Actiniaria Hertwig 1882

Gusmão, Luciana C., Rodríguez, E. & Daly, Marymegan, 2019, Description of Calliactis tigris sp. nov.: reconciling taxonomy and phylogeny in hermit-crab symbiotic anemones (Cnidaria: Actiniaria: Hormathiidae), Organisms Diversity & Evolution (New York, N. Y.) 19 (4), pp. 567-583 : 569-574

Order Actiniaria Hertwig 1882

Suborder Enthemonae Rodríguez and Daly in Rodríguez et al. 2014

Superfamily Metridioidea Carlgren 1893

Family Hormathiidae Carlgren 1932

Diagnosis (modified from Carlgren 1949; Daly et al. 2004; Rodríguez et al. 2012; additions in italics).

Enthemonae with distinct pedal disc with basilar muscles and strong mesogleal marginal sphincter. Mesenteries not divisible into macro and microcnemes. Usually six pairs of perfect mesenteries, sometimes more, but never numerous. Perfect mesenteries rarely fertile. Acontia with basitrichs ol with basitlichs ahd p-mastigopholes B1. Spirocysts usually dimorphic: gracile spirocysts with narrower tubule and small- er capsule than robust spirocysts. Cnidom: robust and gracile spirocysts, basitrichs, p -mastigophores B1.

Included genera. Actihauge Verrill 1883; Allahtactis Danielssen 1890; Calliactis ; Cataphellia Stephenson 1929 ; Chohdlophellia Carlgren 1925; Haddohactis Fautin 2016; Hahdactis Fautin 2016; Holmathiahthus Carlgren 1943; Gliactis Gravier 1918 ; Mohactis Riemann-Zürneck 1986; Palacalliactis ; Palaphelliactis Carlgren 1928b; Phelliactis Simon 1892 ; Stephahauge Verrill, 1899 (according to Fautin 2016; except for Amphiahthus Hertwig 1882 and Stephahauge Verrill, 1899 which were transferred to Amphianthidae Hertwig, 1882 by Rodríguez et al. 2012).

Type genus. Holmathia

Remarks. We made minor modifications to the familial diagnosis to reflect recent changes in higher-level classification of Actiniaria (i.e., Rodríguez et al. 2012, 2014) and the terminology used to classify nematocysts in this study (see Gusmão et al. 2018). These modifications are made in diagnoses throughout this study which have also been rearranged so that they are in parallel. We added the possibility of having p -mastigophores B 1 in addition to basitrichs in the acontia of members of the family based on mounting evidence of long and narrow p -mastigophores B 1 in the acontia of Holmathia pectihata ( Hertwig 1882) in the Southwestern Atlantic ( Riemann-Zürneck 1973; LCG personal observation).

Genus Calliactis Verrill 1869

Diagnosis (modified from Carlgren 1949, England 1971, Daly et al. 2004; additions in italics).

Hormathiidae with well-developed pedal disc, equal to slightly larger in diameter than oral disc, ol bload ahd bi-lobed; may secrete a thin cuticle ol a calcihoecium. Column smooth, rarely with tubercles; divisible into scapus and sholt scapulus; scapus with numerous epidermal pits and a thin, deciduous cuticle. Cinclides always present in proximal column, sometimes ihcohspicuous. Column with basitrichs ol basitlichs ahd p -mastigopholes B1. Tentacles in several cycles, their longitudinal muscles ectodermal. Strong, mesogleal marginal sphincter muscle present. Mesenteries hexamerously arranged, more numerous distally; six pairs of perfect and sterile mesenteries, including two pairs of directives each associated to a siphonoglyph. Retractor and parietobasilar muscles weak. Species often live attached to gastropod shells inhabited by hermit crabs with oral disc directed away from the aperture of the shell ol dilectly below the apeltule.

Type species. Actihia decolata Couthouy in Dana 1846 by original designation.

Included species. Calliactis algoaehsis Carlgren 1938 ; C. ahdlogyha Riemann-Zürneck 1975 ; C. ahhulata Carlgren 1922 , C. algehtacololata Pei 1996 ; C. blevicolhis ( Studer 1879) ; C. cohchiola Parry 1952 ; C. japohica Carlgren 1928a , C. palasitica ( Couch 1842) ; C. polypoles Pei 1996 ; C. polypus ( Forsskål 1775) ; C. leticulata Stephenson 1918 ; C. tlicolol ; C. valiegata Verrill 1869 ; C. xishaehsis Pei 1996 ; C. palliata ( Müller 1776) comb. nov., C. sociabilis comb. nov. ( Verrill 1882).

