Planktonic ostracods are deep dwelling mesozooplankton that are diel migrators and detritus feede... more Planktonic ostracods are deep dwelling mesozooplankton that are diel migrators and detritus feeders. In the Humboldt Current region off Peru they are shown to be strongly influenced by El Niño conditions. Species composition and distribution were compared in day and night (vertically hauled 50–0 m Hensen Net) samples that were collected from three latitudinal zones (3°40' S–6°S; 9°S–12°S and 15°S–18°S) during 1998 (El Niño year) and in 2001 (a year with usual upwelling regime). Unexpectedly, ostracods diversity and abundance were much higher during El Niño than during the upwelling regime. Tropical species that normally occurred north of 6°S, spread southwards and increased in abundance; Euconchoecia aculeata was often dominant, particularly in coastal waters, and the frequency of occurrence of others increased throughout the entire region (e.g. Porroecia porrecta, Archiconchoecia striata). Conversely, Conchoecetta giesbrechti, a species associated with subsurface oxygen minimu...
Environmental variation in signalling conditions affects animal communication traits, with possib... more Environmental variation in signalling conditions affects animal communication traits, with possible consequences for sexual selection and reproductive isolation. Using spectrophotometry, we studied how male coloration within and between populations of two closely related Lake Victoria cichlid species (Pundamilia pundamilia and P. nyererei) covaries with water transparency. Focusing on coloration patches implicated in sexual selection, we predicted that in clear waters, with broad-spectrum light, (1) colours should become more saturated and (2) shift in hue away from the dominant ambient wavelengths, compared to more turbid waters. We found support for these predictions for the red and yellow coloration of P. nyererei but not the blue coloration of P. pundamilia. This may be explained by the species difference in depth distribution, which generates a steeper gradient in visual conditions for P. nyererei compared to P. pundamilia. Alternatively, the importance of male coloration in intraspecific sexual selection may differ between the species. We also found that anal fin spots, that is, the orange spots on male haplochromine anal fins that presumably mimic eggs, covaried with water transparency in a similar way for both species. This is in contrast to the other body regions studied and suggests that, while indeed functioning as signals, these spots may not play a role in species differentiation.
Planktonic ostracods are deep dwelling mesozooplankton that are diel migrators and detritus feede... more Planktonic ostracods are deep dwelling mesozooplankton that are diel migrators and detritus feeders. In the Humboldt Current region off Peru they are shown to be strongly influenced by El Niño conditions. Species composition and distribution were compared in day and night (vertically hauled 50–0 m Hensen Net) samples that were collected from three latitudinal zones (3°40' S–6°S; 9°S–12°S and 15°S–18°S) during 1998 (El Niño year) and in 2001 (a year with usual upwelling regime). Unexpectedly, ostracods diversity and abundance were much higher during El Niño than during the upwelling regime. Tropical species that normally occurred north of 6°S, spread southwards and increased in abundance; Euconchoecia aculeata was often dominant, particularly in coastal waters, and the frequency of occurrence of others increased throughout the entire region (e.g. Porroecia porrecta, Archiconchoecia striata). Conversely, Conchoecetta giesbrechti, a species associated with subsurface oxygen minimu...
Environmental variation in signalling conditions affects animal communication traits, with possib... more Environmental variation in signalling conditions affects animal communication traits, with possible consequences for sexual selection and reproductive isolation. Using spectrophotometry, we studied how male coloration within and between populations of two closely related Lake Victoria cichlid species (Pundamilia pundamilia and P. nyererei) covaries with water transparency. Focusing on coloration patches implicated in sexual selection, we predicted that in clear waters, with broad-spectrum light, (1) colours should become more saturated and (2) shift in hue away from the dominant ambient wavelengths, compared to more turbid waters. We found support for these predictions for the red and yellow coloration of P. nyererei but not the blue coloration of P. pundamilia. This may be explained by the species difference in depth distribution, which generates a steeper gradient in visual conditions for P. nyererei compared to P. pundamilia. Alternatively, the importance of male coloration in intraspecific sexual selection may differ between the species. We also found that anal fin spots, that is, the orange spots on male haplochromine anal fins that presumably mimic eggs, covaried with water transparency in a similar way for both species. This is in contrast to the other body regions studied and suggests that, while indeed functioning as signals, these spots may not play a role in species differentiation.
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