The representatives of the genus Laonice are the most common Spionidae within the Arctic shelves. However, their identification is difficult due the unknown variation of diagnostic characters. The article is the research of the problem. Five species of the genus Laonice Malmgren, 1867 were described from Arctic ocean: L. cirrata (M.Sars, 1851), L. appelloefi Söderström, 1920, L. sarsi Söderström, 1920, L. bahusiensis Söderström, 1920, and L. annenkovae Zachs, 1925. Söderström's species after the short time (Fauvel, 1927) were turned in synonyms of L. cirrata. However Eliason (1962) and Fauchald (1972) didn't agree with and the first considered as distinct L. sarsi, the second - L. appelloefi. To our sorrow neither Eliason, nor Fauchald didn't maintain their points of view with analysis of variation.
There is similar situation in the taxonomy of the whole genus: Forster (1971) turned all species of the genus in the single one, but it didn't threw the obstacle for others authors (Banse, Hobson, 1968; Blake, Kudenov, 1978; Ward, 1981) who have described new species based on characters which Fauchald and Forster didn't suppose as possessing taxonomic value. Due it the taxonomy of the genus mixes more and more.
In our research we tried to estimate suitability of different morphological features for the taxonomy of the genus. The following characters were investigated: the structure of the prostomium and the peristomium (development of furrow, parted them; number of eyes); the length of nuchal ciliary tracts, the number of pair of branchiae; the shape of neuropodial hooded hooks; the segment of starting of genital pouches, neuropodial hooded hooks and inferior capillaries [under the last term we mean the part of the simple neurosetae situated in lower part of neuropodia, distinctly longer others and distinctly turned ventrally, Söderström (1920) called them neuropodiale ventrale Haarborsten]. Due almost complete absence of whole specimens in available material we used as measure of the worm's size the distance between bases of the parapodia of the 7th setiger(S = ÙC). Söderström (1920) used the similar measure: the width of the 7th S.
We investigated material from the Arctic Ocean from the south of the Norwegian Sea to the Chuckchee Sea. The material are characterised more exactly in descriptions of species.
On the first step we found out, that there is distinct polymorphism in: the structure of the prostomium and the peristomium (development of furrow, parted them; number of eyes) and in the shape of neuropodial hooded hooks. There are no polymorphism in: the numbers of segment of starting of inferior capillaries and of starting of neuropodial hooded hooks; the number of pair of branchiae; the length of nuchal ciliary tracts, these characters vary within wide limits. The last character (the segment of starting of genital pouches) is characterised with dimorphism: one morph has in constant, while it vary in another.
Three morphotypes were separated on the base of 4 polymorphous characters; they were called A, Á and B. Morphotype A is characterized with furrow, parted the prostomium and the peristomium to end far from frontal margin; one pair of eyes (very seldom 2); tridentate (very seldom 5-dentate) neuropodial hooded hooks; segment of starting of the genital pouches varies from 17th to 36th. Morphotype Á is characterised with furrow, parted the prostomium and the peristomium to achieve frontal margin, but prostomium is connect with the peristomium by thin translucent membrane; one pair of eyes; bidentate neuropodial hooded hooks; segment of starting of the genital pouches vary from 17th to 31st. Morphotype B is characterised with furrow, parted the prostomium and the peristomium to achieve frontal margin; absence of eyes; 8- dentate neuropodial hooded hooks; segment of starting of the genital pouches is always 3. So long as characters to use for separating morphotypes doesn't connect functionally and morphotypes inhabit the same region (A and B even met in one sample), they have rank no less than species. So variations of other characters as well as serial number of the segment of starting of genital pouches were investigated within each morphotype. To our sorry their were no samples containing number of specimens enough for studying variation within it, so we had to do it in all specimens, so geographical variation left without. It may be that local polymorphism vary less described below. It's necessary to mention that differences between Pearson's correlation coefficient (see below) within morphotype A from the Norwegian and Barents seas from one side and from the White Sea from another (two regions, which were the most number of specimens from) aren't significant.
