Pavona giannii, Benzoni, 2025

Benzoni, Francesca, 2025, A new reef-dwelling coral, Pavona giannii sp. nov. (Scleractinia, Agariciidae), with an overview of the skeletal morphology of the type specimens of the genus Pavona, ZooKeys 1260, pp. 123-147 : 123-147

Pavona giannii sp. nov.

Figs 2 , 3 , , 5 , 6 , 7

Type locality.

Yemen: Shabwa Province, Bir Ali, Hyllanyia Island, 13°59.183'N, 48°19.137'E; depth 5 m; 11 November 2008, F. Benzoni leg.

Type material.

Holotype • 1 colony fragment (10.5 x 5.1 cm, Fig. 2 ); Original label: “ Bir Ali , Hyllanyia Island, Yemen; 13°59.183'N, 48°19.137'E; 11 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; collection code BA 034; MNHN -IK-2012-14233 ”.

Other material.

Djibouti • 1 colony fragment (Fig. 7 C , part of the colony in situ); Maskali Island ; 11°42.38'N, 43°9.24'E; 29 Feb. 2020; F. Benzoni leg.; Dolphin Cruise exped.; KAUST DJ 403 . Yemen • 1 colony fragment (Figs 3 A, H , 5 A, D, F, H – L ); Aden, Ras Antouk ; 12°45.085'N, 45°1.659'E; 8 Mar. 2009; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB AD 016 • 1 colony fragment (Fig. 6 A , whole colony in situ); Balhaf ; 13°58.402'N, 48°11.549'E; 22 Mar. 2014; F. Benzoni leg.; Creocean-Total Balhaf LNG Plant monitoring program exped.; UNIMIB BAL 252 • 1 colony fragment (Fig. 5 B, C, E, G ); Balhaf ; 13°58.413'N, 48°10.532'E; 24 Mar. 2014; F. Benzoni leg.; Creocean-Total Balhaf LNG Plant monitoring program exped.; UNIMIB BAL 253 • 1 colony fragment; Bir Ali ; 13°59.116'N, 48°15.372'E; 16 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BA 010 • 1 colony fragment; Bir Ali ; 13°59.094'N, 48°14.018'E; 16 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BA 017 • 2 colony fragments (Fig. 3 C ); Bir Ali ; 13°59.180'N, 48°15.692'E; 19 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BA 066 • 2 colony fragments (Fig. 6 G , colony in situ); Burum ; 14°19.266'N, 48°59.641'E; 18 Mar. 2009; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BU 049 • 2 colony fragments; Al Mukallah ; 14°30.923'N, 49°9.254'E; 17 Mar. 2007; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB MU 085 • 1 colony (Fig. 3 B ); Al Mukallah ; 14°30.696'N, 49°9.360'E; 18 Mar. 2007; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB MU 128 • 1 colony fragment (Figs 3 D , 6 C , colony in situ); Socotra Island, Hawlaf ; 12°40.662'N, 54°4.497'E; 14 Mar. 2010; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB SO 078 . Oman • 1 colony fragment (10 x 8 cm); Dhalkut ; 16°41.235'N, 53°11.749'E; depth 9.4 m; 4 Dec. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0895 ; UF 17903 • 2 colony fragments (Fig. 6 B , colony in situ); Mirbat, Eagles Bay ; 16°56.377'N, 054°47.799'E; depth 5.4 m; 9 Jan. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0096 ; UF 17957 • 1 colony fragment (Fig. 3 F ); Mirbat, Qinqari Bay ; 17°0.561'N, 55°1.240'E; depth 6 m; 12 Jan. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0226 ; UF 18088 • 1 colony fragment (Fig. 3 G ); Muscat, Jazirat Al Fahl ; 23°40.953'N, 58°30.011'E; depth 5.9 m; 1 Feb. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0722 ; UF 18089 • 1 colony fragment; Mirbat, Marriott Wreck ; 16°56.933'N, 054°43.686'E; depth 10.4 m; 7 Jan. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0017 ; UF 18090 . Mayotte • 3 colony fragments (Figs 3 E , 5 E , part of the colony in situ); Îlot Mtsamboro ; 12°38.031'S, 45°1.140'E; 1 Jun. 2010; F. Benzoni leg.; Tara Oceans exped.; UNIMIB MY 069 . Seychelles • 1 colony fragment; Mahé Island, Horse Shoe Reef ; 24 Feb. 2019; F. Benzoni and R. Arrigoni leg.; University of Seychelles Outer Islands coral collection facility exped.; UNISEY SY 079 • 1 colony fragment; same data as for preceding; UNISEY SY 080 • 1 colony; Mahé Island , Le Cap; 12 Jan. 1966; B. R. Rosen leg.; NHMUK 1981.3.5.425 • 1 colony; Mahé Island, Baie Ternay ; 28 Dec. 1965; B. R. Rosen leg.; NHMUK 1981.3.5.426 • 1 colony (Fig. 4 A, B ); Mahé Island, North East Point ; 22 Dec. 1965; B. R. Rosen leg.; NHMUK 1981.3.5.427 . Sri Lanka • 1 colony (Fig. 4 C, D ); Galle ; W. C. Ondaatje leg.; NHMUK 1883.3.24.4 • 1 colony; W. C. Ondaatje leg.; NHMUK 1883.5.23.8 . Malaysia • 1 colony (Fig. 4 E, F ); Pulau Songsong , West Coast, Peninsular Malaysia; C. Betterton leg.; NHMUK 1979.9.24.66 .

