Amphicteis gunneri ( Sars, 1835 )

Parapar, Julio, Helgason, Gudmundur V., Jirkov, Igor & Moreira, Juan, 2011, Taxonomy and distribution of the genus Amphicteis (Polychaeta: Ampharetidae) collected by the BIOICE project in Icelandic waters, Journal of Natural History 45 (23 - 24), pp. 1477-1499 : 1481-1486

publication ID	https://doi.org/ 10.1080/00222933.2011.558640
persistent identifier	https://treatment.plazi.org/id/03AE87C3-A214-B849-FDC7-09DEF65AFACA
treatment provided by	Felipe
scientific name	Amphicteis gunneri ( Sars, 1835 )
status

Treatment

Amphicteis gunneri ( Sars, 1835) View in CoL

( Figures 2 View Figure 2 , 3 View Figure 3 , 4A–C View Figure 4 , 5 View Figure 5 )

Amphitrite gunneri: Sars 1835: 50–51 , pl. 11, fig. 30a–d.

Amphicteis gunneri: Malmgren 1866:365–366 View in CoL , fig. 46; Fauvel 1927:231; Augener 1928:779 (partim?); Annenkova 1929:497, fig. 47 (partim); Holthe 1986a:89; Holthe 1986b:56–57, fig. 21, map 20; Hartmann-Schröder 1996:495; Jirkov 2001:471–472 (textfigure).

Material examined

BIOICE sample 2049 (five specimens); 2075 (three); 2089 (six); 2090 (one); 2091 (two); 2094 (six); 2100 (12); 2102 (one); 2110 (one); 2111 (one); 2119 (five); 2129 (two); 2131 (one); 2154 (ten); 2161 (three); 2172 (one); 2209 (four); 2212 (eight); 2215 (one); 2216 (two); 2230 (two); 2236 (four); 2239 (one); 2241 (two); 2267 (two); 2277 (three); 2279 (one); 2282 (two); 2299 (one); 2310 (three); 2311 (one); 2314 (fourteen); 2324 (one); 2327 (three); 2328 (two); 2337 (twelve); 2348 (one); 2356 (one); 2358 (one); 2359 (one); 2363 (three); 2372 (two); 2374 (three); 2377 (seven); 2379 (one); 2380 (three); 2385 (one); 2387 (one); 2390 (four); 2397 (one); 2400 (one); 2403 (four); 2417 (two); 2418 (eight); 2423 (two); 2424 (one); 2430 (one); 2434 (two); 2435 (four); 2450 (one); 2466 (one); 2475 (one); 2522 (three); 2524 (two); 2526 (one); 2569 (one); 2572 (one); 2573 (one); 2592 (one); 2594 (two); 2595 (three); 2597 (one); 2603 (two); 2606 (nine); 2610 (four); 2612 (two); 2613 (one); 2615 (two); 2618 (two); 2619 (three); 2629 (one); 2642 (one); 2660 (one); 2666 (five); 2668 (one); 2673 (eight); 2697 (four); 2707 (four); 2710 (five); 2712 (14); 2713 (nine); 2717 (two); 2720 (four); 2743 (two); 2754 (two); 2769 (one); 2772 (ten); 2779 (one); 2791 (one); 2792 (six); 2813 (one); 2830 (one); 2849 (four); 2867 (seven); 2868 (one); 2872 (one); 2873 (four); 2877 (two); 2883 (three); 2884 (one); 2897 (three); 2909 (five); 2937 (eight); 2939 (one); 2965 (one); 2967 (two); 2970 (one); 2976 (three); 2978 (one); 2979 (three); 2983 (one); 3032 (one); 3050 (two); 3061 (one); 3062 (six); 3099 (two); 3114 (four); 3115 (one); 3127 (one); 3204 (three); 3216 (eleven); 3219 (four); 3238 (two); 3259 (two); 3260 (three); 3263 (one); 3280 (twelve); 3281 (three); 3501 (one); 3507 (two); 3518 (one); 3524 (one); 3527 (fourteen); 3528 (two); 3535 (six); 3538 (four); 3543 (eleven); 3544 (two); 3549 (two); 3550 (nine); 3558 (three); 3562 (one); 3591 (one); 3600 (one); 3608 (one); 3609 (one); 3610 (fourteen); 3621 (four); 3624 (fourteen); 3625 (twenty-five); 3627 (four); 3632 (fourteen); 3633 (seventeen); 3634 (four); 3635 (one); 3636 (seven); 3637 (six); 3638 (two); 3639 (one); 3643 (three); 3645 (five); 3648 (one); 3649 (fourteen); 3650 (one); 3652 (four); 3661 (one).

Occurrence

In all, 628 specimens of A. gunneri (35.10% of the total specimens examined) were collected in 176 BIOICE samples. According to its geographical distribution around Iceland, A. gunneri is present in high numbers at all depth and water temperature ranges; it seems to be absent only in shallower localities (less than 100 m depth). Depth range: 100–2613 m; temperature range: − 0.86 to 8.04 ◦ C.

Reported distribution

Arctic and Boreal Atlantic, northeastern South America, Indian Ocean, Japan ( Imajima 2001). Wesenberg-Lund (1951) reported this species from Iceland but regards it as rare, particularly on the northern coast.

Historically, most records of A. gunneri in the literature were not accompanied by descriptions and, when diagnoses were provided, these were usually short and uninformative because generic characters are commonly used to characterize the species. As previously stated by Hartley (1985:313) the confusing definition of the taxon makes it impossible to assess the distribution of A. gunneri from literature. Because of this, we agree with Hartley (1985:314) that a close re-examination of material attributed to the nominal species from different localities around the world will reveal a number of different species. Consequently, the true distribution of the species may be restricted to Arctic and North Atlantic European waters (see map in Jirkov 2001:471) with a southern boundary of distribution probably located in the English Channel. Therefore, until a global revision of Amphicteis is completed, the specific name A. gunneri should be used with caution.

