WILLIAMS & CHEN: GORGONIANS AND PENNATULACEANS 71 
OF THE VERDE ISLAND PASSAGE 
axis (Williams 1992). Sclerites are highly diverse in shape, size, and ornamentation. The compar¬ 
ative microscopic examination of sclerites is necessary for the identification of octocoral taxa. 
Zooxanthellae are single-celled dinoflagellates (Symbiodinium microadriaUcum plus an unde¬ 
termined number of similar species) that act as the photosynthetic endosymbionts in numerous 
organisms from vai*ious invertebrate groups including corals, sea anemones, sponges, flatworms, 
mollusks, foraminiferans, and ciliates. 
Gorgonians are divided into three groups based on axial structure and composition: scleraxo- 
nians (in which the axial structure, the medulla, is composed of sclerites), holaxonians (internal 
axis composed of scleroproteinacous concentric layers around a hollow core), and calcaxonians 
(with a solid, largely calcareous axis) (Grasshoff 1999). Pennatulaceans, on the other hand, are a 
specialized and morphologically distinct group of octocorals with a muscular peduncle for anchor¬ 
ing in unconsolidated benthic substrata (Williams 2011). 
Notes On The Current Status of Knowledge. — Bayer (1981:7-9) reviewed the status of 
knowledge of octocorals in major geogi'aphic regions of the world. He proposed four levels of tax¬ 
onomic knowledge: essentially complete, moderately well-known, poorly known, and minimally 
known. He assigned the Philippines to the third category, poorly known, “where the literature is 
sparse and incomplete. Here the major part of the fauna remains to be described and a large num¬ 
ber of species will inevitably be new to science. The major faunal relationships can be deduced, but 
distributional patterns are not clearly understood.” 
Bayer’s assessment is still considered a valid evaluation of the regional situation at present 
(more than thirty years later). The abbreviation “cf.” used between the words of some binomens 
stands for the Latin word conferre (to compare or compare with). It is used for provisional or ten¬ 
tative identifications at the species level, as opposed to definitive or conclusive ones. 
Throughout the text of this papei; an unidentified species of a paiTicular genus is denoted by 
“sp.” whereas “spp.” refers to more than one species of the genus. Species level identifications in 
Indo-Pacific octocorals remains largely problematic for several reasons. Many genera require thor¬ 
ough taxonomic revisions before an identification can be made with confidence, a particular 
species can be considered valid, or the number of valid species can be accurately ascertained. In 
many genera, a large number of species have been described, some of which may have been 
described in other genera or are conspecific with other named species, while others have been 
described in the wrong genus. Confusion in a good deal of the relevant literature persists. Many 
taxa have been described or illusfrated insufficiently or inadequately for positive identification pur¬ 
poses. Also, the type specimens that represent a paiticular taxon may be unknown or not designat¬ 
ed, unobtainable, damaged, lost, or otherwise not suitable for comparative purposes. 
The relatively few taxonomic papers treating Philippine octocorals include Light (1913, 1914, 
1915a, 1915b, 1915c, 1921), Mai-Bao-Thu and Domantay (1970, 1971), Roxas (1932, 1933a, 
1933b), Stiasny (1940, 1941), and Williams and Alderslade (1999). 
Materials And Methods 
All material used in this study was collected via SCUBA during field operations between 1994 
and 2012. The Philippine Aixhipelago and the Verde Island Passage region are shown in Figs. lA 
and IB. Collecting stations (SCUBA diving sites) of material used in this study from the region of 
the Calumpan Peninsula and Maricaban Island are shown in Fig. 1C. All material is catalogued and 
housed in the marine invertebrate collections of the California Academy of Sciences, San Francis¬ 
co. 
Octocoral sclerites were isolated and prepared following standard protocols (Williams and 
Mattison, 2013). SEM images of sclerites were taken on a LEO 1450VP scanning electron micro- 
