Leptonerilla purschkei, Worsaae, Gonzalez, Kerbl, Nielsen, Jorgensen, Armenteros, Iliffe & Martinez, 2025

Leptonerilla purschkei sp. nov.

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Figs 5–6 View Fig View Fig ; Table 4 View Table 4

Diagnosis

A nine-segmented Leptonerilla diagnosed by a combination of following characteristics: three long antennae all distally wrinkled, median antenna shorter than lateral antennae. Segment I with cirriform, relatively short cirri and chaetae. Trunk segments with long, double parapodial cirri and long pygidial cirri, exceeding half of body length. Gonochoristic with one pair of oviducts in segment VIII, males not observed.

Etymology

The species is named in recognition of the annelid researcher Günter Purschke, who erected the genus Leptonerilla and described the morphologically highly similar L. diplocirrata Westheide & Purschke, 1996 . The Japanese name for this new species is given here as ‘Shimoji-doukutsu-usamimi-gokai’ (meaning ‘Shimoji Island-cave dwelling-rabbit ear-bristle worm’ in English).

Type material

Holotype

JAPAN • ♀ adult; Miyako Islands, Shimoji Island, ‘ Akuma-no-yakata’ (Devil’s Hole); 24.82291° N, 125.13551° E; rubble at 22 meters depth; 26 Oct. 2018; Y. Fujita, M. Mizuyama, P.R. Møller and K. Worsaae leg.; NHMD 1842016 mounted on SEM stub.

GoogleMaps

Paratype

JAPAN • 1 ♀ adult; same data as for holotype; NHMD 1842017 as permanent whole mount GoogleMaps .

Representative DNA sequences

GenBank accession numbers PQ149839 (nuclear 18S rRNA), PQ149820 (nuclear 28S rRNA), PQ570589 (nuclear H3) and PQ421135 (mitochondrial COI); from specimen with same collection data as holotype ( Table 1 View Table 1 ).

Description

Measurements are based on LM of holotype, counts and ciliation from SEM; values for paratype are given in parentheses. Body with nine chaetigerous segments ( Fig. 5A View Fig ), total length about 940 µm (745 µm, n = 1). Segment lengths of holotype 97, 90, 104, 123, 115, 103, 101, 77, 68 µm, pygidium 37 µm long. Maximum width about 195 µm including parapodia (165 µm, n = 1), about 145 µm excluding parapodia (115 µm, n = 1). Max length of parapodium on segment I, 41 µm (38, n = 1), on segments II–IX, 45 µm (53 µm, n = 1).

Prostomium with three long antennae wrinkled distally ( Fig. 5C View Fig ), often lost during fixation. Lateral antenna estimated length up to 485 µm (n = 1) (la, Fig. 5A, C View Fig ), median antenna shorter than lateral antennae (ma, Fig. 5C View Fig ) with estimated length up to 370 µm from photos of live specimen (n = 1). Prostomium with two club-shaped palps up to 78 µm long (65 µm, n = 1) and 31 µm wide (20 µm, n = 1), inserted ventrally on prostomium (pa, Figs 5A, C View Fig , 6A–B View Fig ) with distinct ventral and frontal ciliation. Two dorsal eyes. Paired nuchal organs laterally between prostomium and peristomium (no, Fig. 6B View Fig ).

Segment I with a single, up to 73 µm long, cylindrical (cirriform) cirrus per parapodium ( Figs 5A View Fig , 6B View Fig ). Segments II–IX carrying double, cylindrical interramal parapodial cirri (pc, Figs 5B View Fig , 6A View Fig ), up to 336 µm long, lengths seemingly increasing in posterior segments. Cylindrical pygidial cirri up to 590 µm long (pyc, Fig. 5C View Fig ), estimated relative to body length from live specimen images.

Compound chaetae in all segments (cc, Fig. 5B View Fig ). Segment I with one bundle of up to 18 posteriorly pointing chaetae (up to 148 µm long) per parapodium ( Fig. 6A–B View Fig ). Following segments with dorsal and ventral bundles of chaetae; up to 20 chaetae per parapodia (up to 236 µm long) ( Fig. 6A View Fig ). Shaft up to 169 µm long, blade up to 82 µm long, distal extension on shaft at joint up to 15 µm long ( Fig. 6C–D View Fig ).

