Both
macroalgal species are chemically defended
against herbivory by S. neumayeri and others have
shown that macroalgae are only minor components
of the urchin gut contents. Where macroalgae and
urchins co-occur in the field, over 95% of the
urchins use macroalgae as cover and the vast
majority of available drift is being held by them.
Urchins from sites without macroalgae prefer
macroalgae over other cover materials. Algal
cover significantly increases the likelihood of
escape from their major predator, I. antarctica,
because the anemones' tentacles attach to the
algae. This defense is physical as thalli from
which defensive chemicals have been extracted are
equally protective. Macroalgae benefit from this
relationship because fertile drift plants are retained
in the photic zone where they continue to
contribute to the gene pool. Supported by NSF
awards OPP-9530735 and OPP-9526610.
ABSTRACTS
562
561
INTERTIDAL AND SUBTIDAL LARVAL
RECRUITMENT OF THE REEF-BUILDING
POLYCHAETE PHRAGMATOPOMA
LAPIDOSA
D.A. McCarthy. Harbor Branch Oceanographic
Institution, Ft. Pierce, Florida and Kings
College London, U.K. [email protected]
Recruitment of the sabellariid polychaete
Phragmatopoma lapidosa was investigated by
monthly monitoring of juveniles appearing on
caged, semi-caged and uncaged settlement
plates at several paired intertidal and subtidal
sites off Boynton Beach, Florida. Intertidal
recruitment took place over much of the year,
with a peak in September, whereas subtidal
recruitment occurred only in the Spring.
Predation on early juveniles was no more
important than hydrodynamic artifacts created
by the cages and did not explain
intertidal/subtidal differences in recruitment.
Dissolution rates of plaster spheres were higher
in the intertidal than the subtidal, suggesting
that recruitment patterns may be explained by
differences in larval supply. However, within
the intertidal zone, highest recruitment rates
occured at sites with intermediate dissolution
rates, rather than in the highest flows.
563
WHAT CONTROLS DIVERSITY OF
CHEMOSYMBIOTIC LUCINTD BIVALVES IN
SEAGRASS BEDS?
P.A.G. Barnes* and C.S. Hickman. Smithsonian
Tropical Research Institute, Panama and University
of California, Berkeley, [email protected]
Wallucina assimilis (Bivalvia: Lucinoidea) occurs
in monospecific, dense populations in shallowwater seagrass sediments at Rottnest Island,
Western Australia. Thepreseneceofonly one
lucinid species in these seagrass sediments is in
marked contrast to other localities world-wide,
where the diversity of these chemosymbiotic
bivalves peaks in seagrass beds. This finding is
particularly surprising in light of the vastness of
Western Australia's shallow-water seagrass beds
and the relative abundance of lucinoid genera, with
extant species, found in the deep, offshore waters of
the southern half of the Australian continent.
Comparison of the sediment chemistry of Rottnest
Island seagrass sediments with that of other lucinid
localities, failed to reveal differences that might
account for the diversity anomaly. Fossil evidence
suggests that late Quaternary climate change and
local extinction may have played a role.
163A
Invertebrate Zoology
564
ROOTS AS A SITE OF HYDROGEN SULFIDE
UPTAKE IN COLD SEEP VESTIMENTIFERANS. D.
Julian*, F. Gaill, A.J. Arp and C.R. Fisher. San
Francisco State Univ., Univ Pierre et Marie Curie, Paris,
and Pennsylvania State Univ.
Vestimentiferan tubeworms have no mouth or anus, and
the majority of their nutrition is provided by
endosymbiotic sulfide-oxidizing bacteria. It has been
assumed that all vestimentiferans obtain their sulfide
across the gill (plume) surface. However, some
vestimentiferans live in habitats with little seawater
sulfide. We propose that one of these species,
Lamellibrachia sp. (from hydrocarbon seeps in the Gulf
of Mexico at 700 m), can extend a long tube-enclosed
tendril, which we call a 'roof, into the sea-floor sediment
to take up sulfide directly from the interstitial water. We
found that the sulfide concentration in the seep habitat is
less than luM in the seawater surrounding the gills, but
over 1.5 mM 10-25 cm into substrate. Root tubes are
composed primarily of giant B-chitin crystallites (1230% of mass) embedded in a protein matrix (50%). The
tubeworm typically extends to the distal tip of the root
tube, which can be over 20 cm long and is on average
1.1 mm in diameter with a wall thickness of 50um.