The most part of the material is morphotype A. The variation of meristic characters within it were investigated in 111 specimens from 38 stations from the Norwegian, Barents and the White seas, the shelf of New Siberian Is. and the Chuckchee Sea. All meristic characters of it correlate with worm's size (table 1), the authenticity of the difference of correlations from 0 were more 99.9%. Only correlation between the serial number of the segment of starting of genital pouches and body's wide wasn't significant. However it's equal to 0.3 and significant with probability more 0.95% within material from the Norwegian and Barents seas only. All analogical Pearson's correlation coefficients of morphotypes Á and B aren't significant due to a little number of specimens.
Because any morphotype can't further divide in groups on the base of analyzed features, they have to consider as species. The problem of their names, i.e. identification with nominal ones is situated.
There are all diagnostic features of species of the genus known from Arctic ocean after Söderström (1920) in table 2. The characters of L. appelloefi is given after Fauchald (1972) as well. L. annenkovae isn't included in table, its position will be discussed below. There are characters of all morphotypes and besides for morphotype A characters of different sized classes in table also. Söderström didn't write his way of measurement of worms' width, so his sizes can be not identical ours. Moreover, it's probably so because none from more 400 specimens investigated by us was wider 3 mm while Söderström's specimens were up to 5 mm, probably he measures worms with setae.
The following conclusions can be done with the comparison of the table.
1. Morphotype A is L. cirrata. For this: the equal development of furrow parted the prostomium and the peristomium in morphotype A and L. cirrata sensu Malmgren, 1867 and finding only it within region where Söderström mentioned only L. cirrata from. Tell the truth, morphotype A has neuropodial hooded hooks 3- or 5- dentate, while L. cirrata has bidentate. However, the presence of two instead one small teeth we discovered absolutely by accident, missing it in several dozens of slides. And only post factum we re-investigating slides made sure that our previous opinion was erroneous. So, we don't attach importance to the discrepancy.
2. Morphotype Á is L. sarsi.
3. Morphotype B doesn't mention from the Arctic ocean earlier. The comparison it with another nominal species of the genus allow to conclude that it's new species.
4. L. appelloefi is good species, absent in our material.
5. L. bahusiensis by our opinion is synonym of L. cirrata, for the final statement it's desirable re-investigate the type material (see also description of L. cirrata below).
Given above data about the character of the variation of morphological features allow to determine their taxonomic value. Two characters: the degree of the development of furrow parted the prostomium and the peristomium and the number of the teeth in neuropodial hooded hooks have maximal value. Four characters: the segment of starting of neuropodial hooded hooks and of inferior capillaries, the number of pair of branchiae; the length of nuchal ciliary tracts depend on worm's size so limits of their variations reflect intraspecific variation as well as size of available worms. So it follows to give at least the information about worm's size while one to use them. At the same time, these characters can be even key's (we mean suitable for) if to compare specimens of the different species but the same size. The last character the segment of starting of genital pouches can be constant within species as well as connected with worm's size. So it follows to investigate its connection with worm's size before to use and to give the information about worm's size.
It's necessary to mention extra time that the available
material didn't allow to investigate the geographical variation,
but it seems that there is the difference between L. cirrata
collected in different regions at least in such character as the
segment of starting of genital pouches (for example specimens
from the deep and shallow part of the White Sea). The description
of new species and redescription of two others is given below.
Material. 24 specimens from 8 stations (table 3), holotype from the station 16 R/V"Tunets", deposed in Zoological museum of the Moscow States University, n.Pl-764, the paratypes are deposed in collection of the Department of the Hydrobiology of the Moscow States University.
Description. Frontal margin of prostomium is widely evenly rounded, its maximal width between frontal corner, than it sharply become twice narrower, its lateral margins become parallel each other; slightly in front of well developed occipital tentacle it began to narrow again and behind papilla gradually turn in long narrow ridge, caruncle ended on 10th-11th S as well as nuchal ciliary tracts. The eyes absent. Prostomium is completely separated from peristomium with lateral furrows. Branchiae are smooth, anterior ones longest (almost equal to body's width), further back become shorter and the last pair poor developed. The number of the branchiae isn't known exactly because all present specimens (all are fragments) have the last setiger with branchiae. The longest fragment (holotype) has last branchiae (on the 26th S) very small, guided with fragment from the middle part of the body from the same sample the last setiger should be abranchiate.
