Leptonerilla Diplocirrata, A New Genus And Species Of Interstitial Polychaetes From The Island Of Hainan, South China (Nerillidae)

5 Pages·1996·1.7 MB·

by  W Westheide

PROCEEDINGS OFTHE BIOLOGICAL SOCIETY OF WASHINGTON
109(3):586-590. 1996.
Leptonerilla diplocirratUy a new genus and species of interstitial
polychaetes from the island of Hainan, south China (Nerillidae)
Wilfried Westheide and Giinter Purschke
University of Osnabriick, Fachbereich Biologie/Chemie, Spezielle Zoologie,
D-49069 Osnabriick, Germany
—
Abstract. A new nerillid polychaete, Leptonerilla diplocirrata, new genus
and species, is described from subtidal sandy sediments ofHainan Island, Chi-
na. The species possesses the maximal number of prostomial appendages ob-
served in the taxon: three antennae and one pair of palps. The body is com-
posed of 9 segments, all of which bear cirri and compound chaetae. With the
exception ofone species it differs from hitherto known nerillids by thepresence
of two cirri on the parapodia of segments 2 to 9. This most disparate character
is considered to be primitive for the family Nerillidae: it is the decisive diag-
nostic character of the new genus, which now also includes Leptonerillapros-
&
pera (Sterrer Iliffe 1982).
The Nerillidae are all very small poly- south of China. It is especially interesting
chaetes with a constant number ofsegments because it exceeds all previously described
in each species: they are distributed world- genera in the profusion ofits external struc-
wide, predominantly in the interstices of tures and hence appears especially primi-
coarse sediments in intertidal and subtidal tive.
areas. The only species of this family pre-
viously reported for the Chinese coastline
is Nerilla sinica Wu and Chen, 1980 (Wu Methods
& He 1994). However, it is most likely that Extraction was carried out with a MgClj
the number of species here is no less than
solution isotonic to seawater (for details see
in other coastal regions of the earth, and &
Westheide Purschke 1988). First micro-
that the reason more ofthem have not been
scopic investigation and tracing with acam-
discovered is the paucity of research di- era lucida took place when the animals
rected specifically to the meiofauna. Other
were still alive. For a more detailed obser-
meiofaunal genera, though previously doc-
vation one fixed specimen (with SPAFG)
umented only occasionally or not at all in was whole mounted in Zeiss W15 medium.
this region, have been found in abundance
when a concentrated search is made (see,
e.g., Zhao & Wu 1991, Wu & Zhao 1992, Leptonerilla, new genus
Ding 8l Westheide 1994, Westheide et al. —
1994). These records derive from several Diagnosis. Three thread-like antennae.
expeditions carried out since 1987 as part Two palps. Nine chaetigerous segments.
of ajoint project between the First Institute Parapodia with two cirri except in the first
of Oceanography in Qingdao and the Bi- segment with only one. Chaetae jointed.
ology Department of the University of Os- Two long anal—cirri.
nabriick. In the course of these collecting Etymology. "Lepto" is a greek prefix
trips the nerillid species introduced here for "thin, small, minute" to which "-ner-
was found off the island Hainan in the illa" is attached referring to a nerillid.
VOLUME NUMBER
109, 3 587
Leptonerilla diplocirrata, new species size, except for single simple capillary
Fig. 1 chaetae (Fig. IB), which were found in the
— dorsal bundle of segments 1 and 4. Number
Material examined. Living specimens ofjointed chaetae per bundle differing be-
came from a subtidal patch ofsandbetween tween segments; highestnumber(more than
m
coral reefs, 2-3 deep, Hainan Island, 10) in the first segment and in segments 6
South China Sea: near Island Xizhou off to 8; lowest numbers (1 or 2) in segments
Sanya (18°14'N, 1—09°30'E), 19 Oct 1991. 3 and 4.
Type material. Holotype is a whole Pygidium rather narrow (width ca. 25
mount of the single mature specimen, de- |xm), ventrally with very short appendage,
posited in the Senckenberg Museum, dorsally with two long (ca. 270 |jim) thread-
SMF
Frankfurt (No.— 5300). like anal cirri. Pharyngeal bulb possessing
Description. Almost colorless. Length two (?) buccal pieces, not clearly visible.
ca. 690 fxm. Width between segments 1 and One vitellogenic oocyte (length: ca. 80 jxm)
2: 56 |xm, between segments 4 and 5: 90 positioned in segments 6 and 7; no other
|xm (parapodial cirri not included). Sepa- details of reproductive organs discernible.
