Zoologicheskii Zhurnal 1992:72 (11):128-132
M, I, KISELEVA
New genus and species of a polychaete of the Chrysopetalidae from the Black Sea.
The worms were transferred to me for determination by V. E Zaika, who managed to rear them from the pelagic larvae, always found in the central regions of the sea and earlier described as larva "B" and "C" (Kiseleva, 1959), but since then assumed to belong to the families Hesionidae or Dorvillidae (Kiseleva, 1990). Myrina (1986) determined these larva as Pelagiobia serrata Southern, 1909 (family Lopadorhynchidae). After metamorphosis and settling of the larvae on the bottom it stood clear, that they belong to the family Chrysopetalidae and form a new genus and species thereof. Until now the presence of the family Chrysopetalidae in the Black Sea has not been observed.
I use the opportunity to acknowledge V. E Zaika for giving me the material and G. N. Bysjinsko for consultation.
Genus Victoriella gen. n.
Type species: Victoriella zaikai sp. n.
Diagnosis: Body oblong-oval, constitutes of a smaller number (10-12) of segments. Prostomium anteriorly rounded, inserted at about the peristomial segment. Two small antennae emerge from the anterior part of the prostomium and two relatively stout palps, folded on the ventral side. Eyes not present. On the peristomium there are two pairs of tentacular cirri, situated one above the other, and biramous parapodia with dorsal and ventral cirri. The setae of these parapodia are of two types: on the dorsal ramus - simple, slightly bent, spiny, with transverse patterns, on the ventral ramus - simple, non-spiny, with a marked attenuation at the tip. Parapodia on the following segments biramous, with ventral and dorsal cirri, with simple, transversely striated spinigers on the notopodia and compound heterogomph setae on the neuropodia. Proboscis barrelshaped, with teeth of platelet type. Anal ramus with two cirri.
Discussion: The genus is close to Dysponetus Levinsen, 1879 (family Chrysopetalidae). Nowadays there are six species known from the genus Dysponetus (systematical position of Chrysopetalum caecum Langerhans, 1880, which was wrongly, as Laubier 1964 convincingly argued, synonymized with D. pygmaeus Levinsen, 1879, has until now not been defined). The description of the genus Dysponetus is characterized by numerous morphological characters, and is unified by their character of presence of three (or more) antenna, also by the structure of their parapodia and setae. All species in the genus Dysponetus have biramous parapodia, by these notopodia with simple toothed setae (in D paleophorus Hartmann-Schröder, 1974. Additionally there are a few paleae and long dorsal cirri, situated under the setae; neuropodia - with compound heterogomph setae and dorsal cirri. Neuropodial ramus on the first segment is, as a rule, missing. In those cases where there is a neuropodial ramus on the first segment (D. bulbosus Hartmann-Schröder, 1982) it is without setae and ventral cirri. In the usual case the dental apparatus is of stylet type.
In Victoriella the structure of parapodia and setae, beginning at the second segment, are as in Dysponetus, which allows describing the genus to the family Chrysopetalidae.
The basic characteristics of details in Victoriella that differs from all known types in the genus Dysponetus is appearent in the structure of the peristomial segment. In Victoriella on this segment has, besides a notopodial ramus with typical toothed, slightly bent setae with transverse striation and long dorsal cirrus there is a neuropodial ramus of a well developed process type with a short acicula, a bundle of special simple setae, growing finer to the distal end, and cirri, of the same length as the neuropodial process or slightly exceeding this. More than that, Victoriella has only two short antennae and a digestive apparatus showing small plates and not stylets.
I estimate the morphological differences of the described Chrysopetalidae important enough for a differentiation in a distinct genus.
