Embryonic development and morphology of eggs and newly hatched larvae of Pacific herring Clupea pallasii

Abstract

The embryonic development and morphology of eggs and newly hatched larvae of the Pacific herring Clupea pallasii were described using laboratory-reared specimens originating from the Miyako Bay stock. The eggs were almost spherical in shape, 1.33-1.46 mm (mean: 1.38 mm) in diameter, and had a thick adherent chorion. They had a segmented pale yellow yolk, no oil globule, and a relatively wide perivitelline space. A subgerminal cavity was observed during the gastrula period, whereas the blastocoel did not appear. Mass hatching occurred by 271 h 45 min after fertilization, and the newly hatched larvae were 7.1-7.7 mm (mean: 7.5 mm) in total length with 53-56 myomeres at 9.6°C. The embryonic development of Pacific herring was substantially similar to that of zebrafish Danio rerio, American shad Alosa sapidissima, as well as Atlantic herring Clupea harengus, and generally followed the basic developmental pattern of teleosts. However, Pacific herring larvae hatched at a more developed stage than some other clupeoids, such as Japanese sardine Sardinops melanostictus, and the progressed developmental stage at hatching could be interpreted as an advanced adaptation.

Prolongation of somitogenesis in two anguilliform species, theJapanese eelAnguilla japonicaand pike eelMuraenesox cinereus, with refined descriptions of their early development

“…Somitogenesis initiates around the completion of epiboly and ends when the number of somites reaches the species‐specific number. This pattern has also been reported in the embryonic development of non‐model species such as Pacific herring Clupea pallasii Valenciennes 1847 (Kawakami et al ., ). Compared with this type of developmental pattern, somitogenesis continued relatively longer in A. japonica and M. cinereus .…”

“…Due to this long duration of somitogenesis, the pharyngula period could not be exclusively determined during development of A. japonica and M. cinereus . These results are in contrast to C. pallasii , where somitogenesis completes at a similar timing as it does in D. rerio in relation to formation of organs, despite the larger number of vertebrae (Kawakami et al ., ).…”

“…To clarify the differences in somitogenesis duration among the two eel species and other fishes, the results of this study were compared with the development of the well‐described species D. rerio (Kimmel et al ., ) and to C. pallasii (Kawakami et al ., ) and C. myriaster (Horie et al ., ) (Fig. ).…”

“…Comparisons of developmental trajectory among Anguilla japonica , Muraenesox cinereus and other reference species: Danio rerio (Kimmel et al ., ), Clupea pallasii (Kawakami et al ., ) and Conger myriaster (Horie et al ., ). The developmental periods (cleavage, blastula, gastrula, segmentation and pharyngula) are sequentially represented by different shading bars (from black to white).…”

“…These possibilities can be examined by comparing the developmental pattern of A. japonica and M. cinereus with those of other species. In development of D. rerio, the somitogenesis rate at a particular water temperature can be estimated using the formula suggested by Schröter et al (2008) (Kimmel et al, 1995), Clupea pallasii (Kawakami et al, 2011) and Conger myriaster . The developmental periods (cleavage, blastula, gastrula, segmentation and pharyngula) are sequentially represented by different shading bars (from black to white).…”