Remarks. Because Calliactis palliata comb. nov. nested within a clade of Calliactis with high support in our phylogenetic analyses and previous studies (e.g., Gusmão and Daly 2010; Rodríguez et al. 2012, 2014). We transfer two former valid species of Adamsia ( A. palliata , A. sociabilis ) to Calliactis ( A. obvolva is transferred to Palacalliactis : see “Discussion”). We modify the diagnosis of Calliactis to reflect this decision. These modifications include the possibility of having a bi-lobed pedal disc, oral disc positioned directly below the aperture of the shell, and secretion of a carcinoecium which are considered specific to C. sociabilis comb. nov. and C. palliata comb. nov. (see “Discussion” for more details). After examination of many specimens of C. palliata comb. nov., we consider that the observation of 12 pairs of perfect mesenteries is an artifact of cross-sections taken very high up the column before the second cycle of mesenteries.

According to the Principle of Priority (Art. 23, ICZN 1999), Adamsia is the senior subjective synonym and thus must be used over the junior synonym, Calliactis . Although the genus name Calliactis currently has a broader use than Adamsia (particularly in non-taxonomic works: e.g., Spagnuolo et al. 1994; Williamson et al. 2000; Wiedenmann et al. 2004; Stewart et al. 2017; including having a toxin named after it—calitoxin: Cariello et al. 1989), this name does not fulfill the requirements for a reversal of precedence of a junior synonym—i.e., Art. 23.9.1 of the Code—ICZN 1999). Calliactis (15 species, including C. tiglis sp. nov.), however, is more speciose than Adamsia (two species) and generally emcompasses species living in shallower habitats that are more accessible. In our opinion, the use of the senior synonym ( Adamsia ) will cause confusion and threaten stability, thus we wish to maintain the use of the junior synonym (Calliacti s). Following Art. 23.9.3 of the Code (ICZN 1999), the matter has been referred to the ICZN (Rodríguez and Gusmão submitted: Case 3805) and is awaiting resolution. While the case is under consideration, the junior name is to be maintained (ICZN 1999); thus, here we use Calliactis for species formerly included in genus Adamsia .

We also included in the diagnosis the presence of tubercles in the column of Calliactis given that some species do not have a fully smooth column and some tubercles are visible in live or freshly collected specimens (e.g., C. japohica , C. tlicolol , C. polypus : Gusmão 2010). We replaced the more general term “ectodermal invagination” to describe the invaginations of the epidermis of the column into the mesoglea with “epidermal pit,” which was used by Hand (1975; as ectodermal pit), but not incorporated to the diagnosis of Calliactis in his study. We corrected the information regarding the proportion of tentacles to mesenteries proximally based on our finding of an extra cycle of mesenteries proximally in C. tiglis sp. nov. and confirmed in micro-CT scans of C. tlicolol (see “Discussion”). We also added the possibility of having p -mastigophores B 1 in addition to basitrichs in the column based on mounting evidence for the presence of these nematocysts in the column of Calliactis species (e.g., C. tiglis sp. nov., C. cohchiola , C. polypus ). The lack of p - mastigophores B 1 in the column of other Calliactis species is likely due to the general scarcity of nematocysts in the column compared to other types of tissue (e.g., actinopharynx or filaments).

Calliactis tiglis sp. nov.

Material. Holotype: AM G.17486 (P.77572), F. R. V. Kapala Cruise, Sta. K 85-21-06, north east of Long Reef , New South Wales, Australia, 33°42′ 00″ S, 151° 54′ 00″ E, 466 m depth, 19 December 1985 . Paratypes: AM G.16907 (1 specimen), northeast of Long Reef , New South Wales, Australia, 33° 42′ 00″ S, 151° 54′ 00″ E, 450 m ; AM G.17489 (4 specimens), F . R. V. Kapala, between Sydney and Port Stephens , New South Wales, Australia, 33° 49′ 60.00″ S, 151° 13′ 00″ E, 365 m depth, July 1972 ; AM G.17482 (2 specimens), F . R. V. Kapala, Sta. K 71-10-02, east of Bulli , New South Wales, Australia, 34° 15′ 00″ S, 151° 25′ 00″ E, 275 m depth, 28 June 1971 .

