Grania regina , Wit, Pierre De, Rota, Emilia & Erséus, Christer, 2009

Wit, Pierre De, Rota, Emilia & Erséus, Christer, 2009, Grania (Annelida: Clitellata: Enchytraeidae) of the Great Barrier Reef, Australia, including four new species and a re-description of Grania trichaeta Jamieson, 1977, Zootaxa 2165, pp. 16-38: 21-23

publication ID 10.5281/zenodo.189048

persistent identifier

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scientific name

Grania regina

sp. n.

Grania regina  sp. n.

( Figs. 3View FIGURE 3, 4View FIGURE 4, 10View FIGURE 10 B)

Holotype: AMS type coll. W. 35543, incomplete whole-mounted specimen from Heron Island, stn. H 3.

Description: Body> 5.43 mm long (posteriorly amputated), 0.12 mm wide at III, 0.12 mm at clitellum. Segment number> 40. Prostomium rounded, 60 µm wide, 45 µm long; epidermis 17 µm thick dorsally, 15 µm anteriorly, 11 µm ventrally. Peristomium 87 µm wide at 1 / 2. Ventral chaetae commencing in IV, lateral chaetae commencing in XVII. Chaetae of uniform size throughout body, 40–45 µm long (n= 16); chaetal shaft thickest proximally, tapering distally, proximally bent into an oblique, rather long, narrow foot with indistinct heel and low instep; tip of foot straight, 10–15 µm long ( Figs. 3View FIGURE 3 A, 10 B); chaetal index= 3.46, n= 16, sd= 0.677. Epidermal gland cells inconspicuous. Clitellum 9.5 µm thick, extending from anterior of XII to mid XIII, with transverse rows of granular gland cells interspersed with hyaline cells at a frequency of about 8: 1 ( Fig. 3View FIGURE 3 B), except near male pores where hyaline cells are absent, and midventrally, where no gland cells are present. Midventral copulatory gland in XIV. Spermathecal pores lateral, located immediately behind 4 / 5. Male pores located ventrolaterally in mid XII.

Brain posteriorly indented. Head organ present as round structure anterior to the brain, 19 µm in diameter, with four inclusions of 4 µm diameter each; inclusions showing a central cavity ( Fig. 4View FIGURE 4). Pharyngeal glands in IV –VI; dorsal lobes present in IV –VI, ventral lobes present in V (2 pairs) and VI (2 pairs); not connected dorsally. First pair of nephridia at 7 / 8. Dorsal blood vessel commencing around XL, although difficult to discern due to damaged nature of specimen. Chloragogen cells small (5–7 µm tall). Coelomocytes slightly oval, 13 µm across at the widest point, in higher density in pre-clitellar region. Sperm sac extending posteriorly from clitellum as far back as XIX. Sperm funnels of uniform width, 18–20 µm wide, 8 times as long as wide. Heads of spermatozoa 20 µm long. Vasa deferentia unmodified, loosely coiled in XII –XV; 6 µm wide, internally ciliated. Penial apparatuses ( Fig. 3View FIGURE 3 C) with uniform, slightly oval glandular structures, 30–40 µm long and wide, next to epidermal invaginations which can be as much as 40–50 µm deep; vasa deferentia opening into epidermal invaginations; β-shaped stylets present, 60–80 µm long (penial bulb type 5). Egg sac not seen. Spermathecae ( Fig. 3View FIGURE 3 D) attached to oesophagus near 5 / 6; ampullae saccate, 30 µm long and 45 µm wide, ectal ducts bipartite, with outer part of uniform width, 7 µm, and inner part widening from 7 to 25 µm, with distinct circular muscular bands seen across duct; ectal part 30 µm long, ental part 25 µm long; no sperm rings seen in the ampullae, but walls conspicuously nucleated; no glands at spermathecal pores.

Etymology: Named with the Latin regina  , i.e. queen, for the region of Queensland where it was found.

Remarks: Although based on a single incomplete specimen, this taxon appears to be a distinct species, as it is the only one found in eastern Australia that possesses a head organ. This feature is shared by species in Tasmania, South-West Australia and Antarctica, as well as some species in the Atlantic ( Rota & Erséus, 1996, 1997, 2000, 2003; Rota, Wang & Erséus, 2007). In contrast to many of those, however, G. re g i n a possesses long penial stylets. Other species with both a head organ and penial stylets are G. dolichura Rota & Erséus, 2000  , from Tasmania and southern Australia, and G. bykane Coates 1990  , G. crassiducta Coates, 1990  and G. ersei Coates 1990  from south-western Australia (see Rota, Wang & Erséus, 2007). However, the stylets of G. bykane  , G. crassiducta  and G. dolichura  are all considerably shorter than those of G. re g i n a, whereas those of G. e r s e i are much longer. Furthermore, G. bykane  and G. crassiducta  have short, stout spermathecal ducts, while G. dolichura  and G. ersei  possess spermathecae with long, narrow ectal ducts, distally expanded or with small ectal glands, all contrasting to G. regina’ s bipartite ducts that widen entally and lack ectal glands. The clitellar cell pattern (in rows) is similar among all five species, as is the chaetal distribution; the chaetal shape is also similar, although in G. dolichura  chaetae are more curved entally. Also, G. dolichura  shares with G. regina  a dorsal blood vessel which commences much more posteriorly than usual in Grania  , which further corroborates the phylogenetic affinity between these taxa.

Head organ inclusions with a central cavity have also been described in the south-western Australian G. sperantia ( Rota, Wang & Erséus, 2007)  .

Distribution and habitat: Heron Island, Great Barrier Reef; 15 m, fine sand.