Dendronotus claguei Valdés & Lundsten & Wilson 2018, sp. nov.
Creators: name: Valdés, Ángel
name: Lundsten, Lonny
name: Wilson, Nerida G.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Nudibranchia
Dendronotidae
Dendronotus
Dendronotus claguei

description: Dendronotus claguei sp. nov.
(Figs 2C, 3B, 9–10)
Type material. Holotype: Alarcón Rise, Gulf of California, Northeast Pacific Ocean (23.4549, -108.485405), 2369 m depth, ROV Doc Ricketts (dive 394), 24 Apr 2012, 7 mm preserved length (LACM 3554), GenBank accession number: MH 756144 (H3).
Paratype: Alarcón Rise, Gulf of California, Northeast Pacific Ocean (23.4549, -108.485405), 2368.8 m depth, ROV Doc Ricketts (dive 394), 24 Apr 2012, 18 mm preserved length, dissected.
Description. Body long, narrow, with 4-6 pairs of simple, elongate, dorso-lateral cerata (Fig. 2C). Velum composed of 4 narrow and elongate papillae. Rhinophores with very elongate stalks. Rhinophoral sheaths with 4 elongate, simple papillae on distal edges, the innermost papilla being much larger than the other three. Rhinophoral clubs elongate, with 11 simple lamellae. Color uniformly translucent white with some internal organs visible through the body wall as beige or yellowish areas.
Digestive system with large, muscular buccal bulb (Fig. 9A). Esophagus narrow, short, connecting anteriorly into buccal bulb. Intestine emerging dorsally from left side of digestive gland, forming a loop towards the right side of body where it opens into the anus (Fig. 3B). Radular formula 32 × 7–8.1.7– 8 in the paratype. Rachidian teeth triangular, with arch-like basal end and blunt central cusp, with 11–13 sharp denticles on each side (Fig. 10A). Lateral teeth elongate, with up to 10 apical, sharp denticles, the innermost being the longest. Teeth typically decreasing in size and number of denticles towards outer edge of radula. Jaws elongate with a masticatory border bearing rows of low, irregular denticles (Fig. 10B).
Reproductive system with large, convoluted ampulla forming three loops (Fig. 9B), merging with distal end of the prostate before connecting to female gland complex. Prostate short, composed of ~9 large follicles, connecting to a tubular, elongate and convoluted muscular deferent duct, which progressively expands distally and connects to a long and narrow penis. Vagina wide, elongate, opening into spherical bursa copulatrix. The seminal receptacle is a small, spherical, opening directly into the vagina close to its proximal end.
Biology. This species was collected at 2369 m depth on an inactive hydrothermal chimney of the Alarcón Rise, approximately 53 nautical miles east of Cabo Pulmo, Baja California Sur, Mexico (Fig. 1). Although the inactive chimney itself was mostly devoid of life, other organisms seen in the vicinity of the collection site included Aldrovandia sp. (halosaurid fishes), Biremis sp. (terebellid polychaete), Bonellidae (echiuran), Galatheidae (squat lobster), Liparidae (snail fishes), Synallactidae (holothurian), and dense Xenophyophoroidea (benthic foraminifera).
Phylogenetic position. According to the phylogenetic analyses here conducted (Fig. 6), Dendronotus claguei sp. nov. appears to be sister to a clade containing several specimens identified as D. robustus and also including D. patricki.
Etymology. The species is named in honor of David A. Clague, MBARI Senior Scientist and Volcanologist. Dave was the Chief Scientist of the expedition to Alarcón Rise, where the specimens were collected.
Remarks. Dendronotus claguei sp. nov. is morphologically very different from most other species of Dendronotus. The only exception is the Atlantic deep-sea species D. comteti Valdés & Bouchet, 1998, described from a hydrothermal vent site at 1685 m depth in the mid-Atlantic Ridge, which also has a simple dorso-lateral cerata, with no branching pattern. Additionally, both D. comteti and D. claguei sp. nov. have similarly shaped rachidian teeth, but in D. claguei sp. nov. they are more triangular than in D. comteti. Unfortunately, the reproductive anatomy, external coloration and sequence data of D. comteti remain unknown, therefore it could not be included in the phylogenetic analyses.
Dendronotus claguei sp. nov. is the only Eastern Pacific species of Dendronotus with a uniform white background color and simple dorso-lateral cerata. The only other species of Dendronotus reported from deepwaters in the Northeast Pacific is D. patricki Stout, Wilson, and Valdés, 2011, described from 1819 m depth in the Monterey Canyon, California. These two species are easily differentiated by their radular and reproductive anatomy. Although D. claguei sp. nov. has a triangular rachidian tooth with 11–13 sharp, similar sized denticles on each side, running from the tip of the cups to the base, in D. patricki the teeth are elongate with about 20 denticles on each side, and the cusp is clearly differentiated from the rest of the tooth, with very small denticles. Additionally, D. patricki has simple lateral teeth, devoid of denticles, whereas D. claguei sp. nov. has up to 10 apical, sharp denticles on the lateral teeth. The reproductive system of D. patricki has a very elongate prostate and a large bursa copulatrix in relation to the width of the vagina, whereas in D. claguei sp. nov. the prostate is much shorter and the bursa copulatrix is not much wider than the vagina. Externally, D. claguei sp. nov. is characterized by having a uniformly white body with simple lateral appendages, while D. patricki is reddish brown, with ramified dorsal appendages in a fan-shaped branching pattern.
description: Published as part of Valdés, Ángel, Lundsten, Lonny & Wilson, Nerida G., 2018, Five new deep-sea species of nudibranchs (Gastropoda: Heterobranchia: Cladobranchia) from the Northeast Pacific, pp. 401-433 in Zootaxa 4526 (4) on pages 412-414, DOI: 10.11646/zootaxa.4526.4.1, http://zenodo.org/record/2611755