Macrodactyla aspera ( Haddon and Shackleton,

Yap, Nicholas Wei Liang, Mitchell, Michela Lee, Quek, Zheng Bin Randolph, Tan, Ria, Tan, Koh Siang & Huang, Danwei, 2023, Tripedalia maipoensis Sun & Tsui & Wong & Cheung & Ng & Or & Qiu 2023, sp. nov., Zoological Studies 62 (29), pp. 1-25 : 8-20

Macrodactyla aspera ( Haddon and Shackleton,

1893) ( Figs. 2–6 )

Condylactis aspera – Haddon and Shackleton, 1893: 117, 124–125 [original description]; Dunn 1981: 29; Fautin 2016: 77, 105, 164.

Macrodactyla aspera – Haddon 1898: 398, 415, 431–432; Stephenson 1922: 263; Carlgren 1949: 63; Fishelson 1970: 109, 110; Stephenson 1922: 263; Dunn 1981: 35.

Dofleinia armata – Rowlett 2020: 292, 293.

Nomenclature considerations and type material examined: Two lots of the syntypes of C. aspera that was listed in Fautin (2016), were of sea anemones collected from Murray Islands in the Torres Strait, Australia: i) a nearly complete specimen kept at the Cambridge, UK ( MZC I.33665, previously without a catalogue number assigned) ( Fig. 2A ), and ii) three microscope slides comprising of histological sections kept in Lund, Sweden ( MZL, no catalogue number) ( Fig. 2B ). We confirmed Fautin’s (2016) listing of these specimens; the labels present on these slides indicated that they were prepared from the material collected by Haddon and Shackleton (1893) ( Fig. 2B ). Among these three microscope slides, only histological sections of one closely corresponded to Haddon’s depiction of the musculature, while those present on the other two slides did not agree to his remaining illustrations (see: Haddon 1898: Plate 28, Figs. 3 , 4 and 5 ). Despite this, sections on these slides agreed with the shape of pieces that were missing from the syntype which we had studied at the MZC. These other histological sections from the syntype were likely prepared by O Carlgren, who then kept them at the MZL where he had worked, a practice which he also carried out on other sea anemone species (Fautin 2016: 13; Yap et al. 2021). Pertaining to the original histological sections that were prepared by Haddon and used for his illustrations, we were unable to locate it at the museums we have visited.

To further provide nomenclatural objectivity to the name Condylactis aspera , we hereby designate MZC.I.3365 and the three MZL slides as the lectotype, as the latter slides were prepared from the specimen at MZC. While there was no mention of the number of individuals that were collected and examined in the original description for the species, the account of the species’ tentacle arrangement alludes to more than one individual being examined, as Haddon and Shackleton (1893: 124) stated, “… large tentacles in three or four cycles…” [underlined emphasis, our own]. This observation of a variation is only possible if more than one individual was examined. In this study, NWL Yap attempted to locate other syntypes in other museums where they may be possibly held (e.g., NHM, etc), but failed to find any. Should these other materials be found, they are the paralectotypes of C. aspera (Article 74.1.3, the Code).

Lectotype: Condylactis aspera ( MZC I.3365), collected by Haddon and Shackleton from the Torres Straits ( Fig. 2A ). A single specimen cut into three pieces. Two pieces already removed prior to being examined by the first author: i) a wedge of the oral disc, and ii) a quarter section of the base. Column diameter about 5 mm. Entire specimen greyish, with a dark brown cast ( Fig. 2A ). Gastro-cavity of specimen choked with gametogenic tissue.

Lectotype: MZL (no catalogue number), three microscope slides prepared from MZC.I.3365 ( Fig. 2B ). One labelled as “ Macrodactyla aspera Torres Str AMS 1893 , consists of three transverse sections of the distal most end of the column and tentacle. Second slide, with two labels. The first wider label bears the words, “ Macrodactyla aspera sph”, the second slimmer label has “AMS 187” written on it. The slide bears eight sections, all being the distal most end of the specimen. The third slide has a single label with the following printed on it: “ Macrodactyla aspera Torres Str, AMS 1893 ”. This slide also bears three histological sections of the distal most end of the animal. All sections present on these slides are too faded to infer any useful details from them.

