Loimia aimehoensis, Hutchings & Daffe & Glasby & Lavesque, 2025

Loimia aimehoensis sp. nov.

urn:lsid:zoobank.org:act:13518368-EB34-4DA4-A49D-0A833358933F

Figs 1A, D View FIGURE 1 ; 2A–B View FIGURE 2 ; 3 View FIGURE 3 ; 4 View FIGURE 4

Material examined. Holotype: AM W.55132, complete, South Pacific , French Polynesia, Society Islands , Moorea, Tiahura transect, 17.48°S, 149.83°W, collected P. A. Hutchings, by SCUBA on fringing reef, under coral bommie, 1.5 m, 4 th Dec 1992 GoogleMaps . Paratypes: AM W.55131, complete, South Pacific , French Polynesia, Moorea, east of Lac Temaie, 17.48°S, 149.75°W, collected P. A. Hutchings, by SCUBA on fringing reef, under coral bommie, 20 m, 27 th Oct 1987, some parapodia mounted for SEM; GoogleMaps NTM W029897 View Materials , South Pacific , French Polynesia, Society Islands , Moorea, Motu Iti, 17.54°S, 149.77°W, collected C.J. Glasby & I. Glasby, 11 th Dec 2010, in coral rubble, some parapodia of posterior body used for molecular analyses GoogleMaps .

Description. Holotype: AM W.55132, complete, 350 mm in length (excluding buccal tentacles), 12 mm maximum width, with about 195 abdominal segments, posterior segments very compacted, plus tube. Paratypes: AM W.55131, complete, 160 mm in length (excluding buccal tentacles) and 7 mm maximum width, with about 200 abdominal segments, posterior segments very compacted, plus tube; NTM W29897, posteriorly incomplete, with 17 pairs of notopodia and 25 abdominal segments, 7 mm in length, 2.5 mm in width, buccal tentacles completely detached but retained in a vial. No material gravid. Live animals with both short and long buccal tentacles with transverse reddish bands in addition to many smaller bright white spots ( Fig. 2A, B View FIGURE 2 ), white glandular patches between parapodia, and bright red branchiae ( Fig. 2A View FIGURE 2 ), these glandular spots also visible on preserved specimens ( Fig. 3A View FIGURE 3 ). All preserved material pale yellow lacking pigmentation patterns.

Transverse prostomium attached to dorsal surface of upper lip, basal part lacking eyespots, distal part shelf-like. Peristomium forming lips, hood-like upper lip with crenulated margins and longitudinal lines along lip, lower lip swollen, rectangular, faintly tessellated, with a distal groove ( Fig. 3B View FIGURE 3 ).

Three pairs of branchiae with numerous short stout dichotomous branches arising from short, stout main stalk, all ringed, terminating in numerous compact terminal branches ( Figs 2A View FIGURE 2 ; 3A, C–D View FIGURE 3 ), 1 st pair inserted slightly more dorsally than vertically aligned 2 nd and 3 rd branchiae uniformly shortening from 1 st to 3 rd.

Nephridial papilla not seen on segment 3, presumably hidden by contracted branchiae. Genital papillae on segments 6 and 7, small, inserted at postero-ventral base of notopodia ( Fig. 3C View FIGURE 3 ).

Lateral lobes on segments 1 and 3. Segment 1 reduced dorsally with large oval-shaped glandular lobes with thinner anterior margins, connected mid ventrally by narrow short glandular band, lobes extending almost to mid ventrum ( Fig. 3B View FIGURE 3 ). Segment 2 narrow and covered by lateral lobes of segment 3. Smaller specimen (NTM W029897) with longer mid- ventral band and lateral lobes much smaller relatively ( Figs 2A View FIGURE 2 ; 3E–F View FIGURE 3 ). Segment 3 with lateral lobes which extend dorsally covering base of branchiae forming a flag-like extension split into two lobes dorso-laterally with thinner curled anterior margins; ventral lobe terminates at margins of ventral pads ( Fig. 3B View FIGURE 3 ); smaller specimen (NTM W029897) with less well-developed dorsal extension, but all specimens have a distinct mid-lobe keel running almost entire length of the lobe ( Figs 2A View FIGURE 2 ; 3E, F View FIGURE 3 ). Segment 4 with no lateral lobes. Dorsum smooth.

Ventral pads well developed and segmentally demarcated from segments 2–19, those from segments 2–12 rectangular, glandular; each pad with numerous longitudinal lines, extending to neuropodial margins, 1 st slightly larger than subsequent ones ( Fig. 3B View FIGURE 3 ), after segment 12, pads shortening to last notopodial segment. Mid ventral abdominal groove absent ( Fig. 3G View FIGURE 3 ).

