Microphthalmus Mecznikow 1865
Creators: name: Georgieva, Magdalena N.
name: Wiklund, Helena
name: Ramos, Dino A.
name: Neal, Lenka
name: Glasby, Christopher J.
name: Gunton, Laetitia M.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Phyllodocida
Microphthalmidae
Microphthalmus

description: Microphthalmus Mecznikow, 1865
Microphthalmus sp.
Fig. 11
Material examined. NHMUKANEA 2022.434, NHMUK ANEA 2022.412 – 420, NHMUKANEA 2022.437 – 438, IN2017_ V03 _100; 9 June 2017; off Byron Bay, NSW, Australia, beam trawl, start: 28.05°S 154.08°E, 999 m, end: 28.10°S 154.08°E, 1013 m. DNA vouchers: NHMUK ANEA 2022.434 (COI, 16 S, 18 S), WF_SYL_2 (COI, 16S), same locality.
Description. Complete specimens 1.1–1.8 mm long with 18–42 segments, appearingbiannulate (Fig. 11A). Body width is similar throughout, with its mid-body chaetigers 0.14–0.24 mm wide, not including the parapodia, only slightly taperingon both ends. Ethanol-preserved specimens appearing white to light brown.
Prostomiumsemicircular, anteriorly slightly cleft, broader thanlong (Fig. 11B). Prostomialappendagesare all cirriform. One pair of dorsal antennae and one pair of shorter palps terminally located. Median antenna inserted near posterior end of prostomium. Eyes absent.
First three segments shorter than others andlack chaetae, bearing six pairs of cirriform tentacular cirri (Fig 11B). Dorsal and ventral cirri present from segment 4. Dorsal cirri shorter on segment 4 than those on segment 5 onwards. Ventral cirri triangular, shorter, and thicker than cirriform dorsal cirri. Body width similar along most of the length (0.14–0.24 mm).
Parapodia uniramous. Neuropodia with a pointed prechaetal lobe (Fig. 11C) and blunt postchaetal lobe (Fig. 11D). Length of prechaetal lobe equal to or exceeds that of dorsal cirri. Neurochaetae all heterogomph falcigers with blades of different lengths having serrated edges (Fig. 11E).
Pygidium short, with two short anal cirri with swollen bases. Ventral anal lamellae bilobed, with smooth margins and lacking papillae (Fig. 11F).
Distribution. IN2017_V03, Station 100. Pilot whale carcass, off Byron Bay, New South Wales, Australia in 999–1013 m.
Remarks. The genus Microphthalmus has been identified in previous studies of whale-fall annelids in the Atlantic (Sumida et al., 2016) and the Pacific (Dahlgren et al., 2004) but no descriptions or molecular data for these have been published to date. This genus is also difficult to place phylogenetically (Fig. 12). Sumida et al. (2016) indicatedthat the Microphthalmus collected from the Atlantic whale fall wasanew species, howeverwhether ourspecimens represent the same species cannot be determined at present due to the lack of information from previous studies. Male copulatory organs were not examined, which have been suggested to be the most suitable morpho-anatomical character for differentiating between species (Westheide, 2013).
description: Published as part of Georgieva, Magdalena N., Wiklund, Helena, Ramos, Dino A., Neal, Lenka, Glasby, Christopher J. & Gunton, Laetitia M., 2023, The Annelid Community of a Natural Deep-sea Whale Fall off Eastern Australia, pp. 167-213 in Records of the Australian Museum (Rec. Aust. Mus.) (Rec. Aust. Mus.) 75 (3) on pages 177-180, DOI: 10.3853/j.2201-4349.75.2023.1800, http://zenodo.org/record/10414191