Porites randalli, Forsman, Zac H. & Birkeland, Charles, 2009

Forsman, Zac H. & Birkeland, Charles, 2009, Porites randalli: a new coral species (Scleractinia, Poritidae) from American Samoa, Zootaxa 2244, pp. 51-59 : 53-57

Porites randalli spec. nov.

(figs. 1–3)

Material examined. Holotype: Bishop museum (SC 4161), Ofu, American Samoa. Collector: Charles Birkeland. Colony 5 x 5 cm (figs. 2A, 3A)

Paratypes: 1—Bishop museum () Ofu, American Samoa. Collector: Daniel Barshis. Colony 2 x 3 cm (fig. 3B-SEM image of genetic sample AS 13 from Forsman et al. 2009)

2—Florida Museum of Natural History (UF Cnidaria 5429), Ofu, American Samoa. Collector: Charles Birkeland. Colony 4 x 5 cm (fig. 2B)

3—Museum of Tropical Queensland (G62293), Ofu, American Samoa. Collector: Charles Birkeland. Colony 4 x 6 cm

4—Smithsonian National Museum of Natural History ( USNM 1129921), Ofu, American Samoa. Collector: Charles Birkeland. Colony 2 x 5 cm

5—Smithsonian National Museum of Natural History ( USNM 1129922), Ofu, American Samoa. Collector: Charles Birkeland. Colony 4 x 4 cm

Description. The corallites averaged 1.16 mm (± 0.067 SE) in longest diameter to the midpoint of each wall (min 0.59, max 1.69, n=60 from 6 individuals), with an average distance between corallites of 1.13 mm (± 0.12 SE, min 0.73, max 1.51). The corallites appear more shallow than most Porites , tending to be hexagonal with the ring of pali sunken relative to the wall. The average distance from the center of the corallite wall to the center of the lateral pair pali was 0.39 mm (± 0.017 SE). The columella were small but generally present, with 1,2 or no radii, six pali (five large pali and a small one on the dorsal septum). The dorsal septum tended to be shorter than other septa, and the ventral triplet was either fused or irregular. The corallite walls were perforate, rising gradually next to a concentric row of denticles with 1–2 trabecular rings forming the corallite wall. The 12 wedge-shaped septa became narrow near the pali. The septa extended approximately half way from the corallite wall to the columella. Living colonies are small (typically <5 cm in diameter, rarely approaching 10 cm) usually pale green, or occasionally brown, or blue, with a surface reticulated with small (0.5 cm – 2 cm) protuberances.

Diagnosis. Porites randalli is easily distinguished in the field from other species of Porites . Most colonies of Porites are either mound-shaped or have finger-shaped branches. When these two groups are put aside, those that are left are in a distinct third type of colony morphology that is nodular, with fused or anastomozing columnar knobs or nodes. All but three of these with anastomozing columns in the central Pacific are in the group Synaraea with usually small corallites (0.5 – 0.7 mm diameter) that are separated into groups by coenosteal ridges and can resemble Montipora in the field ( Synaraea was placed in a separate subgenus by Verrill (1864), but Forsman et al. (2009) showed the group to be closely related and nested within Porites ).

Affinities. The three Porites species in the central Pacific that have similar corallites and with colonies formed into anatomosing columnar nodules are Porites randalli , Porites lichen and Porites annae . P. lichen and P. annae generally form larger colonies, often or usually have laminar bases. Porites randalli is usually less than 5 cm diameter and rarely as large as 10 cm, nearly always with knobs rising directly from the substratum without a laminar base. P. randalli typically has shallow corallites while the corallites of P. l i c h e n appear to be deeper with sharper walls and those of P. annae appear to be slightly larger and separated by thickened walls. Although color is somewhat variable and may not be a reliable taxonomic character for Porites , Porites randalli is usually a pale green (occasionally brown or blue), P. lichen is usually a bright greenish or brownish yellow and P. annae is usually a pale greenish brown.

The genus Porites has a complex history of taxonomic confusion with many synonyms. There are as many as 270 extant species named (Don Potts pers. comm.), with only about 52 currently considered valid ( Veron 2000). Of these species, the description of P. purpurea Gardiner 1898 (later synonymized with P. l i c h e n by Wells 1954), was one of the most likely candidates for close affinity with P. randalli . However, the color was described as deep purple and the photograph in Bernard 1905 of one of the three existing specimens was of a colony 12 cm tall, larger and more pointed and cone-shaped than ever observed in P. randalli . The description of skeletal microstructure was also more consistent with P. l i c h e n ( Bernard 1905).

Previous records. Porites sp. 2: Birkeland et al. 1987, 1994, 1996, 2003, 2004; Craig et al. 2001; Fisk & Birkeland 2002; Fenner et al. 2008; Green et al. 1997, 1999, 2005; Mundy 1996; Forsman et al. 2009; McArdle 2003.

Etymology. The specific epithet “ randalli ” was chosen to honor Richard H. Randall, who labeled it “ Porites sp. 2” during survey work that he has performed since 1979 on the hundreds of coral species that occur in American Samoa.

Habitat and distribution. In surveys during 1985 and 1995, Porites sp. 2 was the most abundant coral at many survey sites in American Samoa. The total number of coral colonies recorded from 140 species in the survey of 1995 was 12,640. There were 2,289 recordings of Porites sp. 2 in 1995 which comprised over 18% of the individual colonies out of the total for 140 species. P. randalli spec. nov. occurred rather uniformly at all surveyed depths (ranging from 1 to 12 m) in a variety of habitats that tend to have clear water, including shallow pools and fore reef environments.

Porites randalli has been found at nearly all sites surveyed on the islands of American Samoa ( Birkeland et al. 1987, Mundy 1996) including Fagatele Bay, Leone, Amanave, Massacre Bay, Fagafue, Sita Bay, Cape Larsen, Fagasa, Vatia, Masefau, Aoa, Onenoa, Matuli Point, Auasi, Fagaitua, Onenoa, Leloaloa, Rainmaker Hotel, Faga’alu, Fatumafuti Rock, and Nu’uuli on Tutuila Island, Fagamalo, Faga and Lepula on Ta’u Island, and on Aunu’u Island, Ofu Island and Olosega Island. However, Porites randalli was not found at the surveys sites studied by Mayor (Aua and Utelei).