Hamopontonia nhatrangensis, Marin, Ivan, 2014

Marin, Ivan, 2014, A new species of the pontoniine shrimp genus Hamopontonia Bruce, 1970 associated with caryophyllid coral Euphyllia glabrescens (Chamisso & Eysenhardt 1821) in Nhatrang Bay, Vietnam, Zootaxa 3815 (1), pp. 131-140 : 132-139

Hamopontonia nhatrangensis sp. nov.

( Figs. 1–4 , 5 d–f)

Hamopontonia fungicola .— Marin, 2012a: 348 , Pl. 53C, D.

Material examined. Holotype, ovigerous female—Pacific Ocean, South China Sea, Vietnam, Nhatrang Bay, south-east part of Tre Island, 12°11’26.15” N 109°19′51.99″E, on coral Euphyllia glabrescens , depth 7 meters, collected by I. Marin, SCUBA, 22 March 2014 ( ZMMU). Paratypes: Pacific Ocean, South China Sea, Vietnam, Nhatrang Bay—1 ovigerous female, 1 male—Mun Island, south-eastern bay, on coral Euphyllia glabrescens , depth 10 meters, collected by I. Marin, SCUBA, 15 November 2010 ( LEMMI); 1 ovigerous female, 1 male—Mun Island, north side, on coral Euphyllia glabrescens , depth 5 meters, collected by I. Marin, SCUBA, 15 October 2012 ( LEMMI); 1 ovigerous female—same locality, 21 October 2012 ( LEMMI); 1 ovigerous female, 1 male—Tre Island, south-east side, Light house, on coral Euphyllia glabrescens , depth 12 meters, collected by I. Marin, SCUBA, 0 3 April 2013 ( LEMMI); 1 ovigerous female, 1 male—Tre Island, south-east part near Dam Bay, on coral Euphyllia glabrescens , depth 8 meters, collected by I. Marin, SCUBA, 25 March 2014 ( LEMMI).

Description. Medium-sized pontoniine shrimp with cylindrical slightly depressed body. Carapace swollen in medial part, smooth, with large antennal tooth, without hepatic or supraorbital teeth ( Figs. 2 a – d). Rostrum compressed, pointing distally, straight, reaching to distal margin of basal antennular segment; rostral formula 1 – 3+4 – 5/0 ( Fig. 2 a – c); dorsal rostral carina well developed, reaching to 1/3 of carapace length, with well marked small dorsal teeth; ventral rostral carina poorly developed, unarmed; proximal lateral rostral lamina feebly developed ( Fig. 2 a, b, d). Orbit well developed, deep, unarmed; inferior orbital angle bluntly produced distally. Pterygostomial angle produced, bluntly rounded distally.

Abdominal somites smooth; pleura of abdominal somites I–V rounded ( Fig. 1 ). Telson ( Fig. 2 g, h) relatively stout, about 3 times as long as proximal width, narrow distally, distal margin of telson armed with two hook-like projections (teeth) turned downward ( Fig. 2 i) and distinct notch medially ( Fig. 2 g), with 3 pairs of medium dorsal submarginal spines at 0.6, 0.8 and 0.95 of telson length, with paired most distal tiny dorsal spines in some specimen ( Fig. 2 i).

Eyes well developed, large; eyestalk smooth, cylindrical, about 1.5 times as long as wide; cornea well developed, medium, subovate ( Fig. 2 a – d).

Antennula ( Fig. 2 e) well developed; basal segment stout, about 1.8 times longer than wide, with well developed slender acute stylocerite, with distolateral angle bearing large acute triangular tooth and small rounded medial projection; ventromesial tooth small; intermediate segment stout, about as long as wide; distal segment stout, as long as wide, equal to previous segment; proximal part of upper antennular flagellum with 8–9 separate segments, shorter ramus with more than 15 segments; about 9 or 10 groups of aesthetascs present.

Antenna ( Fig. 2 f) well developed, basicerite about 1.5 times longer than wide, smooth, without distoventral tooth; scaphocerite wide, about 1.5 times longer than maximal width, overreaching the distal margin of antennular peduncle ( Fig. 2 d), distolateral tooth well developed, acute, small, not reaching to distal margin of blade.

Mouthparts characteristic for the genus and previously described species. Maxilliped III with slender unarmed segments; ischiomeral segment about 5 times longer than wide; antepenultimate segment about 3 times longer than wide; penultimate segment tapering distally, about 2.5 times longer than wide.

Pereiopod I ( Fig. 3 a) with relatively slender unarmed segments, without specific features; coxal segment as long as wide, with distoventral lobe; basis as long as wide; ischium about twice longer than wide; merus slender, about 4.5 times as long as wide; carpus about 6 times as long as wide, subequal to merus; propodus about 3 times longer than wide, cylindrical, slightly flaring distally, fingers simple and slender, about 4 times as long as wide, with straight, smooth cutting margins and simple tips.