—
ration of the relatively short prostomium Etymology. The species name refers to
from the trunk not distinctly visible (Fig. the presence of two cirri in the parapodial
lA). With three thread-like, more or less structures.
smooth, non-jointed antennae; the median
one somewhat longer (ca. 250 |xm) than the
Discussion
lateral antennae (ca. 215 |xm); antennae po-
sitioned in a semicircle directly above the As in the case of the small Dinophilidae
anterior margin of the prostomium. Two (Westheide 1985, Eibye-Jacobsen & Kris-
ventrolaterally positioned spoon-shaped tensen 1994), aprogenetic origin can also be
palps (length ca. 56 |xm); partly ciliated. inferred for the Nerillidae. However, there is
Two eyes, probably with lenses. Two lateral strong evidence that the Dinophilidae are
ciliary tufts behind the palps indicate the closely related to the Dorvilleidae, which
nuchal organs. makes it likely that these two groups are
Trunk with 9 chaetigerous segments, the paedomorphic Eunicida; in contrast, theNer-
posteriormostones shortest. Parapodialcirri illidae do not resemble any juvenile stages
thread-like, resembling the antennae. Con- of extant polychaetes in any obvious re-
spicuous constriction of the trunk between spects. The most that can be said is that the
first and second segment. First chaetigerous body configuration of juvenile Onuphidae
segment (buccal segment or peristomium) (Hsieh & Simon 1987) is at least superfi-
different, in possessing only one relatively cially consistent with that of the nerillids.
short (length ca. 50 jxm) posteriorly bent Apart from these considerations, for every
parapodial cirrus on each side and in having group of morphologically distinct paedo-
the two chaetal bundles each conspicuously morphic species thereremainsthepractically
directed backwards. Parapodia in the fol- insoluble question whether they originated
lowing segments with two cirri each, posi- from a single progenetically evolved stem
tioned one above the otherbetween the dor- species or evolved independently several
sal and the ventral bundle of chaetae. Dor- times by progenesis from different though
sal and ventral cirri differing in length, the closely related macrofaunal species (Westh-
ventral one longer than the dorsal cirrus, eide 1987). Only in the first case is it pos-
especially obvious in chaetiger 2 (185 |xm sible to describe a phylogenetic sequence
to 85 |xm), and chaetiger 9 (215 fxm to 130 and to construct a cladogram that illustrates
|xm). Chaetae all jointed (compound) (Fig. the phylogenetic relationships. With this
IC) of identical shape and mostly equal in qualification, we shall briefly discuss the
588 PROCEEDINGS OFTHE BIOLOGICAL SOCIETY OFWASHINGTON
Fig. I. Leptonerilla diplocirrata, new genus and species. A, dorsal view of living specimen, scale = 100
|jLm; B, simple chaeta; C, compound chaeta.
VOLUME 109, NUMBER 3 589
phylogenetic position of the new taxon. As- tigerous segments, 3 threadlike antennae,
suming furtherthat the postulatedprogenetic and compound chaetae, but they differ dis-
stem species was the least paedomorphic in tinctly in their morphometric data: their
general structure (admittedly an a priori as- length ranges from 1500-2050 |xm, their
sumption unsupported by any fundamental maximum width is 250-420 |xm, the me-
arguments), a nerillid species particularly dian antenna is up to 650 (xm long, the
close to the stem species ought to have a palps have a length of 230 |xm and that of
relatively complex configuration, with larger the parapodial cirri is 550 |xm. The single
numbers of segments and of appendages, cirri of the parapodia of the first segment,
more complex and numerous chaetae, etc. however, are much shorter (30 |xm), as are
By these criteria, the new species pre- the anal cirri, with a length ofonly 120 |xm.
sented here is the mostprimitivenerillidyet Hence, this Bermudan species is one of the
known, one that would be especially close largest nerillids, and the females were ob-
to the stem species, as follows. The prosto- served to carry up to 8 mature eggs with a
mium has the greatest number of antennae diameter of up to 200 |xm (Sterrer & Iliffe
(3) and palps (2) known for the Nerillidae 1982). Because this species is consistent
(Westheide 1990); the body is composed of with the new genus Leptonerilla with re-
the maximal number of segments (9), all of spect to the decisive diagnostic character,
which bear cirri and chaetae; anal cirri are the possession of two cirri in the chaetig-
present; the chaetae are jointed; and there erous segments 2 to 9, we likewise assign
are also a few simple chaetae. The append- it to this genus: Leptonerilla prospera
ages are the same as are present in the var- (Sterrer «fe Iliffe, 1982).
