Metapontonia fungiacola Bruce, 1967

Ďuriš, Zdeněk & Lin, Chia-Wei, 2016, The ‘ scorpion shrimp’, a new species of the genus Metapontonia (Crustacea: Decapoda: Palaemonidae) from Taiwan, with new generic record from Papua New Guinea, Zootaxa 4138 (3), pp. 474-490 : 485-489

Metapontonia fungiacola Bruce, 1967

( Figs 8–10 )

Metapontonia fungiacola Bruce, 1967: 24 , figs 10–12.

Metapontonia fungiacola . — Bruce, 1972: 1, fig. 1, Pls 1–2.—1974 b: 196, fig. 5.—1985: 8, fig. 6.— Yamashiro, 1999: 307– 311, fig. 1.

Material examined. Taiwan, Pingtung County, coll. C.-W. Lin:— 1 female ovig. PoCL 2.7 mm (NMMBCD 4050), Hojie, 21º 57’ 20.4" N, 120º 42’ 41.4" E, 15 May 2011, depth 17 m, from coral Symphyllia cf. radians (u/w photo), fcn 20110515-15 (lab. photo). — 1 female post-ovig. PoCL 3.8 mm (NMMBCD 4051), Hojie (as above), 5 Apr. 2013, depth 16 m, from lobophylliid coral (u/w photo), fcn 20130405-04 (lab. photo). — 2 females PoCL 2.7 mm (ovig.), 2.4 mm (NMMBCD 4052), Hojie (as above), 19 Apr. 2013, depth 16 m, from unknown coral, fcn 20130419-10 (lab. photo).—2 spms: 1 male PoCL 2.4 mm, 1 female ovig. PoCL 3.7 mm (NMMBCD 4054), Hojie (as above), 15 Jun. 2013, depth 14m, from lobophyllid coral (u/w photo), fcn 20130615-06 (lab. photo).— 1 female ovig. PoCL 3.8 mm (NMMBCD 4055), Hojie (as above), 11 Dec. 2013, depth 12 m, from unknown coral, fcn. 20131211-14 (lab. photo).— 1 female ovig. PoCL 2.6 mm (NMMBCD 4056), Hojie (as above), 16 Dec. 2013, depth 16 m, from unknown coral, fcn 20131216-11 (lab. photo).— 1 female ovig. PoCL 3.6 mm (bopyrized in branchial chamber) (NMMBCD 4057), Hojie (as above), 23 Feb. 2014, depth 15 m, from unknown coral, fcn 20140223-10 (lab. photo).— 2 females ovig. PoCL 2.6, 2.8 mm (NMMBCD 4058), Green Island, 22º 39’ 08.0" N, 121º 28’ 22.4" E, 10 Apr. 2014, depth 15 m, from coral cf. Micromusa, fcn 20140410-nn.— 1 female PoCL 2.6 mm (bopyrized in branchial chamber) (NMMBCD 4059), Wanlitong, 21º 59’ 46.7" N, 120º 42’ 02.5" E, 5 Sep. 2014, depth 22 m, from unknown coral, fcn 20140905-11 (lab. photo).— 1 male PoCL 2.3 mm (bopyrized in branchial chamber) (NMMBCD 4060), Hojie (as above), 26 Sep. 2014, depth 18 m, from unknown coral, fcn 20140926-32 (lab. photo).— 1 female post-ovig. PoCL 2.8 mm (NMMBCD 4061), Sanjiaoding, 21º 57’ 17.6" N, 120º 45’ 53.5" E, 1 Nov. 2014, depth 19 m, from coral Platygyra lamellina , fcn 20141101.30 (lab. photo).— 1 female post-ovig. PoCL 3.0 mm (NMMBCD 4062), Siaoliouciou, 22º 20′ 41.3" N, 120º 23’19.0" E, 17 Nov. 2014, depth 8 m, from unknown coral, fcn 20141117-nn.— 1 female PoCL 2.6 mm (NMMBCD 4063), Hojie (as above), 1 Jan. 2015, depth 16 m, from unknown coral, fcn 20150101.nn.— 1 female post-ovig. PoCL 3.0 mm (NMMBCD 4064), Hojie (as above), 1 Aug. 2015, depth 14 m, from coral Lobophyllia hemprichii (u/w photo), fcn 20150801.07 (lab. photo).

