Micronephthys longicornis ( Perejaslavtseva 1891 )

Dnestrovskaya, Nataliya Yu. & Jirkov, Igor A., 2019, Redescription of Micronephthys longicornis (Perejaslavtseva, 1891) (Annelida: Nephtyidae), Zootaxa 4550 (3), pp. 391-400 : 393-395

Micronephthys longicornis ( Perejaslavtseva 1891)

Fig. 1 – Fig. 4 .

Nephthys longicornis Perejaslavtseva, 1891: 248 –249, pl. VII, fig. 2 (a,b,c); type locality: Black Sea, Sevastopol Bay;

Vinogradov 1949: 51–52; Vinogradov and Losovskaya 1968: 286, pl. 9, fig. 7. Nephthys cirrosa Ehlers var. longicornis Perejaslavtseva—Jakubova 1930: 871 . Nephtys cirrosa longicornis Jakubovi, 1930 (Sic!).— Hartman 1950: 90. Nephthys stammeri Augener, 1932: 678 , 679, fig. 2; type locality: Adriatic Sea (Timavo-Geviet region). Micronephthys maryae San Martín, 1982: 427 –434, figs. 1–3; type locality: Caló des Moro, Ibiza, Mediterranean Sea; Laborda

2004: 416, fig. 152A–C;? Rainer and Kaly 1988: 696, figs. 5A–E and 6B. Fide Ravara 2010? Micronephthys cf. stammeri— Dixon-Bridges et al. 2014: 515. Micronephthys stammeri ( Augener, 1932) .— Hartman 1950: 131; Banse 1959: 302–305, fig. 6; Marinov 1977: 120–121, pl. 14,

fig 2a–2d, pl. 37, fig. 3; Kiseleva 2004: 106, 110–111, fig. 25; Ravara et al. 2010: 27–30, fig. 9;? Murray et al. 2015: 428–

431 figs 10–11.

Description. Examined specimens with 32–38 chaetigers; size range up to 7.5 mm in length (without pharynx); up to 0.5 mm in width (at C10, including parapodia), length of first ten chaetigers—near 1 mm.

Body slightly wider anteriorly, tapered posteriorly. Preserved specimens colorless. Prostomium of specimens with non-everted pharynx rectangular to subpentagonal (width shorter than length), slightly extended in anterior part, anterior margin straight or slightly convex, sides convex. Antennae long (near 2/3 length of prostomium) and digitiform, with swollen tips, directed forward. Palps single, subequal in form and size to antennae or slightly shorter, inserted ventrolaterally of prostomium, directed sideward or anterolaterally. Nuchal organs at posteriolateral angles of prostomium, rounded (group II after Ohwada, 1985) ( Fig. 1B , Fig. 2C, D ).

One or two pairs (coalesced) of eyespots of irregular form visible on C3 dorsally ( Fig. 1A ). Sometimes some variation may present: two eyespots obliquely (one at C3 and another at C4); three eyespots (two at C3 one at C2); two paired (coalesced) eyespots on each other (four eyespots in total) at C3; two eyespots and scattering of small eyespots at anterior chaetigers dorsally and even on parapodia. Inferior lip of mouth reaching C3.

Specimens with fully everted pharynx ( Fig. 2A ): prostomium convex in anterior and anterolateral parts (width almost two times longer than length). Antennae directed forward, palps anterolaterally. Specimens with semieverted pharynx: prostomium almost quadrangular, palps with bulbous base (anterior part of prostomium supports ventrally by semi-everted pharynx) ( Fig. 2B ).

Fully everted pharynx ( Fig. 2A ): (length up to 0.7 mm) with 18 bifid terminal papillae and unpaired median dorsal terminal papilla with inflated base. Single middorsal and midventral subterminal papillae absent. Subterminal papillae arranged in 20–22 rows distally, proximally number of rows reduced (14 in medium part of pharynx due to few short rows), 5–9 elongate papillae per row, conical, gradually diminishing in size towards base of pharynx, extending over 2/3 length of pharynx, each row finished with several tiny papillae; proximal parts of pharynx smooth.

Two light-brown chitinous teeth of pyramidal shape with triangular base located inside pharynx. Internal chitinized pharyngeal trepans absent. Peristomium neither enlarged nor flattened (group II after Ohwada 1985) ( Fig. 1B , Fig. 2A ).