Dorsal postsetal lobes of the last branchial segment join with transverse dorsal ridge, disappear together with branchiae. Dorsal postsetal lobes are flat, wide, with pointed tips. Ones of holotype turn dorsally and increase slowly caudally achieve maximal size on the segments with transverse ridges. After disappearing branchiae they present on 5 segments, further back almost invisible. Ventral postsetal lobes are flat, wide, well developed anteriorly, widest on 4th-16th S, further back slowly diminish and become almost invisible on abranchiate segments. Genital pouches start always from 3rd S. Inferior capillares start from 11th-15th S. Neuropodial hooded hooks start from 21st S; 5 teeth are visible in profile (fig.1 e): 1 large and 4 small. It seems that 3 small teeth are twin, there is larger unpaired between them (fig.1 ä), upper small and lower large single (the size of small teeth is almost invisible with available microscopes).
Size. Holotype (anterior fragment consisted of 26 S) has width on the level of 7th S 1.2 mm, length 8.5 mm, others not large.
Etymology. The species is named after American polychaetologist James A. Blake.
Comparative remarks. The new species distinctly differs from all another of the genus by the greater number of the teeth (8) in neuropodial hooded hooks. It differs from the most species of the genus by starting of genital pouches always from 3rd S, only L. pugettensis Banse et Hobson, 1968 can have genital pouches to start from 3rd S (2nd - 7th), another have it to start either before or (the most) further back. Probably the prostomium full separated from the peristomium is diagnostic for, but this character didn't described satisfactorily for most species.
Distribution. All known finds are given in table
3. They done on the depth 960-2510 m, bottom temperature from
-0.96 to -0.84C. According to the distribution of co-inhabiting
species, its area embraces the slope of the Arctic ocean and probably
the North Atlantic. However, it doesn't find in the samples from
the slope of the Arctic ocean, probably because small number of
them and not good quality.
Material. The Arctic ocean: 346 specimens from 193 stations: the whole collection of the Department of the Hydrobiology of the Moscow States University - 196 specimens from 125 stations; the whole collection of the Zoological Institute of Academy of Sciences of USSR (ZIN) - 94 specimens from 48 stations; collection of Murmansk Institute of sea biology from the White Sea - 52 specimens from 20 stations; besides there are two specimens from the Ochotsk Sea (443 m and 592 m) and one from Paramushir, Kuril Is. (132-164 m) in ZIN.
Redescription. Prostomium is widely rounded, joined with peristomium. Caruncle as long as nuchal ciliary tracts, ended on 13-36 S. Two eyes, some specimens have extra two, but weaker developed. Branchiae are smooth, 24-48 pairs, onto 2nd S they are small (shorter postsetal lobes and near three times narrower body's width), further back become longer and become as long as body's width. Than sharply become shorter onto last 2-3 branchial segments the last pair is near 1/5 the largest.
Dorsal postsetal lobes are flat, wide, with pointed tips, on the last 6 branchial segments they slowly become shorter and onto the last branchial segment they are near 4.5-5 time smaller the largest onto anterior S; further back they slowly become shorter and onto the posterior part of the body almost invisible. Ventral postsetal lobes on the first 5-6 S increase in 324 times, than are the same, and onto the 5-6 S (including 2-3 last branchial decrease twice, further back slowly decrease. Genital pouches start from 7th-36th S. Inferior capillaries start from 12th-29th S. Neuropodial hooded hooks start from 18th - 56th S; usually tridentate, as exception 5 - dentate.
NOTES. According to Söderström (1920), L. cirrata have bidentate neuropodial hooded hooks, contrary to L. bahusiensis which have 5 - dentate. Really, by our opinion, L. cirrata is characterised usually with tridentate neuropodial hooded hooks. However the fact that there are two upper teeth is almost invisible in profile and even in face they are distinctly seen if hood is missed with cover glass so it to open. So most probably, earlier (and Söderström as well) two upper teeth were considered as single. The structure of upper teeth somewhat varies: they can be low, located near each other so it's difficulty to see the two. It occurs specimens with high teeth and well separated teeth or with distinctly different teeth. At least there were the slim small extra teeth above each upper in specimens from Sturfjord (Spitsbergen, depth 7.8 m) similar to figured for L. bahusiensis.
