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Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton

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Morphological differences between two ecologically similar sympatric fishes.

I P Helland¹, L A Vøllestad, J Freyhof

¹Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, P.O. Box 850 119, D-12561 Berlin, Germany. ingeborg.helland@nina.no

Journal of Fish Biology

|August 27, 2010

Summary

Two similar fish species, Coregonus albula and Coregonus fontanae, coexist in Lake Stechlin. Morphological differences, especially in head and eye shape, may relate to their distinct pelagic microhabitats, aiding their survival.

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Area of Science:

Ichthyology
Ecology
Evolutionary Biology

Background:

Pelagic planktivorous fishes often exhibit niche partitioning.
Understanding morphological and ecological differentiation is key to explaining species coexistence.

Purpose of the Study:

To investigate the morphological differentiation and microhabitat segregation of two ecologically similar fish populations, Coregonus albula and Coregonus fontanae.
To determine if observed morphological differences correlate with ecological niches and contribute to coexistence.

Main Methods:

Diel vertical migration patterns were tracked for both species in Lake Stechlin.
Landmark-based geometric morphometrics were used to analyze external morphology.
Morphological variations were compared across different sizes within each species.

Main Results:

Both Coregonus albula and Coregonus fontanae undertake diel vertical migrations, with C. fontanae consistently occupying deeper waters.
Significant morphological differences were identified between the two species, particularly in head length, eye position, and caudal peduncle dimensions.
Coregonus fontanae exhibits size-dependent morphological changes, with greater differentiation from C. albula at smaller sizes.

Conclusions:

Morphological differences between C. albula and C. fontanae likely reflect adaptations to distinct microhabitats within Lake Stechlin.
While morphological divergence may contribute to coexistence, conclusive evidence linking it as the primary mechanism is lacking.
Further research is needed to fully elucidate the factors driving the coexistence of these closely related coregonids.