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Keywords:

  • Porifera;
  • northeast Pacific;
  • spicules;
  • spermatophores;
  • radial symmetry

Abstract

Chondrocladia (Symmetrocladia) lyra subgen. nov., sp. nov., is described from northeast Pacific sites at Escanaba Ridge and Monterey Canyon at depths of 3316–3399 m. Two retrieved specimens are described in detail, while variations are described in ten photographed or videotaped specimens. The basic structure, termed a vane, is harp- or lyre-shaped. From 1 to 6 vanes extend by radial growth from the organism's center. The orientation among the vanes is approximately equiangular, such that together they display pentaradiate, tetraradiate, triradiate, or biradiate symmetries. Each vane is formed by a horizontal stolon supporting a series of upright, equidistantly spaced branches each of which terminates at its apex in a swollen ball in all observed specimens except the paratype. Swellings occur midway along the branches in the holotype, but not in the paratype. A linear row of filaments project from the sides, front, and back of each branch, and also from the tops of each stolon. The terminal balls are the sites of spermatophore production and release; mid-branch swellings are sites of oocyte maturation. The two megasclere spicule types have specific distributions; styles support rhizoids, stolons, and branches, while subtylostyles support filaments and terminal balls. Anchorate isochelae cover all surfaces. Enclosed crustacean prey on branches and stolons provide direct evidence of carnivory. The structure of the vanes maximizes surface area for passive suspension feeding. Increased surface area could also maximize spermatophore capture, with the sigmas projecting from the spermatophore surface being caught by projecting isochelae on filaments. Swellings on filaments are snared spermatophores, firmly fused to recipient tissues and undergoing destruction. Spermatophores on filaments are present in branch swellings containing early and mature oocytes. Oogenesis and maturation occur only in proximity to branch swellings, suggesting that development is induced by spermatophore reception. Symmetrical development of uniserial branched stolons (the vanes) characterized members of the new subgenus Symmetrocladia.