If the first genital pouch of L. blakei and L. sarsi already well developed and doesn't distinctly differ in size from the next, the genital pouch of L. cirrata developed onto anterior S distinctly less then onto the next. We considered that the genital pouch to start from the segment where the membrane homologous to anterior part of the fully developed genital pouch start on the back side of the parapodial base. The membrane slowly expands onto the anterior side of the next parapodia onto the next three segments (following to segment bearing the membrane).
Distribution. The species is widely distributed all
over the Arctic ocean from the south of the Norwegian Sea to the
Chuckchee Sea from the 7.8 to 1200 m
Material. 10 specimens from 9 stations (table 3).
Description. Prostomium is widely rounded. Prostomium is almost completely separated from peristomium with lateral furrows, but its frontal corners join with slim membrane with ventral surface of the peristomium. This membrane is visible from anterior above best of all, if slightly to part the prostomium from the peristomium. Occipital tentacle well develop. Caruncle as long as nuchal ciliary tracts, ended on 8-13 S. Two eyes. Branchiae are smooth, 25-31 pairs. They are the largest within anterior part of branchial part, anteriorly and posteriorly somewhat decrease. The last pair of the two specimens where it present are twice shorter preceding.
Dorsal postsetal lobes are flat, wide, with tips pointed onto the several anterior segments, further back are blunt. They are longest onto 3rd - 9th S, further back they slowly become shorter and onto the last branchial setiger they are in 1.5 time shorter preceding. Further back they are almost invisible near twice shorter than onto the last branchial setiger. Ventral postsetal lobes oval, from ca. 10th-11th S somewhat decrease, in the middle of the body achieve half of ones of the 10th S. Genital pouches start from 14th - 31st S. Inferior capillaries start from 18th-27th S. Neuropodial hooded hooks start from 28th - 37th S; bidentate. There are notopodial hooded hooks onto posterior segments, but it's impossible to determine where they to start in available posterior fragment. According to Söderström (1920) they present onto last 6-34 S.
Distribution. All our finds were made along Norwegian
coast, from Shetlands to Lofotens Is. on the depth 100-405 m (table
3) bottom temperature 5.05 - 9.48C. Eliason (1962) pointed out
it from Skagerrak (138-358 m, 6.50 - 7.07C). Type locality - the
Norwegian off-shore, from Kattegat to Tromsö (70-195 m).
Laonice annenkovae Zachs, 1925 is the last mentioned from the Arctic Ocean species of the genus. The species was described from the estuaries of East Murman (Kola Peninsula) then was mentioned Dvin and Onega bays of the White Sea (Uschakov, 1939; Slastnikov, 1957) and from the Amur Bay (Uschakov, 1950).
According to the short original description (figures are absent) the species doubtfully belong to the genus Laonice due absence of such characteristics of the genus as occipital tentacle, long nuchal ciliary tracts and genital pouches. At the same time it has branchiae start from 1st S, prostomium widen frontally, hooks present in both neuropodia and notopodia - the characters are characterised to the genus Marenzelleria Augener, 1913.
All available materials from the collections of ZIN,
including the type specimens (estuary of the rivers Tuloma and
Teriberka) were investigated for the understanding of the taxonomical
status of L. annenkovae. Besides materials collected with
R/V C×C-2032 of the White Sea's Biological Station of the
Moscow States University were investigated as well. The research
showed that all specimens agree with diagnosis of Marenzelleria
wireni, thus it follows to consider L. annenkovae
as junior synonym of the species.
Material. Collection of the White Sea's Biological Station of the Moscow States University (41 specimens from 7 stations in Dvin bay; collection of ZIN: the estuary of Tuloma (6 specimens collected at 1923), the estuary of Teriberka (7 specimens collected at 1925), Murmansk (1 specimen collected at 1923), the estuary of Chaun and Paljavaam - The East Siberian Sea (23 specimens), the estuary of Anadyr - The Bering Sea (19 specimens).
Description. Prostomium widens anteriorly and narrows farther back, achieves 2nd S. There are no occipital tentacle and caruncle. Two eyes. There are the nuchal ciliary tracts as two longitudinal band on the dorsal side of 1st and 2nd S. Palps are not long, turned back they achieve 10th-12th S. There are branchiae onto 1st-15th S (rare their number can be less). Branchiae particularly fuse at the base with postsetal lobes. The last are larger and narrower onto anterior part of the body, further back they slowly decrease in size and become more rounded.
