Leptogorgia waltonae, Olvera & Hernández & Sánchez & Gómez-Gutiérrez, 2018

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

Leptogorgia waltonae sp. nov.

( Fig. 4–6 )

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 ). 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 ) ( Table 1).

Holotype sclerites: The dominant type of sclerites is compact capstans (0.11 mm – 0.065 mm) ( Fig. 5C ). Spindles are scarce (0.13 mm – 0.06 mm) with 4–5 whorls of warty tubercles and acute ends ( Fig. 5A,C , Table 1). Coenenchymal crosses are small up to 0.05 mm on each side ( Fig. 5B ). Coenenchymal and anthocodial sclerites are pale yellow ( Fig. 4F , Table 1), the anthocodial sclerites are blunt rods with lobed margins (0.06 mm – 0.03 mm) observed with an optical microscope ( Fig. 4F ) 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 ). 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 ). 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 ). 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 ). 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 ) while L. ena shows the typical thin and homogeneous axis ( Fig. 6A ). 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.

Figures

FIGURE 4. Leptogorgia waltonae sp. nov., A, in situ alive yellow and orange colonies; B, in situ alive purple colony; C, Holotype USNM-1422111 yellow colony; D, dried orange colony; E, dried purple colony; F, Holotype yellow sclerites; G, red sclerites; H, spherical shaped tip. In situ photographs by Enric Ballesteros (A) and Octavio Aburto (B, H).

FIGURE 5. Leptogorgia waltonae sp. nov., holotype USNM-1422111, coenenchymal sclerites: A, spindles; B, capstans; C, cross.

FIGURE 6. Comparison of axis morphology; A, Leptogorgia ena axis (Huatulco Bay, Oaxaca, Mexico); B, Leptogorgia waltonae sp. nov. axis (San Benedicto, Revillagigedo Archipelago).