Material examined from Singapore ( Fig. S1 ): (*- observed alive): Beting Bronok ( ZRC.CNI. 1015 x3), Changi beach ( ZRC.CNI. 1055 x1; ZRC.CNI. 1099 x1 *; ZRC.CNI. 1217 x2 *), Changi East beach ( ZRC. CNI. 1090 x1 *), Cyrene Reef ( ZRC.CNI. 1080 x1; Photographed but not collected), Pulau Sekudu ( ZRC. CNI. 1222 x3 *).

Materials examined from elsewhere ( Fig. S2 ): Israel (Eilat): Gulf of Aqaba (SMNHTAU-Co.7813 x1; SMNHTAU-Co.12133 x1). Australia (Perth): North Fremantle ( WAM Z99100 x1), Cockburn Sound ( WAM Z50023 x1); Rowley Shoals ( WAM Z50026 x2). New Caledonia: Noumea ( MNHN 1321 x1); Unspecific location ( MNHN 1571 x1).

Description: Natural history: Usually solitary, at the middle intertidal of soft silty sand, sandy areas, and among seagrasses ( Fig. 3A–B ). Distal end of animal exposed during low spring tides, when encountered during the early morning or dusk. Animal partially buried in substratum ( Fig. 3A–B ). Tentacles extended and oral disc expanded, flat against substratum ( Fig. 3A ). Often encountered with actinopharynx everted outwards; if everted partially, animal may appear to have luscious lips ( Fig. 3B ). Small shell pieces, coral rubble, sand and/or small stones adhere to exposed verrucae of distal most column end ( Fig. 3C–D ). When disturbed, animal does not retract completely, with tentacles and/or its tips remaining partially exposed ( Fig. 3D ). Cells of symbiotic dinoflagellates not observed in tissue.

Tentacles: 48. Arranged in four cycles, one per endo-/exocoel. Outermost exocoelic; innermost cycles: endocoelic. Innermost cycle longer, greater or equal to length of oral disc radius; outermost shortest, 1/3 length of innermost ( Fig. 3A ). Covered entirely with visible nematocyst batteries ( Figs. 3A–D , 4A, 4B ). Tapering in life; may appear conical in fixed specimens due to contraction by fixative ( Fig. 4B ). Wide at base, narrows to point. Tip pointed-blunt, not perforated. In life, cream-colour with dark-brown splotches on oral side, batteries white or brown ( Figs. 3A–D , 4A ). Sticky; readily adheres to surfaces of containers. Does not abscise readily when disturbed. Preserved specimens coloured grey, brown to mauve, with intense brown (or dark mauve) cast near the tip ( Fig. 4B ).

Oral disc: Outline round, flat when fully expanded ( Fig. 3A ). Diameter up to 45 mm. Nematocyst batteries of tentacles may extend across disc, in some specimens all the way to mouth. Thin-walled; mesenterial insertions as radial lines seen through disc, extending from mouth to tentacles, in life these appear as faint brown lines ( Fig. 3A, B ), in preserved specimens as white lines. Oval central-mouth, flat, may be slightly raised in some. Actinopharynx often everted ( Fig. 3B ), sometimes obscuring entire animal. When alive, edge of mouth typically white in colour, with thick brown splotches radiating outwards, translucent when expanded. In preserved materials, edge of mouth with a brown cast.