Additional material. AM G.15586 (2 specimens), east of Mooloolaba , Queensland, Australia, 26° 52′ 44″ S, 153° 35′ 20″ E, 350 m depth ; AM G.16897 (2 specimens), east of Mooloolaba , Queensland, Australia, 26° 52′ 44″ S, 153° 35′ 20″ E, 300 m depth ; AM G.17484 (2 specimens), Sta . SEAS QLD 1119 , east of Mooloolaba , Queensland, Australia, 26° 52′ 44″ S, 153° 35′ 20″ E, 160 m depth, 3 August 1994, collected by J.K. Lowry, K. Dempsey & J. McIllwain ; AM G.17491 (2 specimens), east of Mooloolaba , Queensland, Australia, 26° 52′ 44″ S, 153° 35′ 20″ E, 312 m depth, 3 August 1994, collected by J.K. Lowry & K. Dempsey ; AM G.17483 (2 specimens), Sta . SEAS QLD 1119 , east of Mooloolaba , Queensland, Australia, 26° 52′ 44″ S, 153° 35′ 20″ E, trawl, 160 m depth, 3 August 1994, collected by J.K. Lowry, K. Dempsey & J. McIllwain ; AM G.17485 (P.77571) (3 specimens), Sta . SEAS QLD 1119 , east of Mooloolaba , Queensland, Australia, 26° 52′ 44″ S, 153° 35′ 20″ E, 160 m, 3 August 1994, collected by J.K. Lowry, K. Dempsey & J. McIllwain.

Material examined for comparison. Calliactis japohica UUZM 688a (1 specimen, syntype), Gote Island, Misaki, Kanagawa-ken , Sagami Bay , Honshu , Japan, 34° 00′ 00″ N, 132° 36′ 00″ E, 165 m depth; UUZM 688 b (1 specimen, syntype), Gote Island , Misaki , Kanagawa-ken , Sagami Bay , Honshu , Japan, 34° 00′ 00″ N, 132° 36′ 00″ E, 110 m depth; USNM 20290 (4 specimens), Suruga Bay , Honshu Island , Shizuoka, Japan, 35° 01′ 58.8″ N, 138° 46′ 1.2″ E, 110– 128 m depth; USNM 50291 (2 specimens), Hong Kong, China, 21° 30′ 00″ N, 116° 31′ 58.8″ E, 256 m depth. Calliactis polypus USNM 50481 (3 specimens), 2 miles South of Agat Bay, Guam, North Pacific Ocean , August 1947, collected by G.S. Mansfield; USNM 50475 (3 specimens), Carolina Islands, Micronesia, North Pacific Ocean, 9° 32′ 31.45″ N, 138° 3′ 21.60″ E, Sta. Y-258, collected by R. W. Hiatt, ID by C.E. Cutress; AM G.17480 (4 specimens), Sta. NSW 1901, south of Smoky Cape , south side of Fish Rock, New South Wales, Australia, 30° 56′ 27″ S, 153° 05′ 58″ E, 20 m depth, 14 February 2002 , hand collected on SCUBA by R. T. Springthorpe. Calliactis tlicolol AMNH 3549 (12 specimens), North Beach, St. Catherines Island, Georgia , collected by C. Boyko & W. Sage III, 21 May 1994 . Adamsia palliata YPM IZ-7145 (4 specimens), off Port Vendres, France, Mediterranean Sea, Atlantic Ocean , collected by Staff of the Laboratoire Arago , ID by Willard D. Hartman , 60–100 m, 25 April 1958 . YPM IZ-7146 (4 specimens),off Port Vendres, France, Mediterranean Sea, Atlantic Ocean , collected by Staff of the Laboratoire Arago , ID by Willard D. Hartman , 60–100 m, 25 April 1958 .

External anatomy ( Fig. 2 ). Pedal disc broad, often circular, adherent, irregularly shaped, wider than column diameter, never bi-lobed or covering the shell completely ( Fig. 2a–d ); two specimens may coexist in the same shell ( Fig. 2c ). Pedal disc diameter 17.0–80.0 mm in preserved specimens; carcinoecium absent, but a thin cuticle may be present. Column cylindrical, usually narrower than diameter of pedal disc, with characteristic pattern in preserved specimens: column white or beige with numerous purple spots not forming longitudinal stripes as in other Calliactis species, but irregular patches ( Fig. 2a–d ) formed by purple colored epidermal pits visible to the naked eye on scapus ( Fig. 2e ). Column firm, with thick mesoglea, divided into scapus and scapulus with differing epidermal thickness and cnidae content; scapus with thick epidermis and longer basitrichs; scapulus with thin epidermis and short basitrichs. Scapus with thin, deciduous cuticle sometimes present. One row of inconspicuous cinclides on limbus close to pedal disc; these communicate to endoceles of first or second cycle mesenteries; in some individuals cinclides hardly visible unless acontia are present ( Fig. 2f, g ). Column 15.0–59.0 mm height and 19.0–75.0 mm diameter in preserved specimens. Oral disc always located opposite to gastropod shell aperture ( Fig. 2a–d ); when relaxed, oral disc circular and wide, slightly wider than pedal disc, diameter 2.0–20.0 mm in contracted specimens. Up to 110 tentacles restricted to outer half of oral disc, hexamerously arranged in 5 cycles (6 + 6 + 12 + 24 + 48 + n); tentacles short, conical, inner longer than outer ones; white/beige with a longitudinal darker line along its length.

