Neue integrative Ansätze für das Sammeln, Bearbeiten und Beschreiben skelettloser Hexacorallia am Beispiel chilenischer Seeanemonen

Actiniaria, Corallimorpharia, Zoanthidae and Ceriantharia belong to the most neglected marine taxa. Habitats that were difficult to access in the past, complicated and doubtful methods for identification, the lack of summarizing literature and the lack of specialists led soft-bodied hexacorals into a dramatic and increasing under-representation in both biodiversity assessments and in ecological studies. The taxonomic state of knowledge for this group is far behind this of other taxa of comparable importance. This global description of the situation is especially valid for the South East Pacific. Therefore important aspects of systematic work with soft-bodied hexacorals have been addressed in the presented dissertation and exemplified by Chilean sea anemones. The results have been presented in specialist journals and at relevant meetings. To fill existing gaps and to alleviate difficulties, traditional procedures have been combined with modern methods. The applied techniques were tested for their expenditure/benefit ratio. On this base a novel, efficient approach for systematic studies of soft-bodied hexacorals was elaborated. With this approach one of the most common shallow-water sea anemones of north and central Chile, which spread out remarkably during the last decades, was described as Anemonia alicemartinae. The two most common shallow-water sea anemone species of the south east Pacific, Phymactis papillosa and Phymanthea pluvia, were re-described and fundamentally revised. The four south-hemispheric genera Isoulactis, Isocradactis, Saccactis and Oulactis, which exhibit extraordinary morphology, were revised and put together in the genus Oulactis. The deep-water genus Actinostola was revised and the species Actinostola chilensis was re-described. Traditionally used characteristics to distinguish species of the genus Actinostola were critically tested and new, alternative features were proposed. The discovery of a colonial sea anemone disproved the common idea of Actiniaria as a purely solitary group. The phenomenon of coloniality in sea anemones was described in detail and phylogenetic consequences were discussed. Some biomechanical and evolutionary-ecological hypotheses, which were used to explain the absence of colonial sea anemones, were questioned by this discovery. The reproductive strategies of the addressed Chilean sea anemone species were summarized and appearance, habitat, bathymetric distribution and reproductive mode were compared. Existing hypotheses about links between these parameters were tested and discussed. A hypothesis on spreading tendencies of some Chilean sea anemone species was elaborated. The effects on populations of other invertebrates, especially on those of economic importance, were discussed on the basis of some examples. The distribution of Chilean species and their relation to the South West Atlantic and the Antarctic fauna was analysed and the discovered zoogeographic patterns were discussed. The problems with identification and taxonomy of soft-bodied hexacorals were summarized, analysed and discussed. A working protocol was proposed as a new standard. An illustrated identification guide, which includes all known species, was made for the better known Mediterranean soft-bodied hexacorals. The crisis in systematics of soft-bodied hexacorals may be overcome by consequent ap-plication of modern methods and the close cooperation of taxonomists, ecologists and mo-lecular biologists. New funding programs and a growing interest within the younger genera-tion give cause for the hope that soft-bodied hexacorals might receive the attention merited by their ecological importance in marine benthic communities.Actiniaria, Corallimorpharia, Zoanthidae und Ceriantharia gehören zu den am stärksten vernachlässigten marinen Taxa überhaupt. Lebensräume, die in der Vergangenheit schwer zugänglich waren, schwierige und umstrittene Bestimmungsmethoden, das Fehlen von zusammenfassender Literatur und der Mangel an Spezialisten führten zu einer zunehmend dramatischen Unterrepräsentanz von skelettlosen Hexacorallia in Biodiversitätsstudien und ökologischen Arbeiten. Der taxonomische Bearbeitungszustand liegt weit hinter dem anderer, vergleichbar bedeutender Taxa zurück. Diese weltweit gültige Situationsbeschreibung trifft in verschärftem Maße für den Südostpazifik zu. Im Rahmen der vorliegenden Dissertationsarbeit wurden deshalb wichtige Themenkomplexe der Systematik skelettloser Hexacorallia aufgegriffen und am Beispiel chilenischer Seeanemonen bearbeitet. Die Ergebnisse wurden in einschlägigen Zeitschriften und auf Fachkongressen vorgestellt. Um bestehende Lücken zu schließen und Schwierigkeiten zu entschärfen, wurden herkömmliche Vorgehensweisen mit modernen Methoden kombiniert. Die angewandten Techniken wurden auf ihr Aufwand/Nutzen-Verhältnis überprüft. Auf dieser Basis wurde ein innovativer, effizienter Ansatz für systematische Studien skelettloser Hexacorallia erarbeitet. Unter Anwendung dieses Ansatzes wurde eine der häufigsten Flachwasserseeanemonen Nord- und Zentralchiles, die sich in den letzten Jahrzehnten stark ausgebreitet hat, als Anemonia alicemartinae erstbeschrieben. Die zwei häufigsten Flachwasseraktinien des Südostpazifiks, Phymactis papillosa und Phymanthea pluvia, wurden wiederbeschrieben und grundlegend revidiert. Die vier südhemisphärischen Gattungen Isoulactis, Isocradactis, Saccactis und Oulactis mit außergewöhnlicher Morphologie wurden revidiert und in der Gattung Oulactis zusammen-gefasst. Die Tiefwassergattung Actinostola wurde revidiert und die Art Actinostola chilensis wiederbeschrieben. Dabei wurden traditionell verwendete taxonomische Unterscheidungs-merkmale für Arten der Gattung Actinostola kritisch überprüft und neue, alternative Merkmale vorgeschlagen. Mit der Entdeckung einer kolonialen Seeanemone wurde die allgemein bestehende Vorstellung der Actiniaria als rein solitäre Gruppe widerlegt. Das Phänomen der Koloniebildung bei Seeanemonen wurde detailliert beschrieben und phylogenetische Konsequenzen diskutiert. Einige biomechanische und evolutionsökologische Hypothesen, die das Fehlen von Seeanemonenkolonien erklären sollten, wurden damit in Frage gestellt. Die Fortpflanzungsstrategien der gefundenen chilenischen Seeanemonen wurden zusammengefasst und Habitus, Habitat, Tiefenverteilung und Fortpflanzungsmodus verglichen. Bestehende Hypothesen über mögliche Zusammenhänge wurden anhand der Ergebnisse diskutiert. Eine Hypothese über Ausbreitungstendenzen einiger chilenischer Seeanemonenarten wurde erarbeitet. Mögliche Auswirkungen auf Populationen anderer, z.T. wirtschaftlich wichtiger Invertebraten, wurde anhand einiger Beispiele überprüft und diskutiert. Die Verbreitungen der chilenischen Arten und ihre Beziehungen zur südwestatlantischen und antarktischen Fauna wurden analysiert und die gefundenen zoogeographischen Muster diskutiert. Die Problematik der Identifikation und Taxonomie von skelettlosen Hexacorallia wurde zusammengefasst, analysiert, diskutiert und ein Arbeits-protokoll als neuer Standard vorgeschlagen. Für die besser bearbeiteten, mediterranen skelettlosen Hexacorallia wurde ein alle bekannten Arten umfassender, bebilderter Bestimmungsführer erstellt. Durch die konsequente Anwendung moderner Methoden und die enge Zusammenarbeit von Taxonomen, Ökologen und Molekularbiologen kann die Krise in der Systematik skelettloser Hexacorallia überwunden werden. Neue Förderprogramme und wachsendes Interesse in der jüngeren Generation geben Anlass zur Hoffnung, dass die skelettlosen Hexacorallia in Zukunft die Aufmerksamkeit erfahren, die ihrer ökologischen Rolle in marinen Benthosgesellschaften angemessen ist

