5-5.5 Days Post-Fertilization
A single plexiform DLAV is now present throughout the caudal trunk and tail, although a pair of simple right and left DLAVs persist in the cranialmost regions of the trunk. This state is basically maintained through 7 dpf, with some additional "zippering up" of the cranial paired DLAV vessels, moving the rostral border of the single plexiform DLAV further cranially. PAV and VTA continue to elongate across some of the segments, although in most segments these vessels still remain as sprouts [5.5 dpf overview]. A few VI have extended ventro-caudally from the LB along the ventral transverse septa; many more can be seen by 6 and 7 dpf [6.5 dpf overview], [7.5 dpf overview]. The distance between the DA and PCV is no longer increasing, and the transient short vessels that had appeared between these two trunk axial vessels (DA and PCV) have by now mostly disappeared. The CV continues to remodel and condense.

With the loss of the yolk, the cranial and caudal left SIV become disconnected from one another at the hindgut, while the right SIV remains intact as the main longitudinal drainage to the liver. As a result, blood in the vascular plexus of the hindgut is forced to flow into the hepatic sinusoid via the right SIV and right HPV (except for the caudalmost portions of the left SIV, which maintain a minimal drainage to the PCV). In the cranial midgut, the remnants of the left SIV are still providing for absorption of the small amount of yolk that remains beneath the gut. A few intestinal veins that had also appeared at 4 dpf in this area extend more caudal ward, and drain the most ventral regions of the cranial midgut as supplementary HPVs. The SBA and its branches are actively circulating around the completely inflated swim bladder.

In the branchial arch system, the ABA and ABF are entirely separate vessels running next to one another for most of their length. The ALB continue to lengthen, additional ALB appear and some existing ALB vessels also branch to form multiple loops from a single root, although this does not begin to any significant extent before approximately 5 dpf.

Few changes in major vessels are apparent in the cranial vasculature, although many more new capillaries appear linking the major vessels. Circulation is now strong through the NA and NV. As mentioned earlier, the PHS has become the main route for venous drainage from the head, subsuming in large part the early role of the PHBC. Blood flows in a rostral direction through rostral portions of the PHBC, draining the hindbrain and rostral medulla oblongata to empty into the PMBC-PHBC junction, and from there into the PHS. The middle and caudal PHBC drain the middle and caudal hindbrain, emptying into the ventral PCeV, and from there into the ACV [later 2.5 dpf head lateral], [2.5 dpf head dorsal multilayer composite] (lower middle layer), [3.5 dpf head dorsal multilayer composite] (upper middle layer), and [4.5 dpf head dorsal multilayer composite] (top layer). The rostral, middle and caudal PHBC segments have continued to remodel and form numerous additional branches, and the portions of the PHBC draining into the PHS or PCeV become completely separated from one another during this stage. The elongated DLV forms a "T" junction, with the MsV and MsV’ branching off from the rostral "T" and the PCeV and PCeV’ branching off from the caudal "T" (see [4.5 dpf head dorsal multilayer composite], and [6.5 dpf head dorsal multilayer composite]).