Internal anatomy and microanatomy ( Fig. 3). Body wall with thick mesoglea 2690–3102 μm and gastrodermis 46– 59 μm ( Fig. 3a); epidermis thinnest in scapulus (5–9 μm) ( Fig. 3b), thickest at distal scapus (27–80 μm) with intermediate thickness at mid-scapus (33–47 μm). Numerous epidermal pits (i.e. invaginations of the epidermis of the column into the mesoglea) on scapus ( Fig. 3c); these are mostly single ( Fig. 3d), rarely fused together ( Fig. 3e), always open to the exterior ( Fig. 3c–e); diameter of major axis 117–318 μm. Marginal sphincter muscle mesogleal, well-developed ( Fig. 3a), occupies most of mesoglea close to base of tentacles ( Fig. 3a, b) decreasing proximately at distal scapus, always closer to epidermis than gastrodermis ( Fig. 3a); alveolar with tendency to horizontal stratification distally ( Fig. 3f), less so proximally ( Fig. 3g). Tentacle longitudinal muscle ectodermal ( Fig. 3h); tentacles without basal mesogleal thickening ( Fig. 3i). Forty-eight pairs of mesenteries, hexamerously distributed in four cycles (6 + 6 + 12 + 24) distally ( Fig. 3j) and at mid-column ( Fig. 3k); incomplete fifth cycle of mesenteries only proximally very close to the base (32 pairs; 80 pairs of mesenteries total). Mesenteries of first cycle perfect, sterile, including two directive pairs ( Fig. 3j) each associated to a well-developed siphonoglyph; second and third cycles imperfect, fertile ( Fig. 3l–n); fourth cycle imperfect, sterile ( Fig. 3l, o); mesenteries of fifth cycle poorly developed, found only very proximally. Mesenteries more developed proximally ( Fig. 3k). Mesenterial filaments and acontia restricted to first, second and third cycles at mid-scapus ( Fig. 3l); mesenteries of first to fourth cycles with filament and acontia proximally. Retractor muscle diffuses in cycles 1–4 ( Fig. 3l); absent from mesenteries of fifth cycle. Parietobasilar muscle weak in mesenteries of first to third cycles ( Fig. 3l–n); stronger in mesenteries of fourth cycle, but with no mesogleal flap ( Fig. 3o). Basilar muscle strong (not shown). Species gonochoric: major axis of oocytes 23–58 μm in diameter; major axis of spermatic cysts 34–93 μm in diameter.

Cnidom. Gracile and robust spirocysts, basitrichs, and p - mastigophores B1 ( Fig. 4 ). For size and distribution, see Table 1.

Natural history and distribution. Usually only one specimen is found per shell, rarely two individuals cohabit a single shell ( Fig. 2c ). Calliactis tiglis sp. nov. is known only from the western Pacific Ocean , off the coast of New South Wales and Queensland in Australia. The new species has been collected between 166 and 508 m depth .

Etymology. The species epithet “ tiglis ” refers to the characteristic feline-like coloration pattern of the column of species of Calliactis , more specifically the tiger-like coloration pattern of C. tiglis sp. nov.

Genus Palacalliactis Carlgren 1928a

Diagnosis (modified from Carlgren 1949, Hand 1975, Daly et al. 2004; additions in italics).