A SAMPLING STRATEGY FOR RECENT AND FOSSIL BRACHIOPODS: SELECTING THE OPTIMAL SHELL SEGMENT FOR GEOCHEMICAL ANALYSES

Recent and fossil brachiopod shells have a long record as biomineral archives for (palaeo)climatic and (palaeo)environmental reconstructions, as they lack or exhibit limited vital effects in their calcite shell and generally are quite resistant to diagenetic alteration. Despite this, only few studies address the issue of identifying the best or optimal part of the shell for geochemical analyses. We investigated the link between ontogeny and geochemical signatures recorded in different parts of the shell. To reach this aim, we analysed the elemental (Ca, Mg, Sr, Na) and stable isotope (δ18O, δ13C) compositions of five recent brachiopod species (Magellania venosa, Liothyrella uva, Aerothyris kerguelensis, Liothyrella neozelanica and Gyphus vitreus), spanning broad geographical and environmental ranges (Chile, Antarctica, Indian Ocean, New Zealand and Italy) and having different shell layer successions (two-layer and three-layer shells). We observed similar patterns in the ventral and dorsal valves of these two groups, but different ontogenetic trends by the two- and three-layer shells in their trace element and stable isotope records. Our investigation led us to conclude that the optimal region to sample for geochemical and isotope analyses is the middle part of the mid-section of the shell, avoiding the primary layer, posterior and anterior parts as well as the outermost part of the secondary layer in recent brachiopods. Also, the outermost and innermost rims of shells should be avoided due to diagenetic impacts on fossil brachiopods

All you can eat: the functional response of the cold-water coral Desmophyllum dianthus feeding on krill and copepods

The feeding behavior of the cosmopolitan cold-water coral (CWC) Desmophyllum dianthus (Cnidaria: Scleractinia) is still poorly known. Its usual deep distribution restricts direct observations, and manipulative experiments are so far limited to prey that do not occur in CWC natural habitat. During a series of replicated incubations, we assessed the functional response of this coral feeding on a medium-sized copepod (Calanoides patagoniensis) and a large euphausiid (Euphausia vallentini). Corals showed a Type I functional response, where feeding rate increased linearly with prey abundance, as predicted for a tentaculate passive suspension feeder. No significant differences in feeding were found between prey items, and corals were able to attain a maximum feeding rate of 10.99 mg C h−1, which represents an ingestion of the 11.4% of the coral carbon biomass per hour. These findings suggest that D. dianthus is a generalist zooplankton predator capable of exploiting dense aggregations of zooplankton over a wide prey size-range

Estudios en un fiordo chileno con un fuerte gradiente de pH – regulación del pH interno por el coral de aguas frias Desmophyllum dianthus

El fiordo Comau en la Patagonia chilena norte se caracteriza por presentar un marcado gradiente de pH, de 7.4 a 8.1. Bajo estas condiciones, las cuales corresponden al pH pronosticado para los océanos en el año 2100, están prosperando bancos de mitílidos, bancos de braquiópodos, acumulaciones de picorocos, praderas de gorgonias y bancos de corales de aguas frías. Estos “bosques” de animales marinos forman la base estructural y funcional de un ecosistema bentónico marino muy diverso. La comunidad que domina principalmente en paredes rocosas desde los 80 m son los bancos de corales, con la especie matriz Desmophyllum dianthus. Interesantemente, D. dianthus crece en aguas de alto (sobresaturadas de aragonita) y bajo pH (insaturadas de aragonita), así como en aguas someras y profundas (desde aprox. 15 m hasta más de 400 m). Esto indica que el coral es capaz de regular y controlar su calcificación. Se incubó D. dianthus simulando futuros escenarios de acidificación oceánica y en dichas incubaciones se midió la composición isotópica del boro en su esqueleto (11B). D. dianthus presentó incrementos del pH interno de calcificación (pHcf) como respuesta reguladora frente a pH externos (pHsw) más bajos. Todavía falta una explicación fisiológica del pHcf en corales bajo diferentes pHsw. Utilizando microsensores para pH, calcio y oxígeno medimos el pHcf en D. dianthus en relación a la dinámica del calcio y la respiración a lo largo del pólipo del coral bajo diferentes pHsw. Encontramos que el pHcf y el pHsw están relacionados, pero no de forma directa debido a la gran heterogeneidad del pHcf. Esto sugiere una regulación del pHcf altamente compleja e inconsistente con los modelos anteriores, indicando que D. dianthus incrementa probablemente el pool interno de carbono y no el pH para facilitar la calcificación

