Iphione wilsoni, Salazar-Vallejo & Piotrowski & Paulay, 2024

Salazar-Vallejo, Sergio I., Piotrowski, Christina N. & Paulay, Gustav, 2024, Revision of Iphione Kinberg, 1856 (Annelida, Aphroditiformia, Iphionidae), Zootaxa 5548 (1), pp. 1-84 : 73-77

Iphione wilsoni sp. nov.

urn:lsid:zoobank.org:act:8EE1E870-B326-4A0A-B375-BE8782A39B0D

Figs 34 , 35

Iphione muricata : Hanley & Burke 1991: 39–41, Fig. 11 (non (Savigny in Lamarck, 1818)).

Type material. Australia. Holotype ( NMV F164310 ), Western Australia, Ashmore L 30 Transect, SS 05/2007 Sta. 188 (12°26’42.0” S, 123°36’03.6” E), 95 m, beam trawl, 6 Jul. 2007.

Additional material

Coral Sea. One specimen ( MAGNT W5511 ), Cruise Corail 2, RV Coriolis, Fairway Atoll (Reef) , Sta. RH 88.46 (20°53’ S, 161°41’ E), 60 m, 20 Aug. 1988, J.R. Hanley, coll.

Indonesia. One specimen ( ZMA V471.5 ), Sulawesi, RV Siboga Exped., Sta. 125 ( Siau Island , anchorage off Sawan), 27 m, dredge, townet, Monaco trap, reef-exploration, stones, 18–19 Jul. 1899 (markedly bent ventrally; juvenile; right elytra 3, 6 and 9 removed for observation; elytra yellowish without black spots; macrotubercles in two rows, towards posterior margin, each erect, subcylindridal, brittle, with many spines along stem; no further dissected nor measured to avoid further damage) .

Diagnosis. Iphione with median antenna reduced to nuchal papilla; elytra with margins smooth, non-fimbriate; macrotubercles cylindrical or tapered, with distal spines, in six or more rows, first row with macrotubercles markedly larger than those in other rows; cirrigerous segments with dorsal cirrophores with basal tubercle projected; neurochaetae unidentate.

Description. Holotype (NMV F164310) bent ventrally ( Fig. 34A ), 22 mm long, 12 mm wide, 29 chaetigers; first four pairs of elytra previously removed; right elytron 6 and left parapodium of chaetiger 12 removed for observation.

Elytra yellowish with an oblique, irregular black band, and darker along posterior margins, almost without calcareous epibionts, without fimbriae ( Fig. 34B ). Macrotubercles arranged in 5–6 rows, subcylindrical, largest along external margins, markedly larger and bent middorsally, other erect or bent anteriorly, with spiny stems and stellate tips, each with 4–5 spines ( Fig. 34C ). Macrotubercles with spines more abundant along posterior margins ( Fig. 34D ).

Prostomium retracted, roughly hexagonal, as long as wide, with a deep longitudinal depression along anterior prostomial half. Anterior lobes projected into ceratophores, blackish, longer than prostomium, ceratostyles lost. Palps pale, three times longer than ceratophores. Eyes blackish, positioned in posterior prostomial half, anterior eyes lateral, 1/3–1/2 as large as posterior, dorsal eyes. Nuchal papilla not visible.

Tentacular segment dorsally reduced, cirri as long as palps, chaetae not seen, probably lost. Facial tubercle blackish, visible dorsally.

Segments 2–4 directed anteriorly. Second segment not visible dorsally; nuchal lappet hidden below anterior margin of segment 2, semicircular. Ventral buccal cirri inserted ventrally, longer than following ventral cirri, right one lost, left one not surpassing chaetal tips. From segment 3, one pair of depressed, separate dorsal nodules per segment, only first pair visible, the others distorted by body contraction. Segments 2–3 with finer neurochaetae, barely swollen subdistally, with a longer region covered by series of transverse denticulations.

Median cirrigerous segments ( Fig. 34E ) with dorsal cirri slightly surpassing chaetal tips (many cirrostyles lost), resembling tips of tentacular cirri; dorsal cirrophores smooth, basal tubercle projected. Notochaetae whitish, very abundant, delicate capillaries with series of transverse funnel-shaped spinose rows, tips bare. Neuropodia with neuracicular lobe 2–3 times longer than wide, blunt; neurochaetal lobe with small globular papillae. Neurochaetae golden, thick abundant, basally smooth, subdistally swollen, with series of denticulations along swollen region, tips falcate, sharp ( Fig. 34F ).

