Pareurythoe dubia (Horst), 2025

Pareurythoe dubia (Horst) comb. n.

or 59), right parapodium, posterior view (insets: notochaetae, spurred neurochaeta, and acicular neurochaeta). (F) region, dorsal view. Scale bars: A = 13.3 mm; B = 1.9 mm; C, D = 0.4 mm; E = 1.2 mm; F = 2.4 mm (authors’ work

Eurythoe chilensis View in CoL : Horst 1912: 36, pl. 9, figs 21–23 ( partim, non Kinberg, 1858).

Pareurythoe pitipanaensis de Silva, 1965: 540–542 View in CoL , fig. 3; Gibbs 1971: 132.

Type material

Indonesia. Holotype of E. dubia ( ZMA V.Pol 293), Irian Jaya, RV Siboga Exped., Sta. 272 (Aru Island, pelagic, 21–23 December 1899.

Sri Lanka. Holotype of P. pitipanaensis de Silva, 1965 ( BMNH 1963.14.1), Pitipana, Negombo sticks immersed in water as fish traps, in Teredo tunnels, December 1962, April 1963.

Additional material. Madagascar

One specimen ( UF 761), Nosy Be, E of Hellville, at CNRO complex, intertidal, sandy mudflat with rocks

S, 48.29°E), 18 May 2008, A. Anker, coll. (body tapered at both ends, medially wider, regenerating region; 112 mm long, 8 mm wide, 124 chaetigers; right parapodia of chaetigers 13 and 83 removed observation (kept in container); other data in ‘Variation’ section).

One specimen ( USNM 58945 About USNM ), Tulear, B . Thomassin, coll . (no further data; mature female, 90–100 µm; pale; several parapodia previously removed (kept in container); caruncle reaches margin of chaetiger 2; branchiae from chaetiger 3, with 6 filaments; eyes colourless; anus terminal plate minute, round, entire; body 24 mm long, 2.5 mm wide, 61 chaetigers).

JOURNAL OF NATURAL HISTORY parapodia removed (some in container); branchiae from chaetiger 3 with 5 filaments, continued end of body; body 30 mm long, 2 mm wide, 77 chaetigers).

One specimen ( ZMA V.Pol 292.4), Lesser Sunda Islands, RV Siboga Exped ., Sta. 315 ( Paternoster anchorage E of Sailus Besar), 36 m, dredge, coral, 17–18 February 1900 (contracted; brown parapodia previously removed (not in container); caruncle in a furrow, sinuous, reaching anterior of chaetiger 3; median antenna as long as laterals; branchiae from chaetiger 3 with 2 filaments filaments in median chaetigers, continued to last chaetiger with fewer filaments; body 11.5 mm 2 mm wide, 41 chaetigers) .

Vietnam. One specimen ( USNM 58943 About USNM ), Tonkin, M . Lichtenfelder, coll . (no further data; body pale, several parapodia previously removed, including the right ones of chaetigers 1–4 (some in

39.5 mm long, 4.5 mm wide, 81 chaetigers; caruncle reaching posterior margin of chaetiger 2;

from chaetiger 3, with 10 filaments, up to 22 in median chaetigers, down to 10 in posterior ones; anterior posterior eyes large, of similar size; median notopodia with aciculars, harpoon chaetae, and capillaries; neuropodia with abundant capillaries, thin spurred, and furcate with small to distinct tine; anus terminal, anal plate minute).

Solomon Islands. One specimen ( USNM 58942 About USNM ), Graham Point , Guadalcanal, 21 September 1965, P .E coll. (markedly bent ventrally; pale, with a brown spot where it was fixed with a pin; several left from first, anterior, median and posterior chaetigers previously removed (many in container); reaching chaetiger 2; branchiae from chaetiger 3 with seven filaments; anus dorsoterminal, anal round, margin entire; body 21 mm long, 2.5 mm wide, 60 chaetigers).

Diagnosis

Pareurythoe with caruncle extended along chaetigers 1–2, reaching anterior area of chaetiger 3; furrow deep. Anterior eyes round, anterior and posterior eyes of similar size. Branchiae from chaetiger 1–3 stems. Median segments with spurred neurochaetae.