Growth rates and skeletal density of Desmophyllum dianthus - Effect of association with endolithic algae

It has been suggested that endolithic algae inside the skeleton of cold-water corals might have a symbiotic relationship with the coral host and would positively affect coral calcification. However, so far this hypothesis has not yet been further explored. This study investigated the effect of endolithic algae on the growth performance and skeletal density of the cold-water coral Desmophyllum dianthus at Fjord Comau, southern Chile. The fluorescent staining agent calcein was used to document coral growth by measuring the upward linear extension of septa for a period of one and a half years. Observations on skeletal density were recorded using x-ray computed tomography. The results of this study show a severe reduction of growth rates associated with the presence of endolithic algae. Infested individuals grew about half as fast as non-infested polyps with median value of 1.18μm/day compared to 2.76μm/day. Data on skeletal density revealed a similar – although not statistically significant – trend displaying mean values of 2.160g/cm³ compared to 2.294g/cm³, respectively. These results point towards a parasitic relationship between D. dianthus and its endolithic algae refuting the hypothesis of a mutually beneficial association. However, although this study appears to conclusively indicate a negative effect of the association of D. dianthus with endolithic algae, controversial evidence has been discovered regarding the mode of the relationship. Despite the decrease in growth performance, the coral host seems to benefit from a low transfer of metabolites from the endoliths to the coral tissue. Further research will be necessary to fully resolve the matter

