Fine structures of oocyte envelopes of three related cobitid species in the genus Iksookimia (Cobitidae)

Abstract

Fine structures of the oocyte envelope (zona radiata) in three spined loaches, Iksookimia longicorpus, I. hugowolfeldi, and I. yongdokensis, are examined and compared. The zona radiata surrounding the oocyte is composed of two layers, a zona radiata externa, which comprised the outermost zona radiata (Z 1 ) of a homogeneous less electron dense single layer and the middle zona radiata (Z 2 ) of a homogeneous more electron dense single layer, and a zona radiata interna, which comprised the innermost zona radiata (Z 3 ) of heterogeneous electron-dense multilayers. Especially, the surface of the outermost zona radiata (Z 1 ) showed a morphological difference in its external appearance among the species. In the surface structures of Z 1 , I. yongdokensis had a round granule appearance, and both I. hugowolfeldi and I. longicorpus were villus in morphology. In the villus appearance of these two species, however, there were clear differences between I. hugowolfeldi and I. longicorpus: the former had a few short thin villi, 1.0-1.7 µm in length, but in the latter species the villi were numerous, long, and thick, 2.0-2.5 µm long. The variety of such structures in these three species of Iksookimia may be a useful aid in taxonomic relationships and closely related to their habitats.

External Egg Membrane Characteristics of Landlocked Fall Chinook Salmon Eyed Eggs Treated with Hydrogen Peroxide or Formalin

“…The internus is similar in thickness to that reported by Groot and Alderdice (1985), 50.5 m, for Chinook salmon eyed eggs and is much thicker than in the eggs of rainbow trout (Grierson and Neville 1981) and other reported species (Park and Kim 2001). Quagio-Grassiotto and Guimarães (2003) suggested that the external egg membrane is thicker in eggs subjected to heavy mechanical stress, and Kjørsvik and Lønning (1983) suggested that a thinner membrane could facilitate oxygen diffusion.…”

Adhesive structures in the eggs of Corydoras aeneus(Gill, 1858; Callichthyidae)

“…The presence of these structures can be related to the turbid habitat in which this species lives, but further studies on eggs of phylogenetically related and of nonrelated sympatric fishes will further have to clarify this hypothesis and demonstrate the true relation. The results of this study could possibly be used also in a taxonomic perspective, since morphological characters of teleost eggs have already been used this way (Kim & Park, 1996;Park & Kim, 2001) (Britto & Castro, 2002). Patzner & Glechner (1996), however, question such an application since no association between egg morphology and taxonomy exists, at least not within the family Cyprinidae.…”

Early life history of the eastern Korean tetraploid spined loach,iksookimia yongdokensis(Pisces: Cobitidae)

“…A relatively large number of loach species (16 species in five genera of Cobitidae and three species in two genera of Balitoridae) inhabit Korea showing either an allopatric or sympatric distribution pattern, and among them, 13 species are endemic (Kim 1997, Kim & Park 2007, Vasil'eva et al 2016). These cobitid species vary in their spawning periods and spawning grounds (Ko & Won 2015, Ko & Bang 2016, and occupy diverse habitats that have been associated with the distinctive structure of egg envelopes (Kim & Park 1995, 1996, 1997, Park 1996, Park & Kim 2001. The eastern Korean spined loach, Iksookimia yongdokensis, belonging to the endemic genus Iksookimia, was established as a new species by Kim & Park in 1997, and it inhabits streams in the south-eastern region of Korea (Kim & Park 1997).…”

“…It inhabits the bottom of streams with cobbles, pebbles and sands, and it spawns between June and July . The structure of the egg envelope of this species has the shape of a granular form (Park & Kim 2001). From the perspective of conservation, I. yongdokensis has been evaluated as Least Concern (LC) in the Red Data Book of endangered fishes in Korea due to environmental pollution and development of rivers ).…”