Description

Holotype of E. dubia ( ZMA V.Pol 293), complete, pale, mature female; body depressed, bent laterally,

at both ends ( Figure 5 View Figure 5 (A)), both body sides almost rectilinear; left parapodia of chaetigers 1–2, and parapodia of chaetigers 4–5, 58–59, 104–105 previously removed (some in container), body wall chaetigers 76–77; body 260 mm long, 13 mm wide, 131 chaetigers.

Anterior region tapered ( Figure 5 View Figure 5 (B)); prostomium round, anterior lobe bent ventrally, with antennae and palps directed laterally; palps and lateral antennae of similar size. Posterior lobe with Black ( Figure 5 View Figure 5 (C)), anterior eyes not visible dorsally, directed frontally, about two times as large as eyes ( Figure 5 View Figure 5 (D)). Median antenna lost, scar visible ahead of caruncle (illustrated as slightly larger laterals).

Caruncle sinuous, tapered, blunt, as long as first chaetiger, reaching anterior portion of chaetiger 2 included in middorsal furrow running along chaetigers 1–2, indistinct in following chaetigers. Pharynx exposed. Mouth between chaetigers 3 and 4.

Branchiae from chaetiger 3, with 8 filaments; dorsal and ventral cirri biarticulate, cirrostyles Anterior chaetigers with branchiae with up to 26 filaments; median and posterior chaetigers with filaments; prepygidial chaetigers with up to 5 filaments.

Parapodia biramous ( Figure 5 View Figure 5 (E)). Notopodia with short conical lobes; dorsal and ventral cirri dorsal cirri longer than ventral ones throughout body. Chaetae observed in a median segment;

include abundant thin capillaries, often finely denticulate, and white harpoon chaetae with many ( Figure 5 View Figure 5 (E), insets); neurochaetae mostly capillaries, some finely denticulate, and a few spurred Description of atoke

Syntype of P. pitipanaensis (BMNH 1963.14.1) pale, atoke, several parapodia previously removed (4

in BMNH); body depressed, tapered at both ends, body sides roughly rectilinear ( Figure 6 View Figure 6 (A)), 86 mm 4.5 mm wide, about 110 chaetigers.

Anterior region tapered ( Figure 6 View Figure 6 (B)); prostomium round; anterior lobe with lateral antennae

JOURNAL OF NATURAL HISTORY

Caruncle sinuous, tapered, blunt, as long as first chaetiger, reaching half of chaetiger 2, partially in a middorsal furrow running along chaetigers 1–3, slightly damaged after dissection of right parapodia chaetigers 1–3, and branchiae and dorsal cirrus of chaetiger 4.

Branchiae from chaetiger 3, with 1–3 short stems and long filaments, looking pectinate. Second branchia with 6–8 filaments, progressively increasing in number and size up to chaetigers 20–25, in number and size of filaments posteriorly.

Parapodia biramous, notopodia with short conical lobes; dorsal and ventral cirri biarticulate, dorsal longer than ventral ones throughout body. Anterior chaetigers ( Figure 6 View Figure 6 (C)) with about 20 filaments, up to 40 filaments by chaetiger 20, posterior chaetigers with 6–8 filaments ( Figure 6 View Figure 6 (D)).

Chaetae damaged (after long time in formalin); notochaetae originally described as harpoon chaetae furcates with long tine denticulate (a few of the latter still visible in median chaetigers); described as furcates, some with denticles along longer tine, others with smooth longer tine and tine minute ( Figure 6 View Figure 6 (F,G)); neuraciculae distally expanded, expanded region about twice longer than ( Figure 6 View Figure 6 (E)).

Posterior region tapered; pygidium described as round, without anal cirri.

Variation

A prenatatory female epitoke (UF 761) shows some features no longer visible in the holotype of P Body wall brown, convoluted. Prostomium oval, as long as wide; eyes Black, round, anterior and eyes of similar size ( Figure 7 View Figure 7 (H)); median antenna about as long as caruncle, 2 times as large as caruncle reaching about half of chaetiger two; branchiae from chaetiger 3 with 10 filaments, about chaetiger 10, progressively smaller and less abundant along posterior chaetigers; notopodia and of similar size, neurochaetae longer and more abundant than notochaetae in anterior ( Figure 6 View Figure 6 posterior segments ( Figure 6 View Figure 6 (J)). Chaetae variably damaged after being fixed with formalin;

include long spurred capillaries finely denticulate and harpoon chaetae ( Figure 6 View Figure 6 (I), inset), whereas chaetae include long capillaries, spurred shorter chaetae, and acicular chaetae ( Figure 6 View Figure 6 (J), inset). 90–100 µm in diameter.

