Grania curta, Wit, Pierre De & Erséus, Christer, 2007

Wit, Pierre De & Erséus, Christer, 2007, Seven new species of Grania (Annelida: Clitellata: Enchytraeidae) from New Caledonia, South Pacific Ocean, Zootaxa 1426, pp. 27-50 : 38-40

Grania curta sp.n.

( Figure 5 , Table 1)

Holotype: SMNH type coll. 6583, whole-mounted specimen from Lifou, stn. NC00-43.

Paratypes: SMNH type coll. 6584-6588, 5 whole-mounted specimens from type locality.

Description: Body 2.6–4.1 mm long (n=6), 0.16–0.18 mm wide at III, 0.17–0.20 mm at clitellum (n=6). Segment number 26–34 (n=6). Prostomium rounded, 65–75 μm wide, 50–60 μm long (n=6); epidermis 15–25 μm thick on occipital lobes, 15–20 μm on upper lip, 10–15 μm at front side (n=6). Peristomium 110–130 μm wide at 1/2 (n=6). Ventral chaetae commencing in IV, absent in XII; lateral chaetae commencing in XIII or XIV. Chaetae increasing in size posteriorly, 25–35 μm long in preclitellar segments, 45–65 μm long near posterior end (n=6); chaetae sharply pointed, proximal end curved, hook 5–13 μm long ( Figure 5 A). Epidermal gland cells inconspicuous, interspersed irregularly. Clitellum 15–20 μm thick, starting at anterior end of XII and extending to chaetal position in XIII, consisting of transverse rows of granular gland cells irregularly interspersed with hyaline cells at a ratio of about 4–5:1 ( Figure 5 B), except around male pores where hyaline cells are absent. “Copulatory glands” not observed in XIV. Spermathecal pores lateral, located immediately behind 4/5. Male pores located ventrolaterally in mid XII.

Brain in II–III, posteriorly indented in “head” region. Head organ absent. Pharyngeal glands located from 4/5 to 6/7, not united dorsally; dorsal lobes present in IV–VI, ventral lobes present in V (2 pairs) and VI (2 pairs), in VI ventrally pressing septum 6/7 as far back as chaetal position of VII); no ventral lobes present in IV ( Figure 5 C). First pair of nephridia at 7/8. Dorsal blood vessel commencing in XIV–XVI. Chloragogen cells small (5–7 μm tall). Coelomocytes not observed. Sperm sac extending posteriorly from clitellum as far back as XV. Sperm funnels bell-shaped, 65–70 μm wide at collar, 2 times as long as wide. Heads of spermatozoa about 20 μm long. Vasa deferentia long, loosely coiled in XII–XVI; 6 μm wide, internally ciliated. Penial apparati ( Figure 5 D) with oval glandular structures, 35–45 μm long, 25–30 μm wide, vasa deferentia opening into epidermal invagination from male pores (Penial bulb type 3). Stylets absent. Egg sac extending to XVI. Spermathecae ( Figure 5 E) attached to oesophagus near 5/6; ampullae roughly spherical, 50–55 μm in diameter, ectal ducts bipartite, ental part uniformly 15 μm wide, 20 μm long, ectal part covered by glandular cells, 20–25 μm long; somewhat larger glandular cells also surrounding spermathecal pores; sperm present freely in ampullae as well as in rings; 4–8 sperm rings per spermatheca, 13–18 μm in diameter, located throughout ampullae.

Etymology: Curta is a Latin word meaning “too short” or “mutilated”. This refers to the short, stubby body shape of this species.

Remarks: This is one of the shortest species of Grania described up to date. Other short taxa, such as G. papillinasus Rota & Erséus, 2003 , from the Atlantic deep sea, are typically also thin (and thus slender), but this is not the case in G. c u r t a, which gives an impression of it being mutilated. However, as the appearance (also of the pygidium) is similar in all observed specimens, the specimens are most likely intact. The peculiar spermathecal ectal duct structure, with glandular cells covering the ectal part of the duct, is similar to that of G. c i n c t u r a sp.n., with the difference that in G. c u r t a the spermathecal pores are also surrounded by glandular cells. This kind of gland arrangement along the spermathecal ectal duct is similar to what has been described in G. p a r v i t h e c a Erséus, 1980, a South Atlantic species. However, while in G. c u r t a and G. c i n c t u r a the ectal duct is bipartite, with the ental part lacking glandular cells, in G. parvitheca the entire duct is covered by such cells.

Distribution and habitat: Loyalty Islands, New Caledonia, shallow subtidal (0.5 m), heterogeneous sand.

Figures

FIGURE 5. Grania curta sp. n.. A: Chaetae. B: Clitellar cell pattern. C: Overview of I – VIII. D: Penial apparatus. E: Spermatheca.