Iphione Kinberg 1856

Iphione Kinberg, 1856 Iphione Kinberg, 1856: 383, 1858: 8; Baird 1865: 181; de Quatrefages 1865: 266; Grube 1876: 50; Grube 1878: 21; Darboux 1900: 108 (syn.); Gravier 1901: 226; Izuka 1912: 63; Horst 1917b: 65; Fauvel 1932: 12; Fauvel 1953b: 32; Day 1967: 43; Fauchald 1977: 63; Pettibone 1986: 6; Hanley & Burke 1991: 38 (diagn., key); Wehe 2006: 61 (diagn., key). Norepea Baird, 1865: 200 (type species: Polynoe peronea Schmarda, 1861 by monotypy); synonymy after Chamberlin 1919: 40, Fauchald 1977: 65, and Pettibone 1986:6. Type species. Iphione ovata Kinberg, 1856, by subsequent designation (Hartman 1959: 82). Diagnosis. Iphionids with prostomium with long lateral antennae, median antenna rarely present; two pairs of eyes; palps with longitudinal rows of papillae; 13 pairs of elytra on segments 2, 4, 5, 7, alternating segments to 23, and then on 27; elytral surface with macrotubercles usually projected, spinous or smooth, elytral margins smooth or with fimbriae; most neurochaetae thick, rarely acicular, tips unidentate or bidentate, rarely hooded, with subdistal transverse rows of spinules. Remarks. Baird (1865) was first to designate a type species for Iphione, stating: “The typical species is the Polynoë muricata of Savigny, so beautifully represented by that author in his great work on Egypt.” Further, Farber (1976: 95, footnotes 5, 6) noted that this type of phrasing was common in the 1840s, and while the Code has not been established, there were recommendations for using types and type species (Gray 1840, Strickland 1845), although the first draft of the Rules for Nomenclature was published in 1843, and adopted in 1865 (Strickland 1843, Sclater 1878). This subsequent designation was accepted by Pettibone (1986: 2). Regretfully, Article 67.5 of the Code (ICZN 1999) explicitly rules out type species designations based on the word ‘typical’, making Baird’s designation not valid. Hartman (1959) was first to validly designate a type with Iphione ovata Kinberg, 1856. While the type species of Norepea Baird, 1865 is clearly an Iphione, what species it represents has been contentious. Michaelsen (1892: 95) regarded Polynoe peronea Schmarda, 1861 described from Sri-Lanka, as a junior synonym of I. spinosa Kinberg, 1858, probably because both have elytra with smooth margins, without fimbriae. However, he noted differences: “The present specimen deviates from Kinberg’s description markedly, as the antennae are not quite smooth, but with sparse (ca. 15), cylindrical papillae.” In contrast, Willey (1905: 246–247) regarded P. peronea as a junior synonym of I. muricata (Savigny in Lamarck, 1818), even though I. spinosa was described with smooth elytral margins and that he noted that Grube (1878: 22) “states that the outer and posterior margin of the scale is fimbriated which is not so in I. peronea.” Pettibone (1986: 4) regarded P. peronea as an unidentifiable Iphione species and the lack of type material implies that it will remain a nomen dubium. Distribution. Iphione appears to be restricted to, but ranges across, the entire tropical Indo-Pacific, from the Red Sea to South Africa and east to the Hawaiian and Tuamotu Islands and Americas, mostly in shallow rocky or mixed bottoms. No specimens are known from the tropical Atlantic, except one Red Sea species has recently invaded the Mediterranean Sea (Goren et al. 2017). The record by Gibson (1886: 150) of I. muricata from the Liverpool area was shown to be erroneous (Hornell 1891: 224). Diagnostic characters for Iphione species Elytra Variation in some morphological features of the elytra have been explored by Piotrowski et al. (2024). Because the elytra in Iphione are overlapped, portions are exposed, others are covered by adjacent elytra. Elytra are usually wider than long, the first pair oval, the second and third U-shaped, and the last roughly triangular. Elytral surface is mostly areolated, and areolation varies with size, less well-developed, but covering larger areas in small than large specimens (Piotrowski et al. 2024). Elytra have distinct anterior and posterior regions, and outer and inner areas. There is often a hyaline marginal band, usually along the outer elytral margins. Elytra are ornamented by diverse projecting structures that are categorized as macrotubercles, microtubercles, and fimbriae. These can all be broken, eroded or overgrown by epibionts. Finer details are best seen in smaller specimens because their elytra are thinner and are less obscured by foreign particles. Macrotubercles are distributed over much of the elytral surface, are fragile and often eroded, conical to digitate, ornamented by short stem spines and larger, stiff distal filaments (Fig. 1E, F), and retain a small amount of sediment. Microtubercles are similar to macrotubercles, but small and arranged in several densely packed rows, especially along the posterior elytral margin (Fig. 1D, G). Fimbriae typically occur in a marginal or submarginal band (rarely in inner