Column: Thin-walled. Fosse present, very shallow in vivo; in preserved specimens fosse not distinct. When expanded, distal end flared outwards, overhangs slightly. Distal end with marginal projections, endocoelic ( Fig. 3C, D ). Longitudinal rows of conspicuous verrucae present, extending from distal end to mid-column, 6 to 13 per row; endocoelic ( Fig. 3C, D ). Verrucae oval, edges slightly raised and thickened, middle thin and translucent; in life, verrucae cream-white with a pink dot in the middle ( Fig. 4C ), colour is lost in preserved specimens ( Fig. 4D ). Verrucae adhesive, with small shell fragments, sand, small stones, and/or coral rubble often attached ( Fig. 3C, D ) even after preservation ( Fig. 4D ). Mesenterial insertions seen as light lines extending from the distal to proximal end. Remainder of column smooth, no other structures present (e.g., cinclides). In life, distal end brown, region from mid-column to proximal end bright orange; once preserved, specimen may be entirely cream-white, dark brown or grey.

Pedal disc: Overall oval in outline, flat; thin-walled. Mesenterial insertions seen through as white lines. Limbus slightly scalloped. In life, orange with splotches; once preserved entirely cream-coloured or greyish, with a dark-brown cast.

Internal morphology: 24 pairs of mesenteries regularly arrayed in three cycles (6 + 6 + 12), with two pairs of directives symmetrically opposite each other, each pair attached to a siphonoglyph. Mesenteries in primary and secondary cycles complete (i.e., 6 + 6 pairs); those in third cycle, incomplete (i.e., 12 pairs). All mesenteries extended through entire length of column. Mesenterial retractor muscles diffuse-circumscribed, well-developed ( Fig. 5A ). Parietobasilar muscles of first two cycles well-developed, with pennon ( Fig. 5A ). Marginal sphincter muscle conspicuous, diffuse-circumscribed. Oral and marginal stomata present ( Fig. 5B ), but in some specimens may be difficult to view (e.g., SMNHTAU-Co.12133). Parietobasilar muscle present but not easily discernible. Actinopharynx extends proximally slightly past mid-column, longitudinally pleated, pinkish translucent in live, cream-white when preserved ( Fig. 5C ).

Cnidom: Spirocysts, basitrichs, and microbasic p -mastigophores. Sizes and distribution are shown in table 2; illustrations in figure 6.

Distribution ( Fig. S2 ): Type locality: Australia, Torres Straits, Mabuiag Reef ( Haddon and Shackleton 1893; Haddon 1898). Published records: Israel, Red Sea, Gulf of Aqaba, Eilat ( Fishelson 1970). New records: Australia, Indian Ocean, Perth (i.e., Cockburn Sound, North Fremantle, and Rowley Shoals); New Caledonia, Coral Sea, Noumea; Singapore, in the Straits of Johor (i.e., Beting Bronok, Changi region beaches, Pulau Sekudu) and Singapore Strait (i.e., Cyrene Reef).

Comparisons with other similar sea anemones: In having nematocyst batteries densely covering its tentacles, other discerning taxonomic features (e.g., adhesive verrucae) hidden in the sand, and in sharing a similar habitat, M. aspera have been misidentified as D. armata (e.g., WAM Z99100), or assumed to be a different morphotype of the latter (i.e., Rowlett 2020: 292, 293). However, the presence of longitudinal, adhesive verrucae rows is the obvious feature that distinguishes these two species. These rows are only present on the distal end of M. aspera , while they are absent in D. armata ; the absence of verrucae is consistent with taxonomic accounts of D. armata and its holotype ( Wassilieff 1908; Carlgren 1949). When alive, another trait that distinguishes D. armata from M. aspera is that the former readily autotomises its tentacles when disturbed, but those of the latter will remain intact.

Remarks: The animal that we have found closely matches the species and its type specimen that was collected and described by Haddon and Shackleton (1893). In all these specimens studied, we found that: i) their tentacles were densely covered with nematocyst batteries, ii) visible, adhesive verrucae were present at the distal end of the column, iii) cnidom data agreed between these specimens, and iv) as stated in our revised definition of the genus, the mesentery arrangement and number were also consistent.