Prostomium with anterior and posterior fields of presumed sensory cilia and lateral rows of cilia extending between lateral antenna and palp insertion ( Fig. 6B View Fig ). Paired, densely ciliated nuchal organs on lateral border between prostomium and segment I. Palps with ventral longitudinal dense ciliary row from insertion point to tip of palps, dorsal row of minimum 4 ciliary tufts on distal half of palp (each tuft with>15 cilia), and lateral row of indistinct small tufts of cilia ( Fig. 6B View Fig ). Segment I with paired dorsolateral transverse rows of each two ciliary tufts (each tuft with>20 cilia) at the level of parapodia. Following trunk segments with dorsal transverse continuous row of up to 14 ciliary tufts at level of parapodia (tdc, Fig. 6A–B View Fig ); tufts increasing in numbers, ciliary length and showing remarkable density in posterior segments. Segment II with an additional lateral pair of longitudinal ciliary bandlets (ldc, Fig. 6B View Fig ). Ventral ciliation could not be observed.

Four pairs of segmental nephridia positioned laterally, parallel to ventral nerve cord, opening in segments IV, V, VI and VII (n4–n7, Fig. 5E View Fig ). Enteronephridia not distinguished. Gonochoristic reproduction; females with one pair of straight oviducts opening latero-ventrally just anterior to the segmental nerve in segment VIII (ov, Fig. 5D View Fig ). Spermioducts unknown. A single mature egg (about 80 µm long) observed in segments VI–VII (n = 2).

Distribution and habitat

Devil’s Hole ‘Akuma-no-yakata’, northwestern coast of Shimoji Island, Ryukyu Islands, Miyako Islands, Japan. Anchialine cave located on coral reef slope. Specimen collected from rubble patches in middle zone of cave at about 22 meters depth (see Osawa & Fujita 2019 for the description of the cave). Associated nerillids from the cave include Mesonerilla sp. (Worsaae, unpubl. record and not sequenced), N. irabuensis and Leptonerilla sp. 2 .

Molecular information

Leptonerilla purschkei sp. nov. constitutes a fully supported clade with L. westheidei sp. nov. and Leptonerilla sp. 1 ( Fig. 2 View Fig ). The clade is sister to a larger clade comprising the remaining Leptonerilla spp.

Pairwise comparison of L. purschkei sp. nov. sequence similarity to other Leptonerilla spp. : 18S rRNA – 99.43–99.89% similar to its sister group (clade comprising L. westheidei sp. nov and L. sp. 1) – 97.13– 98.24% similar to the remaining Leptonerilla spp. ; 28S rRNA – 96.16% similar to its sister group – 79.30–82.72% similar to the remaining Leptonerilla spp. ; COI – 88.62–89.57% similar to its sister group – 79.12–80.40% similar to the remaining Leptonerilla spp. ; H3 – 96.59% similar to its sister group – 88.09–89.31% similar to the remaining Leptonerilla spp.

Remarks (see also Table 4 View Table 4 for Leptonerilla spp. comparisons)

Leptonerilla purschkei sp. nov. shows the greatest morphological and molecular similarity to L. westheidei sp. nov., but differs from it by a larger body size, segment I with much shorter cirri, and double as many chaetae. Both species share a small body size compared to L. diatomeophaga (Núñez in Núñez, Ocaña & Brito, 1997) and especially L. prospera Sterrer & Iliffe, 1982 ( Sterrer & Iliffe 1982; Núñez et al. 1997; Worsaae et al. 2009). Leptonerilla purschkei differs from these latter two species by having longer cirriform, cylindrical parapodial cirri on segment I, although these are similar in shape and relative length to those of L. diplocirrata . Leptonerilla purschkei differs from all other species of Leptonerilla by the very long pygidial cirri and by the very long antennae, more than half the body length, with a wrinkled appearance, otherwise only described for the distantly related Micronerilla and Aristonerilla ( Swedmark 1959; Saphonov & Tzetlin 1997; Müller 2002). It thereby also differs from the only other described species of Leptonerilla from the West pacific region, L. diplocirrata found more than 1000 kilometres away, near Hainan, China. Leptonerilla purschkei also differs molecularly from both L. sp. 2 found within the same cave and L. sp. 3 found further North off Okinawa in ‘unnamed cave’ of Ie Island. Both two latter potential new cave species were only found as single specimens with very limited morphological information obtainable prior to DNA extraction of all their tissue.