ious Mesonerilla species (e.g., M. interme-
A Acknowledgments
dia Wilke, 1953) (Westheide 1990). dis-
parate character, which could be considered The authors express their thanks to Pro-
especially primitive, is the presence of two fessorWu Baoling, Honorary Directorofthe
cirri on the parapodia of each of the seg- First Institute of Oceanography in Qingdao,
ments 2 to 9; like the two bundles of chae- for making possible their stay on Hainan Is-
tae, these can be interpreted as indicating a land, and for his continuous support of the
biramous structure of the parapodia in the joint project. They thank Xiong Shi Lin,
macrofaunal species from which the Neril- Vice Director, Oceanic Administration of
lidae are derived. The attempt to homolo- Hainan Province, for his hospitality. They
gize these cirri with specific structures of are grateful to Huang Fengpeng for his con-
typical biramous parapodia, such as the tinuous help during their stay on Hainan, es-
neuropodial or notopodial cirri or lobes, pecially to Ding Zhihu for performing the
would be premature. Two cirri have been arduous task of diving for sand samples off
reported for some of the individuals in a the coast of Hainan. Thanks are also due to
population of Micronerilla minuta (Swed- Anna Stein, who prepared the drawings, to
mark, 1959) (Jouin 1970); they occurred in Andrea Noel for her help in preparing the
segments 2 to 6 (Westheide 1990), an in- manuscript and to Monika C. Miiller for a
dication that this otherwise distinctly dif- most valuable suggestion. A travel grant
ferent and more highly evolved form orig- from the German Federal Ministry ofTech-
inated from a species with double cirri like nology and Research and the kind assistance
the new species presented. Another form of Mrs. E. Hongsemant (DLR, Koln) are
with two cirri on just the same segments, 2 also gratefully acknowledged.
&
to 9, is Mesonerilla prospera Sterrer II-
iffe, 1982 from inland marine caves ofBer- Literature Cited
muda. These animals are relatively close to Ding, Z., & W. Westheide. 1994. Two new interstitial
the new species in also possessing 9 chae- Streptosyllis species from South China (Poly-
—
590 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
— —
chaeta: Syllidae). Microfauna Marina 9:303- evolution. JournalofNaturalHistory 21:843-
312. 854.
—
Eibye-Jacobsen. D.,&R.M. Kristensen. 1994. Anew . 1990. Polychaetes:Interstitalfamilies. Syn-
genus and species of Dorvilleidae (Annelida, opsis oftheBritishFauna (New Series): 1-152.
Polychaeta) fromBermuda, withaphylogenetic Universal Book Services/Dr. W. Backhuys,
analysis of Dorvilleidae, Iphitimidae and Di- Oegstgeest, 152 pp.
nophilidae.—Zoologica Scripta 23:107-131. , & G. Purschke. 1988. Organism processing.
Hsieh, H.-L. & J. L. Simon. 1987. Larval develop- Pp. 146-160 in R. P Higgins & H. Thiel, eds..
ment of Kinbergonuphis simoni, with a sum- Introduction to the study ofmeiofauna. Smith-
mary of development patterns in the family sonian Institution Press, Washington, D. C,
Onuphidae (Polychaeta).—Bulletin of the Bio- London, 488 pWp.
logical Society ofWashington 7:194-210. , , & Mangerich. 1994. The inter-
Jouin, C. 1970. Recherches surles Archiannelidesin- stitial hesionid Sinohesione genitaliphora gen.
terstitielles: Systematique, anatomic et devel- et. sp. n. (Annelida, Polychaeta) together with
oppement des Protodrilidae et des Nerillidae. a des—cription of its dimorphous genital or-
gans. Zoologica Scripta 23:95-105.
Unpublished These Doctorat, Faculte des Sci- Wu, B., & J. Zhao. 1992. Preliminary studies on spe-
Sterrer,enWc,es&deTParMi.s,Iplpi.ffe1.-210948.2. Mesonerilla pros- cSieeas.—ofJoHuersnailoniodfaeOc(ePaonloygchraaepthay) fofroHmuaYneglhlaoiw
pera, a ne—w archiannelid from marine caves in and Bohai Seas 10:36-41.
Bermuda. Proceedings of the Biological So- Wu, Q., & M. He. 1994. Polychaeta. Pp. 343-375 in
ciety ofWashington 95:509-514. Z. Huang, ed.. Marine species and their contri-
Westheide, W. 1985. The systematic position of the butions in China's seas. China Ocean Press,
Dinophilidae and the archiannelid problem. Pp. Beijing, 764 pp.
310-326 in S. ConwayMorris, J. S. George, R. Zhao,J.,&B.Wu. 1991. Anewinterstitialpolychaete
Gibson, & H. M. Piatt, eds.. The origin and re- Hesionura shangdongensis sp. n. (Polychaeta:
lationships of lower invertebrates. Clarendon Pisionidae) from Yantai; the Huanghai Sea.
Press, Oxford, 397 pp. Acta Oceanologica Sinica 10:447-450 (in Chi-
. 1987. Progenesis as aprinciple inmeiofauna nese, English abstract).