Although the distinct tentacles of M. aspera (i.e., it being densely covered by nematocyst batteries) were not mentioned in its Haddon and Shackleton’s (1893) original description of the species, nor in the main text of Haddon’s (1898) expanded account, they were illustrated in the latter (see: Haddon 1898: Plate 22, Figs. 10 and 11 ). His depiction also provided a closeup view of a studded tentacle, clearly showing the nematocyst batteries. In examining the lectotype, Dunn (1981: 35) also found this feature to be obvious. The presence of nematocyst batteries densely covering each tentacle was also observed in fresh material collected, and in museum voucher specimens we have found and studied. Because the tentacles of M. aspera strongly resemble those of D. armata , many museum vouchers of the former species were identified and labelled as the latter (e.g., MNHN 1321, WAM 67). We have also examined specimens that Fishelson (1970) had collected (i.e., SMNHTAU-Co.7813 and SMNHTAU-Co.12133), and verified them to be M. aspera .

Like Haddon and Shackleton (1893), we found large visible, adhesive verrucae present on the distal end of the anemone, with shell fragments and small rocks often attached to them. While Haddon and Shackleton (1893: 124) also mentioned that the column of the anemone was also “covered with small, very adhesive suckers,” we failed to find any structural indication of this feature in both the lectotype and the voucher specimens.

The few published accounts pertaining to this species and its lectotype provided no detailed measurements of cnidom data (e.g., Haddon 1898; Fishelson 1970; Dunn 1981). We report these here for the first time. Broadly, measurements made on undischarged capsules extracted from tissues of the voucher material fell within the range of those obtained from the lectotype ( Table 2). We were unable to assess cnidae of the lectotype’s actinopharynx as we failed to obtain a piece of tissue for it. Pertaining to the tentacle spirocysts of the lectotype, we found these to be degraded in the tissue, hindering measurements. Despite these two caveats, cnidae measurements of the lectotype and voucher materials agreed well.

Macrodactyla fautinae , sp. nov. Yap, Mitchell, Quek, and Huang ( Figs. 7–11 ) urn:lsid:zoobank.org:act:DC99CC5F-0956-47A9-B0E9-A0B3206F5ADE

Material examined: Holotype: ZRC.CNI.1300

( Fig. 7 ), collected from the beach off Changi Beach (near Carpark 7), Singapore, on 5 July 2016 by the staff of LKCNHM. An individual of unknown gender, cut longitudinally into two equal pieces. Tissue from the pedal disc sampled for genetic work ( Table S1).

Paratypes: ZRC.CNI.1156, collected from Changi Beach (near Carpark 4) ( Fig. S1 ), Singapore, on 4 August 2016 by NWL Yap. Tissue sampled from its pedal disc for genetic work ( Table S1). ZRC.CNI.0296, collected from Changi Point Beach on 22 July 2009 by DG Fautin et al. A dissected female from which 10 microscope slides with histological sections of the animal were prepared.

Material examined from Singapore ( Fig. S1 ) (*- observed alive): Changi Beach ( ZRC.CNI. 1020 x5 *; ZRC.CNI. 1156 x1 *; ZRC.CNI. 1159 x1 *; ZRC. CNI. 1300 x1 *), Changi Point beaches ( ZRC.CNI.0022 x1; ZRC.CNI.0025 x1; ZRC.CNI.00296 x1; ZRC. CNI.00297 x1), Changi Point SAF Chalet beach ( ZRC. CNI.0558 x1*; ZRC.CNI.0559 x1*; ZRC.CNI.0566 x1*; ZRC.CNI.0598 x1*; ZRC.CNI.0648 x3*), Changi Point Ferry Terminal beach ( ZRC.CNI.0023 x1; ZRC. CNI.0024 x1), Chek Jawa ( ZRC.CNI. 1370 x1 *), Pasir Ris ( ZRC.CNI.00254 x1; ZRC.CNI.00255 x1), Pulau Ubin, OBS Camp beach ( ZRC.CNI.0788 x1*), Pulau Sekudu ( ZRC.CNI.0026 x1).

Etymology: The name Macrodactyla fautinae sp. nov. honours the late Emeritus Professor Daphne Gail Fautin. Throughout her career, she had worked tirelessly to advance the knowledge of sea anemones.