Paraisanthus fabiani Häussermann & Försterra, 2008, new species

Paraisanthus fabiani new species External anatomy (Fig. 2). Size in vivo, measured in aquaria: oral disc 7–12 mm diameter, column to 10 mm diameter, pedal disc to 19 mm diameter, 13–20 mm long, tentacles about half as long as diameter of oral disc. Size preserved: oral disc to 8 mm diameter, pedal disc to 19 mm diameter, column to 16 mm long, tentacles to 5 mm long. Colour (Figs. 3 A–G). Oral disc red, orange, yellowish, pale rose, pink, light brown or ochre; uniformly coloured or with (often 12) reddish-brown radial lines visible on endocoels, or with 12 -lobed, petal-like white and yellow pattern (Fig. 2 B). Mesenterial insertions visible through oral disc. Actinopharynx yellow to light brown. Tentacles slightly transparent, rose to red or pink, yellowish, light brown or ochre; uniformly coloured (Figs. 2 D–G) or with 3–6 brown transverse bands at inner and outer or only inner side (Figs. 2 A–C). Column rose-coloured, reddish, yellowish, orange to ochre, or light brown; uniformly coloured or distalmost 1 / 4 – 1 / 5 more intensely coloured (often brown; Fig. 2 D) with a short transition to paler proximal portion of column; colour generally continuously fading towards pedal disc. Pedal disc coloured as column, not transparent. Preserved specimens whitish to brown. Oral disc and tentacles. Between 66 and 110 conical tentacles, hexamerously arranged in 5–6 cycles, last cycle generally not complete, length about half diameter of oral disc, inner longer than outer, situated on outer third to half of oral disc, innermost 12 (two cycles) in many animals slightly more central (Fig. 2 A), more intensely coloured and directed upward. Oral disc circular, mesenterial insertions in many specimens visible as darker lines (Figs. 2 A,C,D,E). Mouth opening central, slightly oval, slightly elevated in many specimens. Column. In situ higher than broad, after sampling broader than high, proximally broader than distally; smooth, often with loose ring of mucus and dirt in proximal part (Figs. 2 C,D,G). Small fosse. Column can completely cover tentacles when retracted. Pedal disc. More or less circular, generally wider than column and oral disc, limbus slightly lobed. Internal anatomy. In most parts of column, 24 mesenteries hexamerously arranged in four cycles, first cycle (six pairs) including directives fertile macrocnemes with strong circumscript retractors, second and third cycle (six plus 12 pairs) sterile microcnemes without retractors, fourth cycle incomplete, pairs of extremely small microcnemes only just below margin, unequal proximal extension of mesenteries of a pair. Mesenteries of second cycle wider than those of third cycle. More tentacles than mesenteries in mid-column and at base. Actinopharynx deeply furrowed, with two distinct siphonoglyphs, about half length of column; two pairs of FIGURE 3. Histological sections of Paraisanthus fabiani: A, macrocneme with retractor and parietobasilar muscle; B, transverse section of the upper column; C, transverse section of the lower column; D, longitudinal section of the upper column with sphincter; E, cross section through tentacle; F, longitudinal section of the pedal disc with basilar muscles. 1 st to 3 rd cycle of mesenteries I, II, III, basilar muscles bm, directives d, ectoderm ec, endoderm en, ectodermal longitudinal muscles of tentacle et, mesogloea m, macrocnemes ma, filaments mf, microcnemes mi, parietobasilar muscles pb, actinopharynx ph, retractor muscles r, sperms s, siphonoglyph si, sphincter sp. TABLE 2. Size and distribution of cnidae of Paraisanthus fabiani n. sp. (ZSM 20070247 / 1, letters refer to Fig. 4), in each tissue in order of abundance: s: sporadic, f: few, c: common and v: very common. “m l“ and “m w” are the means, “d l” and “d w” are the standard deviations (all in µm), “t” is the apparent total number of turns of spine-rows on the