Remarks Fauvel (1953, 16–17) compiled the chaetal modifications in amphinomid epitokes, after details recorded by Augener (1918), and his own observations ( Fauvel 1927). Fauvel indicated that the differences between atokes and epitokes were chaetae type and abundance. He noted that appear first in neuropodia, becoming abundant and very long, whereas typical furcates can be some species, or be completely replaced in other ones. In later stages, Fauvel noted that capillaries present also in notopodia, and they can be even more numerous than in neuropodia, and can be smooth, replacing some spurred chaetae. Fauvel added that E. dubia Horst was an epitoke whose podia has numerous smooth capillaries, and a few furcates with very small shortest tines’ (Fauvel Despite the long distance between the type localities of E. dubia and E. pitipanaensis , herein both belonging in Pareurythoe , they are regarded as conspecific, the former as the epitoke, the latter atoke.

Eurythoe dubia Horst belongs in Pareurythoe , and hence the new combination. Horst (1912, 37) noted the epitoke he described had a caruncle resembling the one present in P. californica ; his illustration fig. 1) also shows that branchiae start in chaetiger 3 with 4–5 filaments. It might be possible specimens of what he identified as E. chilensis are conspecific with P. dubia ( Horst, 1912) comb. n so, this would be the name available for the Indonesian species.

Other specimens included by Horst in E. chilensis do not match Eurtythoe or Pareurythoe ; one (ZMA V.Pol 292.2) matches Linopherus de Quatrefages by having a minute caruncle and branchiae to the anterior region, whereas these two other genera have them along the body.

Horst (1912) indicated that in what he regarded as E. chilensis , there was some variation in the

Kudenov (1993, 103) remarked that Hartman (1948, 46) noted that Indonesian specimens had furcate neurochaetae instead of being completely denticulate, harpoon chaetae had small denticles of well developed ones, and that smooth acicular notochaetae were missing.

Pareurythoe pitipanaensis de Silva, 1965 View in CoL was described with 11 specimens, but it seems that only deposited in London. The other specimens were not deposited and can be presumed lost, such that available specimen is the holotype, although it was referred to as the lectotype ( de Silva 1965, holotype was 60 mm long, 3.5 mm wide, 65 segments. It was found together with specimens ‘ E. complanata ’.

Pareurythoe dubia resembles P. heterotricha (Potts) comb. n., described from the Maldives, as the key above, because both species have branchiae from chaetiger 3, and median antenna at least long as caruncle. Their main difference is in the size of eyes and the type of neurochaetae in segments; in P. dubia anterior eyes are slightly larger than posterior ones, and neurochaetae are whereas in P. heterotricha anterior eyes are 2–4 times as large as posterior ones, and neurochaetae furcate.

Some amphinomid species have been regarded as widely distributed. Bhaud (1972) studied larvae collected in Madagascar. These larvae have been regarded as belonging to amphinomids, and (1972, 204) noted they were common across the Atlantic Ocean, and he identified his larvae amphinomid described from Indonesia ( Bhaud 1972, 208). Ahrens et al. (2013) noted that there was homogeneity throughout the Atlantic Ocean for one of the largest amphinomid species ( Hermodice unculata ), whereas for another large-sized amphinomid species described from the Caribbean Sea ( complanata ), at least three cryptic species were documented, two of them for the Atlantic ( Barroso 2010). Surprisingly, this same species was regarded as cosmopolitan by some of the authors involved in the recognition of cryptic species; further, they included as junior synonyms 10 other described from different localities in the Indian and Pacific oceans ( Arias et al. 2013) but no type material examined. Further, the analysis of specimens of Amphinome rostrata from Australia, the Mariana Islands Caribbean Sea resulted in a single group ( Borda et al. 2012), and this was later confirmed with specimens of other genera ( Wang et al. 2025). However, deep-water species can also have very distributions, and one species, Archinome jasoni , has been found in Atlantic, Indian and Pacific ( Borda et al. 2013).

Distribution

Indonesia to the Solomon Islands, in shallow-water sediments, or in decaying wood.