Asteronotus namuro Donohoo & Gosliner 2020, sp. nov.
Creators: name: Donohoo, Samantha A.
name: Gosliner, Terrence M.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Nudibranchia
Discodorididae
Asteronotus
Asteronotus namuro

description: Asteronotus namuro sp. nov.
(Figs. 2D, 4B, 5B, 6)
urn:lsid:zoobank.org:act: A7E57F60-38DA-4AD9-85DC-940DA349736F
Thordisa sp. 16— Gosliner et al. 2015: page 182, top left photograph.
Thordisa sp. 18— Gosliner et al. 2018: page 103, middle right photograph.
Type material. Holotype: CASIZ 192297, one specimen, dissected, foot subsampled for molecular analyses, Tigerhead Island, 16.79097° N 41.199012° E, Red Sea, Saudi Arabia, 17.4m depth, 10 March 2013, T. M. Gosliner.
Type locality. Tigerhead Island, Saudi Arabia, Red Sea.
External morphology. The living animals (Fig. 2D) are oval in shape, approximately 45–55 mm in length, and were found under coral rubble on steep sandy slopes 17m in depth. The body color is a pinkish pale red with random dark red and white flecks that increase in concentration moving away from the mantle’s edge; numerous red and white tubercles that vary in size; and random dark red blotches surrounding a medially light pink crest with a central brown line. The underside of the mantle is a pinkish pale red color with random dark-red flecks across the entire mantle. The gill surrounds the anus and consists of 6 light brown tripinnate brachial leaves with light brown rachises and scattered opaque white spots. The gill pocket consists of six distinct lobes that are red in color with a large patch of white at the apex. The rhinophores are perfoliate with 15–20 dark purple lamellae. The base and middle regions of the rhinophores are purple with scattered red spots. The two rhinophoral sheaths are crenulated and purple in color with random patches of reddish pink. The foot is broad, anteriorly notched, and cream in coloration with random red flecks. An elongate, digitiform oral tentacle is found laterally on either side of the labial region and mouth.
Internal morphology. Buccal mass and radula. The buccal mass is muscular and anteriorly connects to a thin labial cuticle which is devoid of armature or rodlets. The radula (Fig. 6A) is composed of predominantly smooth hamate teeth and has the radular formula 34 × 29.0. 29 in the holotype CASIZ 192297. The inner lateral teeth (Fig. 6B) are short with a broad base which abruptly curve at the cusp. The first tooth of the inner teeth has one to two triangular denticles along either the outer side of the cusp. The remainder of the inner laterals are smooth. The middle lateral teeth (Fig. 6C) are larger with a shorter, elongated narrow cusp and lack denticles. The outer lateral teeth (Fig. 6D) are also larger and slightly elongate, but have a shorter, rounder cusp than the middle laterals and also lack denticles.
Reproductive system. A thin preampullary duct widens into a thick ampulla that abruptly narrows into the vas deferens and a short oviduct (Fig. 4B). The vas deferens widens into an ovoid prostate, which quickly narrows distally into a convoluted, elongate muscular ejaculatory portion. The ejaculatory portion connects with an elongate penis which shares a common genital atrium with the accessory gland and vagina. A narrow, elongate vagina enters a rounded bursa copulatrix that is larger than the prostate. A short, thick duct connects the bursa to the irregular receptaculum seminis, while the uterine duct also connects near the base of the receptaculum and enters the female gland mass. An irregular-shaped nodular accessory gland is connected to the common genital atrium by a convoluted, looping, elongate duct. Within the base of the accessory gland is an elongate, slightly curved accessory spine with a broad base (Fig. 5B).
Etymology. This species is named Asteronotus namuro after “namur” the Arabic word for tiger, since the type material is found around Tigerhead Island.
Geographical distribution. The Saudi Arabian Red Sea.
Remarks. Our molecular phylogeny shows that Asteronotus namuro is sister to a clade that includes A. hepaticus (Fig. 2E) and A. cespitosus (Fig. 2F). The ABGD and bPTP analyses within the clade supports A. namuro as a distinct species since there is a minimum divergence of 16.60% between A. hepaticus and A. namuro, as well as a minimum divergence of 14.55% between A. cespitosus and A. namuro for the COI gene. Due to the unavailability of additional specimens, intra-specific variation is not studied here; however, A. namuro is supported as a distinct species based on the strong external and internal morphological differences combined with the large genetic divergence between sister taxa. Externally, the body coloration of A. namuro is a pinkish pale red with red blotches and numerous red and white tubercles; whereas, A. hepaticus is a uniformly dark red color with scattered, minute tubercles, and A. cespitosus varies in color from yellow to various shades of brown and red with large irregular tubercles that may be fused together in groups (Valdés & Gosliner 2001, fig. 1A).
The radula and reproductive system of A. hepaticus are undescribed and the holotype unavailable for morphological study. Furthermore, the reproductive system of the A. hepaticus specimen used in this study could not be reliably described. Therefore, no internal comparisons were made between A. hepaticus and A. namuro. The radular teeth in A. namuro are similar to all Asteronotus; however, there is a single triangular denticle on the first tooth in the inner lateral teeth and the outermost tooth is a reduced version of the rest of the outer lateral teeth. In contrast, none of the radular teeth in A. cespitosus have denticles and the outermost tooth is elongate rather than simply reduced or an ovoid plate (Valdés & Gosliner 2001, fig. 4). The reproductive system also varies as A. namuro has a larger, rounded bursa copulatrix with a smaller ovoid prostate and an irregularly shaped receptaculum seminis; whereas, A. cespitosus has a bursa copulatrix and prostate of a similar size with a smaller rounded receptaculum seminis (Valdés & Gosliner 2001, fig. 3B). Additionally, the accessory gland in A. namuro is elongate and irregular with a slightly curved accessory spine; whereas, A. cespitosus has a more regular shaped accessory gland with a thin, straight accessory spine (Valdés & Gosliner 2001, fig. 5E).
description: Published as part of Donohoo, Samantha A. & Gosliner, Terrence M., 2020, A tale of two genera: the revival of Hoplodoris (Nudibranchia: Discodorididae) with the description of new species of Hoplodoris and Asteronotus, pp. 1-37 in Zootaxa 4890 (1) on pages 11-14, DOI: 10.11646/zootaxa.4890.1.1, http://zenodo.org/record/4301483