shaft, “#” is the number of capsules measured, “p” is the proportion of specimens having this cnida type. Exceptional sizes in parentheses. Spirocysts (A,M), basitrichs (B,C,D,F,H,J,L,O), microbasic p-mastigophores (E,N,P), microbasic pmastigophores B 1 (G,I,K). directives. Oral and marginal stomata; marginal stomata circular, in the centre of stronger mesenteries (stomata not always visible in smaller specimens). Sexes separate, no signs of asexual reproduction. Five of the sectioned specimens with reproductive tissue, collected in February and March, four male (ZSM 20070246, ZSM 20070247 / 1, ZSM 20070249, USNM 1101612), one female (ZSM 20051690). No zooxanthellae. Sphincter mesogloeal, strong, nearly entire width of mesogloea (Fig. 3 D), restricted to uppermost part (~ 1 / 8 – 1 / 10) of column. Macrocneme retractors strong, strongly restricted to circumscribed (Figs. 3 A–C). Parietobasilar muscles distinct on perfect mesenteries (Figs. 3 A–C); basilar muscles distinct (Fig. 3 F). Longitudinal muscles of tentacles (Fig. 3 E) and radial muscles of oral disc ectodermal. Endodermal circular muscles of column well marked, weaker at sphincter level (Fig. 3 D). Cnidom. Spirocysts, basitrichs, microbasic p-mastigophores B (Fig. 4). Cnidae of eight specimens were examined. Etymology. The species is dedicated to our son Fabian who was born on May 16 th 2007 some days after the submission of this paper. Habitat, distribution, and zoogeography. Shallow subtidal to at least 30 m in less protected channels and at exposed islands of Chilean fjord region between Faro Corona, Chiloé Island (41 ° 47 ’02.0’’S; 73 ° 52 ’ 58.8 ’’W) and Archipelago Madre de Dios (50 ° 20 ’ 23.1 "S; 75 ° 22 ’ 39.2 "W) (Fig. 1). Not present along exposed coast north of fjord region between Faro Corona, North Chiloé Island, and Arica, North Chile (41 ° 47 ’S to about 15 °S), or in southern third of fjord region between Archipelago Madre de Dios and Straits of Magellan (50 ° 20 ’S to about 53 °S) (Fig. 1); neither present in protected fjords and channels with superficial fresh water layer. Thus, it is present in both the Northern and the Central Patagonian Zone (see Pickard 1971; Häussermann 2006), which are separated by Peninsula Taitao and Golfo de Penas (Fig. 1), hypothesized by Lancellotti and Vasquez (2000) and Häussermann and Försterra (2005) to be zoogeographic barriers, but not in the Southern Patagonian Zone south of the Straits of Magellan. Natural history and field notes. Not abundant at any site, but if present, generally several clustered specimens found (Fig. 5). Pedal disc and column generally hidden in holes or crevices of rocky substrate, between stones or between polychaete tubes into which entire animal retracts when disturbed (Fig. 5). Tentacles of neighbouring specimens regularly in contact with each other. Specimens observed in same habitat with the sea anemones Halcurias pilatus McMurrich, 1893, Phellia exlex McMurrich, 1904, Sagartiidae sp. (Fig. 5 C), and a corallimorpharian (Corynactis sp.); in Central Patagonian Zone also with the sea anemone Metridium senile lobatum Carlgren, 1899 (Riemann-Zürneck 1975). Difficult to collect without injury due to cryptic microhabitats; ideally collected with hammer and chisel together with substrate. Specimens relatively sensitive; reattach only slowly to hard substrate in aquarium even if not injured. In the aquarium, specimens soon hide column between or under stones or in holes in substrate (such as dead barnacles). Addition of MgCl 2 to aquarium water (for relaxation) provoked spawning in one specimen collected in February 1998 at Quellón.Published as part of Häussermann, Verena & Försterra, Günter, 2008, A new species of sea anemone from the Chilean fjord region, Paraisanthus fabiani (Actiniaria: Isanthidae), with a discussion of the family Isanthidae Carlgren, 1938, pp. 27-42 in Zootaxa 1897 on pages 32-39, DOI: 10.5281/zenodo.18446

