One of my graduate students is attempting to characterize the ontogeny of the
olfactory apparatus of larval fishes, specifically the leptocephalus ("slender
head") larvae of tarpon/bonefish/eels, and to develop a comparison with
olfactory morphology in larvae of other fishes.
She's interested in using fluorescent staining with confocal microscopy of
whole larvae and histological sectioning of the olfactory apparatus and nerve,
as well as employing more traditional histological staining techniques to
visualize the olfactory pits, sensors, and neurons that innervate the organ.
She'll also use SEM for high-resolution imagery of the physical structures on
the surface of the heads of the larvae.
My lab is pretty good with fish biology and ecology, but we're novices when it
comes to histological analysis of tissues. As we got into the literature on
fluorescent, visual, and histological stains of neurons in general, we quickly
got overwhelmed with variety of stains and techniques that have been used, but
the literature seems pretty sparse on olfactory apparatus of fish larvae.
If Histonet folks have any advice on stains and staining protocols that she can
use to visualize the components of the olfactory and nervous system of these
transparent larvae, we'd be very appreciative of the guidance.
A quick guide to Leptocephali: these larvae are beautiful, transparent
laterally-compressed ribbons, clear as glass, with tiny heads. They typically
hatch into 3-4 mm long larvae, and grow to different sizes (tarpon = about 25
mm; bonefish about 50 mm; an unknown eel species has a larva that reaches
nearly a meter in length).
Why are we focusing on leptocephalus olfaction? Lepto olfactory pits are about
as big as their eyes; their early retinas are rod-based w/out cones, so they
can't see plankton particles (most higher teleost larvae have densely-packed
cones in their retinas that help them visualize planktonic prey, and they have
small olfactory pits); leptos have long projecting teeth (fangs) that suggest
they "carve" chunks out of mucous aggregates called "marine snow" and
gelatinous plankton for food; and the stable isotope signature of their bodies
closely mirrors that of marine snow.
How do they find their food? We're betting on olfaction/chemosensory cues, but
we'd like to confirm that hypothesis with morphological and histological
characterization of their olfactory apparatus, and hopefully combine it with
behavioral analysis of live larvae (if we can get them). It'll make a very
interesting study.
Any suggestions about how to visualize their olfactory apparatus will be
greatly appreciated!
Jon
Jon Shenker, Ph.D.
Associate Professor of Marine Biology
Department of Biological Sciences
Florida Institute of Technology
150 West University Boulevard
Melbourne, FL 32904
321-674-8145
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"...a constant stream of eager young folk, men and women, come to me with the
same query. 'My present
work is dull. How do I become an ichthyologist?'" J.L.B. Smith, 1956 "The
Search Beneath The Sea."
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