elytral areas except in regenerating elytra), are flexible and easily bent, globular to cylindrical, ornamented with long, thin spines of similar size along their length and with long, flexible distal filaments, and usually covered by a thick layer of sediment particles that are difficult to remove. Hanley & Burke (1991: 41) indicated that fimbriae might become macrotubercles depending on “the degree of chitinization of the outer edge of the elytron.” This is hardly the case; first, fimbriae and macrotubercles can be present side by side, but no intermediate forms have been documented, and their basement lies along different elytral areas (opaque versus hyaline), especially in larger specimens, and second, along posterior elytral margins, some small macrotubercles might proceed from a low conical stiff structure into a larger, stiff one as elytra continues growing peripherally, whereas adjacent fimbriae are shape-conservative, and do not seem to re-shape themselves into small macrotubercles. Elytral morphology varies with growth in some species and not in others. Additional rows of macrotubercles are added with growth in Iphione ovata (Piotrowski et al. 2024), but not in I. readi sp. nov. as shown in Fig. 1 A–C based on three specimens from one lot collected in the Sudanese Red Sea (NMH 1941.4.4.168–172) that were 9–25 mm long, 7.0– 12.5 mm wide. Neurochaetal rows of denticles The number of rows of denticles on neurochaetae appears not to be a reliable diagnostic feature, because it varies substantially within species with size. One median cirrigerous parapodium was removed from seven specimens from New Caledonia, two in I. hyndmani sp. nov. (UF 5689, 15 mm long, 8 mm wide; UF 5695, 28 mm long, 13 mm wide), and five others of I. fimbriata de Quatrefages, 1866 (UF 5020, 5025, 5620, 5656, 5677; 20–27 mm long, 10–13 mm wide), and four specimens of I. ankeri sp. nov. from the Mariana Islands (UF 134, 217, 1691, 1704; 12–15 mm long, 6–9 mm wide). The New Caledonia smaller specimen had 17–25 transverse rows of denticles in neurochaetae, whereas the larger specimen had 14–38 rows. Other New Caledonia specimens had 19–29 rows in the smallest specimen (UF 5656), and 28–44 in the largest one (UF 5677). Thus, some smaller specimens had 10–18 rows (UF 134, 1704), whereas the largest one (UF 217; 15x 9 mm) had 20–26 rows. Consequently, the number of transverse rows of denticles is size-dependent and is discarded as diagnostic. On the other hand, even though they can be finer along first two chaetigers, most Iphione species have neurochaetae subdistally swollen with falcate tips, and only one species (I. hourdezi sp. nov., see below) has barely swollen neurochaetae, such that they can be regarded as acicular, with tips mostly straight. Anatomy The ventral surface is almost completely flat (Fig. 2A), with very shallow intersegmental borders, and a midventral longitudinal whitish band posteriorly. The digestive system is a straight tube, narrowing posteriorly (Fig. 2B); the pharynx extends 2/5 body length, connects to a long, funnel-shaped stomach, the connection lies within a rather homogeneous sheath, the stomach connects to the intestine and progressively narrow towards the posterior end. The pharynx and stomach walls do not stain with Methyl Green. The pharynx wall is very thick, about 4–5 times thicker than the stomach wall (Fig. 2C), and its connection includes an elastic collar that must be fully expanded when the pharynx is exposed. Two blunt enteric caeca project near the junction of the stomach and intestine. There are additional large, globular, lateral caeca entering parapodial coelom in chaetiger 8. Histological analysis in other aphroditoideans have indicated a very narrow enteric connection, and carmine injection has shown that gut contents do not enter the metameric lateral caeca (Darboux 1900: 222); further, despite the presence of glandular epithelia, the role of lateral caeca in digestion is not completely understood. Dissection of the pharynx revealed upper and lower jaws. Middorsal and midventral papillae at the apex of the everted pharynx are larger than the others; jaws have a roughly triangular shape, with an apical fang and two accessory denticles, the latter larger in upper (Fig. 2D) than lower jaws (Fig. 2E). The pharynx is cylindrical with 11 pairs of marginal papillae in all specimens having pharynx exposed. In dorsal view (Fig. 3A), the marginal papillae are lobate, almost of the same size, and arranged in a row except for with two middorsal papillae that are stacked one above the other; behind the papillae there is a smooth area, followed by a rugose surface. The same smooth area is also present ventrally behind the papillae (Fig. 3B). Upper and lower jaws are both paired and very close to each other. In both frontal and lateral views (Fig. 3C, D), the main fang and accessory denticles are conspicuous because they are darker than surrounding tissues. In lateral view the pharynx aperture is semicircular