Sulfide permeability measurements in vitro demonstrate
that root tube is over 700 times more permeable than
trunk tube (D = 2.1 x 10"6 cmVsec at 20°C). We propose
that roots could increase the surface area available for
sulfide uptake and provide a low-resistance pathway for
sulfide diffusion from the deeper substrate.
AUTO-, ALLO-, AND XENOGRAFTS IN
566
BIOMPHALARIA GLABRATA (MOLLUSCA:
PULMONATA)
D.A. Farengo * and J.T. Sullivan. University of the
Incarnate Word, San Antonio, TX.
The goals of this study were to (1) test for the
occurrence of allorecognition in a mollusc, and (2)
further examine the previously reported
histocompatibility between the subfamilies
Planorbinae and Helisomatinae. NIH albino
Biomphalaria glabrata were simultaneously
implanted with one of their own tentacles
(autograft) and a tentacle from a wild-type donor
(allograft), and the histological condition of the two
types of implants was compared at 1,3, 7,15, and
30 days post-implantation (DPI). Both types of
implants appeared similar to each other at each DPI,
and neither was attacked by host hemocytes,
suggesting an absence of allorecognition in this
system. Beginning at 7 DPI, tentacle implants
turned inside out, such that the external ciliated
epithelium faced inward, into a debris-filled vesicle.
Additional snails received heart transplants from
Planorbula armigera. Most xenografts still showed
rhythmic contractions at 15 DPI, thus supporting
previous observations of histocompatibility between
B. glabrata and Helisoma trivolvis. Supported by
NIH grant GM55337.
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565
ALGAE OF THE GENUS SYMBIODMIUM HAVE
CHEMORECEPTORS FOR TAURINE, AN AMINO
ACID THAT INDUCES THESE SYMBIOTIC
ORGANISMS TO EXPORT CARBOHYDRATE TO
THEIR CNIDARIAN HOSTS.
E G . Trapido-Rosenthal* and PA. Vallejo. Bermuda
Biological Station for Research, and University of
Wisconsin, Madison, [email protected]
It is thought that free amino acids may be the CEhost
factor' that is involved in the symbiotic association of
zooxanthellae and cnidarians (Gates et al., 1995; Bester
et al., 1997). Recently, Wang and Douglas (1997) have
shown that the sulfonic amino acid taurine possesses
host factor activity, in that it can stimulate the export of
photosynthetically-generated carbohydrate from the
dinoflagellate Symbiodinium. This work has led to the
hypothesis that the effect of taurine could be mediated
by cell-surface chemoreceptors. We present results of
tests of this hypothesis. Algal cells interact with
radiolabeled taurine in a manner mat is sodiumindependent, saturable with time, reversible, and
structurally specific. This interaction of taurine with
algal cells obeys Michaelis-Menten kinetics and is
characterized by a Km of 25 micromolar and a Bmax of
756 finoles/million cells. We are now designing
experiments to probe the means by which the taurine
signal is transduced and linked to the export of
photosynthate. This work was supported in part by NSF
grant OCE 96-19718.
MAGNETIC ORIENTATION OF SPINY LOBSTERS: A
TEST OF THE MAGNETITE HYPOTHESIS.
567
S.D. Cain. University of North Carolina at Chapel
Hill
The ability to detect earth-strength magnetic fields
has been demonstrated for a diverse assemblage of
animals. However, the neural mechanisms that
underlie this sensory modality are poorly
understood. Using the spiny lobster, Panulirus
argus, this study investigated the role of
permanently magnetic material in
magnetoreception. Lobsters were exposed to a
strong, brief magnetic field capable of re-aligning
the magnetic moment of magnetite particles. The
lobsters were placed in a holding tank overnight and
their orientation behavior tested the following
morning. The non-pulsed or control animals had a
significant orientation (p <; 0.01) roughly in the
direction of the capture site. Lobsters treated with a
magnetic pulse of 900 G and at varying directions
with respect to the ambient field had no significant
orientation. These results are consistent with the
hypothesis that magnetite is involved in transducing
information about the magnetic field to the nervous
system. Conversely, the results are inconsistent with
the hypothesis that phototransduction and
photopigment chemistry are involved in
magnetoreception.
SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
Invertebrate Zoology
568
TEMPERATURE DIFFERENTIALLY ALTERS
MOTOR OUTPUT IN THREE SPECIES OF CRAB.
P. S. Dickinson, K. Graesser, and R. Rynning
We examined the functional changes that occur in the
gm4 muscle of 3 crab species as temperature changes. In
all 3 species (Cancer irroratusfromME, Cancer
magister and PugetliaproductafromWA), muscle
tension in response to a constant stimulus decreased with
increasing temperature. However, the mechanisms
underlying this decrease differed. In all species, muscle
membrane potential hyperpolarized with increasing
temperature. In Pugettia, EJP amplitude decreased with
increasing temperature, thus contributing to the
decreased tension. In both Cancer species, however, EJP
amplitude increased over at least a part of the
temperature range tested. In C. irroratus, EJP amplitude
increased over the entire temperature range, whereas in
C. magister, it increased up to 10-12&deg:C, then
decreased slightly. At the same time, EJPs in Cancer
decreased in duration as temperature increased, with the
result that less summation took place, helping account
for the decreased tension.The output of the motor neuron
that innervates this muscle also changed with
temperature, with spike frequency increasing and burst
duration decreaing. Because tension in these muscles is
strongly influenced by spikefrequency,we predict that
these changes would partly compensate for the decrease
tension produced by the muscle at higher temperatures.
RESILIN IN WATERSCORPION MALE
GENITALIA (INSECTA: HETEROPTERA:
NEPIDAE). S. L. Keffer and S. K. Babcock.
James Madison Univ., Harrisonburg, VA.
keffersl @jmu.edu
Resilin is an invertebrate protein rubber found
in insect wing hinge ligaments, blood-sucking
pharyngeal pumps, and nectar-sucking
proboscises. Here we report on the presence of
resilin in the waterscorpion phallus. We
confirmed the presence of resilin using selective
staining with toluidine blue, autofluorescence,
birefringence, and mechanical manipulation of
whole-mounts. Paraffin sections stained with
Mallory's trichrome were used to further identify
locations in the phallus containing resilin. The
waterscorpion phallus consists of a complex
series of articulating rods, struts, and diverticula.
The rods and struts are composed of a chitinous
core surrounded by resilin. Resilin is also found
in the articulations between chitinous structures.
We hypothesize that the resilin lendsflexibilityto
the chitinous rods during copulation and facilitates
retraction of the phallus at the conclusion of
copulation. Thus, the structural protein resilin
functions not only in insect locomotion and
feeding but also in mating and reproduction.
ABSTRACTS
570
569
LOST LIMBS, LEFTYS AND LEVERAGE (OR
CRAB CHELA REVERSAL AND THE
IMPORTANCE OF SHAPE).
S.C. Schenk. Florida State Univ., Tallahassee.
[email protected]
Heterochelous brachyuran crabs frequently
experience chela reversal following major chela
autotomy. During chela reversal, the minor chela
becomes a major chela over successive molt cycles,
and the lost major chela regenerates as a minor
chela. A similar phenomenon has been observed in
snapping shrimp. The cue producing 'reversal of
handedness' in crabs could either be an intrinsic cue
(e.g. hormonal or neurological) or an extrinsic
functional cue. I will present the results of an
experiment designed to identify this cue in the stone
crab Menippe mercenaria. It is also important to
consider the relevance of this phenomenon with
regard to chela evolution and chela performance
(i.e. speed and power). I will present a brief
overview of evolutionary interest in chela reversal,
including issues of general shape and asymmetry, as
well as address the adaptive potential of chela
asymmetry and reversal.
571
MECHANICAL PROPERTIES OF
LATRODECTUS HESPERUS DRAGLINE
SILK
N.L. Vuong and A.M.F. Moore,
Scripps College, Claremont,CA.