Patrones de distribución de anémonas de mar chilenas de aguas someras (cnidaria: anthozoa: actiniaria, corallimorpharia); con una discusión de las relaciones taxonómicas y zoogeográficas de la actinofauna del Pacífico sudoriental, el Atlántico sudoccidental y la Antártida

The first complete zoogeographical analysis of Chilean shallow water sea anemones (Actiniaria and Corallimorpharia) and their taxonomic relations with neighbouring faunas is provided, based on extensive recent sampling in combination with a literature review. Between 1994 and 2004, we collected more than 1000 specimens of 32 distinct species of Actiniaria and Corallimorpharia at more than 100 sites along the Chilean coast between Arica (18°30’S; 70°19’W) and the Straits of Magellan (53°36’S 70°56’W). Sampling was done in the intertidal during low tides and in the subtidal by means of SCUBA diving down to depths of 40 m. The northern part of the Chilean fjord region showed the highest number of species (23). Our results contradict an abrupt general change in the marine faunal composition at 42°S, instead showing the continuation of species of the exposed coast and the joining of fjord species due to the availability of additional habitats in the richly structured fjord region south of 42°S, and also to eurybathy. The southern distribution limits of the species we found in northern and central Chile show only one significant concentration around the Peninsula Taitao (approx. 48°S). This either indicates a zoogeographic barrier for shallow water species at the Peninsula Taitao, or is a sampling artifact caused by poor data from the region between the Peninsula Taitao and the Straits of Magellan. According to the literature, 18 of the 63 described Chilean sea anemones (Pacific Ocean) can also be found in Argentina (Atlantic Ocean) and 13 in the Antarctic. However, many records and statuses of the common species of the South East Pacific and the South West Atlantic/Antarctic are uncertain or doubtful and need revision or confirmation.La presente publicación provee un primer análisis zoogeográfico completo de las anémonas de mar (Actiniaria y Corallimorpharia) de las aguas someras a lo largo de la costa chilena y de sus relaciones con faunas vecinas, basando en un extenso muestreo en los últimos años en combinación con revisiones de la literatura. Desde 1994 hasta 2004 obtuvimos mas de 1000 ejemplares pertenecientes a 32 especies de Actiniaria y Corallimorpharia. Se muestrearon mas de 100 lugares enclavados en el intermareal y el submareal hasta 40 metros de profundidad, a lo largo de la costa chilena entre Arica (18°30’S 70°19’W) y el Estrecho de Magallanes (53°36’S 70°56’W). La parte norte de la región de los fiordos chilenos presenta el máximo número de especies (23). Nuestros resultados muestran la continuación de especies características de costas expuestas y la agregación de especies típicas de los fiordos, lo cual se contradice con el concepto arraigado del cambio brusco y general en la composición de la fauna marina a partir de 42ºS. Los límites de distribución sureña de especies que encontramos en la región del centro-norte de Chile muestran solamente una concentración significativa alrededor de la Península Taitao (aprox. 48ºS). Esto bien indica una barrera zoogeográfica para especies de aguas someras en la Península Taitao o también puede ser debido a un artefacto de muestreo causado por la falta de datos que existe de la región entre la Península Taitao y el Estrecho de Magallanes. Según la literatura, 18 de las 63 especies de anémonas de mar descritas para Chile (Pacifico Sudoriental) han sido también citadas en Argentina (Atlántico Sudoccidental) y 13 en la Antártida. Sin embargo muchos registros y estatus taxonómicos de las especies comunes del Pacifico Sudoriental y del Atlántico Sud-occidental/Antártida son dudosos y requieren revisión y confirmación