Description: Natural history: Occurs as solitary individuals, at the middle intertidal in soft silty, sandy areas, and also found in seagrass meadows ( Fig. 8A– E ). Animal partially buried in substratum, distal end of animal exposed during the low tides, with small shell pieces, sand and/or rocks adhering to verrucae ( Fig. 8C ). Oral disc and tentacles typically expanded, with actinopharynx often everted and inflated outwards, in many instances obscuring the animal ( Fig. 8D ). This species has also been observed to swallow its prey whole ( Fig. 8E ). When disturbed, animal does not retract completely, tips of tentacles remaining partially exposed ( Fig. 8C ). In the process of contraction, water may also be expelled from verrucae-like structures, akin to a watering can.

Tentacles: 96. Arranged in five cycles, one per endo-/exocoel. Outermost exocoelic; innermost cycles, endocoelic. Innermost cycles longer and of similar length, greater or equal to length of oral disc radius; outermost shortest, ½ length of innermost cycles ( Fig. 8A, B ). All alike in appearance; simple, smooth without nematocyst batteries, tapering to a blunt end in life; in preservative all appeared similarly sized, short, conical with a blunt end, possibly due to contraction in fixative. Colour in life translucent with horizontal bands of dark brown and white bands ( Fig. 8A, B ); in fixative, colours retained in freshly preserved specimens (i.e., <two years) but are expected to be lost over time, to become translucent cream in colour.

Oral disc: Outline round, flat when expanded ( Fig. 8A, B ). Diameter up to 80 mm. Smooth and thin-walled, mesenterial insertions may be seen as dark radial lines extending from mouth to disc margin, more prominent in individuals with colourless disc or in fixed specimens (e.g., Fig. 8A ). In life, colour and pattern variable among individuals: may be completely colourless, greenish-grey, entirely dark-brown, or brown with white markings or vice-versa, sometimes accompanied by markings of cross bands being V- or W-shaped (seen typically larger individuals; see also Fig. 8A, B ); disc in fixative all appear translucent cream-coloured. Central mouth lipless and oval in outline, with actinopharynx everted to some extent ( Fig. 8C, D ). Two symmetric siphonoglyphs, each marked by bright pink dot in live individuals ( Fig. 8A, B ); pink dot may be visible in freshly preserved specimens but fades over time.

Column: In life, translucent cream-coloured, with reddish-orange splotches present on lower end ( Fig. 9A ); once fixed, colour may be retained in specimens, but fades over time. Fosse present, shallow to deep. Thin-walled, mesenterial insertion visible through wall as longitudinal light lines, extending from distal most to proximal end ( Fig. 9B ); visibility most prominent when animal is expanded and/or relaxed, may be obscured when animal is slightly contracted ( Fig. 9A ). Distal end with marginal projections, perforated, both endo-/ exocoelic ( Fig. 9C ). Conspicuous adhesive, verrucae present, endocoelic, arranged in vertical rows that extend proximally from the distal end to mid-column, five to seven per row. Verrucae raised, outline round, with a pink dot in the middle ( Fig. 9B, C ), perforated. When extended, verrucae papillae-like ( Fig. 9B ). In fixed specimens, verrucae contracted but still prominent. From mid-column to proximal end, without any obvious structures (e.g., cinclides, etc.); smooth.

Pedal disc: Outline irregular oval in outline, following contours of surface it clings onto. Thin-walled; mesenterial insertions visible through it as radiating while lines. Scattered reddish-orange splotches present on base. Adheres readily to surfaces.

Internal morphology: 48 pairs of regularly arrayed mesenteries arranged in four cycles (6 + 6 + 12 + 24); all extend the entire length of column. Two pairs of diametric directives, each pair attached to a siphonoglyph. Mesenteries in first two cycles complete, those in third and fourth incomplete. Gametogenic tissues on all mesenteries, if present. Sexes separate. Mesenterial retractor muscles well-developed, diffusecircumscript ( Fig. 10A ); mesenteries of lower orders more circumscribed than those higher. Parietobasilar well-developed; free pennon associated with mesenteries of lower orders ( Fig. 10A ). Oral and marginal stomata present, however former may be difficult to visualise in some individuals (e.g., ZRC.CNI.0566). Marginal sphincter muscle conspicuous and circumscribed, close to fosse ( Fig. 10B ). Parietobasilar muscle present but not easily discernible. Actinopharynx longitudinally pleated and thin-walled, translucent-white in life, cream-coloured in preserved specimens; extends proximally towards pedal end, slightly pass mid-column.

