Leocratides ehlersi (Horst, 1921) reinstated

Figure 42

Leocrates ehlersi Horst, 1921: 82; Hessle 1925: 15, Fig. 3 a–c, Pl. 1, Figs 1–3, Pl. 2, Figs 1–3.

Leocrates (Leocratides) ehlersi: Horst 1924: 194–195, Pl. 36, Figs 10–12 (n. comb.); Augener 1926: 452.

Leocratides ehlersi: Fauvel 1932: 62, 1953b: 107–108, Fig. 51 a–c.

Leocratides filamentosus: Pettibone 1970: 230–233, Figs 27–29 (partim, figure 29, non Ehlers, 1901).

Type material. Indonesia. Fifteen syntypes in two museums: 13 syntypes (ZMA V.Pol. 533), and two others (USNM 37646), Lesser Sunda Islands, Sumbawa, North coast, Saleh Bay, R / V Siboga Exped., Sta. 312 (08°19’ S, 117°41’ E), 274 m, trawl, muddy bottom/sand, 14 Feb. 1900 .

Additional material. Philippines. Two specimens (ECOSUR 3078, Musorstom 3-143), Sta. 143 (11°28’ N, 124°12’ E), 205–214 m (190–198 m in label), 1 Jun. 1985 [15.5–16.0 mm long, 2.5 mm wide] . New Caledonia. One specimen (MNHN Musorstom SMIB 3-17), Campagne SMIB 3, R/V Vauban, Sta. 17 (23°40.60’ S, 167°59.40’ E), 238 m, 23 May 1987 [This looks like a different species. It has entire, smooth dorsolateral tubercles; median antenna more than twice longer than prostomium, lateral antennae about three times longer than prostomium. Nuchal organs lobes markedly projected beyond lateral prostomial margin. Parapodia are in poor shape and better specimens are needed for its formal description, provided they confirm a different species is involved].

Description. Largest syntype (ZMA V.Pol. 533) complete, slightly damaged, bent laterally. Body blunt anteriorly, wider anteriorly, tapered posteriorly (Fig. 42A); 28 mm long, 3.5 mm wide, 16 chaetigers; right parapodia of chaetigers 8 and 15 removed for observing parapodial features. Tentacular and dorsal cirri without tips. Dorsal surface pale, venter with a wide longitudinal brownish band along body, triangular in tentacular belt. Becoming roughtly X-shaped along chaetigers 5–6, less defined in middle and posterior chaetigers (Fig. 42B).

Prostomium slightly wider than long, slightly wider anteriorly, lateral margins curved, convergent (Fig. 42C). Lateral antennae with ceratophores distinct, as long as prostomium, slightly longer than palps; palpophores twice longer than palpostyles; median antenna thinner and slightly shorter than lateral antennae, markedly surpassing anterior prostomial margin, inserted centrally among eyes.

Eyes barely pigmented, round, anterior ones twice larger and more separated than posterior ones; in lateral view, anterior and posterior eyes separated from each other.

Nuchal organs lobes completely exposed, divergent oval ridges, markedly separated middorsaly; lateral ciliated bands not visible dorsally. Tentacular cirri without tips, longest ones reach chaetiger 7. Lateral cushions projected, swollen, bipartite along body, longitudinal striae not visible.

Pharynx partially exposed (Fig. 42D, E). Upper jaw double, missing in largest syntype, present in other ones; crescent shaped, lower jaw single, tapered. Anterior margin smooth, without papillae. Lateral vesicles round, low, not fully projected.

Peristomial dorsolateral tubercles projected, narrower than prostomium, each with 2 low, round, wider than long lobes. Ventral ridge with 7–8 regular constrictions, barely projected, markedly wider than long.

Dorsal cirri mostly broken or without tips, longest one longer than body width including parapodia. Neuracicular lobes tapered, three times longer than wide, tips blunt, directed distally or slightly upwards (Fig. 42F). Neurochaetae about 18 per bundle, blades most missing, apparently decreasing in size ventrally, bidentate, without guards, blades 3–4 times longer than wide (Fig. 42F, insets).

Posterior region tapered. Prepygidial segment short, with dorsal cirri 3–4 times longer than ventral ones. Pygidium with anus terminal, anal cirri broken, reaching chaetiger 16.

Oocytes visible in posterior chaetigers, each about 120 µm. Gonad fragments in middle chaetigers contain only spermatids.

Variation. Syntypes 18–28 mm long, 3.0– 3.5 mm wide. Dorsolateral peristomial tubercles always narrower than prostomium, with up to three lobes each, but sometimes they barely defined by shallow furrows, whereas the ventral ridge can have up to 9 round lobes, each as long as wide. Eyes are round, most barely pigmented, or colorless. Median antenna, or its scar, always inserted centrally between eyes. The lateral pharynx vesicles rarely fully projected, when it occurs, they are globose, blunt. Midventral pigmented longitudinal bands is constant (a badly damaged specimen has a double, longitudinal thin band, leaving a paler middle area). Most neurochaetal blades missing, probably they are delicate, or easily torn off when specimens are removed from the hexactinellid sponge they live in.

Remarks. Leocratides ehlersi (Horst, 1921) reinstated, has been regarded as a junior synonym of L. filamentosus Ehlers, 1908 by Augener (1926: 452) and Pettibone (1970: 230), but others have regarded it as a distinct species (Fauvel 1932: 62, 1953b: 107; Pleijel 1998: 112, 160). These two species differ, as indicated in the key above, and consequently it is formaly reinstated. In fact, L. ehlersi resembles L. kimuraorum Jimi, Tanaka & Kajihara, 2017 from Japan, by having peristomial dorsolateral ridges with a few to none lobes, and ventral pigmentation. However, these species differ, in the type of neuracicular lobes and pigmentation patterns. In L. ehlersi neuracicular lobes are markedly longer than wide, triangular, non-mucronate, and there is a ventral continuous brownish band, whereas in L. kimuraorum the neuracicular lobes are as long as wide, mucronate, and ventral pigmentation is spotty, never continuous.

There are other records for the Andaman Sea by Fauvel (1932: 62, 1953b: 107–108, Fig. 51 a–c), and for the Red Sea by Fishelson & Rullier (1969: 59–60). However, because their specimens were not available, they cannot be confirmed.

Distribution. Originally described as living in an hexactinellid sponge, Aphrocallistes sp., in 274 m deep, off Sumbawa, Indonesia.