Thelepus parapari, Jirkov, Igor, 2018

Jirkov, Igor, 2018, Three new species of Thelepus Leuckart, 1849 from Europe and a re-description of T. cincinnatus (Fabricius, 1780) (Annelida, Terebellidae), ZooKeys 759, pp. 29-56 : 29

Thelepus parapari sp. n. Figs 9, 11D

Material

(Table 1): 177 specimens from 11 stations collected 26.03.1986 between rhizomes of Posidonia , coralligenous formations, calcareous concretions and under stones, 2-15 m, Andalusia, Spain. Holotype MNCN 16.01/17774 (previously part of MNCN 16.01/5706), 5 paratypes previously deposited in MNCN 16.01/5706 now deposited in KGB.

Description

(based on holotype and paratypes). Holotype with 58 segments, 50 of them with notopodia, 50 mm length. Paratypes up to 60 mm in length, 2 mm in width, 60-70 segments, posterior segments clustered and developing with poorly-developed neuropodia, so not possible to count total number of segments.

Several tens of buccal tentacles, their length in fixed specimens equal to half of body. Eyespots absent in most specimens (Fig. 9A), only some with reddish eyespots forming a band without dorsal gap (Fig. 9B). Eyespots probably fade during preservation or variation in this character. Preserved body uniformly beige to yellowish, without distinct patterns of pigmentation; one specimen with eyespots with reddish spots around branchiae. BS1 with up to 12 filaments (11 in holotype); BS2 with slightly fewer filaments (eight in holotype; generally,>70% number on BS1). Filaments thin and very long, reaching more than half of corresponding segment’s width (Fig. 9A, C). Number of filaments increases as worm grows; smallest observed worms (width <0.5 mm) with 1-2 filaments on BS1 and one on BS2. Branchial filaments of BS1 attach in an irregular row on a slightly elevated stump and extend laterally to a point level with notopodia of C1 or sometimes level with upper margin of uncinal row of C3. Filaments of BS2 do not reach notopodia and usually form two rows. A wide medial gap separates left and right groups of filaments. Lateral lobes absent.

Notopodia commence from S3, almost cylindrical anteriorly; those from C1 onwards of equal size. Posterior notopodia poorly developed (almost no rami), with few notochaetae that are several times shorter than most developed notochaetae; neuropodia also reduced. Notochaetae absent only in developing segments near pygidium, approximately ten such segments, exact number difficult to determine as both annulation and neuropodia poorly developed (Fig. 9D). Characteristic number of segments with notopodia less than 60 (based on few available complete worms). Segments without notopodia from only ca. 5% of total worm length. Relatively distinct (in comparison with species described above), small nephridial papillae on S4-S7, above neuropodia (Fig. 9A). Ventrum glandular, without distinct pads (Fig. 9A, E).

Notochaetae sometimes form two distinct transverse rows: anterior row with short chaetae, posterior row with longer chaetae, distal half (winged part) becomes stained with methylene blue, but usually in one row with mixed short and long chaetae; flanges appear to be wider than in species described above (Fig. 11D).

Neuropodia from C3, tori. Uncini in a single row. Uncini of U1 with two teeth in profile above main fang, unlike three species described above (Fig. 9F). However, posteriorly, uncini have only one tooth in profile, in common with species described above (Fig. 9G).

Pygidium with crenulated margin, without cirri or papillae.

Differential diagnosis.

Only one previously known species, T. pascua (Fauchald, 1977), from the Caribbean coast of Panama has two pairs of branchiae and no eyespots. It differs from T. parapari in the lower number of branchial filaments: single filament in BS1 and BS2 in T. pascua ; up to 11 filaments in BS1 and up to 8 filaments in T. parapari . Thelepus parapari differs from T. davehalli (described above) in the absence of fully-developed segments without notopodia. Thelepus parapari differs from T. crassibranchiatus Treadwell, 1901, T. hamatus Moore, 1905 and T. pascua (Fauchald, 1977) (all of which have eyespots) in the higher number of branchial filaments and segments with notopodia. Thelepus parapari differs from T. cincinnatus and T. antarcticus in the lower number of branchial filaments and segments with notopodia. Thelepus parapari differs from T. cincinnatus and T. marthae (described above) in the shape of the uncini of U1. Thelepus nucleolata ( Claparède, 1870), as Heterophenacia nucleolata , was described from nearby (Gulf of Naples), but T. parapari has uncini in a single row, whilst in T. nucleolata they form two rows.

Etymology.

Species is named after my friend Dr. Julio Parapar, Universidade da Coruña, Spain (Fig. 10).