In the present EM study, we investigate the retina of Belone belone, a visually‐orientated marine predator living close to the water surface. In the duplex retina, four morphologically different cone types are observed: unequal and equal double cones, long single cones and triple cones. In the light‐adapted state, five different cone patterns occur: row, twisted row, square, pentagonal and hexagonal patterns. High double cone densities are found ventro‐nasally, ventro‐temporally and dorso‐temporally. Throughout the retina the double cone/single cone ratio is 2 : 1, in the ventral part, however, a 1 : 1 ratio occurs. In the vitreous body we found a curtain‐like intraocular septum dividing the retina into two morphologically different regions. In most areas of the dark‐adapted retina the cone patterns are absent at the ellipsoid level, with long single cones standing more vitreally in the light path than double cones. The mosaics are retained, however, in the outer nuclear layer. Typical dark adaptation, i.e. the retinomotor movements of the retinal pigment epithelium and photoreceptors in response to the dark adaptation (light change) is not present in the peripheral ventral and parts of the central ventral area. In both regions we found a twisted row pattern of cones having a vitreal position. The findings are discussed with respect to the photic habitat and feeding habits of this species.

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We investigated the spectral and morphological features of the photoreceptors of five atherinomorph teleosts, representing two different orders, and with different life styles and habitats, the Beloniformes and Atheriniformes. The retinae of Belone belone (Belonidae), Dermogenys pusillus (Hemiramphidae), Atherina boyeri (Atherinidae), Marosatherina ladigesi (Telmatherinidae), and Melanotaenia maccullochi (Melanotaeniidae) were examined by light and electron microscopy and microspectrophotometry. In addition to rods, five morphologically different cone types were identified: short, intermediary and long single cones, and double cones which are arranged in distinct specific mosaics. Sporadically, triple cones were also found. Double cones were longer-wave-sensitive, but no general correlation between single cone morphology and spectral sensitivity could be demonstrated. The rods had λ_max close to 506–509 nm. The λ_max of cone visual pigments ranged from about 368 nm to 578 nm. Ultraviolet-sensitive single cones were present in the three freshwater species, M. ladigesi, M. maccullochi and D. pusillus and three spectrally distinct short-wave-sensitive single cone classes were identified in M. maccullochi. In M. ladigesi, spectral sensitivity varied among individuals due to varying rhodopsin/porphyropsin mixtures. In D. pusillus and M. maccullochi polymorphism of the longer-wave cone pigments might occur. These findings are discussed with respect to phylogeny, photic habitat, behavior and feeding habits.

We saw our null hypothesis that "hair in the sinus cavity is from the intergluteal region" rejected by each of three different approaches. There is strong evidence that occipital hair is present regularly in pilonidal sinus nests. We should start thinking of occipital hair as an important hair source for the development of the pilonidal hair nest.

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