Myxicola dilianae, Tovar-Hernández & León-González & Hendrickx, 2025

Tovar-Hernández, María Ana, León-González, Jesús Angel De & Hendrickx, Michel E., 2025, Polychaeta collected during the research cruises TALUD aboard the R / V “ El Puma ” in the Mexican Pacific: Sabellidae and Serpulidae, Zootaxa 5663 (1), pp. 1-80 : 46-49

Myxicola dilianae sp. nov.

urn:lsid:zoobank.org:act:C8B14500-7F10-4C08-A4C4-4A99B4BA31FE

( Figs 25 , 40E–F , Table 3)

Material examined. Type material. Holotype, ICML-EMU-14036: TALUD XIV, St. 33, BS, 27º47'52"N 111º09'30"W, 11 April 2011, 319– 344 m. Additional material. ICML-EMU-14037: TALUD XV, St. 23, BC, 27º08'11"N 114º32'54"W, 01 August 2012, 681 m, 1 specimen .

Description. Preserved color pale over body. Body flattened dorso-ventrally ( Fig. 25A–B ), widest around chaetiger 4, then tapering posteriorly to a blunt pygidium. Trunk 11.7 mm long, body 1.5 mm wide. Branchial crown 7.8 mm long with nine pairs of radioles. Thorax with eight chaetigers. Abdomen with 50 chaetigers. Radioles connected by palmate membrane along 7/8 of their length with broad radiolar flanges. Radiolar tip bare, as long as 1/8 the radiolar length, triangular, elongating evenly to tip and surrounded by a semi-transparent broad flange ( Fig. 25C ). Longest pinnules at 3/4 of the radiolar length, gradually shortening to the end of radiolar membrane. Number of vacuolated skeletal cells not determined. Radiolar eyes absent. Dorsal lips short, rounded with a long radiolar appendage arising from ventral internal border of ventral lips ( Fig. 25F ). Ventral lips extending dorsoventrally along inner surface of base of radiolar lobes and connecting ventrally to the radiolar lobes. Ventral radiolar appendages, parallel lamellae and ventral sacs absent. Anterior peristomial ring with a mid-ventral, triangular lobe, slightly higher than the length of second chaetiger ( Fig. 25D ). Anterior peristomial ring lower laterally, with a lateral notch reaching next segment ( Fig. 25E ). Posterior peristomial ring collar absent. Junction between crown and body not visible. Glandular ridge present on chaetiger 2, whitish, homogeneously narrow ( Fig. 25D ). Ventral shields not developed ( Fig. 25D ), except for a reminiscent ventral circular shield on chaetiger 1. Interramal eyespots absent. Thorax with narrowly hooded notochaetae ( Fig. 25H ). Thoracic tori inconspicuous. Thoracic neurochaetae acicular uncini with long handles; long elongate fang, slightly bent with several minute teeth above and a slight constriction at top of shaft ( Figs 25I , 40E ). Companion chaetae absent. Lateral eyes in abdomen absent. Abdominal chaetigers with narrowly hooded neurochaetae in less conspicuos tufts. Abdominal notopodial tori forming almost complete cinctures around body ( Fig. 25G ), with avicular uncini with 1–2 large teeth over main fang ( Figs 25J–K , 40F ); breast rounded, slightly longer than main fang, handle absent ( Fig. 25J–K ). Pygidium rounded, eyespots absent. Pygidial cirrus absent. Tube unknown.

Etymology. This species is named after Dilian Anguas-Cabrera, a hardworking colleague that helped us during the TALUD cruises and other field activities on land, sorting polychaetes from diverse projects on fouling polychaetes. The species-group name is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Remarks. The specimen here reported as Myxicola dilianae sp. nov., from the northern Gulf of California closely matches with the redescription provided for Myxicola affinis Bush, 1905 by Putignano et al. (2024), basically in the shape and size of the mid-ventral lobe of the anterior peristomial ring (triangular) and the presence of dorsal lips with radiolar appendages. However, lateral eyes are present in M. affinis starting at chaetiger 4 (absent in Myxicola dilianae sp. nov.) and the glandular ridge on chaetiger 2 is hardly visible in M. affinis (well developed glandular ridge on chaetiger 2 in Myxicola dilianae sp. nov.) ( Table 3).

Myxicola dilianae sp. nov., differs from M. bruscai sp. nov., by: 1. The absence of radiolar eyes (composed and paired in M. bruscai sp. nov.). 2. Radiolar tips triangular with broad lateral flanges (radiolar tips filiform, without flanges in M. bruscai sp. nov.). 3. A well developed glandular ridge only on chaetiger 2 (glandular ridges on chaetigers 1 and 2 in M. bruscai sp. nov.). 4. Lacking glandular longitudinal bars in posterior thoracic and abdominal segments (present in M. bruscai sp. nov.). 5. Dorsal lips with radiolar appendages (radiolar appendages absent in Myxicola bruscai sp. nov.) and 6. Abdominal uncini forming almost complete cinctures around body (cinctures interrupted for a half of the segment width, dorsally and ventrally in Myxicola bruscai sp. nov.) ( Table 3).

Abiotic conditions. The specimen of M. dilianae sp. nov., was collected from 319‒681 m deep, under the following environmental conditions. Temperature: 6.44‒10.4°C; salinity: 34.45; dissolved oxygen: 0.07 ml O 2 /l; %MO: 5.15; sediments dominated by sand and silt (46.6% each) ( Table 1).

Distribution. Northern Gulf of California and west coast of Baja California Sur, Mexico.

Genus Perkinsiana Knight-Jones, 1983

Figures

FIGURE 25. Myxicola dilianae sp. nov. A) Body, dorsal view, B) same, ventrolateral view, C) radiolar tip, D) thorax, ventral view, E) same, dorsal view, F) dorsal lips, G) abdominal cinctures of uncini pointed with arrows, H) thoracic chaetiger, I) thoracic uncini, J–K) abdominal uncini. Abbreviations: dl—dorsal lip, gr2—glandular ridge on chaetiger 2, ra—radiolar appendage. Scale bars: A–B) 5 mm, C) 0.3 mm, D–E) 1.5 mm, F–G) 0.5 mm, H) 200 μm, I) 10 μm, J–K) 20 μm. A–J: holotype ICML- EMU-14036.

FIGURE 40. Line drawings of chaetae and uncini. A, G–H, L–M, S) Thoracic chaetae. B, E, J, O, Q, T) Thoracic uncini. C–D, F, K, P, U) Abdominal uncini. I, N, R) Companion chaetae. A–D) Myxicola bruscai sp. nov. E–F) Myxicola dilianae sp. nov. G–K) Perkinsiana araceliae sp. nov. L–P) Perkinsiana nuriae sp. nov. Q–U) Potamethus pepei sp. nov. Scale bar: 30 μm.