Abstract Some octocorals (Cnidaria, Anthozoa) can produce a sub-millimeter to a millimeter-range skeleton of calcium carbonate, known as sclerites. Sclerites have diverse morphological characters, such as size, and shape features that give them relevance as taxonomic characters at different levels. Renilla Lamarck, 1816, is a genus of the order Pennatulacea (Octocorallia), in which colonies are characterized by two distinct zones: a peduncle, which anchors them to the substrate, and a rachis that supports the polyps. In the case of Renilla muelleri Kölliker, 1872, prior research established the presence of similar sclerites in both the peduncle and the rachis. Nevertheless, the potential morphological variations of these sclerites among colonies and within different colony regions have yet to be assessed to determine the stability of these characteristics at the species level. This study aimed to describe and compare the external microscopic morphology and biometry of the sclerites of Renilla muelleri, enhancing their identification and assessing their consistency within the species. Sclerite composition was examined across the entire colony, and we analyzed length variation among colonies using generalized linear models (GLM) and within colony zones using generalized linear mixed models (GLMM). Additionally, the external microscopic morphology of all sclerites was examined through scanning electron microscopy (SEM). Based on size, two types of sclerites, namely large and small, were identified within the colonies. Both types exhibited significant size differences among colonies. Furthermore, the large sclerites displayed notable variations between zones, with those in the rachis being the largest and holding the highest rank within the colonies. In terms of external microscopic morphology, the sclerites exhibited considerable variability, making it challenging to establish clear groupings based on these characteristics. Based on the obtained results, it can be concluded that both the biometry and external microscopic morphology of sclerites do not exhibit consistency as characteristics in Renilla muelleri highlighting the ambiguity in defining Renilla species. Cnidaria, Cnidaria (Cnidaria Anthozoa submillimeter sub millimeter millimeterrange range carbonate levels Lamarck 1816 Octocorallia, Octocorallia , (Octocorallia) substrate polyps Kölliker 1872 Nevertheless level GLM (GLM GLMM. GLMM . (GLMM) Additionally SEM. SEM (SEM) small Furthermore variability results 181 (Octocorallia 187 (GLMM (SEM 18 1

Resumen Introducción: La diversidad de anémonas de mar en el Parque Nacional Isla del Coco, Costa Rica, está aún poco estudiada. Objetivo: Reportar por primera vez la presencia de la anémona de mar Exaiptasia diaphana. Métodos: Algunos rodolitos fueron examinados in situ en Punta Ulloa a 14 m. de profundidad mediante SCUBA durante la expedición UCR-UNA-COCO-I al Parque Nacional Isla del Coco el 24 de abril de 2010. Especímenes vivos fijados sobre rodolitos fueron fotografiados y sus medidas y carácterísticas morfológicas externas fueron registradas in situ. Resultados: Varios individuos de E. diaphana fueron observados sobre rodolitos y observamos repetidamente pequeños individuos rodeando a un individuo mayor (presumiblemente la anémona fundadora) sobre rodolitos de Punta Ulloa. Conclusiones: La distribución geográfica de esta especie es extendida, como así también su distribución batimétrica desde el intermareal hasta los 14 m de profundidad. Las imágenes obtenidas aportan evidencia de reproducción clonal por laceración pedal.

Abstract Introduction: The sea anemones diversity is still poorly studied in Isla del Coco National Park, Costa Rica. Objective: To report for the first time the presence of the sea anemone Exaiptasia diaphana. Methods: Some rhodoliths were examined in situ in Punta Ulloa at 14 m depth, by SCUBA during the expedition UCR-UNA-COCO-I to Isla del Coco National Park on 24th April 2010. Living anemones settled on rhodoliths were photographed and its external morphological features and measures were recorded in situ. Results: Several individuals of E. diaphana were observed on rodoliths and we repeatedly observed several small individuals of this sea anemone surrounding the largest individual in an area (presumably the founder sea anemone) on rhodoliths from Punta Ulloa. Conclusions: The geographic distribution is extended as well as their bathymetric distribution from the intertidal to 14 m depth. The photographs provide evidence of clonal reproduction by pedal laceration.

