Tentacle cnidae of the sea anemone <i>Metridium senile</i> (Linnaeus, 1761) (Cnidaria: Anthozoa)

Abstract

SUMMARY: Tentacle cnidae of Metridium senile (Linnaeus, 1761) were examined by light microscopy. In addition to spirocysts, feeding-tentacles had 3 nematocyst categories grouped into medium and small size-classes, including 5 types. Spirocysts dominated, especially distally, followed by medium b-mastigophores. The density of cnidae decreased towards the tentacle base. Early cnidoblasts were numerous on the tentacle tip. Late cnidoblasts appeared in a moderate number on the mid-tentacle. Catch-tentacles, found in two Metridium specimens, had a maturity gradient of isorhizas and gland cells along their length. Their tip had two distinct types of mature isorhizas in great numbers and large gland cells, but lacked spirocysts. Mature isorhizas and gland cells decreased in number towards the tentacle base. On the mid-tentacle differentiating ages of isorhizas were numerous. Ordinary feeding-tentacle cnidae, abundant at the tentacle base, decreased in number distally along the tentacle.Keywords: sea anemone, nematocysts, cnidae, catch-tentacles. RESUMEN: Cnidoma de los tentáculos de la anémona de mar MetridiuM senile (Linnaeus, 1761) (Cnidaria: Anthozoa). -El cnidoma de los tentáculos de Metridium senile (Linnaeus, 1761) se examinó mediante microscopio óptico. Además de espirocistos, los tentáculos tenían 3 categorías de nematocistos agrupados en clases de talla medianas y pequeñas, incluyendo 5 tipos. Los espirocistos fueron dominantes, en particular distalmente, seguidos por b-mastigióforos medios. La densidad de cnidoma decreció hacia la base del tentáculo. En la punta del tentáculo fueron abundantes los cnidoblastos jóvenes. Los cnidoblastos avanzados aparecieron en número moderado a mitad del tentáculo. Los tentáculos hallados en dos especímenes de Metridium presentaron un gradiente de madurez de isorhizas y células glandulares a lo largo de su longitud. La punta tenía dos tipos distintos de isorhizas maduras en gran número y grandes células glandulares, pero les faltaban espirocistos. Las isorhizas maduras y las células glandulares disminuyeron en número hacia la base del tentáculo. A mitad del tentáculo, se observaron numerosas isorhizas de diferentes edades. Los cnidocistos de los tentáculos, abundantes en la base del tentáculo, disminuyeron en número distalmente a lo largo del tentáculo.Palabras clave: anémona de mar, nematocistos, cnidoma, tentáculos.

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

“…A), as previously noted in the sea anemones Metridium senile and Sagartiogeton viduatus (Östman et al . ,b, ).…”

“…The classification system and nomenclature of cnidocysts, including nematocysts and spirocysts, established by Weill () with modifications made by Carlgren (), Cutress (), Mariscal (), Östman () and Östman et al . () were used.…”

“…Documentation of the morphology of developing cnidae (cnidoblasts) in different stages of maturation has been carried out for the anthozoans Metridium senile and Sagartiogeton viduatus by Östman et al . (,b, ). Möbius () suggested that cnidoblasts differentiate beneath the mature cnidocytes (commented in Robson ).…”

Sea Anemones through X-Rays: Visualization of Two Species ofDiadumene(Cnidaria, Actiniaria) Using Micro-CT

“…Absence of visibly differentiated fighting tentacles in most specimens of D. manezinha and all specimens of D. leucolena is not exceptional within Diadumenidae, as these structures have never been observed in some species (e.g., D. fransciscana and D. lighti) and when present may appear in frequencies as low as 1.7% in some populations (e.g., populations of D. lineata in England: Williams, 1975). Likewise, fighting tentacles are ephemeral during an individual's lifespan, being induced by territorial threats from non-clonemates (Williams, 1975;Purcell, 1977;Watson and Mariscal, 1983a;Östman et al, 2010a) and restricted to individuals along the border of an aggregation facing other aggregates (Purcell, 1977;Purcell and Kitting, 1982). The reversal from fighting tentacles is also possible, being correlated with isolation of individuals to areas with non-clonemates or an animal's nutritional state (Williams, 1975;.…”

Cnidae in the sea anemone Sagartiogeton viduatus (Muller, 1776) (Cnidaria, Anthozoa); A comparison to cnidae in the sea anemone Metridium senile (Linnaeus, 1761) (Cnidaria, Anthozoa)

“…The present work, as well as our previous cnidae studies of Metridium senile (Östman et al . , b, c), is crucial for our ongoing investigations on nematocyst incorporations in the nudibranchs A. glauca and Aolidia papillosa (Linnaeus, 1761) (C. Östman, F. Gustavsson, A. Karlsson, C. Roat, in preparation). To gain an insight, if these nudibranchs have a preference for storing‐specific cnidae (see Conklin and Mariscal ; Day and Harris ; Frick , ) and if immature nematocysts are incorporated into their cnidosacs (see Greenwood and Mariscal ; Martin and Walther ), we first performed a similar detailed study of the cnidocysts of S. viduatus as we did with M. senile (Östman et al .…”