Category: Uncategorized

Modern sword in the stone. View in LinkedIn

ASSUMPTION BUSTED. "However, careful morphological examination reveals instances of asymmetry, biradiality, tetraradiality, or even bilaterality in the internal anatomy of cnidarians." https://lnkd.in/dph5vzr View in LinkedIn

CNIDARIAN RADIAL ASSUMPTION. "Since Cuvier erected the “Radiata” as one of four metazoan “embranchments” cnidarians have generally been described as radially-symmetrical animals. Indeed, many cnidarians exhibit radial symmetry. The body plan of Hydra is a simple cylinder, radially symmetrical about the primary body axis, the oral-aboral axis." https://lnkd.in/dph5vzr View in LinkedIn

SEPARABLE MULTIGENIC AXES. "The bilateral symmetry of Bilateria is a complex multigenic trait achieved by the intersection of two axes of polarity: a primary body axis (the anterior-posterior axis) and a secondary, orthogonal axis (the dorsal-ventral axis). These two axes are logically and evolutionarily separable." https://lnkd.in/dph5vzr View in LinkedIn

NEW THINKING. "The extant members of the phylum Cnidaria (sea anemones, corals, jellyfishes, and hydras) are widely invoked as proxies for the pre-bilaterian ancestral condition. However, careful examination of cnidarians based on morphology and the deployment of developmental regulatory genes suggests some putative bilaterian "novelties" might be traced to the cnidarian-bilaterian ancestor (CBA)." https://lnkd.in/dph5vzr View in LinkedIn

ACCEPTED DOGMA. "Conventional wisdom holds that the bilaterian condition arose from an ancestor that displayed radial symmetry instead of bilateral symmetry, diploblasty instead of triploblasty, a blind sac for a gut, no coelom, and a decentralized nerve net." https://lnkd.in/dph5vzr View in LinkedIn

MONOPHYLETIC ORIGINS. "At one time or another, all of these traits have been implicated as bilaterian synapomorphies, though arguments have also been made for multiple independent origins of mesoderm, coeloms, and through-guts within Bilateria. Comparative molecular developmental data have provided support for the monophyletic origin of these traits." https://lnkd.in/dph5vzr View in LinkedIn

PATTERNED GENE EXPRESSION. "The anterior-posterior axis of bilaterians is known to be patterned by staggered Hox expression domains. In cnidarians, Hox expression domains are similarly staggered along the oral-aboral axis. The dorsal-ventral axis of bilaterians is patterned partially by the asymmetrical expression of dpp/BMP4. Likewise, dpp is expressed asymmetrically relative to directive axis of sea anemones." https://lnkd.in/dph5vzr View in LinkedIn

CONSISTENCY IN DIVERSITY. "Despite their morphological diversity, most bilaterians are united by a handful of fundamental body plan features including bilateral symmetry, triploblasty, a coelom, a through-gut, and a central nervous system." https://lnkd.in/dph5vzr View in LinkedIn

STAGGERED GENE DOMAINS. "Typically, each individual Hox gene is expressed in a band of cells representing a subset of the animal’s anterior-posterior axis. Different Hox genes have distinct domains of spatial expression along the primary body axis. Collectively, the staggered Hox expression domains specify regional identity over the majority of the body axis, as each region of the body comes to express a different Hox gene or combination of Hox genes. The “Hox code” effectively subdivides the bilaterian body plan into distinct regions." https://lnkd.in/dph5vzr View in LinkedIn