Description.

Colonial, corallum encrusting with attached margins, growing on the underlying substrate and broadly following its surface relief (Figs 2 – 4 , 6 , 7 ); maximum observed thickness 1 cm. Corallum surface smooth and devoid of ridges, crests, monticules or hydnophorae (Figs 2 B – D , 3 , 4 ). Corallites crowded, less than a corallite diameter apart, and thamnasteroid in arrangement (Figs 2 B – D , 3 , 4 , 5 A – F ). Budding intratentacular, locally leading to the formation of variably developed corallites series by repeated incomplete separation of walls after budding. Their outline is variable even within the same colony ranging from elliptical to kidney-shaped (Fig. 3 H ), polygonal (Fig. 3 F ) or irregular (Figs 2 C , 3 C ). Corallites 2.4 mm (± 0.1 SE) in average maximum diameter and 1.7 mm (± 0.1 SE) in average minimum diameter. On average, 23 septa (± 1 SE) occur per corallite (Table 1 ), the 6 S 1 reaching the columella, their inner margin fusing with it; their average length is 0.9 mm (Table 1 ). Septa arranged in three orders (Fig. 5 G, K, L ), those of the first and second (S 1 and S 2, respectively) sub-equal in thickness and length, all attaining the same height (Fig. 5 J – L ). S 2 may reach the columella or remain slightly shorter either with free margin or occasionally fusing with the columella more deeply in the fossa. Third order septa (S 3) are always present, almost complete. S 3 septa are less than ½ of S 1 and S 2 in length (Fig. 5 J, K ), never reaching the columella, and are thinner and shorter in height than S 1–2 (Fig. 5 L ). Septal sides of S 1 and S 2 ornamented with scattered blunt granules, S 3 sides smooth (Fig. 5 J – L ). Synapticulae connecting radial element lateral sides horizontally can be visible in less densely calcified specimens (Fig. 5 B, C, E ). S 1 and S 2 upper margins flush, flattened and running parallel to corallum surface giving it an overall even appearance (Figs 2 D , 5 C, F ). Where corallite series occur, radial elements run beyond the series shared wall to the adjacent series, perpendicularly to its axis (transparent pink dashed lines in Figs 2 C , 3 A – F, H , 5 A – C, J ). Above the shared wall, they are mostly parallel, their upper margin flattened and flush with the corallum surface (Fig. 5 C ). Viewed from above, the radial elements running over the adjacent corallite series shared wall resemble frets over a guitar fingerboard (Fig. 5 J ), their ladder-like arrangement identical to that usually observed over the ridges forming in other congeners ( Veron and Pichon 1980: figs 21, 24). Columella present, solid and made of a single blunt process its tip sitting lower than the upper septal margin (Fig. 5 D – I ). Maximum and minimum average columella diameter 0.5 and 0.2 mm, respectively (Table 1 ). Columella transverse section below the tip shape ranging from circular to elongated and dash-like in outline.

