Developmental anatomy of lampreys

Abstract

Lampreys are a group of aquatic chordates whose relationships to hagfishes and jawed vertebrates are still debated. Lamprey embryology is of interest to evolutionary biologists because it may shed light on vertebrate origins. For this and other reasons, lamprey embryology has been extensively researched by biologists from a range of disciplines. However, many of the key studies of lamprey comparative embryology are relatively inaccessible to the modern scientist. Therefore, in view of the current resurgence of interest in lamprey evolution and development, we present here a review of lamprey developmental anatomy. We identify several features of early organogenesis, including the origin of the nephric duct, that need to be re-examined with modern techniques. The homologies of several structures are also unclear, including the intriguing subendothelial pads in the heart. We hope that this review will form the basis for future studies into the phylogenetic embryology of this interesting group of animals.

Body wall development in lamprey and a new perspective on the origin of vertebrate paired fins

“…S1 A and B). During subsequent stages of development (stages [24][25][26][27][28][29][30], the embryo straightens, the yolk ball elongates into a tube, and new myotomes form from somitic mesoderm in an anterior to posterior direction (Fig. S2).…”

“…S4 and S5). In total, we performed 188 somite and 209 LPM injections, which were then collected either within 12 h of injection to evaluate DiI targeting or at developmental stages with varying degrees of body wall closure (stages [25][26][27][28][29][30] (Table S1). We sectioned embryos with the brightest whole-mount fluorescence (18 somite injections; 29 LPM injections) (Table S1) and stained sections from older embryos for skeletal muscle.…”

“…Recent studies have shown that the lamprey myotome is dorsoventrally compartmentalized, despite lacking a horizontal septum (26), and that the LPM is patterned into distinct cardiac and posterior regions (14,15). Few studies, however, have characterized the lamprey LPM during stages of body wall formation (15,27). Here, we examine the morphological changes taking place during this process in both the Sea Lamprey Petromyzon marinus and the Japanese Lamprey Lethenteron japonicum to extend classical descriptions (28)(29)(30) and provide long-term fate maps of somitic and LPM in an agnathan vertebrate.…”

Discovery of fossil lamprey larva from the Lower Cretaceous reveals its three-phased life cycle

“…Lampreys have been extensively studied for nearly two centuries, and the last two decades have witnessed an accelerated progress on lamprey studies, especially in areas such as chordate phylogeny (26)(27)(28), metamorphosis in vertebrates (29), and molecular and developmental biology (30,31). Although "lampreys enter the genomic era" (25, p. 223), their fossils only begin to emerge in an unprecedented rate and quality.…”

The lamprey: A jawless vertebrate model system for examining origin of the neural crest and other vertebrate traits

“…Embryonic lamprey hearts have been reported to have multiple valves, including a sinoatrial valve, an atrioventricular valve, and outflow valves (Farrell, 2007; Lee et al, 2013; Richardson et al, 2010; Shipley). However, the outflow valves are not necessarily homologous to the semilunar valves of amniotes (Bullock et al, 1984; Peters, 1960; Richardson et al, 2010; Schultz et al, 1956), which include neural crest-derived cells (Jain et al, 2011; Nakamura, 2006; Smith et al, 2013). …”