Remarks

The transition from thorax to abdomen in Ampharetidae is marked by the loss of notochaetae and either the complete loss, or a reduction, of notopodia ( Hutchings, 2000:206). The genus Amphicteis , along with other ampharetid genera such as Amage Malmgren, 1866 , Amagopsis Chlebovitch, 1964 , Amphisamytha Hessle, 1917 , Anobothrus Levinsen, 1884 , Asabellides Annenkova, 1929 , Hobsonia Banse, 1979 , Mexamage Fauchald, 1972 , Paramage Caullery, 1944 , Phyllampharete Hartman and Fauchald, 1971 , and Samytha Malmgren, 1866 , is characterized by the presence of so-called “rudimentary notopodia” in abdominal chaetigers (see Fauchald 1977:125; Holthe 1986b:56; Reuscher et al. 2009:5). The study of several BIOICE specimens of A. gunneri using SEM revealed that the abdominal notopodia are reduced entirely except for a clavate ciliated papilla, which is already present in the ventral part of thoracic notochaetal bundles in anterior chaetigers ( Figure 2A–C View Figure 2 ), remaining as a solitary papilla in abdominal chaetigers ( Figure 2D View Figure 2 ). Both in thorax and abdomen, those papillae are provided with an apical ciliated band ( Figure 2B, E, F View Figure 2 ). This particular feature was previously suggested by Hartley (1985:310) for A. gunneri and for A. midas by Holthe (1986a:21). The location of these papillae at the base of the notopodium and the presence of apical ciliature might suggest some kind of sensory function linked to the role of the thoracic notochaetae in the movement of the animal inside the tube or in its irrigation ( Holthe, 1986a:21). Hence, these structures would have remained in the abdominal region for that purpose, after evolutionary reduction of notopodial bundles in the genus. Perhaps linked to some kind of sensory perception, a high number of cuticle pori and a dense cover of ciliated tufts ( Figure 3A, B View Figure 3 ) has been observed by SEM on the dorsal surface behind the branchiae.

The clavate papillae are referred to as rudimentary abdominal notopodia by many authors. Similar abdominal structures in other genera, such as Amage , may correspond to a formation of different origin from that proposed here for Amphicteis . The study of some BIOICE specimens of Amage auricula Malmgren, 1866 , the type species of the genus, did not reveal the presence of such papillae in the thoracic notopodia whereas rudimentary abdominal notopodia were much more noticeable. Both presence and nature of this character across ampharetid genera seem far from being definitively clarified, and the real value of this character in the taxonomy of this family can only be assessed after a thorough revision of the taxa endowed with this apparently diverse configuration.

The study of some specimens of A. gunneri under SEM also provided information on other diagnostic characters of the genus Amphicteis , namely the shape of the prostomium, thoracic and abdominal uncini and nephridial pori. The prostomium of A. gunneri ( Figures 3C View Figure 3 , 4B View Figure 4 ), A. ninonae ( Figure 4D View Figure 4 ) and A. wesenbergae sp. nov. ( Figure 10A View Figure 10 ) correspond well with Jirkov’s Amphicteis - type, bearing a pair of longitudinal ridges and a pair of transverse nuchal grooves ( Jirkov 2001). We agree with Reuscher et al. (2009:4) on the desirability of not using terms like “glandular” when describing these prostomial structures, because no histological studies support their use. Jirkov (2008:112) denies that these are of glandular nature, as many authors since Hessle (1917) have claimed. According to Mackie (1994:248) and Jirkov (2008:115), thoracic and abdominal neuropodia in Amphicteis differ in shape and uncini disposition, in that all thoracic uncini are of a thoracic type and all abdominal uncini are of abdominal type. Uncini are located in deep grooves in the thoracic uncinigers and on the edge of erect pinnules in the abdominal uncinigers; this feature ( Figure 3D, E View Figure 3 ) is not exclusive to Amphicteis , but is shared with other genera of Ampharetidae . Thoracic and abdominal uncini in Amphicteis are characteristically provided with one vertical row of teeth of similar size ( Figure 3D, E View Figure 3 ) and two anal cirri are inserted in the pygidium ( Figure 3F View Figure 3 ). The nephridial papillae, always present in Terebellomorpha but often hardly visible ( Jirkov 2008), open in a pair of nephridial pores located on the branchial ridge between both groups of branchiae ( Figure 4A View Figure 4 ). The shape of the paleae, slender and evenly tapered ( Figure 4B, C View Figure 4 ), distinguish A. gunneri from A. ninonae . Their number, which seems to be related to the body size in both species ( Figure 5 View Figure 5 ) was counted in some specimens revealing a similar range in A. gunneri (8–18) and A. ninonae (8–19).

Hartley (1985), after studying British and North Sea material, provided a redescription of A. gunneri and re-established A. midas (Gosse, 1855) as a valid species. He found that both species could be readily distinguished by morphological and ecological features. While A. midas is a shallow-water species (<30 m) in the studied area, A. gunneri is restricted to deeper waters. Amphicteis midas was not found among the BIOICE material, which was mostly collected from deep waters. The presence of A. midas in shallow coastal waters of Iceland cannot, however, be ruled out because it is likely that it might have previously been confused with A. gunneri in previous works in the same area, such as those by Saemundsson (1918), Ditlevsen (1929, 1937), Spärck (1937), Einarsson (1941) and Wesenberg-Lund (1950, 1951).