Typically, polyp tentacles are extended in the daytime; therefore, coenosarc, tentacle, oral disc, and mouth coloration is usually visible in situ. Living tissue surrounding the mouth orifice and the oral disc is white (Figs 6 D – G , 7 ) to light grey (Fig. 2 A ). Tentacles commonly white, giving colony surface a bearded appearance (Figs 2 A , 6 A – F , 7 ). Occasionally, tentacles can also be light green or brown (Fig. 6 A ), seldom brown (Fig. 7 C ). The coenosarc is typically brown (Figs 2 A , 6 A, C, D, F, G , 7 A, B ) to savora mustard yellow (Fig. 6 B, E ).

Etymology.

This species is named after Giambattista J. d. C. Benzoni, known as Gianni (1946-2024) for his unconditional support throughout my personal and professional life, and the graceful pride he took in being a coral taxonomist’s father.

Distribution and habitat.

Pavona giannii sp. nov. is a reef-dwelling species known from multiple localities north and south of the equator in the tropical Indian Ocean (Fig. 1 ). This species can be part of shallow water coral reef communities occurring in well-lit conditions between 1 and 15 m depth. It can encrust blocks of coral rubble, dead coral colonies or limestone, and can also grow on non-carbonate bedrock as observed in the Gulf of Aden and Arabian Sea. There, Pavona giannii sp. nov. seasonally withstands the low temperature and nutrient rich waters brought by the summer Arabian Sea upwelling ( Sheppard and Sheppard 1991). These recurrent conditions limit coral reef formation and select the scleractinian taxa able to withstand a pseudo-high latitude effect ( Benzoni et al. 2003, 2012).

Figures

Figure 1. Map showing the type (star) and other collection (circle) localities of Pavona giannii sp. nov. A. Collection localities in the SW Indian Ocean, and B. The seas around the Arabian Peninsula. 1 = Maskali Island, Djibouti; 2 = Aden, Yemen; 3 = Balhaf, Yemen; 4 = Hyllanyia Island, Bir Ali, Yemen; 5 = Burum, Yemen; 6 = Al Mukallah, Yemen; 7 = Hawlaf, Socotra Island, Yemen; 8 = Dhalkut, Oman; 9 = Mirbat, Oman; 10 = Qinqari Bay, Oman; 11 = Muscat, Oman; 12 = Mayotte Island; 13 = Mahé Island, Seychelles; 14 = Galle, Sri Lanka; 15 = Pulau Songsong, Malaysia. Scale bar: 200 km.

Figure 2. Holotype of Pavona giannii sp. nov. MNHN - IK- 2012-14233 A. the whole colony in situ at Hyllanyia Island, Bir Ali, Yemen, prior to sampling and B. corallum of the sampled fragment. C. Top view of the corallum showing corallite arrangement and the position of some of the corallite series boundaries (dashed pink lines) marked by the presence of parallel radial elements running over and across them, and D. side view showing its even surface given by equally high and flat top margins of S 1 and S 2 septa, and the deep-seated fossae. Scale bars: 1 cm (B); 5 mm (C, D).

Figure 3. Top views of the coralla showing corallite arrangement in the Pavona giannii sp. nov. specimens collected for this study: A. UNIMIB AD 016, from Aden, Yemen; B. UNIMIB MU 128, from Al Mukallah, Yemen; C. UNIMIB BA 066, from Bir Ali, Yemen; D. UNIMIB SO 078, from Socotra Island, Yemen; E. UNIMIB MY 069, from Mayotte Island; F. UF 18088 (collection code OM 226), from Mirbat, Oman; G. UF 18089 (collection code OM 722), from Muscat, Oman; H. Same specimen as in A. Dashed pink lines indicate the position of some of the corallite series boundaries marked by the presence of parallel radial elements running over and across them. Scale bars: 1 cm (A, B); 5 mm (C – H).