*based on Australian material, species complex

** sequences from type locality

*** sequences not from type locality

Loimia ingens described by Grube, 1878 — Bohol syntype in Berlin- Q4969 was seen in a jar by Glasby in 1986, but in 1987 when we requested type material from the Museum this was not included in the loan of material of other Grube’s species

L. annulifilis (MPW— type and non-type material 2MB 920); L. crassifilis (MPW 309— type and probably non type material 2MB Q5635); L. montagui (MPW 404); L. variegata (MPW— type and non-type material 2MB Q4968, 2MB 522, 2MB 519)] has been examined and all is in poor condition. but not of L. ingens ”

Anterior notopodia and neuropodia forming single structure ( Fig. 3A, C, D View FIGURE 3 ), with neuropodia as raised glandular ridges becoming more prominent posteriorly. Notochaetae all simple capillaries with finely serrated margins, arranged in two graded tiers, with shorter ones about 2/3–3/4 length of longer ones; notochaetae with faint microtexture visible under SEM ( Fig. 4A, B View FIGURE 4 ).

Neuropodia with uncini arranged in single straight rows from segments 5–10, then in double rows back-to-back from segments 11–20 ( Fig. 4G View FIGURE 4 ), then in single rows on all abdominal segments. Thoracic pectinate uncini with six teeth with the main fang, 5+1 visible under SEM ( Fig. 4C, D View FIGURE 4 ); distal-most one not visible under light microscopy ( Fig. 4G View FIGURE 4 ). Abdominal uncini with 5+1 pectinate teeth visible under both SEM and light microscopy ( Fig. 4E, F, H View FIGURE 4 ). Subrostral process low, rounded ( Fig. 4G, H View FIGURE 4 ). Abdominal neuropodia well developed, with elongate, rectangular raised glandular podia, with uncini arranged in straight rows, shortening far posteriorly ( Fig. 4H View FIGURE 4 ).

Pygidium lacking anal cirri, margins crenulated, divided into numerous small, compact lobes ( Fig. 3G View FIGURE 3 ).

Tube composed of shell fragments and coral rubble attached to thin mucous layer ( Fig. 3H View FIGURE 3 ).

Variation. Paratype NTM W029897 is 7 mm in length (far posterior removed for molecular) and 2.5 mm with 45 segments compared to the holotype which is 350 mm in length (excluding buccal tentacles), 12 mm maximum width, with about 195 abdominal segments. The smaller paratype came from the mid-east coast of Moorea, whereas the holotype was found on its mid north coast, both only about 10 km apart following the coastline. Paratype AM W.55131 was collected about halfway between these two locations. Although the smaller NTM paratype differs from the holotype in the extent of the lateral lobe development – the holotype has a pronounced basal ridge on lateral lobes of segment 3 and glandular patches ( Fig. 3E, F View FIGURE 3 ), both specimens exhibit banded buccal tentacles [lost upon fixation ( Fig. 2A View FIGURE 2 )], the glandular patches are less marked in preserved specimens ( Fig. 3B View FIGURE 3 )] and have a ridge or flange postero-ventrally on lateral lobe 3, albeit very small in the paratype. Loimia davidi Martin, Capa, Martinez & Costa (2022 , table 2) exhibited size-related differences in the development and extent of lateral lobes ( Martin et al. 2022), which agrees with the variation exhibited by the small and a large individuals of L. aimehoensis sp. nov., supporting the proposition that some morphological characters change slightly in shape and dimensions as individuals grow. Such variation is rarely discussed when new polychaete species are described, as typically a range of different sized individuals is not available.

Etymology. The species name refers to the type locality in the Tahitian language. Aimeho was the island’s former name before it became Moorea, based on variants of the oral language.

Type locality. French Polynesia, Society Islands , Moorea, fringing reef .

Distribution. Known only from NE Moorea.

Habitat. Associated with dead coral substrates on the fringing reefs from 1–10 m depth.

Remarks. Loimia aimehoensis sp. nov., is characterised by having banded buccal tentacles and white spots, and white patches between parapodia; smooth dorsum and ventrum; large lateral oval-shaped lateral lobes on segment 1 and segment 3 with lobes with a dorsal flag-like extension ( Table 2 View TABLE 2 ). We discuss how this new species can be distinguished from other species in the region, including L. poraporaensis sp. nov., in the Remarks of this latter new species.