Cnidom: Spirocysts, basitrichs, and microbasic p -mastigophores. Sizes and distribution are shown in table 3; illustrations in figure 11.

Distribution: This species has so far been encountered only along the northern shoreline of Singapore, in the Straits of Johor ( Fig. S1 ).

Comparisons with M. aspera : The most obvious feature that distinguishes these two species is the texture of the tentacles of their type species. Those of M. aspera appear rough to the eye, as they are densely covered with nematocyst batteries, while the tentacles of M. fautinae sp. nov. are smooth. We have not encountered any individuals of M. fautinae sp. nov. that bear nematocyst batteries on their tentacles.

Oral disc appearance also differed between the two type species. As with the tentacles, nematocyst batteries are often on the oral disc of M. aspera , while M. fautinae sp. nov. lacks this feature. In many of the examined live M. aspera individuals, the oral disc is often marked by dark brown splotches, whereas those of M. fautinae sp. nov. may vary in appearance, and markings – if present – are typically cross bands that are V- or W-shaped. Consistently in all individuals we have encountered and collected, bright pink dots demarcate the siphonoglyphs of M. fautinae sp. nov., a feature not observed on the oral disc of live M. aspera individuals examined (see Figs. 3A, B ; 8A, B ).

The appearance of the column also differed consistently between the two species. In general, colour may not be a useful feature when distinguishing between sea anemone species ( Stephenson 1928: 69), however, we found this feature to be consistent as a whole in all individuals of both species studied. Macrodactyla aspera has a dark-coloured distal-end and the remainder of its column being bright orange, whereas that of M. fautinae sp. nov. is entirely cream-white, with pink splotches. Columnar structures also differ between both species. While verrucae found in these two species are adhesive, those of M. fautinae sp. nov. are lobe-like when extended, and expels jets of water when the animal contracts, a feature not observed in M. aspera .

Ecological remarks: Both M. fautinae sp. nov. and M. aspera are found to occur in similar habitats along Singapore’s northern coastline, in the Straits of Johor. However, while we have found the latter to also occur in intertidal areas of Singapore’s southern shoreline (i.e., in the Singapore Strait), we have only encountered M. fautinae sp. nov. on the northern shoreline and in no other southern locations that bear a similar habitat ( Fig. S1 ). Apart from sharing similar habitat types, both species also exhibit a curious behaviour of everting an extensive part of the actinopharynx when exposed during the low tide, obscuring most of the animal. The exact rationale of this behaviour is unclear. Inferring from the presence of nematocysts present in the tissue of the actinopharynx and the extent of the eversion, we hypothesize that this behaviour aids in the capture of larger prey, as we have observed ( Fig. 8E ). To test this hypothesis, further experimental studies involving prey size and measuring the extent of actinopharynx eversion may be conducted.

Similar species: Macrodactyla fautinae sp. nov. may be confused with three other similar looking species that also occur at its type locality, Singapore: Anthopleura buddemeieri Fautin, 2005 , An. handi Dunn, 1978 , and Paracondylactis singaporensis ( England 1987).

While both M. fautinae sp. nov. and An. buddemeieri have a column patterned with splotches of red, with both species having adhesive verrucae on its distal most end, these two species occupy different habitats. Macrodactyla fautinae sp. nov. tends to occur in silty, sandy areas, among seagrasses meadows of the middle intertidal zones, while An. buddemeieri occurs underneath rocks in the upper intertidal zone ( Fautin 2005; Fautin et al. 2009). While the size of a sea anemone may not be a good character to distinguish species ( Stephenson 1922; Fautin et al. 2008), we have consistently found that adult individuals of M. fautinae sp. nov. are much larger than An. buddemereri (e.g., oral disc diameter: 80 mm versus 7 mm, respectively; see Fautin (2005) for size of An. buddemeieri ).