Victoriella zaika Kisseleva, sp. n. *
Material: Holotype: No. 1/47370 (1 ex), Paratypes: 2/47371 (4 ex). Stored at the ZIN RAM, sankt-Petersburg. Worms brought up from pelagical larva, collected at the 4615 station (43°29'3" N, 37°35'1" E) on 130-100 m depth, 1990-09-07, on the 32nd tour NIS "professor Vodjanitskij":
Description: Length of the holotype is ca. 1, width 0.3 mm; number of segments 10. Prostomium inserted in the peristomial segment (fig. 1, a, b). There are, on the prostomium, two short, thin antennae, far separated from each other. On the lower side of the prostomium are two palps inserted. (In living specimen the palps from time to time extend forward, situated between the antenna). Eyes not present. Peristomium consists of two fused somites (bodysegments?). On the first of these there are two pairs of tentacular cirri ca. 0.08 and 0.06 mm in length, situated one under the other, and dorsally a bundle of simple, bent, toothed on the convex side of the setae, which are transversely banded. On the second peristomial segment there are modified parapodia. Notopododial ramus with long dorsal cirri, widened at the basal part and tapering in the distal part, with acicula and simple, bent, toothed transversely banded setae. Neuropodial ramus at sight well marked process on the ventral side of the segment, with acicula, a bundle of simple setae, very attenuated at the distal end, and bottleshaped ventral cirri exceeding in length the neuropodial process (fig. 1 B, G, g). Proboscis, extending ca. two segments, muscular, barrelshaped, with teeth looking like plates, size is equal to 0.020 mm (fig 1 D, a, b). Parapodia biramous, the notopodia are noticeably shorter than the neuropodia. On both parapodial rami there are distinct acicula of 0.175 mm length (fig. 1 G, a). The distal end of the notopodial acicula forms a small triangular process. A dorsal cirri is situated at the side of the distal end of the acicula, below the bundle of setae. It is widened at the basal part and attenuated at the distal. Length of dorsal cirri is up to 0.120 mm. Setae of the notopodia are simple, slightly bent, with teeth on the convex side and transversely banded (fig. 1 G, b). Setae are in numbers of 13-15 situated in bundles, diverging upwards from all sides. The longest seta measures 0.137 mm.
Neuropodia with ventral cirri of bottle shape and compound setae from the neuropodial ramus. On the two anterior segments the ventral cirri emerges from the base of the bundle on the neuropodial ramus, on all the following segments from about the middle of neuropodia. The length of the ventral cirri is much shorter than the dorsal and is 0.50 mm. The compound setae are of the heterogomph type with delicate toothing and transverse patterns on the basal part. The setae are laterally positioned in the horizontal plane. Their size vary: the outer setae are shorter than the middle. The length of the longest setae measures 0.385 mm. In the central parts of the body there are 18-20 setae in a bundle.
The pygidium is surrounded on both sides by parapodial processes of the preceeding segments (fig. 1, V). At the end of the anal ramus there are two cirri of bottle shape. Their length is equal to 0.027 mm.
The location in the Black Sea of the adult is not established.
Notes. Polychaetes of the genus Victoriella are small forms, but, obviously, the number of segments might be greater than in our specimens. We have several times noted, that individuals from different species, brought up in laboratory conditions, shows to be smaller, than inhabitants of natural populations.
The presence of dorsal setae on the first peristomial segment, noted in the holotype is, by all possibilities, a peculiarity of young individuals. In worms containing gametes, the dorsal setae of the first peristomial segment is absent. The generation of gametes comes from the notopodia, starting from the sixth segment.
In adult specimens of V. zaikai, there is only one pair of dental plates, while in the nektochaete there are two pairs. Obviously, the second pair of plates grows into the tissue, so that they are barely visible.
Larvae: Metatrochophoras and nektochaetes of V. zaikai are found in the pelagial of the Black Sea. Larvae are present all over the year in the central parts of the sea in the 100-150 m. layer
Metatrochophora (fig. 2 A). A very widened episphere hanging over a short, narrowing hyposphere. The length of larva is 0.286 mm, the greatest width is 0.220 mm. At the top of the episphere is a convex skullish plate with small bundles of cilia at the fringes. The cilia are also situated on the border between epi- and hyposphere and on the posterior end. There are to the left and right on the lower regions of the episphere rounded outgrowths carrying bundles of simple, toothed setae, with transverse striation. (fig. 2 A, a). By irritating the larvae or by fixating them the setae diverge in all directions. The longest setae measures 0.300 mm. The larva are thorough with nutritional material and looks black in transparent light. Due to the wealth of encapsulated nutritional spheres it wasn't possible to take a closer look at the internal structures of the larva.
Nektochaeta (fig. 2 B). In the plankton one finds nektochaetes with three to five pairs of parapodia 0.336-0.509 mm in length. Prostomium rounded. Peristomium with one pair of tentacular cirri in young nektochaetes and with two pairs in older ones. In addition they have on the peristomial segment a bundle of simple setae on the dorsal side and compound setae on the ventral side. Young nektochaetes retains on the peristomium a bundle of temporary long tooted setae with transverse striation. Parapodia biramous, with short dorsal and long ventral rami. Notopodia with acicula, a bundle with simple toothed setae with transverse striation and a long dorsal cirrus, situated below the bundle of setae. Neuropodia with acicula, a bundle of compound heterogomph setae, the basal part has transverse striation, and a ventral cirrus. Proboscis barrelshaped with two pair of digestive plates (fig 2 B, b). Pygidium with two cirri. There are, in young nektochaetes, ciliated belts on the segments and on the anal ramus.
The larvae are filled with nutritional spheres and looks hump-backed in profile.
*) named in honor of V. E. Zaika