Postembryonic development of the posterior lateral line in the zebrafish

Abstract

The posterior lateral line (PLL) of zebrafish comprises seven to eight sense organs at the end of embryogenesis, arranged in a single antero-posterior line that extends along the horizontal myoseptum from the ear to the tip of the tail. At the end of larval life, four antero-posterior lines extend on the trunk and tail, comprising together around 60 sense organs. The embryonic pattern is largely conserved among teleosts, although adult patterns are very diverse. Here we describe the transition from embryonic to juvenile pattern in the zebrafish, to provide a framework for understanding how the diversity of adult patterns comes about. We show that the four lines that extend over the adult body originate from latent precursors laid down by migrating primordia that arise during embryogenesis. We conclude that, in zebrafish, the entire development of the PLL system up to adulthood can be traced back to events that took place during the first 2 days of life. We also show that the transition from embryonic to adult pattern involves few distinct operations, suggesting that the diversity of patterns among adult teleosts may be due to differential control of these few operations acting upon common embryonic precursors.

Origin and Early Development of the Posterior Lateral Line System of Zebrafish

“…For fate-mapping experiments, Kaede photoconversion was performed as described previously (Nuñez et al, 2009) using a 0.05 mm pinhole positioned as a field diaphragm in the excitation path of an Axioplan microscope (Zeiss) and a 20ϫ water-immersion objective, achieving an actual diameter of illumination of 25 m. For fate mapping at 17.5 hpf, we used a pinhole of 0.16 mm and an eyepiece reticle with a square lattice to position the beam relative to the outline of the otic vesicle. For synapse conversion, we also used a 0.16 mm pinhole and delivered two pulses of 30 s each, separated by 5 min.…”

“…B, A case in which LI neuromasts, but not LII, are completely absent. LI and LII neuromasts can be distinguished based on the central, unlabeled region that is oriented along the anteroposterior axis in LI neuromasts and along the dorsoventral axis in LII (Nuñez et al, 2009). C, A case in which LII neuromasts, but not LI, are absent.…”

“…One migrates along the horizontal myoseptum, much as primI did, and has been called primII; the other one migrates along the dorsal midline and has been called primD (for review, see Ghysen and Dambly-Chaudière, 2007). primII and primD deposit seven to eight and five neuromasts, respectively, as well as a trail of interneuromast cells that proliferate later during larval development and form two new lines of neuromasts (Nuñez et al, 2009). primII and primD are therefore at the origin of three of the four anteroposterior lines of neuromasts present in juvenile and adult zebrafish, yet their origin has never been investigated.…”

“…By 48 hpf, the embryonic pattern is complete. In addition to the neuromasts, primI deposits a trail of interneuromast cells that will later proliferate and form intercalary neuromasts during larval development (Grant et al, 2005;LopezSchier and Hudspeth, 2005;Nuñez et al, 2009).…”

Innervation is required for sense organ development in the lateral line system of adult zebrafish

“…5 for zebrafish) lead to the juvenile stage, around 1 month post fertilization (mpf). At this stage, about 50 PLL neuromasts are aligned as four antero-posterior lines (6) (Fig. S1A).…”