— Japan: 1 spm, NTOU [GenBank: KX169192 , KX245152 ], KUMEJIMA 2009 Expedition, 26º 20.409– 20.018′ N 126º 49.675–49.224′ E, 5.1– 4.5 m, dead coral branches, rubble, dredge 52, 17 Nov. 2009.

— Papua New Guinea: 1 female ov. PoCL 1.3 mm, MNHN IU- 2013-11055 [GenBank: KX245153 ], Papua- Niugini Expedition 2012, st. PR 225, N. Kranket Is., Madang Bay, 05º 11,3'S - 145º49,5'E, 10 Dec. 2012, depth 6- 7.5 m, from coral Galaxea sp., coll.: Z. Ďuriš, fcn PNG 12-639D (lab. photo).

Remarks. As Bruce (1972) suggested, M. fungiacola appears to be one of the smallest palaemonid shrimpsthe holotype has PoCL 2.6 mm ( Bruce, 1967), with the total length (TL) at least 8 mm, estimated from the original picture ( Bruce, 1967: Fig.10 ), and the smallest and largest reported ovigerous females reaching 1.55 and 1.7 mm of PoCL ( Bruce, 1972, 1974, resp.); the length of the Japanese specimens examined by Yamashiro (1999) was about 5 mm. In regard of the present material, the ovigerous females from Taiwan range from 2.6 to 3.8 mm in their PoCL, with the largest ones measured 13.5 mm of the total body length. The only two available males are distinctly smaller, with their PoCL 2.3 and 2.4 mm.

Most of the 17 Taiwanese specimens examined, especially larger and more brightly coloured adult females, thus seem to be considerably larger and more diverse in coloration than the previously reported specimens. They also show a remarkable variability in the shape of the rostrum (slender—styliform or stout—blade-like, horizontal or upturned), or orbits (entire or sinuate posteriorly), in the anteroventral extension of the branchiostegites (not reaching or overreaching anteriorly extended eyes), and in the size and symmetry of the second pereiopods (subequal or distinctly unequal chelae; small chelae with subparallel fingers or large robust chelae with widely gaping space between fingers). The comparative morphological analysis performed by us for females (expressed in the Fig. 8 ) revealed a total mixture of those characters with no one of them related to the body size, nor mutually correlated to each other. Those distinctions thus illustrate the intraspecific morphological variation of M. fungiacola .

The only specimen from Papua New Guinea available ( Fig. 9 F,G), an ovigerous female, is, with its PoCL 1.3 mm and TL 5.0 mm, the smallest ovigerous female of the species reported. The specimen has a well developed anteriad-directed rostrum and the rectangular median tooth anteriorly on the carapace, the orbital margin well developed, entire, the branchiostegite not considerably produced, failing to reach the distal end of the anteriorly extended eyes, and a pair of second pereiopods with small similar but unequal chelae. The female bears about 10 early-stage ova 0.67 mm long under its pleon. Except the size, the PNG specimen thus well falls to the intraspecific variability demonstrated above for Taiwanese specimens. The molecular comparison of obtained COI gene sequences for both examined PNG and Japanese specimens revealed their high genetic identity (distinction 3 of 508 bp, i.e. 0.6%) that confirms their conspecific status.

Colour ( Fig. 9 ). Bruce (1972) described the appearance of his Kenyan female of M. fungiacola as yellowgreen, feebly speckled with pale yellowish chromatophores and with the post-orbital region with a larger transverse patch of white across the gastric region, and the males more highly transparent. The present specimens of M. fungiacola from Taiwan ( Fig. 9 A-E) are semitranslucent, whitish, with white anterolateral and anterior borders of the gastric region and a diffusely or more densely white banded pleon. Ovigerous females have their orange ovaries visible as extending to the middle of the pleon. The cornea of the eyes are white or reddish. The ovigerous female from Papua New Guinea ( Fig. 9 F,G) is also semitranslucent whitish with scattered red dots medially on the carapace and pleon, with feeble white gastric borders, and a line of some reddish spots laterally on the abdomen; an orange tinge from the ovaries is visible on the carapace and pleon; eyes’ cornea are white.