Pereiopods II similar in shape and dissimilar in size ( Figs. 1 , 3 b, d); with robust and smooth segments; coxal segment as long as wide, with small distoventral lobe; basis as long as wide; ischium about 3 – 4 times longer than wide; merus robust, about 3.5 – 4 times longer than wide, with straight lateral margins; carpus triangular in shape, stout, flaring distally, slightly overlapping carpo-propodal articulation, with smooth distal margin ( Fig. 3 c, e); palm ( Fig. 3 c, e) smooth, cylindrical, about 3.5 – 4 times as long as wide, slightly narrowing medially; fingers relatively slender, about twice shorter than palm, about 3 times as long as wide; fixed finger (pollex) compressed, about 3 times longer than wide, with two medial teeth situated in proximal 1/3 of length, with simple sharp curved tip, with small medial depression opposite to tooth on movable finger; movable finger (dactylus) slender, compressed, with large tooth situated in proximal 1/3 of cutting margin, with simple curved tip.

Pereiopod III ( Fig. 3 f) with smooth slender unarmed segments; coxal segment as long as wide, unarmed; basis as long as wide; ischium robust, about twice longer than wide; merus slender, about 4 times as long as wide; carpus about twice longer than wide, about half shorter than propodus and merus; propodus relatively stout, about 4.5–5 times as long as proximal its width, with smooth unarmed parallel margins, without ventral or distoventral teeth ( Fig. 3 g); dactylus ( Fig. 3 g) simple, with basal part about 1.5 times as long as wide, with simple slender and curved unguis. Pereiopods III–V similar.

Pleopods normal, without specific features. Uropods slender, not exceeding telson; distolateral margin of uropodal exopod ( Fig. 2 j) with small movable distolateral spine, fixed tooth absent.

Males morphologically similar to females, but smaller in size, with more developed strongly dissimilar pereiopods II ( Fig. 1 , 2 c).

Measurements. Medium-sized pontoniine shrimp. The largest studied ovigerous female has pcl. 21 mm, tl. 35 mm; the largest studied male has pcl. 18 mm, tl. 28 mm.

Coloration. Coloration of the new species clearly imitates the coloration of tentacles of host coral Euphyllia glabrescens (Chamisso & Eysenhardt, 1821) (Hexacorallia, Scleractinia , Caryophyllidae ( Fig. 5 d–f).

Females. Body and appendages generally transparent, covered with tiny red dots; cornea black, eyestalk transparent, covered with tiny dots; almost all dorsal surface of carapace and dorsal half of its lateral margins covered with uniformly white or white-pinky patch; dorsal surface and dorsal half of pleurae of abdominal somite II with large semicircular white-pinky patch, dorsal surface and dorsal half of pleurae of abdominal somite III with large circular white-pinky patch, dorsal surface of abdominal somite V mostly covered with small semicircular or oval white-pinky spot, sometimes this spot absent, especially in smaller specimens ( Fig. 4 ).

Males. General coloration similar to females, with less number of dorsal patches. Body and appendages transparent, covered with tiny red dots; cornea black, eyestalk transparent, covered with tiny dots; dorsal surface of carapace covered with medium uniformly white or white-pinky patch; with uniformly white or white-pinky oval dorsal patch on abdominal somite III ( Fig. 4 ).

Host. The species was found in association with the caryophyllid coral Euphyllia glabrescens (Chamisso & Eysenhardt, 1821) . The coral-associated pontoniine shrimp Vir euphyllius Marin & Anker, 2005 (Crustacea, Decapoda , Palaemonidae , Pontoniinae ) is the other pontoniine species living on colonies of E. glabrescens in Nhatrang Bay, Vietnam (Marin & Anker, 2005; Marin, 2007a). At the same time, both species have been never observed on the same coral colony, possibly showing a competitive pair of pontoniine shrimp species (see remarks of similar competitive pair Philarius condi Marin, 2012 — Harpilius consobrinus De Man, 1902 (Marin, 2012b)).

Distribution. The species is presently known exclusively from its type locality, Nhatrang Bay, Vietnam.

Differential diagnosis. The new species can be easily differentiated from congeners by specific coloration and occupied host (following Bruce, 1986; Marin, 2012a).

Moreover, Hamopontonia nhatrangensis sp. nov. can be separated:

- from H. essingtoni by absence of specific blunt median process between hook-like distolateral processes on

telson.

- from H. corallicola by swollen carapace, more slender and shorter rostrum, shorter dorsal spines on telson and

stouter segments of ambulatory pereiopods, especially propodus.

- from H. physogyra by slender rostrum, shorter dorsal spines on telson and stouter ambulatory pereiopods

without distoventral spines.

- rom H. fungicola by shorter rostrum, shorter dorsal spines on telson, smaller and dissimilar in size pereiopods

II and stouter ambulatory pereiopods.