Figure 4. Corallum and corallite macro-morphology of the Natural History Museum (UK) specimens originally identified as Pavona explanulata and here re-identified as Pavona giannii sp. nov. from localities 13–15 in Figure 1. A. View of the whole corallum of specimen NHMUK 1981.3. 5.427 from Mahé Island, Seychelles, encrusting a large piece of coral rubble also colonized by other benthic organisms including crustose coralline algae (CCA) and benthic foraminifera; B. Detail of A showing corallite arrangement; C. Top view of specimen NHMUK 83.3.24.4 from Galle, Sri Lanka; D. Detail of the corallum surface of the specimen in C; E. Top view of specimen NHMUK 1979.9. 24.66 from Pulau Songsong, Malaysia, encrusting a block of coral rubble also overgrown by CCA (bottom right); F. Closer view of the same specimen in E. Scale bars: 1 cm (A – E); 5 mm (F).

Figure 5. Scanning Electron Microscopy of the skeletal micromorphology of Pavona giannii sp. nov. A. Top view of a well-calcified specimen showing crowded corallite arrangement and thick radial elements masking the underlying skeletal structures. B. Same view in a less calcified specimen showing thinner radial elements connected by visible synapticulae and a corallite series at the top left corner (the position of the series boundary marked by the dashed pink line). C. Side view of B showing the flattened corallum surface and the flush top margins of the S 1–2 radial elements. D. Closeup of one of the corallites of the specimen in A. E. Closeup of the corallites of the specimen in B. F. Side view of the specimen in A showing the flattened and flush top margins of the S 1–2 going from one corallite center to the adjacent ones. G. Top view of a corallite where the three radial elements orders (S 1> S 2> S 3) are indicated by the arrows. H. Side view of a laterally flattened columella sitting deep in a corallite fossa. I. Inner septal margins fusing with the columella. J. Top view of the parallel radial elements running over the synapticular corallite walls, perpendicularly to the series boundary direction (pink dashed line), the thicker S 1–2 are indicated by the transparent yellow arrows and the thinner S 3 by the transparent turquoise arrows. K. Close up of J showing the difference in lateral side ornamentation between the thicker S 1–2 and the thinner S 3. L. Side view of the radial elements in K showing the difference in height between the taller S 1–2 and the shorter S 3. A, F, H, I – L = UNIMIB AD 016; B, C, E, G = UNIMIB BAL 253. Scale bars: 1 mm (A – F); 500 mm (G, H, J); 200 mm (I, K, L).

Figure 6. Pavona giannii sp. nov. in situ. A. Typically white extended tentacles in the colony, from which specimen UNIMIB BAL 252 was collected, encrusting a submassive Porites (living portion at the top right-hand side) at Balhaf, Yemen; B. Colony of UF 17957, Mirbat, Oman; C. Fully extended white tentacles covering the whole surface of the colony of UNIMIB SO 078 at Socotra Island, Yemen; D. Colony with partially retracted tentacles allowing the polyps’ white oral disks to show, Mahé Island, Seychelles; E. Colony of UNIMIB MY 069 at Mayotte Island; F. Colony with white tentacles and grey oral disks Balhaf, Yemen; G. Close-up of the polyps of colony UNIMIB BU 049 with beige tentacles and white oral disks at Burum, Yemen.

Figure 7. Pavona giannii sp. nov. and congeners side-by-side in situ allowing a direct comparison of the polyp macro-morphology and coloration. A. P. giannii sp. nov., Pavona decussata and Pavona varians at Bir Ali, Yemen; . B. Detail of A showing a margin of the P. giannii sp. nov. colony, devoid of ridges and with the typical white tentacles, actively growing over the P. varians one with well-developed ridges and shorter brown tentacles; C. Margin of a P. giannii sp. nov. with crowded polyps, light brown tentacles and white oral disks, a less commonly observed color variant, being overgrown by Pavona explanulata with extended brown tentacles and well-distanced polyps. Dashed polygon in A shows the portion of the image shown in B.