There are only long simple setae in both notopodia and neuropodia in anterior part of the body. Neuropodial hooded hooks start from 38th - 43rd S in neuropodia and from 43rd - 48th in notopodia. Parapodia of the posterior part of the body bear in each rami: 3-4 large simple setae (the same as in anterior part), 5-7 hooks and 6-7 very slim simple setae, alternated with hooks. Hooks are bidentate or tridentate, hooded. Pigidium is secondary annulated, bear 6-18 short anal cirri. Anus somewhat turned dorsally. Length to 40 mm, width to 2.2 mm, 60-90 S. Dark-white in alcohol.
Variations. All specimens completely agree with short description of Auger (1913) and fuller one of Holmquist (1967). It follows to mention, that number of anal cirri of specimens from the White Sea is more (12-18) than ones from Barents (6-10); specimens form Pacific are slender.
Distribution. Boreal-arctic species: European shores,
East Murman, the White Sea, Spitsbergen, Franz - Joseph Land,
the Kara Sea, estuary of Enisey, Dikson bay, estuaries of Chaun
and Paljavaam (the East Siberian Sea), of Anadyr, Avachinsk and
Amur bays, estuaries of rivers of north-west and arctic shores
of North America. It is the common in Dvin bay of the White Sea,
where occurs in number of 60 specimens per square meter.
Table 1. Variation of taxonomic characters within morphotypes
character Morphotype A Morphotype Á Morphotype B
limits r n width limits n width limits n width
r - Pearson's correlation coefficient; n - number of specimens were investigated on the character.
Characters: 1 - the segment of starting of neuropodial hooded hooks; 2 - the number of pair of branchiae; 3 - the segment of ending of nuchal ciliary tracts; 4 - the segment of starting of inferior capillaries; 5 - the segment of starting of genital pouches.
Table 2. Morphological characters of different species of Laonice mentioned from the Arctic ocean.
species characters after
1 - width mm; 2- the segment of starting of genital pouches;
3 - the segment of starting of neuropodial hooded hooks; 4 -
the segment of starting of inferior capillaries;
5 - the number of pair of branchiae; 6 - the segment of ending
of nuchal ciliary tracts; 7 - the number of teeth in neuropodial
hooded hooks; 8 - notopodial hooded hooks; 9 - eyes ('+ ' - is;
' ' - no; '? ' - unknown).
Table 3. Finds of L. blakei and L. sarsi.
ship year of collection station N latitude longitude
depth m number of specimens
Fig.1. Laonice blakei sp. n. (specimens from st.16 R/V"Tunetz"): a - anterior end dorsally (setae omitted), paratype; á - anterior end in profile, paratype; â, ã - neuropodial hooded hook from 26th S; ä, e - the same, its tip. Scale: a, á - 1 mm; â, ã - 20 mkm; ä, e - 5 mkm.
Fig.2. Laonice cirrata (a-ã) and L. sarsi (ä - e): a - anterior end dorsally (setae omitted); á - the tip of neuropodial hooded hook from 48th S in profile; â, ã - its scheme in face; ä - anterior end dorsally (setae omitted); e - the tip of neuropodial hooded hook from 36th S in profile. Specimens from stations: a - 20 R/V"Tunetz"(7301' N, 2200' E, 440-450 m); á - 12 R/V"Alaid"(6930' N, 3330' E, 245-260 m); e - 1406 R/V"Sebastopol". Scale: a, ä - 1 mm; á - 30 mkm; e - 10 mkm.
Fig.3. Distribution of Laonice cirrata in the Polar Basin (investigated material only).
Fig.4. Marenzelleria
wireni: a - anterior end laterally; á - posterior
end laterally; â - anterior end dorsally, nuchal ciliary
tracts stricken; ã - anterior end dorsally; ä -. parapodia:
ä - 6th S, e - 30th S, æ - 60th S; ç-k - uncini.
Specimens from a, á, ç - syntypes; â - from
the White Sea. Scale (mm): a, á, ã - 1; â
- 0,5.
[Literature cited not included. Please see original text]