The cnidome and internal morphology of Lophelia pertusa (Linnaeus, 1758) (Cnidaria, Anthozoa)

Abstract

The cnidome of the scleractinian cold‐water coral Lophelia pertusa (Linnaeus, 1758, syn. Lophohelia prolifera) was described by Carlgren in 1940. Due to a renewed interest in the cnidae of L. pertusa, specifically comparisons of adult and larval cnidae and their functions, we now redescribe the cnidome from material collected at the Tisler reef in Norway, close to Carlgren's collection site at Saekken (Sweden). Cnidae from column, tentacles, actinopharynx, mesenterial filaments and acontia were investigated. Fresh tissue preparations were compared to histological preparations of decalcified polyps to verify the presence of cnidocysts and secretory cells, and their composition and organization within tissues. The cnidome included microbasic b‐mastigophores, microbasic and mesobasic p‐mastigophores, holotrichous isorhizas and spirocysts. The nematocyst type cnidae (b‐, p‐mastigophores, isorhizas) appeared in different size classes with different distributions within the tissue. Spirocysts were highly variable in shape and size, without distinct size classes. In addition, developing stages of cnidae were documented, with new observations on the succession of p‐mastigophore shaft development. The present observations were in general congruent with the cnidocyst descriptions from L. prolifera made by Carlgren; however, a tiny cnida, possibly of isorhiza type, has been added. Finally, the use of the term acontia is discussed.

The cnidome and ultrastructural morphology of late planulae in Lophelia pertusa (Linnaeus, 1758)—With implications for settling competency

“…Everted b-mastigophores and p-mastigophores are usually distinguished from each other by the shorter spines on the everted shafts, and a shaft diameter barely wider than the tubule in the b-mastigophores. This is in contrast to the prominent spines of the p-mastigophore shaft that also have a more conspicuous change of diameter between shaft and tubule (Strömberg & Östman, 2016). In adult polyps, these nematocysts have a role in prey capture, toxin delivery and defence, while the function in planulae needs further investigation.…”

“…The cnida composition of L. pertusa larvae is different from the cnidome of the adult polyps. Neither of the two (or three) types of isorhizas present in planulae are present in adult polyps (Strömberg & Östman, ). The adult polyp has one type of holotrichous isorhiza in two size classes, a broad, oval in the tentacles, and a longer in the acontia.…”

“…The discharged cnidocysts observed included atrichous isorhizas, a cnida type not present in adult polyps (Strömberg & Östman, ), indicating a unique function for this cnida type in the planulae. The actinula larva of the hydrozoan Tubularia mesembryanthemum (now accepted as Ectopleura crocea ) has been shown to use atrichous isorhizas for primary anchoring during settling (Yamashita, Kawaii, Nakai, & Fusetani, ).…”

Recognition of Cold-Water Corals in Synthetic Aperture Sonar Imagery

“…An important question that so far hasn't been answered, is the applicability of this method and sonar imagery to determine the state of corals in the instance where they are dead or dying, but still intact in shape. Only approximately the outermost meter of corallites contains live polyps, while older polyps beneath die due to reduced water exchange and food supply [39], [40]. We can thus divide a reef into three habitats; coral rubble zone with small pieces of skeleton, followed by the coral block zone dominated by large blocks of coral skeleton, and finally the live coral reef on top where the current provides food [41].…”

Gonadal cnidocytes in the cubozoan Tripedalia cystophora Conant, 1897 (Cnidaria: Cubozoa)

“…This is supported by the finding that the cnidocytes transferred along with the sperm are of the isorhiza type (Garm et al, ). They have no stylet but have numerous barbs and are typically used for attachment to objects (Strömberg & Östman, ; Yamashita, Kawaii, Nakai, & Fusetani, ).…”