Behaviour. As noted above for the new species, M. fungiacola also frequently holds the pleon in an elevated position ( Bruce, 1972). This species was reported by Yamashiro (1999) in regards to its masking behaviour observed on the mushroom corals ( Scleractinia , Fungiidae ) where the shrimp hides itself under fold of host tissue. For this behaviour, the shrimp possesses sharp hooked dactylus on the dorsad twisted last three pereiopods. A similar behaviour, dorsad upturned walking legs, and hooked dactyli, are known for shrimps of another symbiotic palaemonid genus Pliopontonia Bruce, 1973 ( Bruce, 1973; Okuno, 2009). Such positioned walking legs are present also in M. scorpio n. sp.

Hosts ( Fig. 10 ). Scleractinia , Fungiidae : Fungia spp., Lithophyllon concinna (Verrill) , L. repanda (Dana) , Halomitra pileus (Linnaeus) , Herpolitha limax (Houttuyn) ; Merulinidae : Goniastrea pectinata (Ehrenberg) , Hydnophora microconos (Lamarck) ( Bruce, 1967, 1972, 1974a, b, 1975, 1984, 1985; Yamashiro, 1999; Hoeksema et al., 2012). The present specimens from Taiwan were collected from scleractinian corals—Merulinidae: Platygyra lamellina (Ehrenberg) ; Lobophylliidae : Lobophyllia hemprichii (Ehrenberg) , cf. Micromusa sp., Symphyllia cf. radians Milne Edwards & Haime , and unidentified lobophyllid corals. The single PNG specimen was found by dissecting a colony of the scleractinian coral Galaxea sp. ( Scleractinia : Oculinidae ). All those corals are new host records for the shrimp M. fungiacola .

Distribution. Comoro Archipelago ( Bruce, 1967), western Indian Ocean. The species is actually known also from Kenya, Tanzania, Réunion, Seychelles, and Okinawa, Japan ( Bruce, 1995); New Caledonia ( Chan & Mitsuhashi, 2007); southern Taiwan, and Kavieng lagoon, Papua New Guinea (present report, new records).

GenBank accession numbers. KX169192 ; KX245152 ; KX245153 (see Material paragraph, above).

Figures

FIGURE 8. Comparison of size and shape of anterior carapace, lateral, and second pereiopod chelae (outer faces) of selected adult females of Metapontonia fungiacola Bruce, 1967 from Papua New Guinea (A) and Taiwan (B – I). A, ovig. female 1.3 mm (MNHN). B, female 2.6 mm (NMMBCD 4059). C, ovig. female 2.6 mm (NMMBCD 4058). D, ovig. female 2.7 mm (NMMBCD 4050). E, ovig. female 2.7 mm (NMMBCD 4052). F, ovig. female 2.8 mm (NMMBCD 4061). G, ovig. female 3.6 mm (NMMBCD 4057). H, post-ovigerous female 3.8 mm (NMMBCD 4051). I, ovig. female 3.8 mm (NMMBCD 4055). Sizes in mm refer to PoCL. Scale bar— 1 mm.

FIGURE 9. Colour pattern of Metapontonia fungiacola Bruce, 1967 specimens from Taiwan (A – E) and Papua New Guinea (F, G). A, post-ovigerous female 3.8 mm (NMMBCD 4055). B, ovig. female 3.7 mm (NMMBCD 4054). C, female 3.8 mm (NMMBCD 4064). D, female 2.6 mm (NMMBCD 4059), dorsolateral aspect. E, male 2.3 mm (NMMBCD 4060), bopyrized in left branchial chamber. F – G, ovig. female 1.3 mm (MNHN), same specimen, lateral and dorsal view. Sizes in mm refer to PoCL. Scale bar— 1 mm. Photos: A – E, C. - W. Lin, F – G, Z. Ďuriš.

FIGURE 10. Taiwanese specimens of Metapontonia fungiacola Bruce, 1967 on their scleractinian coral hosts: A, Symphyllia cf. radians (Lobophylliidae), Hojie, 15 May 2011. B, Platygyra lamellina (Merulinidae), Sanjiaoding, 1 Nov. 2014. C, (?) Lobophyllia / Symphyllia (Lobophylliidae), Hojie, 5 Apr. 2013. D – F, Lobophyllia hemprichii (Lobophylliidae), Hojie (D, E, 1 Aug. 2015. F, 15 Jun. 2013). G, cf. Micromussa (Lobophylliidae), Green Island, 10 Apr. 2014. Photos: C. - W. Lin.