Tail regeneration in a cephalochordate, the Bahamas lancelet,Asymmetron lucayanum

Abstract

Lancelets (Phylum Chordata, subphylum Cephalochordata) readily regenerate a lost tail. Here, we use light microscopy and serial blockface scanning electron microscopy (SBSEM) to describe tail replacement in the Bahamas lancelet, Asymmetron lucayanum. One day after amputation, the monolayered epidermis has migrated over the wound surface. At 4 days, the regenerate is about 3% as long as the tail length removed. The re‐growing nerve cord is a tubular outgrowth of ependymal cells, and the new part of the notochord consists of several degenerating lamellar cells anterior to numerous small vacuolated cells. The cut edges of the mesothelium project into the regenerate as tubular extensions. These tubes anastomose with each other and with midline mesodermal canals beneath the regenerating edges of the dorsal and ventral fins. SBSEM did not reveal a blastema‐like aggregation of undifferentiated cells anywhere in the regenerate. At 6 days, the regenerate (10% of the amputated tail length) includes a notochord in which the small vacuolated cells mentioned above are differentiating into lamellar cells. At 10 days, the regenerate is 22% of the amputated tail length: myocytes have appeared in the walls of the myomeres, and sclerocoels have formed. By 14 days, the regenerate is 35% the length of the amputated tail, and the new tissues resemble smaller versions of those originally lost. The present results for A. lucayanum, a species regenerating quickly and with little inter‐specimen variability, provide the morphological background for future cell‐tracer, molecular genetic, and genomic studies of cephalochordate regeneration.

Three‐dimensional fine structure of fibroblasts and other mesodermally derived tissues in the dermis of adults of the Bahamas lancelet (Chordata, Cephalohordata), as seen by serial block‐face scanning electron microscopy

“…Table 1 reviews the various names applied to cephalochordate fibroblasts (all from the genus Branchiostoma) and shows how a consensus to use the term "fibroblast" eventually emerged. The present SBSEM study demonstrated that, like Branchiostoma, Asymmetron has fibroblasts; those of the latter genus were too few to have been noticed previously by light microscopists (Andrews, 1893;Holland & Somorjai, 2021). In the present study, we found fibroblasts were relatively rare-only 20 of them were detected in the reconstructed region (Figure 2a,b).…”

Epidermal changes during tail regeneration in the Bahamas lancelet, Asymmetron lucayanum (Cephalochordata)

“…It is likely that lobopodia provide much of the motive force for the migration of epidermal cells over the wound surface. These lobopodia are evidently in direct contact with the cut tissues at the amputation surface (Figure 2b, asterisk) because transmission electron microscopy (N. D. Holland & I. M. L. Somorjai, unpublished…”

“…The present study concerns tail regeneration in a small, tropical cephalochordate, the Bahamas lancelet ( Asymmetron lucayanum ), a species that regenerates rapidly and with close synchrony from one animal to the next. Holland and Somorjai (2021) recently described tail regeneration in this lancelet by light microscopy and serial blockface electron microscopy; however, they focused mainly on the internal tissues (celomic mesothelium, notochord and dorsal nerve cord) and paid relatively little attention to the epidermis. Here, we use conventional scanning electron microscopy ( SEM ) for a more detailed look at the lancelet epidermis during tail regeneration.…”

Combined loss of obscurin and obscurin-like 1 in murine hearts results in diastolic dysfunction, altered metabolism and deregulated mitophagy

“…The method to prepare and image serial block face electron micrographs has been described in detail elsewhere 126 . Hearts from 9 months old male animals from each group were perfused with Ringers Solution containing xylocaine (0.2mg/ml) and heparin (20 units/ml) for 2 minutes at 35°C, before being fixed by perfusion using 0.15M cacodylate buffer (pH 7.4) containing 2% formaldehyde and 2.5% glutaraldehyde (Electron Microscopy Sciences) as well as 2mM CaCl 2 at 35°C for 5 minutes.…”