Some genera of Ampharetinae are characterised by presence of modified notopodia. Modified notopodia - notopodia with setae, differing from other notopodia by position (usually elevated dorsally), setae and form. Modified notopodia always are situated in posterior thorax. There are two types of modification, each are characteristic for certain segment. The most simple - modified notopodia are similar to normal by form, but slightly elevated dorsally and setae are more or less different (judging to REM photo they are covered by bigger scales). This type of modification one can find in Anobothrus Levinsen, 1884, Anobothrella Hartman, 1967, Melythasides Desbruyeres, 1986, Sosanides Hartmann-Schroder, 1965 and Zatsepinia Jirkov, 1986. I propose to name such type Anobothrus-type. The second type - modified notopodia and their setae sharply differ from normal, they are distinctly flattened across the body. I propose to name such type Sosane-type. Till now, including newly described species, it is known 12 species with Sosane-type modification, it was proposed 7 genera for them. Taxonomic characters of these species are given in the table 1.
It can be seen, that modified notopodia is situated on 9-11 thoracic uncinigers (TU), in 7 species - on 10, so position of modified notopodia on 9-11, usually 10 TU can be count as characteristic for such modification (for Anobothrus-type is characteristic position of modified notopodia on 8 TU). Besides similarity in notopodial modification, species of Sosane group have prostomium Ampharete type (trilobed, middle lobe anteriorly rounded or straight, without ridges or any other structure) and smooth buccal tentacles.
Genera of Sosane group are differed by presence or absence of palea, different number of TU and branches.
5 species have more or less developed palea, the rest 7 have no. As it was shown earlier (Jirkov, 1994), presence or absence of palea - character varies intraspecifically, so it seems unreasonable to use it for separation of genera.
The number of TU also varies intraspecifically (Jirkov, 1986, 1989), despite the part of population with different, unusual number of TU and amplitude is much smaller. It can be seen from the table, that similar to all other aspects species differing by number of TU form complete, full row, cline and it seems artificial to divide this row into separate genera, based on difference in a meristic character, which varies intraspecifically. Thus it is necessary to take Sosanopsis as junior synonym of Sosane, and Melinnata, Muggoides, Sosanella and Genus A as junior synonyms of Mugga.
Thus there are as maximum only two genera in Sosane group: Mugga s.lato. and Sosane s.lato., they are different by number of branchiae only.
Type species: Sosane sulcata Malmgren, 1865.Prostomium Ampharete-type. Buccal tentacles smooth. 4 pairs of branchiae. Notopodia of IX-X (usually X) TU foliaceous and bear modified setae.
Systematic position of three more species - Sosane fauveli Caullery, 1944; S.procera Ehlers, 1887 (including subspecies S.procera malayensis Caullery, 1944); S.wireni Caullery, 1944 (HOMONYM) within Sosane needs in collaboration, as it has been said nothing in the original description about their modified notopodia.
Day (1964) and Hartmann-Schroder (1971) considered Anobothrus Levinsen, 1884 as junior synonym of Sosane. I had followed this opinion earlier (Jirkov, 1989). Holthe (1986) have shoved the sharp difference between these genera in the type of notopodial modification (it is not followed from the original description). Here I follow Holthe's opinion. They differ by their anatomy as well (Hessle, 1917). Hartmann-Schroder (pers.comm.) agrees with Holthe.
As it is often difficult to count the number of branchiae, below the joint key to both genera is given.
Material. 50 specimens, including HOLOTYPE, all from station 12 cruise 34th R/V "Ädissey", 47°N 153° E, depth 450-480 m, 30.12.84, coll. M.V.Kolesnikov, deposed in collection of Department of Hydrobiology Biological faculty Moscow State University.
Description. Prostomium Ampharete-type, middle lobe anteriorly wider than posteriorly, its anterior margin almost straight, somewhat similar to Amage-type; there are no any additional processes and eyespots on prostomium. Buccal tentacles smooth, numerous (several tens). Lower lip is not enlarged, weakly crenulated. Paleae absent, but usually there are small tubercles instead. 4 pairs of smooth cirriform branchiae in two groups, separated by distance equal to branchial base diameter. Branchophores of 3 pairs of branchiae joined longitudinally, place in one transversal line. Inner branchophores joined by slim dermal membrane as high as they. The most parts of branchophores of these 3 pairs are not joined to body wall and form comparatively high transversal ridge. Branchophores of 4th pair contrary, join to dorsum almost completely and quote separate from others, they start between 3rd pairs of notopodia (on 6th segment) extend straight forward and end between 1st and 2nd pairs of notopodia. The innermost branchophores seem to be connected with notopodia of 2nd TS (= 5th segment). There are small nephridial papillae medially to branchophores of 4th pair and medially to 3rd pair of notopodia. 15 TS, the size of notopodia gradually increase before 4th-5th pairs, but even 1st are quite developed. Notopodia 3rd from the last TS moved dorsally and flattened, their inner corners turned to sharp short cirrus; these notopodia are connected by transversal ridge in some worms, but the same number of worms have no any trace of it. It seems that development of ridge depends on degree of muscle retraction due fixation. There is no trace of glandularity on this ridge (as in all others species with Sosane-type modification) contrary to analogical ridge of Anobothrus-group, where the degree of ridge development varies as well, but ridge is always glandular. Last 12 TS with neuropodia. There is no variation of number of TS and TU. 14-17 AU, variation does not depend on size within 7-21 mm; 43 worms possess the whole abdomen, among them 1 possesses 14 AU, 2 - 15 AU, 28 - possess 16 AU, 12 - 17 AU, the average number of AU = 16.2, holotype possess 17 AU. Rudimental notopodia as small tubercles are visible anteriorly, posteriorly they decrease in size and slowly disappear completely. There are no noto- and neuropodial cirri. Pigidium with 2 short lateral cirri, the same length as last neuropodia; papillae are absent. Notosetae narrow bilimbate capillaries, modified notopodia possess besides similar shorter and twice slimmer ones, normal are rare. Number of setae in modified notopodia several time more, that in normal ones. Neurosetae of 3rd TS (1st TU): number ca. 80 per neuropodium; neurosetae avicular, lower tooth large, subrostral unpaired, more apical paired, on the top the semicircle of small dents. Up to 21 mm length. Tube smooth, soft, detritus with incrustations of large particles don't extended above its surface, grey with rare irregular dark grey transversal lines. Tube twice longer worm.
Etymology. The species is named after Dr. Torleif Holthe (Trondheim, Norway) well known specialist in Terebellomorpha.
Taxonomic remark. The difference between new and already known species is clear from the table 1.
Table 1. Taxonomic characters of species Sosane group (original species names are given).
|Genus A sp.||A||0||-||12||11||3||11|
1 - prostomial structure A - Ampharete-type;
2 - buccal tentacles 0 - smooth;
3 - palea: + - present, - - absent;
4 - number of TU;
5 - number TU with modified notopodia;
6 - number of pairs of branchiae;
7 - number of AU;
Space- there are no data,
* marked species I have seen, characters of others followed to the original description and re-description of type material.
Fig. 1 Sosane holthei sp.n.: A - anterior end, from above, Á - modified
notopodia, from behind; B - neurosetae of 1st TU face and profile.
Scales: A, Á - 1 mm, B - 0.05 mm.
[Literature cited not included. Please see original text]
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