In occupying the same habitat types (i.e., silty and sandy substratum), and having translucent, patterned tentacles, M. fautinae sp. nov. may be mistaken for either An. handi , or P. singaporensis in the field. However, M. fautinae sp. nov. can be immediately distinguished from these other two species by using the following features: 1) a pair of conspicuous pink dots, each marking a siphonoglyph ( Fig. 8A, B ) – a feature that is absent in both An. handi and P. singaporensis ; 2) a light coloured column with bright pink splotches, which differs from the consistently dull and darklycoloured columns of An. handi and P. singaporensis ( England 1987; Fautin et al. 2009; Fautin and Tan 2016); and 3) differing ecology, as M. fautinae sp. nov. does not burrow deeply into the substratum with its column completely buried as P. singaporensis does ( England 1987; Fautin and Tan 2016); nor, does it occur in dense clusters like An. handi , ( Dunn 1978; Fautin et al. 2009) but rather often occurs singly. For these reasons, M. fautinae sp. nov. cannot be confused for the other two species.

Figures

Fig. 2. Type material of Condylactis aspera Haddon and Shackleton, 1893. A, lectotype of C. aspera (MZC I.33665), in three pieces, top view. Note the gastro-cavity of specimen is filled densely with gametogenic tissue. B, Paralectotypes of C. aspera, as three histological slides at MZL (no catalogue number). Abbreviations: gt, gametogenic tissue; m, mesenteries; o, oral disc; s, siphonoglyph; t, tentacle. Scale bar = 10 mm.

Fig. 3. Living individuals of Macrodactyla aspera, external morphology. A, B, expanded individuals extending from the substratum, in situ, top view. Note splotchy brown patterns on oral disc and tentacles in both A and B, and partially everted actinopharynx resembling thick lips in B. Photographs by KS Loh. C, a live collected specimen (ZRC.CNI.1099), side view. Note reddish-orange column and adhesive, conspicuous verrucae, with grains of substratum attached to it. D, a partially retracted specimen (ZRC.CNI.1099), top view. Note that individual does not completely retract its tentacles; note also the presence of marginal projections.Abbreviations: mp, marginal projections; v, verrucae. Scale bars = 10 mm.

Fig. 4. Close-up appearance of tentacles and distal most column of Macrodactyla aspera, external view.A, extended tentacles of a live specimen (ZRC. CNI.1080), covered densely with nematocyst batteries. B, tentacles of a fixed specimen (i.e., lectotype, MZC.I.33665). Note the overall stout, conical shape of tentacles once fixed, and the bumpy texture for each of them, indicating the presence of nematocyst batteries. C, marginal projections and adhesive verrucae of a live individual (ZRC.CNI.1080). D, marginal projections and adhesive verrucae of a fixed specimen (SMNHTAU-Co.7813). Note how the shallow fosse had inflated. Also note how the grains of substratum remained attached to the specimen, when it was collected by L Fishelson in 1968. Abbreviations: f, fosse; mp, marginal projections; nb, nematocyst batteries; v, verrucae. Scale bars = 10 mm.

Fig. 5. Macrodactyla aspera, internal morphology. A, mesenteries of the lectotype (MZC.I.3365), cross section at mid-column. Note the diffuse circumscribed appearance of the retractor muscles, and presence of the retractor pennon. B, transverse section of the distal most end of column (SMNHTAU-Co.7813). Note the presence of a conspicuous, restricted marginal sphincter muscle and the presence of both oral and marginal stomata. C, everted actinopharynx of a live specimen (ZRC.CNI.1090). Note its pinkish appearance, and the presence of a diametric pair of siphonoglyphs. Abbreviations: a, actinopharynx; mf, mesenterial filaments; ms, marginal stomata; o, oocytes; os, oral stomata; p, pennon; s, siphonoglyph; sph, marginal sphincter muscle. Scale bars = 5 mm.