Parapodia of C1 directed forward, similar in size to subsequent ones. Notopodia small, pre-and postacicular lobes rudimentary, acicular lobes conical. Neuropodia conical with truncated tips; pre- and postacicular lobes growing together to form cylinders around acicular lobes. Ventral cirri of C1 long, digitiform, with swollen tips, similar in size to antennae and palps; dorsal cirri minute and spherical ( Fig. 1B , Fig. 2A, C, E ).

Branches of subsequent parapodia short, directed perpendicular to body, widely separated, never overlapped. Parapodia biramous with poorly developed lobes, single aciculum with curved tips in each ramus. Notopodia and neuropodia with conical or slightly rounded acicular lobes and rudimentary pre- and postacicular lobes ( Fig. 2F ); surface of interramal space smooth ( Fig. 1 D, E , Fig. 2 F ).

Branchiae absent. Dorsal and ventral cirri small, subglobular; dorsal cirri larger than in C1 ( Fig. 1 C–E, Fig. 2F ). Pygidium with short ventral cirrus equal in length to last 2–3 chaetigers.

Chaetae of five types: dentate, capillary, barred, lyrate chaetae and chaetae with small spines. Thick dentate chaetae with peak in center of each bar in preacicular rows in notopodia of first chaetigers only ( Fig. 4 A–C). Capillary chaetae in noto- and neuropodia of first chaetigers ( Fig. 4C ). Following parapodia: barred chaetae in preacicular rows ( Fig. 4 G–I); lyrate chaetae with unequal rami and long thin spines on inner surface in postacicular rows from C3 ( Fig. 4 D–F); chaetae with small (about 0,0 0 1 mm) spines randomly scattered along one side of chaeta in postacicular rows ( Fig. 4 J–L).

Distribution. Black Sea ( Perejaslavtseva 1891; our data), Adriatic Sea, Mediterranean Sea (Balearic Islands) ( Augener 1932; Banse 1959; San Martín 1982). Reports from other localities need to be verified.

Habitat. Upper sublittoral (above tidal front) within Mediterranean, median sand with gravel, 3.6–7 m depth ( Banse 1959; Laborda 2004; San Martín 1982); in the Black Sea much deeper, up to 47.4 m., sand, shells with sand, slightly silty until very silty sand.

Figures

FIGURE 1. Micronephthys longicornis (Perejaslavtseva, 1891), pharynx retracted, B, C, D—SEM photo. A. Anterior and median chaetigers, dorsal view; B. Prostomium with C1, dorsal view; C. Neuropodia with ventral cirri, median chaetigers, ventral view; D. Parapodia of median chaetigers, lateral view; E. Parapodium with dorsal and ventral cirri, median chaetiger. Abbreviations: C1—first chaetiger, dc—dorsal cirrus, e—eyes, n—nuchal organs, p—palp, vc—ventral cirrus. Specimens from BS-ML-1 (B, C), specimens from Ashamba-2017-4-44-2 (D, E). Scale bars: A—1 mm, B, C, E—0,03 mm, D—0,1 mm.

FIGURE 2. Micronephthys longicornis (Perejaslavtseva, 1891), (chaetae omitted). A. Prostomium, C1, and fully everted pharynx with pharyngeal papillae, dorsal view; B. Prostomium of specimen with semi-everted pharynx, dorsal view; C. Prostomium of specimen with retracted pharynx and neuropodiae C1, ventral view; D. Prostomium of specimen with retracted pharynx, dorsal view; E. C1, dorsal view, left side; F. Parapodia of C10, anterior view. Abbreviations: C1—first chaetiger, C10—tenth chaetiger. Specimens from BS-ML-1 (A, C, E), specimens from BS-ML-2 (B, D, E). Scale bars: all 0,1 mm

FIGURE 4. Micronephthys longicornis (Perejaslavtseva, 1891). A, D, G, J – chaetae drawings (after Perejaslavtseva); B, C, E, F, H, I, K, L—chaetae SEM photos. A, B. Dentate chaetae of C1; C. Dentate and capillary chaetae of C1; D–F. Lyrate chaetae; G–I. Barred postacicular chaetae; J–L. Chaetae with small spines scattered along one side. Abbreviations: c—capillary chaeta, d—dentate chaeta. Specimens from BS-ML-1 (B, H, L), specimens from Ashamba-2017-4-44-2 (C–E, I, K). Scale bars: B, E, F, H, I, K, L—0,003 mm, C—0,01mm.