The cnidae are the exclusive diagnostic structures of phylum Cnidaria. The inventory of all cnidae types of a particular species is called the cnidom. The study of cnidae has been widely addressed in all classes of cnidarians. Particularly in the order Actiniaria (sea anemones), the study of the composition, size and distribution of cnidae is essential to the identification and description of species. In the present study, we examine the cnidom of the sea anemone Aulactinia marplatensis in three different stages of development throughout its life cycle. We found that the composition and abundance patterns are very similar between the adult and juvenile stages, although significant differences in the size capsules were found between both stages and in all cnidae types observed, being bigger those from the adult forms. The planula larvae stage presents a less diverse cnidom in comparison to the juvenile and adult stages; however, it presents an exclusive cnidae type (the mesobasic p-mastigophore) which is the biggest in size of all the cnidae types observed in the species. These results highlight the importance of considering the stage of development when cnidae is used as a diagnostic character, and the particular relevance of the study of the cnidom in larval stages.

Resumen La anémona Condylactis gigantea es un miembro ecológicamente importante de la comunidad bentónica en arrecifes de coral del Atlántico tropical, y exhibe dos morfotipos con respecto al color de las puntas de sus tentáculos: el morfotipo de puntas verdes y el morfotipo de puntas rosadas/púrpuras. Aunque se han encontrado algunas diferencias moleculares y ecológicas entre estos morfotipos, no se han reportado otras distinciones morfológicas, y actualmente ambos siguen siendo considerados una sola especie taxonómica. En el presente estudio, realizamos una exploración sobre la variabilidad en el tamaño de los cnidocistos entre estos dos morfotipos y realizamos un análisis estadístico de 10 categorías de cnidocistos a partir de especímenes albergados en la Colección de cnidarios del Golfo de México y Caribe Mexicano, de la Universidad Nacional Autónoma de México, los cuales fueron previamente recolectados en varias localidades arrecifales de la Península de Yucatán. Los resultados no revelan variación significativa en el tamaño de los cnidocistos entre los dos morfotipos, aunque fueron encontradas variaciones significativas dentro de cada morfotipo. Adicionalmente, actualizamos la composición del cnidoma de C. gigantea, y discutimos sobre la utilidad de la talla de los cnidocistos para distinguir entre morfotipos o entre especies estrechamente relacionadas.

Abstract The sea anemone Condylactis gigantea is an ecologically important member of the benthic community in coral reefs of the tropical Atlantic, and displays two morphotypes with respect to the color in their tentacular tips: the green tip morphotype and the pink/purple tip morphotype. Although some molecular and ecological differences have been found between these morphotypes, no other morphological distinctions have been reported, and currently both are still considered a single taxonomic species. In the present study, we perform an exploration on the variability in the size of cnidae between these two morphotypes and performed statistical analyses to compare the 10 categories of cnidae from specimens hosted in the Cnidarian Collection of Gulf of Mexico and Mexican Caribbean, of the Universidad Nacional Autónoma de México, which were previously collected in several coral reefs localities of the Yucatán Peninsula. Results reveal no significant variation in cnidae size between the two morphotypes, but significant variations were found within each morphotype. In addition, we update the composition of the cnidom of C. gigantea, and the utility of the size of cnidae to distinguish between morphotypes or closely related species is discussed. Rev. Biol. Trop. 66(3): 1055-1064. Epub 2018 September 01.

