Grania colorata, 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 : 25-27

Grania colorata sp. n.

( Figs. 6 , 7 , 10 D)

Holotype: AMS type coll. W.35545, a whole-mounted front end from Lizard Island, stn. L19, also serving as voucher specimen for COI barcode (GenBank accession no. GQ247639 ); posterior end used for DNA extraction.

Paratypes: AMS type coll. W.35546, whole-mounted front end from Lizard Island, stn. L21, voucher specimen for COI barcode (GenBank accession no. GQ247641 ). AMS type coll. W.35547-W.35553, 7 wholemounted specimens: 1 each from stns. L1, L2, L10, L11, L12, L25 and L28. SMNH type coll. 7768-7772, 5 whole-mounted specimens, of which 3 are from stn. L10 and 2 from L11.

Other material examined: SMNH main coll. 105500-105539, 40 whole-mounted specimens from Lizard Island (stns. L8 (12), L11 (15), L20 (4), L21 (9)). First author’s collection: 38 whole-mounted specimens from Lizard Island (stns. L1 (1), L2 (17), L5 (2), L9 (3), L10 (7), L16 (1), L19 (1), L24 (1), L27 (2), L29 (3)).

Description: Living specimens greenish-yellow. Body 4.3–5.1 mm long (n=30), 0.08–0.12 mm wide at III, 0.09–0.14 mm at clitellum (n=30). Segment number 35–38 (n=30). Prostomium rounded, 40–60 µm wide, 30–45 µm long (n=30); epidermis 6–14 µm thick dorsally and anteriorly (n=30), 5–11 µm ventrally (n=30). Peristomium 70–90 µm wide at 1/2 (n=30). Ventral chaetae commencing in XIV (XV in one specimen); lateral chaetae commencing in XVI–XVIII. Chaetae of uniform size throughout body, 55–70 µm long (n=30); chaetae L-shaped: shaft thickest at base and sharply pointed distally, foot 10–15 µm long, with broad instep, flat sole and conspicuous heel; chaetal index= 4.63 n =30, sd=0.791 ( Figs. 6 A, 10D). Epidermal gland cells inconspicuous. Clitellum 8–14 µm thick, extending from anterior of XII to mid XIII, with an irregular pattern of granular gland cells interspersed with hyaline cells at a frequency of about 4:3 ( Fig. 6 B), except near male pores where hyaline cells are absent, and midventrally, where no gland cells are present. Copulatory gland in XIV in some specimens. Spermathecal pores lateral, located immediately behind 4/5. Male pores located ventrolaterally in mid XII.

Brain posteriorly indented. Head organ absent. 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 in XVI–XIX. Chloragogen cells small (5–7 µm tall). Coelomocytes oval, small with stained nucleus, in high densities anterior to clitellum. Sperm sac extending posteriorly from clitellum as far back as XV; loose sperm packages also present in X–XII. Sperm funnels of uniform width, 45–50 µm wide, 1.5 times as long as wide. Heads of spermatozoa 13–17 µm long. Vasa deferentia unmodified, loosely coiled in XII; 5 µm wide, internally ciliated. Penial apparatuses ( Fig. 6 C) with uniform oval glandular structures, 40–55 µm long, 20–40 µm wide; vasa deferentia opening into epidermal invaginations; stylets absent (penial bulb type 3). Egg sac reaching as far back as XIX. Spermathecae ( Fig. 7 ) attached to oesophagus near 5/6; ampullae roughly spherical, relatively small (30–45 µm in diameter), ducts of uniform width, 50–70 µm long and 7–10 µm wide; very few sperm rings in ampullar walls, most of sperm freely dispersed in bundles throughout ampullar lumen; no glands at spermathecal pores.

Etymology: The Latin colorata refers to the conspicuous greenish-yellow coloration of the living worm, which is an unusual feature in Grania .

Remarks: The peculiar coloration of this species resembles that of G. galbina De Wit & Erséus, 2007 , a recently described species from New Caledonia, and preliminary molecular analyses also support that G. galbina and G. c o l o r a t a are closely related (De Wit, unpubl. data). The two species are easily distinguishable from each other, however, by the body size, where G. c o l o r a t a is much smaller than G. g a l b i n a both in length and segment number (maximum length of G. c o l o r a t a is 5.1 mm with 38 segments; minimum length of G. galbina is 6.4 mm with 51 segments), the chaetal distribution ( G. galbina possesses pre-clitellar ventral chaetae, G. colorata does not) and the sperm distribution in the spermathecal ampullae. In Grania the sperm are usually segregated in hollow spherical compartments in the walls of the ampullae, which gives the impression of the sperm being organized in rings. Grania galbina has many such rings in its spermathecae. In G. colorata , however, bundles of sperm are distributed mostly in the lumen of the ampullae. Grania colorata is also similar to, but clearly distinguishable from, G. homochaeta sp. n. described herein from Heron Island (see above for details). Interestingly, G. colorata , G. galbina and G. homochaeta all lack ventral lobes of the pharyngeal glands in IV. This is an uncommon feature within Grania , and further supports the close relationship between these three taxa.

Another interesting characteristic of G. colorata , not seen in any other member of Grania to date, is the presence of large masses of developing sperm in segments X–XII; this was observed in all specimens studied. In fixed Grania material it is not uncommon to observe limited amounts of developing sperm in front of the sperm sac, due to rupture or partial emptying of the sperm sac during fixation. That this would have happened consistently to all 91 individuals studied is highly unlikely, however, suggesting that this species uses its coelomic cavity as a storage place for maturing sperm which might not fit into the relatively small sperm sac.

Distribution and habitat: Lizard Island, Great Barrier Reef, subtidal (to 7 m), heterogeneous sand.

Figures

FIGURE 6. Grania colorata sp. n. (Holotype, stn. L 19). A: Chaetae. B: Clitellar gland cell pattern, dorsal view, anterior end to the top. C: Penial apparatus, side view, anterior end to the top.

FIGURE 7. Grania colorata sp. n. (Holotype, stn. L 19). Segment V with spermatheca, side view, anterior end to the right.

FIGURE 10. Chaetae. A: G. breviductus sp. n.. B: G. regina sp. n.. C: G. ho m o c ha e ta sp. n.. D: G. c o lor at a sp. n.. E: G. trichaeta Jamieson 1977.