Anus dorsal, positioned between elytral pairs 12 and 13.

Etymology. This species is being named after Robin Wilson, a well-known polychaete specialist working in the Museums Victoria Research Institute, Australia, in recognition of his many publications on taxonomy of marine annelids, and by his support for our studies on scaleworms. The specific epithet is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Variation. A large specimen (MAGNT W5511) has a body rather truncate, instead of being oval, 30 mm long, 18 mm wide, 29 chaetigers. The anterior 7 pairs of elytra, and two left and one right parapodia previously removed (most elytra in container, parapodia lost), right parapodium of chaetiger 12 removed for observation. Elytra yellowish with an oblique longitudinal black band ( Fig. 35A, B ); macrotubercles subcylindrical, tapered, bent middorsally or anteriorly, smaller ones erect, tips stellate, arranged in 6 rows, progressively smaller posteriorly. Cirrigerous segments with basal tubercle of dorsal cirrophores projected ( Fig. 35C ); dorsal cirrostyles tapered, ventral cirrostyles mucronate; neurochaetal lobe with one long cirriform papillae, if seen in anterior view ( Fig. 35D , inset), other papillae globular; neurochaetae unidentate.

Remarks. Iphione wilsoni sp. nov. separates from other species of Iphione lacking elytral fimbriae by the type and shape of macrotubercles, and by the type of neurochaetae. In I. wilsoni macrotubercles are subcylindrical with tips stellate, whereas they are blunt in the other species, and it has unidentate neurochaetae, whereas they can be bidentate in some other species.

Hanley & Burke (1991: 39) illustrated what they regarded as I. muricata (Savigny in Lamarck, 1818). However, the elytra lack fimbriae and are different from I. muricata by having thinner, mostly erect macrotubercles, and the additional smaller ones have stellate tips. These specimens were not available but they seem conspecific with I. wilsoni .

Distribution. Western Australia through Indonesia to the Coral Sea, in deeper subtidal mixed bottoms (27–95 m).

Concluding remarks

The most useful morphological characters for differentiating Iphione species include the eyes (size and position), relative length of palps and lateral antennae, and some elytral and parapodial features.

The highly developed oblique muscles of Iphione ( Storch 1967) that are responsible for these worms’ ability to attach themselves to hard bottoms, together with the intrinsic musculature of cephalic appendages, can impact the shape and length of cephalic appendages as well as the position of eyes. Consequently, size relationships of palps and antennae and size and position of eyes are too variable to be reliable for separating species. Other scaleworm groups have a stiffer prostomium and their bodies have less developed oblique muscles system, such that the relative shape of prostomium and size and position of eyes can be diagnostic.

The main features of elytra are the fimbriae and macrotubercles. Because fimbriae filaments are elastic, they were regarded as fragile and of little diagnostic relevance. We conclude otherwise; fimbriae are distinctive, even if the filaments are very short, and provide a reliable diagnostic feature. Macrotubercles show two different trends regarding the number of rows per elytron. There are some species where the number of rows is size-dependent, with larger specimens having more rows than smaller ones, as it was shown elsewhere ( Piotrowski et al. 2024) for I. ovata Kinberg, 1856 , or as indicated above for I. fimbriata de Quatrefages, 1866 , and there are other species where the number of rows does not change with body size, such that there can be a single row, like in I. treadwelli Pettibone, 1986 or I. corbariae sp. nov., or two rows as in I. muricata (Savigny in Lamarck, 1818), or I. hourdezi sp. nov.

Shapes of macrotubercles are also useful, especially if the impact of erosion that can damage tips and more exposed surfaces, is taken into consideration. Macrotubercles can be conical, digitate, subcylindrical, or cushion-shaped, and useful to separate species. Most species have conical macrotubercles, a few have them digitate (e.g., I. muricata ), cushion-shaped ( I. treadwelli ), or subcylindrical ( I. wilsoni sp. nov.).

The most useful parapodial features are the degree of development of the basal tubercle of dorsal cirrophores, and the shape and type of neurochaetae. The basal tubercle is often projected laterally as a low blunt cone; rarely it is not developed and indistinct. In a few species, pigmented globular glands can be seen in the basal tubercle, distally or basally, and can be diagnostic, although their persistence in preserved specimens deserves to be assessed. When specimens are fixed in ethanol, or placed in the fixative after they are dead, deterioration of body wall muscles can lead them to become transparent, and the basal tubercle can be completely reduced. A comparison with betterpreserved specimens from the same locality, can help clarify if the basal tubercle is really indistinct or reduced due to inadequate fixation.