Isanthidae Carlgren 1938

Family Isanthidae Carlgren, 1938 <p>Definition of the family Isanthidae</p> <p> Carlgren (1938, p. 59) defined the family Isanthidae as “ Nynantheae with basilar muscles. Sphincter mesogloeal. Mesenteries divisible into macro- and microcnemes. No acontia.” In his catalogue, Carlgren (1949, p. 76) changed the family definition to “Thenaria (Mesomyaria) with well developed mesogloeal sphincter. Mesenteries divisible into macro- and microcnemes. No acontia. Retractors of mesenteries very strong, strongly restricted (reniform) to almost circumscribed.” Due to the weak sphincter of <i>Eltaninactis infundibulum</i>, Dunn (1983, p. 58) proposed to alter the first sentence of the generic description to “Thenaria (Mesomyaria) with mesogloeal sphincter...” instead of “….with well developed mesogleal sphincter…”. Uncertainty remains over the affiliation of the genus <i>Eltaninactis</i> to the family Isanthidae, as noted in Sanamyan’s (2001) description of <i>E. psammophorum</i>.</p> <p> <b>Type species:</b> <i>Isanthus capensis</i> Carlgren, 1938 (Fig. 6)</p> <p> Definition of the genus <i>Paraisanthus</i> Sanamyan and Sanamyan, 1998:</p> <p>Isanthidae with well-developed pedal disc. Column smooth. Margin distinct. Sphincter mesogloeal, well developed. Radial muscles of oral disc and longitudinal muscles of tentacles ectodermal. Two siphonoglyphs, two pairs of directives. Six pairs of macrocnemes. More mesenteries distally than proximally, at least in adults.</p> <p>Cnidom: spirocysts, p-mastigophores, basitrichs, heterotrichs, holotrichs.</p> <p> <b>Type species:</b> <i>Paraisanthus tamarae</i> Sanamyan and Sanamyan, 1998</p>Published as part of <i>Häussermann, Verena & Försterra, Günter, 2008, A new species of sea anemone from the Chilean fjord region, Paraisanthus fabiani (Actiniaria: Isanthidae), with a discussion of the family Isanthidae Carlgren, 1938, pp. 27-42 in Zootaxa 1897</i> on pages 31-32, DOI: <a href="http://zenodo.org/record/184465">10.5281/zenodo.184465</a&gt