Ecomorphology of retinal structures in zooplanktivorous haplochromine cichlids (Pisces) from Lake Victoria

Meer, H.J. van der; Anker, G. Ch.; Barel, C.D.N.

doi:10.1007/bf00005910

Cited by 23 publications

(13 citation statements)

References 35 publications

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“…Witte 1984b, Goldschmidt et al 1990), morphology (e.g. van der Meer and Bowmaker 1995, van der Meer et al 1995), behavioral biology (Smith and Wooton 1994) and physiology (Rosenberger and Chapman 2000, Melnychuk and Chapman 2002). The second species, which closely resembles Haplochromis “argens,” was nicknamed Haplochromis “dusky argens”.…”

Section: Introductionmentioning

confidence: 99%

Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

Zeeuw¹,

Westbroek²,

Oijen³

et al. 2013

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Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania, are described and illustrated. These species closely resemble each other. Their affinities to other zooplanktivorous haplochromines from Lake Victoria are discussed. Haplochromis argens sp. n., which featured under nicknames (mainly Haplochromis “argens”) in more than 50 papers, was caught both in the Mwanza Gulf and the Emin Pasha Gulf, whereas Haplochromis goldschmidti sp. n. was only found in the Emin Pasha Gulf. Of the latter species only males are available, but it seems unlikely that it represents a case of male colour polymorphism as several presumably unrelated characters differ in sympatry between the two species, suggesting that there is no gene flow. Statistical analysis revealed that the overall difference between the two species is greater than that between the populations from the two locations. Body depth of the two species in sympatry in the Emin Pasha Gulf was more similar than that of Haplochromis goldschmidti sp. n. and the allopatric population of Haplochromis argens sp. n. from the Mwanza Gulf,which mayindicate an overall environmental effect. However, several measurements related to the width of snout and mouth differed more between the populations of the two species in sympatry than between the allopatric populations. In contrast to a group of zooplanktivorous species that recovered successfully after environmental changes in the lake, Haplochromis argens sp. n. is among a group that became extremely rare and probably is in danger of extinction; the conservation status of Haplochromis goldschmidti sp. n. is currently unknown.

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Section: Introductionmentioning

confidence: 99%

Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

Zeeuw¹,

Westbroek²,

Oijen³

et al. 2013

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“…Thus, the reduced eye size found in the modern population of H. pyrrhocephalus was unexpected in relation to the assumed visual demands. Studies of the retina of H. pyrrhocephalus from before the environmental changes (old populations) revealed exceptionally large long‐wavelength‐sensitive (LWS) double cones (Van der Meer, Anker & Barel, 1995). In addition, Van der Meer & Bowmaker (1995) showed that the spectral sensitivity of this species covered significantly longer wavelengths compared to other haplochromines investigated.…”

Section: Introductionmentioning

confidence: 85%

“…There is some discrepancy regarding the double cone size of the old H. pyrrhocephalus population from the present study, and that of the sample used by Van der Meer et al . (1995).…”

Section: Discussionmentioning

confidence: 99%

“…This may have been less intense in the light‐adapted specimens used in the present study. Moreover, the number of samples from one retina reported by Van der Meer et al . (1995) was much larger (over 30 regions) than in the present study (12 regions).…”

Section: Discussionmentioning

confidence: 99%

“…The higher the PhCA, the sooner a fish can respond, either by approaching or escaping the object of detection. According to retinal studies on haplochromines reported by Van der Meer et al . (1995), such detection is most profitable in a lateral direction.…”

Section: Introductionmentioning

confidence: 99%

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Photopic adaptations to a changing environment in two Lake Victoria cichlids

Meer

Rijssel

Wagenaar

et al. 2012

Biological Journal of the Linnean Society

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During the past 30 years, Lake Victoria cichlid fishes have encountered severe environmental and ecological changes including an introduced predator and new prey types. Furthermore, increased eutrophication has led to reduced water transparency and shifted the spectral composition of underwater light to longer wavelengths. In the present study, collections of two cichlid species, Haplochromis pyrrhocephalus and Haplochromis tanaos, from before and after the environmental changes, were compared with respect to their photopic resolution and sensitivity. Eyes of both species were dissected and retinal features were measured from tangential sections. In both species, the eyes became smaller, independently of body size. This decrease possibly occurred to make space for other structures that increased in size. In H. pyrrhocephalus, a significantly lower resolution was found. However, the size, and thus photon‐catching ability of the double cones, remained unchanged, despite the smaller eyes. In the modern populations of H. tanaos, the double cone size increased in relation to eye size, so that the photon‐catching ability of the smaller fish remained the same. However, no significant decrease in resolution was found. Shortwave sensitivity was found to be lower in both modern populations because of a reduction or the complete absence of single cones. The results obtained in the present study imply that these resurgent zooplanktivores are capable of adapting their eye morphology to the changed environmental conditions without losing crucial aspects used for survival and reproduction. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 328–341.

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Regional variations in the outer retina of atherinomorpha (Beloniformes, Atheriniformes, Cyprinodontiformes: Teleostei): Photoreceptors, cone patterns, and cone densities

Reckel¹,

Melzer

2003

Journal of Morphology

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The outer retinae of adults of 13 atherinomorph species, representing nine different families, were examined by both light and electron microscopy. The retinae were investigated with respect to photoreceptor types, cone densities, and cone patterns. All data were composed to eye maps. This procedure allows an interspecific comparison of the regional differences within the outer retina among these shallow-water fish. Furthermore, for a more detailed pattern analysis nitro-blue tetrazolium chloride- (NBT)-stainings in the retina of Melanotaenia maccullochi are presented. Apart from rods, eight morphologically different cone types could be identified: short, intermediate, and long single cones, double cones (equal and unequal), triple cones (triangular and linear), and in Ameca splendens one quadruple cone. Dimensions and occurrence of photoreceptors vary among the respective species and within the retinal regions. In the light-adapted state, the cones are arranged in highly ordered mosaics. Five different cone tessellation types were found: row patterns, twisted row patterns, square patterns, pentagonal patterns, and, exclusively in Belone belone, a hexagonal pattern. In Melanotaenia maccullochi the different spectral photoreceptor classes correspond well with the distribution of morphological photoreceptor classes within the mosaic. Double cone density maxima together with a highly ordered cone arrangement usually occur in the nasal and/or ventral to ventrotemporal retina. In most of the species that were examined these high-density regions are presumed to process visual stimuli from the assumed main directions of vision, which mainly depend on feeding behavior and predator pressure. Our findings are discussed with respect to the variable behavioral and visual ecology and phylogeny of the respective species.

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Ecomorphology of retinal structures in zooplanktivorous haplochromine cichlids (Pisces) from Lake Victoria

Cited by 23 publications

References 35 publications

Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

Photopic adaptations to a changing environment in two Lake Victoria cichlids

Regional variations in the outer retina of atherinomorpha (Beloniformes, Atheriniformes, Cyprinodontiformes: Teleostei): Photoreceptors, cone patterns, and cone densities

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