[email protected]
The mechanical properties of the dragline silk
of the cobweb-building spider Latrodectus
hesperus were investigated. Atensiometer
was used to stretch the silk at 0.21 lm/s. It
measured the force and extension every 0.02
seconds until the silk broke. The cross
sectional area of the silk was measured using
two techniques, the vibroscope and the light
microscope at lOOOx magnification oil
immersion. Values from the two techniques
are found to be in agreement. Results indicate
that the L. hesperus dragline silk has the
typical stress-strain curve of dragline silks,
with initial stiff region followed by a more
elastic region. Characteristic breaking stress
occurred at 800 MPa, with breaking strain of
10-20% and stiffness averaging 8%. These
results show that the dragline silk is different
from the spider's scaffolding silk in the shape
of stress-strain curve and strength.
Work supported by NSF grant DBI-97-11031.
165 A
Invertebrate Zoology
572
PRESSURE GRADIENTS ACROSS AND AIR FLOW
THROUGH SILKMOTH ANTENNAE.
C. Loudon* and J. Zhang. Univ. of Kansas, Lawrence.
Silkmoth antennae are pinnate structures that intercept
chemical signals from the air. In order to understand the
rate at which these structures sample the air we directly
measured the flow through single antennae for given
applied pressure differentials. For these measurements,
individual antennae were mounted inside a closed flowthrough system so that all of the flowing air was forced
to pass through the antenna while the pressure was
monitored immediately upstream and downstream of the
antenna. Our experiments showed that antennae from
male moths have greater drag per unit cross-sectional
area than antennae from female moths. That is, less air
will pass through male moth antennae than female moth
antennae for the same pressure differential applied
across the antennae. The pressure/flow relationship for
male moths is comparable to that reported in the
literature for air flow through antennae from male luna
moths (Actias luna) despite the differences in their gross
overall morphology. In addition we have developed a
terminal velocity technique to measure the total drag on
single antennae as a function of ambient flow rate. By
combining this information with the pressure results
described above, we will be able to estimate the
proportion of air approaching a silkworm moth antenna
that will pass through and hence be available for
chemical sampling.
NEUROPEPTIDE AND SEROTONIN EFFECTS
O N CILIARY BEAT FREQUENCY IN THE
574
BIVALVE CHLAMYS HASTATA.
M.B. Claremont*, A.O.D. Willows, M.P. Morse.
Swarthmore College, PA, University of
Washington, [email protected]
The effect of TPep-NLS (Tritonia diomedia pedal
peptide) and serotonin on ciliary beat in the scallop
Chlamys hastata was investigated. The gill was
excised from the animal and maintained at 13° C
while the flow of ink in the dorsal groove was
videorecorded. Measurements of the speed of ink
transport were made blind at a later time. A
significant increase in transport rate (p < 0.0001), as
compared to a sea water control, was found after the
external application of TPep-NLS and serotonin at a
concentration of 10 uM. Immunofluorescent
localization of TPep-NLS in the gill of C. hastata
was also performed. TPep immunolabelling was
observed in several locations along the gill
filaments: along the frontal axis, lining the dorsal
groove, and at the ciliary discs. Implications of
these results are discussed. Since TPep-NLS has
been found to be localizable in the gill and also
causes a physiological effect, this may indicate that
this peptide, or another with similar amino acid
structure, is conserved across the molluscan classes.
166A
573
STRUCTURAL AND FUNCTIONAL
RELATIONSHIPS BETWEEN BROODING
DEMIBRANCHS AND GLOCHIDIA LARVAE IN
UNIONID MUSSELS.S. Medler*and H. Silverman.
Suspension feeding bivalves sustain themselves by
producing water currents that draw food and nutrients
into the mantle cavity. The factors involved in water
pumping have been of interest for years since they are
integral to vital processes including particle capture,
feeding, and respiration. The most apparent contributor
to water flow is the beat of the lateral ciliated cells,
oriented to drive water into the gill from the mantle
cavity. Once inside the central water channel of the gill,
water travels through water tubes to the suprabranchial
chamber before leaving the animals by the excurrent
siphon. Most researchers have focused on ciliary
activity of the gill when studying the bivalve water
pump, treating the water passageways through the gill
and suprabranchial chamber as passive conduits to water
flow. Recent anatomical evidence paired with
observations of live gills in freshwater eulamellibranchs,
suggest that the musculature of the gill contributes to the
alteration of water flow. An abundant supply of smooth
muscles is oriented to reduce the dimensions of water
passageways upon contraction. Live gills, including
those observed in vivo, demonstrate the ability to alter
the size of these passageways. Muscles of the gills,
together with those of the siphons and mantle margins,
appear to play a role in the pumping activities of
bivalves.