Fig. 6. Cnidae of Macrodactyla aspera. A, spirocyst. B, small basitrich. C, basitrich. D, large basitrich. E, small basitrich. F, basitrich. G, small basitrich. H, basitrich. I, small basitrich. J, large basitrich. K, wide basitrich. L, small basitrich. M, large basitrich. N, wide basitrich. O, microbasic p-mastigophore. Scale bar = 10 µm. Refer to table 2 for key to letters.

Fig. 1. Phylogeny reconstruction of Macrodactyla aspera and Macrodactyla fautinae sp. nov. among actiniid sea anemones. Tree topology a result of maximum likelihood (ML) analysis, using a concatenated dataset (i.e., cox3, 12S, 16S, 28S). At the branches, bootstrap ML resampling values, and Bayesian inference (BI) posterior probability values, are presented as ML/BI. Only bootstrap values> 50, and posterior probability> 0.8 are indicated here; those less than 50 and 0.8 are denoted by (-). Taxa indicated in bold denotes the presence of new sequences obtained for this study. Indicated by an asterisk (*), we retain the name Macrodactyla doreensis in this figure to aid with the discussion within the main-text. For sequences used and the full tree, refer to table S1 and figure S3, respectively.

Fig. 10. Macrodactyla fautinae sp. nov., internal morphology. A, diffuse-circumscript mesenteries of an individual (ZRC.CNI.0296), cross section at mid-column. Note the presence of the retractor pennon. B, a conspicuous, circumscribed marginal sphincter muscle of another individual (ZRC.CNI.0255). Abbreviations: f, fosse; mf, mesenterial filaments; p, pennon; sph, marginal sphincter muscle; t, tentacles. Scale bars = 1 mm.

Fig. 11. Cnidae of Macrodactyla fautinae sp. nov. A, spirocyst. B, large spirocyst. C, basitrich. D, large basitrich. E, basitrich. F, basitrich. G, basitrich. H, microbasic p-mastigophore. I, small basitrich. J, microbasic p-mastigophore. K, large basitrich. Scale bar = 10 µm. Refer to table 3 for key to letters.

Fig. 7. Holotype of Macrodactyla fautinae sp. nov. (ZRC.CNI.1300). Abbreviations: a, actinopharynx; m, mesenterial filaments; mp, marginal projections; pd, pedal disc; s, siphonoglyph; sph, sphincter muscle; t, tentacles; v, verrucae.

Fig. 8. Living individuals of Macrodactyla fautinae sp. nov., external morphology, in situ, top view.A, an expanded individual with a pale oral disc. B, another expanded colour morph with a dark-brown oral disc. Note that in both A and B, a pair of diametric bright pink dots marks the position of the siphonoglyphs. C, a contracted individual with adhesive, papillae-like verrucae at its distal end. Note that shell fragments are attached to the verrucae. D, an individual with much of its actinopharynx everted, obscuring the animal. E, a sea pen (Pteroeides sp.) being swallowed whole by a M. fautinae sp. nov. individual. Abbreviation: s, siphonoglyph; v, verrucae. Photographs by R Tan.

Fig. 9. Column appearance of Macrodactyla fautinae sp. nov., external morphology, side view. A, a freshly collected individual that is slightly contracted (ZRC.CNI.0648). Note the pale pinkish column and the presence of splotchy dark pink patches from mid-column to the proximal end. Note also that the mesenterial insertions are not visible when the anemone is in a contracted stated. B, a live individual (ZRC.CNI.1159) with a column that is expanded, with mesenterial insertions that extend the entire column visible as light lines. Note also the extended papillae-like verrucae. C, close-up of the marginal projections and verrucae at the distal end of a live individual (ZRC.CNI.1159). Note that marginal projections are perforated, and a pink dot marks the middle of each verruca. Abbreviations: mi, mesenterial insertions; mp, marginal projections; v, verrucae. Scale bars = 10 mm.