Bunodactis Verril, 1899 comprises at present 19 nominal species of sea anemones. The validity of the genus is under discussion. The description of the species, Bunodactis octoradiata Carlgren, 1899, is insufficient for reliable identification, and although subsequent works have provided additional information on the species, its description still needs to be complemented. Herein we describe B. octoradiata based on histological sections of the internal anatomy, and give a complete and detailed description of the external anatomy. The cnidom is composed of spirocysts, basitrichs and microbasic p-mastigophores; their distribution in the organism, sizes and relative abundances are provided. The presence of zooxanthellae is reported for the first time. Bunodactis octoradiata is distributed in groups that vary from 5.6 to 45 ind./m² in the field. Additionally, our data extends the distribution of the species along the coast of southern Patagonia (47°44'36"-49°15'13"S and 65°50'26"-67°39'45"W).

Despite being important components in coastal marine systems, sea anemones have been poorly studied on both coasts of Costa Rica. In this paper new records of sea anemones are mentioned for the Caribbean and Pacific coasts of Costa Rica and the Isla del Coco National Park. Additionally, the presence of other species previously recorded in Costa Rica based on single observations or photos, is reconfirmed. An updated inventory of these cnidarians is provided, and with the corallimorpharians, comprises of 16 species (10 in the Caribbean and 6 in the Pacific and Coco Island). A comparison with the sea anemone fauna of Panama is added.

A pesar de ser componentes importantes en los sistemas marino-costeros, las anémonas de mar han sido poco estudiadas en las costas de Costa Rica. En el presente trabajo se dan a conocer registros nuevos de anémonas de mar para las costas del Caribe y Pacífico de Costa Rica, incluyendo el Parque Nacional Isla del Coco. Se han confirmado también la presencia de otras especies que habían sido registradas para Costa Rica, pero sólo en base a observaciones visuales o fotografías. Se actualiza el inventario de este grupo de cnidarios que, junto a los corallimorpharios, está constituido por 16 especies (10 en el Caribe y 6 en el Pacífico e Isla del Coco). Asimismo, se realiza una comparación entre las faunas de anémonas de mar de Costa Rica y Panamá.

La fauna de anémonas de mar es prácticamente desconocida para el Parque Nacional Isla del Coco (Costa Rica). En el presente trabajo se reporta por primera vez la presencia de la especie Telmatactis panamensis. Individuos de esta anémona de mar fueron colectados en el intermareal de Bahía Chatham y a 15m de profundidad en Punta Ulloa, en ambos casos adheridas a rocas; durante la expedición UCR-UNA-COCO-I en Abril de 2010. Se proveen fotografías de ejemplares vivos, datos de su anatomía externa y un inventario del cnidae de los especímenes estudiados. Posiblemente esta especie se extienda a mayor profundidad, tal como fue observado por otros autores para ejemplares de las Islas Galápagos.

The sea anemone fauna of Isla del Coco National Park (also known as Cocos Island Nacional Park), Pacific Costa Rica is poorly known. In the present work we report the first occurrence of the species Telmatactis panamensis. Individuals of this sea anemone (n=24) were collected at Chatham Bay intertidal and at 15m depth in Punta Ulloa, in both cases attached to rocks; during the expedition UCR-UNA-COCO-I in April 2010. We provide photographs of live individuals, external anatomy and an inventory of cnidae of the studied specimens. Possibly this species is extended to greater depth as observed by other authors in the Galápagos Islands.

A partir de la literatura existente se realizó una lista actualizada y revisada de las anémonas de mar de ambas costas de Panamá, que incluyó 26 especies válidas (22 pertenecientes al orden Actiniaria, tres al orden Corallimorpharia y una especie de ubicación sistemática incierta). La especie Calliactis polypus es un registro nuevo para esta región. Siete de las especies se conocen solamente en Panamá. La riqueza de especies es predominante en el Golfo de Panamá, debido probablemente a un esfuerzo de muestreo mayor y desproporcionado en relación a otras zonas. El hecho que los registros existentes estén fuertemente sesgados hacia un centro de intenso muestreo, indica la necesidad de muestreos adicionales en otras áreas. Estudios posteriores deberán estar orientados no sólo a la búsqueda de nuevos taxa, sino también a la verificación de las descripciones y el status taxonómico de las especies registradas.