(Supported by ZM R/ZMM - 5)
575
VIRTUAL SNAILS IN 5 DIMENSIONS:
A BETTER WAY TO STUDY NEURODEVELOPMENT IN PULMONATE
GASTROPODS.
T.L. Murphy. Michigan State Univ.
To understand the changes in development
underlying the morphological changes in the eyetentacle complex of gastropod molluscs, I
developed a novel technique utilizing laser
scanning microscopy and computer graphic
workstations to create 3D volume reconstructions of
the developing snail embryos. This allows for more
accurate and precise spatial-temporal analysis of
tissue level changes during development, as well as
for discovering the developmental changes which
underlie the morphological changes. Pulmonate
snail embryos (_Helisoma anceps_ & _Anguispira
altemata_) where collected in sequence, sectioned
& stained, digitized using a Zeiss Laser Scanning
Microscope, and rebuilt using 3D volume
reconstruction software on an SGI graphics
workstation. The interaction of the cerebral ganglia,
eyes, and tentacles was studied to look for changes
in the developmental pattern that would help
explain the morphological changes in the eyetentacle complex of pulmonate snails.
SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
Invertebrate Zoology
NEUROGENESIS IN LARVAE OF THE SERPULID
POLYCHAETE HYDROIDES ELEGANS.
B. T. Nedved*, M. G. Hadfield and R. P. Croll.
University of Hawaii and Dalhousie University.
[email protected]
Induction of metamorphosis in larvae of Hydroides
elegans is believed to be under neuronal control. The
temporal development of the nervous system of H.
elegans and the role neurotransmitters play in
metamorphosis has not been described. We used
antibodies raised against serotonin (5-HT) and the
FMRF-amide to label cells expressing these molecules.
These cells are large component of the nervous system
of other polychaetes, and the pattern of labeling through
ontogeny should allow us to follow the development of
the nervous system. In H. elegans, both 5-HT and
FMRF-amide are expressed as early as 12 h after
fertilization. After 3 days, the central nervous system of
the larva is almost completely developed. At
metamorphic competence, the number of apical/cerebral
cells expressing either 5-HT or FMRF-amide has
increased, to 8-9 cells and 12-14 cells respectively.
Serotonergic cells may be involved in metamorphosis.
A 0.5 h pulse of the 5-HT precursor 5-HTP induces
larvae to metamorphose in response to a sub-optimal
inductive cue. Additionally, the 5-HT depletor PCPA
inhibits the induction of metamorphosis. These data
suggest that 5-HT may potentiate metamorphosis.
ABSTRACTS
576
577
DEVELOPMENTAL EXPRESSION OF DIGESTIVE
ENZYMES IN PROCAMBARUS CLARKU.
H.S. Hammer*, S.A. Watts and C D . Bishop.
The red swamp crayfish is the dominant
macrocrustacean in many freshwater ecosystems and is
the most extensively cultured crustacean in the US.
Despite the importance of this species, the ability of
these organisms to utilize nutrients, particularly during
early developmental stages, is unclear. Crayfish were
assayed for the presence of the digestive enzymes
trypsin, alpha-amylase and nonspecific esterase during
several stages of development. Enzyme activities were
relatively low in the egg, with the exception of
nonspecific esterase. The activity of alpha-amylase,
nonspecific esterase and trypsin increased 9,1 and 4
fold, respectively, as animals hatched into first instar.
The enzymatic activities of alpha-amylase, nonspecific
esterase and trypsin increased an additional 2,2 and 4
fold as animals molted to the second instar prior to first
feed. These data indicate that larval crayfish develop the
capacity to digest carbohydrate, lipids and proteins prior
to first feed. After the first feed enzymatic activities
continued to increase 7,4 and 5 fold, respectively, to
maximal specific activities at approximately 40 days.
This research was supported by the Tennessee Valley
Authority.
167A