Hormathiidae with well-developed, broad, and asymmetric pedal disc but hot bi-lobed as ih some Calliactis species. Pedal disc slightly wider than oral disc; secretes carcinoecium that may or may not project beyond shell aperture. Column

without basal thickening (arrows). j Cross section through distal column showing 48 pairs of mesenteries attached to oral disc. k Cross section through proximal column showing pairs of mesenteries distributed in four cycles (cycles indicated by numbers). l Histological cross-section through mid-scapus showing four cycles of mesenteries (indicated by numbers); note a pair of first cycle of mesenteries still attached to siphonoglyph. m Detail of mesenteries of third cycle; note diffuse retractor and weak parietobasilar muscles. n Detail of mesentery of second cycle; note diffuse retractor muscle. o Detail of mesentery of fourth cycle; note weak retractor and well-developed parietobasilar muscle. D directive pair of mesenteries. Scale bars, a, j–l 4 mm, b 2 mm, c 0.4 mm, e, l, n 1 mm, f–h 0.35 mm, i 0.03 mm, m 0.5 mm, o 0.2 mm

divisible into scapus and scapulus; smooth or with distal tubercles that may form a complete corona; may have a thin, easily deciduous cuticle. No cinclides. Column with basitrichs and p -mastigophores B1. Tentacles hexamerously arranged, about the same number as mesenteries proximally, their longitudinal muscles ectodermal. Strong, mesogleal marginal sphincter muscle present. About the same number of mesenteries proximally and distally; six pairs of perfect and sterile mesenteries, including two pairs of directives each associated to a siphonoglyph. Retractor and parietobasilar muscles weak. Species live attached to gastropod shells inhabited by hermit crabs with oral disc positioned directed away from the aperture of the shell (dorsally) or below the aperture of the shell (ventrally).

Type species. Palacalliactis valdiviae Carlgren 1928a by original designation.

Included species. Palacalliactis azolica Doumenc 1975; P. cohsols ( Verrill 1882) ; P. meditellahea Ross and Zamponi 1982 ; P. michaelsalsi Carlgren 1928a ; P. obvolva comb. nov. ( Daly et al. 2004); P. losea Hand 1975 ; P. sihica Pei 1982 ; P. stephehsohi Carlgren 1928a ; P. valdiviae Carlgren 1928a .

Remarks. We maintain the original intention of Carlgren (1928a) for the genus but modify the diagnosis of the genus to differentiate the asymmetry of the pedal disc of Palacalliactis species from the bi-lobed shape of those seen in some Calliactis species formerly belonging to Adamsia ( C. sociabilis comb. nov., C. palliata comb. nov.). Although the position of the anemone on the shell has been shown to vary within hermit-crab genera and not carry phylogenetic signal (see “Discussion”), we included this information in the diagnosis given the uniqueness of this feature within the order Actiniaria which may aid in its generic placement. After examination of the holotype (KUNHM 01595) and paratypes (KUNHM 01591, USNM 1004627, USNM 1004630) of P. obvolva comb. nov., we found that the cinclides described by Daly et al. (2004) for the species are likely an artifact and result from observation of longitudinal ridges characteristic of species of Palacalliactis that may become indented both longitudinally and transversely ( Doumenc 1975; Hand 1975; personal observation) and give the impression of small perforations in the column, similar to cinclides. The location of the cinclides described for P. obvolva comb. nov. (i.e., mid-column) also indicates they might not be true cinclides as these are restricted to the proximal part of the column close to the pedal disc as in all species of Calliactis (after adjusted diagnosis). Under close inspection, the structures observed by Daly et al. (2014) are not cinclides, which precludes the inclusion of P. obvolva comb. nov. within Calliactis . In addition, because P. obvolva comb. nov. presents other features characteristic of Palacalliactis (e.g., asymmetrical pedal disc), this species is transferred to Palacalliactis ( P. obvolva comb. nov.). In addition, we agree with Hand (1975) and do not consider P. lacazei Dechancé and Dufaure 1959 a valid species as it possesses cinclides in the proximal column. Whether P. lacazei should be transferred to Cataphellia as suggested by Hand (1975) is uncertain, pending a detailed examination of this species. Unfortunately, no specimens of P. lacazei were available for study.

Figures

Fig. 2 External anatomy of preserved specimens of Calliactis tiglis sp. nov. a Oral view of a specimen with characteristic column coloration pattern. b Lateral view of a specimen attached to a shell; note remains of cuticle produced by pedal disc. c Two specimens attached to a single shell, one of which has lost part of its coloration pattern. d Lateral view of a specimen attached to a shell with hermit crab visible. e Detail of epidermal pits on proximal column; note white and purple epidermal pits. f Cinclides on proximal column (arrows). g Detail of a cinclide (arrow). Scale bars, a 50 mm, b 30 mm, c 21 mm, d 30 mm, e 1.6 mm, f 4 mm, g 2 mm

Fig. 4 Cnidom of Calliactis tiglis nov. sp. a, b, f–k, m, n Basitrich. c, l P- mastigophore B1. d Gracile spirocyst. e Robust spirocyst