Mycetomorpha abyssalis sp. nov.

Figs 2, 3, 4

Etymology.

The specific name abyssalis (Latin: abyssal) is an adjective referring to the collection of this species from an abyssal depth.

Type host.

Sclerocrangon zenkevitchi Birshtein & Vinogradov, 1953 ( Decapoda: Caridea: Crangonidae).

Attachment site.

Pleonite 1 sternite.

Type locality.

Off the eastern coast of Iwate, Japan, northwestern Pacific (39°28.555'N, 143°47.347'E to 39°27.934'N, 143°47.240'E), depth 3893-3890 m.

Material examined.

Holotype, female (CBM-ZC 17789), one vial, ex. S. zenkevitchi (cl 26.7 mm; CBM-ZC 17788), collected on 29 September 2023 at the type locality, R/V Hakuho-maru cruise KH-23-5, coll. by Keiichi Kakui.

Representative DNA sequences.

One sequence each was determined from the holotype (CBM-ZC 17789) for COI (INSD accession number LC799150; 637 bp, encoding 212 amino acids), 16S (LC799151; 490 bp), 18S (LC799152; 1826 bp), and 28S (LC799153; 1169 bp). One sequence each was determined from the host (CBM-ZC 17788) for COI (LC799154; 658 bp, encoding 219 amino acids) and 18S (LC799155; 1846 bp).

Description of female holotype.

Externa (Figs 2, 3) 16.6 mm in length, thinner than broad, a little over twice as long as maximum width (8.1 mm), rounded at ends, pale yellow (faded in ethanol, slightly yellowish); except dorsal and anteroventral regions, externa surface covered with short lobes; filled with developing embryos. Root system not observed. Stalk short, cylindrical, at one-quarter of length from posterior end of externa. Triangular shield lacking (Figs 3C, 4). Anterior, middle, and ventral lobes short, and ovoid or digitiform; posterior lobes short and branched. Tubular lobe anterior to stalk, at one-fifth of length from anterior end of externa, arising from right margin of externa, with mantle opening at tip; mantle opening anterior to stalk.

Distribution.

Presently known only from the type locality.