Leptogorgia waltonae

Olvera, Ursula, Hernández, Osvaldo, Sánchez, Carlos & Gómez-Gutiérrez, Jaime, 2018, Two new endemic species of Gorgoniidae (Cnidaria, Anthozoa, Octocorallia) from Revillagigedo Archipelago, Mexico, Zootaxa 4442 (4), pp. 523-538: 530-533

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Leptogorgia waltonae

sp. nov.

Leptogorgia waltonae  sp. nov.

( Fig. 4–6View FIGURE 4View FIGURE 5View FIGURE 6)

Holotype: USNM-1422111, dried specimen, Las Cuevas (19°17'54.026" N, -110°48'16.030" W), San Benedicto, Revillagigedo Archipelago, 20 m depth, January 20, 2000.

Paratypes: USNM-1422112 dried specimen, San Benedicto, Revillagigedo Archipelago, 18 m depth, 2006. USNM-1422113, dried specimen, San Benedicto, Revillagigedo Archipelago, 18 m depth, 2006. USNM-1422114, dried specimen, Las Cuevas, San Benedicto, Revillagigedo Archipelago, 20 m depth, January 20, 2000.

Holotype colony: A yellow colony considerably small (cluster growth), 1.7 cm in height and 1.3 cm in width ( Fig. 4C View Figure ). Holdfast rectangular (3–5 mm) from which arises a main stem 7 mm in width and 2 mm in diameter; which is divided by laterally growing into secondary branches <13 mm in length and 3 mm in diameter. The first and second branches branch off in ~45° angles, and the third in angles of ~90°, laterally. All terminal twigs show characteristic warty-like ends of 4 – 6 mm in diameter. Polyps arranged irregularly all along the colony except in the main steam where they are absent. Polyps are fully retractile into the coenenchyme forming slightly raised polyp mounds 0.5 mm with oblong apertures (1 mm in length). The first lateral branch is missing showing the nude dark brown axis of about 1 mm in diameter ( Fig. 4C View Figure ) ( Table 1).

Holotype sclerites: The dominant type of sclerites is compact capstans (0.11 mm – 0.065 mm) ( Fig. 5C View Figure ). Spindles are scarce (0.13 mm – 0.06 mm) with 4–5 whorls of warty tubercles and acute ends ( Fig. 5A,C View Figure , Table 1). Coenenchymal crosses are small up to 0.05 mm on each side ( Fig. 5B View Figure ). Coenenchymal and anthocodial sclerites are pale yellow ( Fig. 4F View Figure , Table 1), the anthocodial sclerites are blunt rods with lobed margins (0.06 mm – 0.03 mm) observed with an optical microscope ( Fig. 4F View Figure ) but not observed with SEM.

Variability. Colonies of Leptogorgia waltonae  sp. nov. commonly have a highly varying coloration with polychromatic range of yellow, orange, pink, red, and purple in live and dried colonies and their sclerites (coenenchymal and anthocodial) ( Fig. 4A–G View Figure ). Larger but relatively uncommon colonies are bushy small (4.5 cm in height and 3.9 cm in width) with reddish-purple or pink coloration ( Fig. 4B,D,E View Figure ). All branches grow irregularly in several directions including some directed towards the substrate. Main branches of 5 to 15 mm in length and 2 – 4 mm in diameter arise from a holdfast up to 5 mm in length and 4 mm in width with a long main steam of 11 mm in length and 3 mm in diameter showing polyp mounds in the half top. Terminal twigs with conspicuous wart-like tips up to 6 mm in diameter are always present. Polyp mounds are slightly raised or prominent (about 2 mm) showing small circular or oval openings ( Fig. 4H View Figure ). The brownish nude axis (free of coenechyme) from ten colonies always shows several thin branches (1 mm diameter) at the base, but with conspicuously swollen, wart-like ends up to 3 mm in diameter ( Fig. 6B View Figure ). The main distinctive morphological character between small colonies and large colonies is that polyp mounds are slightly raised in small colonies and prominent in large colonies, so this attribute gives the colony a crumpled appearance.

Remarks. Breedy & Guzman (2011) divided all the species of the genus Leptogorgia  from the American Pacific within three morphological groups according to internal and external morphological traits: alba  (5 spp.), rigida  (8 spp.), and pumila (11 spp.). Leptogorgia waltonae  sp. nov. is different because colonies are clustershaped with few short branches that grow downward in angles between 90° and 180° with unequal thicknesses, tipped with sphere-shaped warts. We compared morphology of L. waltonae  sp. nov. with Leptogorgia ena ( Breedy et al. 2012)  because it is the species of the genus with more morphological similarities ( Table 1). Leptogorgia ena  resembles L. waltonae  sp. nov. because both species are small (<5 cm) and both have an uneven thickening along their branches. Leptogorgia ena  has branches divided into two types of ramifications: (1) line with greater thickness in the intermediate zone but thinner in both the base and the tip, which can be sharpened and (2) thin branches at the base, but thick in both the intermediate portion and the tip; which are blunt. In contrast, L. waltonae  sp. nov. has tips with sphere-shaped warts. We removed the coenenchyme from 10 colonies of L. ena  collected at Oaxaca and 10 colonies of L. waltonae  sp. nov. from Revillagigedo Archipelago, only the axis of L. waltonae  sp. nov. always shows the tips with sphere-shaped warts ( Fig. 6B View Figure ) while L. ena  shows the typical thin and homogeneous axis ( Fig. 6A View Figure ). Therefore, the thickness and shape of the branches in L. ena  is due to thickening of the coenenchyme, while the thickness and shape of the branches in L. waltonae  sp. nov. is due to the thickening of the axis. In fact, there is no other known Leptogorgia  species in the American Pacific with the presence of this morphological character. Additionally, unlike L. ena  , no tentacular sclerites were observed in L. waltonae  sp. nov. These two distinctive morphological traits provide strong evidence that this is a new species ( Table 1).

For practical purposes Leptogorgia ena  was tentatively classified within the pumila group, however, Breedy et al. (2012) emphasized that for its particular traits (the small colony, the dominance of wide capstans, barrels and double heads, the low occurrence of spindles, the maximum length of spindles 0.10 mm, and lastly, the presence of tentacular sclerites) it should be segregated from their mutual resemblance ( Table 1). We propose to group the species L. ena  and Leptogorgia waltonae  sp. nov. into a new group called ena  group, because both species grow as small-grouping cluster-shaped colonies, their branching is asymmetric in thickness, and have wide capstans, barrels, double heads ( Table 1).

Habitat. The colonies of Leptogorgia waltonae  sp. nov. were collected attached to volcanic rocks up to 25 m depth and the highest density was observed at 10 m depth. Observations with the submersible DEEPSEE up to 200 m depth done in April 2016 confirmed this species has a shallow distribution pattern (<25 m depth). Leptogorgia waltonae  sp. nov. shares its benthic habitat with a dominant sponge ( Aplysina revillagigedi Cruz-Barraza, Carballo, Rocha-Olivares, Ehrlich & Hog, 2012  ), which has a high percentage of covered area on the volcanic rocks.

Distribution. Leptogorgia waltonae  sp. nov. is only known from Revillagigedo Archipelago (Socorro and San Benedicto Islands). Type locality: San Benedicto.

Etymology. Leptogorgia waltonae  sp. nov. is named in honor of Christy Ruth Walton ( USA) underwater adventurer and photographer. A passionate woman that supports multiple research programs and expeditions in the tropical eastern Pacific providing enthusiasm, funding, equipment, and travel support to scientists who are involved in research and conservation efforts of biota in the Gulf of California and the Mexican Pacific Ocean.