Geography Reference
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for subsequent biological or ecological considerations. For
example, automatic or semi-automatic measurements of
body length can give useful ecological information, such
as the population structure in terms of length classes.
Alvarez and Pardo (2005) estimated the body length
of the Trichoptera Agapetus quadratus using IA. The
stage-frequency size histograms suggested a trivoltine
population, with an average cohort period of 4 months.
Slight morphological (or anatomical) differences
assessed from IA can also help to distinguish between
different life-stages of a given species. From Procrustes
superimposition of 2D landmark data and subsequent
analyses, morphological shifts in Eurasian perch ( Perca
fluviatilis ) during its growth were demonstrated (Hjelm
et al., 2001). By examining otoliths of the eastern
rainbowfish ( Melanotaenia splendida splendida ) under
cross-polarised light, Humphrey et al. (2003) showed
that circuli discontinuities appeared at hatching and
during yolk sac absorption. Moreover, among other
features, accurate head measurements from microscopic
views can be used to differentiate instars of insect larvae
(Hanus et al., 2006).
between hydrodynamic abilities and the current velocities
used by the successive morphological groups. The rela-
tionship between the hydrodynamic abilities of fishes and
their utilisation of different flow velocities has been quan-
tified and confirmed, using IA, for many riverine French
species (Sagnes and Statzner, 2009).
Spatial segregation between species may also be due
to feeding behaviour or kinematics. Maie et al. (2009)
compared food capturing kinematics and performance
of two Hawaiian stream fish species, Awaous guamensis
and Lentipes concolor , using morphological data and high-
speed video. They analysed in-lever and out-lever arms for
both jaw opening and closing (from digital photographs)
and digitally synchronised lateral and ventral views of
feeding strikes (movies). Landmarks on the heads of the
fishes were digitised for each frame (Figure 17.9). They
concluded that an elevated suction pressure (due to jaw
morphology) would enhance the ability of L. concolor
to successfully capture food in the fast stream reaches it
typically inhabits.
Body ornamentation (e.g. pigmentation) can also be
used for ecomorphological purposes. After scanning indi-
viduals of freshwater isopods ( Asellus aquaticus )and
determining the optical density of the substrate, Hargeby
et al. (2005) showed that Asellus pigmentation was
correlated with substrate darkness across 29 localities.
This differentiation suggested that habitat heterogene-
ity promotes genetic diversity. In newts ( N. viridescens
viridescens ), Davis and Grayson (2007) showed that terres-
trial post-breeding specimens were browner than aquatic
ones (which were greener), postulating that the former
developed greater skin granulation, for camouflage and
resistance to desiccation. This example shows that IA of
body ornamentations can give significant informations
about individuals' way of life or strategies.
Architecture of animal building is poorly known
for freshwater species (except for beaver), although
some constructions may have important implication
in ecosystems functioning. Using a variety of electron
microscopic and computer image enhancement tech-
niques, Schultze-Lam et al. (1992) showed the specific
involvement of bacterial surfaces in natural mineral
formation processes. From detailed ultrastructural
studies of cell surfaces (Figure 17.10), they demonstrated
that the S-layer 6 of a cyanobacteria (belonging to the
Synechococcus group) acted as a template for fine-grain
gypsum and calcite formation by providing discrete,
17.2.3 Ecomorphological studies
Some morphological or anatomical characteristics of an
organism may be related to its ecological role or pref-
erences. Therefore, the power of IA to discriminate
fine morphological features may be very useful in eco-
morphological studies. Li and Yu (2009) scanned and
subsequently analysed leaf outlines of Ranunculus natans
and found that intra-specific foliar morphological varia-
tions were important and traduced functional responses
to water-quantity and water-availability factors (e.g. alti-
tude, pH). Sagnes et al. (2008) measured body lengths
in numerous individuals of aquatic insect larvae, using
semi-automated IA methods. They showed that, for a
given species, habitat use could be different with respect
to body size and concluded that future instream habitat
models should consider the respective habitat require-
ments of different size classes of invertebrates.
Spatial segregation of species (or ontogenetic stages
of a given species) living in the same system can be
inferred from the ecomorphological study of specific
functions, such as locomotion (Wood and Bain, 1995).
After describing and analysing body lengths, widths
and fin areas from photographs, Sagnes et al. (1997,
2000) demonstrated that the body shape of the Euro-
pean grayling ( Thymallus thymallus ) changed during its
ontogenesis towards hydrodynamically efficient shape
at highest velocities. Moreover, there was a relationship
6 An S-layer (surface layer) is a part of the cell envelope commonly
found in bacteria. It consists of a monomolecular layer composed
of identical proteins.
 
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