The new species is morphologically most similar to H. physogyra and H. fungicola , resembling them in coloration (see Marin, 2012a). At the same time, the coloration of the new species clearly differs from H. physogy by being generally translucent with tiny small dots on the body and appendages as well as having uniformly white or pinky-white colored dorsal patches on carapace and abdomen (vs. body and appendages covered with numerous white and blue dots as well as dorsal patches consisting of white spots in the centre of the patch fringed with broad white or creamy band in H. physogyra (see Marin, 2012a: 55, fig. 13)). The new species also can be clearly separated by coloration from H. fungicola by having smaller dorsal spots on the carapace, not covering almost all dorsal surface, as well as a different pattern and smaller dorsal spots on abdominal somites II and III not almost covering the abdominal pleurae (see Marin, 2012a: fig. 7; present paper, fig. 4).

Renewed key to the species of the genus Hamopontonia Bruce, 1970 (after Marin, 2012a)

1. Distal margin of telson with small blunt median process between hook-like distolateral processes. Small species; with translucent body and appendages covered with numerous tiny red dots. Without large bright colored spots or patches on dorsal surface of carapace and abdominal somites. Associated with Stylophora pistillata (Pocilloporidae) ....... H. essingtoni Bruce, 1986

- Distal margin of telson without blunt median process between hook-like distolateral processes. Large bright colored spots or patches present on dorsal surface of carapace and abdomen.................................................... 2

2. Pereiopods II large, longer than carapace length, equal in size. Almost all dorsal and lateral surface of carapace and pleura of abdominal somites II–III covered with large white or creamy colored patches. Associated with fungiid corals, mainly with Heliofungia actiniformis (Fungidae) .................................................. H. fungicola Marin, 2012

- Pereiopods II equal or smaller than carapace length, unequal in size. Carapace and abdominal somites with only dorsal and upper half of lateral margin covered with brightly colored patches............................................... 3

3. Rostrum relatively short, reaching to distal margin of basal antennular segment. Associated with Euphyllia glabrescens (Euphyllidae) .................................................................... H. nhatrangensis sp. nov.

- Rostrum long, significantly overreaching the distal margin of basal antennular segment reaching to distal margin of antennula peduncle........................................................................................... 4

4. Rostrum with well developed deep dorsal carina. Single large dorsal circle patch presents on dorsal surface of abdominal somite III. Associated with caryophyllid coral Physogyra lichtensteini ( Caryophyllidae )................... H. physogyra

- Rostrum with shallow dorsal carina. Dorsal surface of abdominal somites I–IV covered with brightly colored patches. Associated with poritid coral Goniopora spp ( Poritidae )................................................. H. corallicola

Remarks. The Torch coral Euphyllia glabrescens belongs to the family Euphyllidae , not the Fungiidae , but the colonies of E. glabrescens and Heliofungia actiniformis (Quoy & Gaimard, 1833) (Hexacorallia, Scleractinia , Fungidae) are greatly similar (see Fig. 5 a–c; Veron, 2000). The coloration of the tentacles of E. glabrescens bears a striking resemblance to the coloration of tentacles of H. actiniformis . At the same time, a multi-year survey (2005–2014 years) of coral reef communities in Nhatrang Bay revealed the absence of Heliofungia actiniformis in the Bay and adjacent localitites ( Latypov, 2006; Yu. Latypov, I. Marin, pers. observ.) as well as two specialized associated pontoniine shrimp species, H. fungicola and Cuapetes kororensis (Bruce, 1977) , specific to H. actiniformis , have never been observed in the Bay.

This record increase the number of scleractinian coral-associated pontoniine shrimp species known from Nhatrang Bay, Vietnam up to 31, while H. fungicola should be excluded from the list (Marin & Anker, 2005; Marin, 2007b, 2008; reviews in Marin & Savinkin, 2007 and Marin, 2013).

Figures

FIGURE 1. Hamopontonia nhatrangensis sp. nov.: a — ovigerous female; b — mature male.

FIGURE 2. Hamopontonia nhatrangensis sp. nov., ovigerous female (a, b, d – j), male (c): a – c – carapace, lateral view; d — carapace, dorsal view; e — antennula; f — antenna; g—sixth abdominal somite, telson and uropods, dorsal view; h — same, lateral view; i — distal margin of telson, lateral view; j — distolateral margin of uropodal exopod.

FIGURE 3. Hamopontonia nhatrangensis sp. nov., ovigerous female: a — pereiopod I; b — major pereiopod II; c — same, chela; d — minor pereiopod II; e — same, chela; f — pereiopod III; g — same, distal part of propodus and dactylus.

FIGURE 4. Coloration of Hamopontonia nhatrangensis sp. nov.: a — holotype, ovigerous female, dorsal view; b — ovigerous female, dorsal view; c—same specimen, lateral view; d — mature male, lateral view; e — same specimen, dorsal view; h — same specimens among tentacles of its host, f — different ovigerous females, dorsal and lateral views (g, h represent the same specimen).

FIGURE 5. Coral host Euphyllia glabrescens and Hamopontonia nhatrangensis sp. nov.: a, c — whole colony of host coral Euphyllia glabrescens; b — part of colony with ovigerous female H. nhatrangensis sp. nov. (arrow) in situ; d – f — ovigerous female of Hamopontonia nhatrangensis sp. nov. in natural habitat—among tentacles of coral host E. glabrescens.