Neurochaetae include diagnostic as well as size-dependent features.Among the latter is the number of transverse rows of denticles along the subdistally swollen region; we have confirmed that these changes depending on the position of chaetae in the chaetal bundle and noted their dependence on body size. Neurochaetae are typically subdistally swollen, but in one species ( I. hourdezi ) they are barely swollen and, although thin, can be regarded as acicular. Neurochaetal tips are also diagnostic; most species have unidentate tips, and a few species have them bidentate.

These characters allowed us to better understand the taxonomy of Iphione species, further tested with COI sequence data ( Fig. 36 ). We now recognize 8 described and 9 new species in the genus, and regard I. peronea ( Schmarda, 1861) as indeterminable, whereas I. hirotai Izuka, 1912 from Japan, could not be clarified, and this requires the study of topotype material, which were not available.

The species of Iphione can be grouped after some morphological features as follows:

1) Elytra fimbriate.

1A) Neurochaetae unidentate.

1A.1) Macrotubercles arranged in 1(–2) rows: I. treadwelli Pettibone, 1986 , I. hourdezi sp. nov.; I. richeri sp. nov.

1A.2) Macrotubercles arranged in 2–3 rows: I. muricata (Savigny in Lamarck, 1818); I. malifera Piotrowski, 2014 ; I. ankeri sp. nov., I. readi sp. nov.

1A.3) Macrotubercles arranged in 3–5 rows: I. fimbriata de Quatrefages, 1866 , I. hyndmani sp. nov.

1A.4) Macrotubercles arranged in about 10 rows: I. henshawi Pettibone, 1986

1B) Neurochaetae bidentate: I. corbariae sp. nov.

2) Elytra with smooth margins.

2A) Tips unidentate: I. ovata Kinberg, 1856 , I. wilsoni sp. nov.

2B) Tips bidentate: I. coriolis Hanley & Burke, 1991 ; I. harrisae sp. nov.

Some Iphione species have very large distributions. For example, I. ovata can be found from the Red Sea to the Eastern Pacific ( Piotrowski et al. 2024), I. muricata and I. readi range from the Red Sea to Samoa, and I. henshawi thrives from the Red Sea to Hawaii. On the contrary, some other species are only known from a single locality such as I. hirotai from Japan, I. malifera from the Philippines, and I. peronea from Sri Lanka. However, because we ignore the reproductive biology and larval dispersal for all Iphione species, we have no means to explain the larger distributional ranges and, likewise, we have no idea about any ecological segregation for those species living in the same area. We wish to encourage our fellow colleagues to undertake some studies on the ecology and reproduction of Iphione species.

Figures

FIGURE 11. Iphione henshawi Pettibone, 1986, non-type specimen (BPBM R481). A. Anterior end, dorsal view (elytra 1–3 removed). B. Left elytra 1–3, dorsal view. C. Elytron 3, close-up of fimbriae, some macrotubercles in the lower area. D. Same, close-up of macrotubercles. E. Cirrigerous left parapodium of median segment, posterior view. Scale bars: A, 0.8 mm; B, 1.4 mm; C, D, 0.3 mm; E, 0.5 mm.

FIGURE 34. Iphione wilsoni sp. nov., holotype (NMV F164319). A. Dorsal view. B. Right elytron 6, dorsal view. C. Same, close-up of external margin after Shirlastain-A. D. Another elytron, transverse section across central macrotubercles region. E. Chaetiger 12, left parapodium, posterior view after removal of notochaetae. F. Same, neurochaetal tips. Scale bars: A, 2.7 mm; B, 0.8 mm; C, E, 0.4 mm; D, 150 µm; F, 130 µm.

FIGURE 35. Iphione wilsoni sp. nov., non-type specimen (MAGNT w5511). A.Anterior left elytron. B. Median left elytron. C. Chaetiger 12, right parapodium, posterior view (after Methyl green staining). D. Same, anterior view (inset: tip of neuracicular lobe). Scale bars: A, 1.1 mm; B, 1.2 mm; C, 0.7 mm; D, 0.5 mm.

FIGURE 36. Maximum Likelihood phylogeny of Iphione species with localities and catalog numbers. Numbers above branches are bootstrap support (>70 only) (PNG: Papua New Guinea) (modified after Piotrowski et al. 2024).