Grania novacaledonia, 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 : 31-33

Grania novacaledonia sp. n.

( Figure 2 , Table 1)

Holotype: SMNH type coll. 6549, whole-mounted specimen from Touho, stn. NC93-25.

Paratypes: SMNH type coll. 6550-6558, 9 whole-mounted specimens from Touho, 4 of which from type locality, and 1 from each of stns. NC93-14, NC93-15, NC93-49, NC93-50 and NC93-82.

Other material examined: SMNH Main coll. 87841-87847, 7 specimens from CENTOB collected off Nouméa, New Caledonia, during the Nouvelle Calédonie 78 excursion in 1978 (stns. NC78-31, NC78-43, NC78-49A and NC78-51A); SMNH main coll. 87848-87860, 13 whole-mounted specimens from Touho (stns. NC93-14, NC93-15, NC93-25, NC93-26, NC93-49).

Description of type material: Body 5.7–7.7 mm long (n=8), 0.14–0.17 mm wide at III, 0.14–0.19 mm at clitellum (n=10). Segment number 41–50 (n=8). Prostomium rounded, 70–85 μm wide, 35–60 μm long (n=10); epidermis 15–23 μm thick on occipital lobes, 10–18 μm on upper lip (n=9), 5–15 μm at front side (n=10). Peristomium 118–143 μm wide at 1/2 (n=10). Chaetal distribution irregular, with preclitellar ventral chaetae frequently occurring only in VII and sometimes VI and VIII, although sometimes completely absent; ventral chaetae occurring at all postclitellar locations; lateral chaetae commencing in XVII–XXI. Chaetae increasing in size posteriorly, 43–55 μm long pre-clitellum (n=7), 58–73 μm near posterior end (n=10); chaetae L-shaped; sharply pointed with distinct heel, foot 8–15 μm long (chaetal index=5.38, n=14, sd=0.78) (Figure 2A). Epidermal gland cells inconspicuous, interspersed irregularly. Clitellum 13–23 μm thick, starting in anterior of XII and extending to chaetal position of XIII, consisting of transverse cell rows with granular gland cells interspersed with hyaline cells at a ratio of about 2:1 ( Figure 2 B), except around male pores where hyaline cells are absent. “Copulatory glands” present midventrally in XIV. Spermathecal pores lateral, located right behind 4/5. Male pores located ventrolaterally in mid XII.

Brain in II–III, posteriorly indented in “head” region. No true “head organ” present, but bilobed vesicle present immediately behind 0/1, dorsal to the anterior furcation of blood vessel, between the circumpharyngeal commissures; no inclusions present, but hollow compartments visible with internal whorls of cilia. Pharyngeal glands located from 4/5 to 6/7, not united dorsally; dorsal lobes present in IV–VI, ventral lobes present in IV (1 pair), V (2 pairs) and VI (2 pairs), largest in VI ( Figure 2 C). First pair of nephridia at 7/8.

Dorsal blood vessel commencing in XVII–XXII. Chloragogen cells small (5–7 μm tall). Coelomocytes not observed. Sperm sac extending posteriorly from clitellum as far back as XVII. Sperm funnels of uniform width, 40–50 μm wide, 5 times as long as wide. Heads of spermatozoa about 20 μm long. Vasa deferentia long, loosely coiled in XII and XIII; 6 μm wide, internally ciliated. Penial apparati ( Figure 2 D) with uniform oval glandular structures, 48–58 μm long, 25–35 μm wide; vas deferens opening into epidermal invagination (Penial bulbs type 3). Stylets absent. Egg sac extending as far back as XVIII. Spermathecae ( Figure 2 E) attached to oesophagus near 5/6; ampullae pear-shaped, 53–58 μm wide, with small diverticulum on anterior side of each ampulla, ectal ducts uniform in thickness, 40 μm long and 25 μm wide; 4–8 sperm rings per spermatheca, 13–18 μm in diameter, located throughout ampullae; 4 ectal glands present at each spermathecal pore.

Etymology: Named after New Caledonia.

Remarks: The irregular pre-clitellar chaetal distribution with chaetae present in only one to three segments (VI, VII and/or VIII) is unusual, yet not unique to this species. Similar distributions have been described for Grania variochaeta Erséus & Lasserre, 1976 , and in G. ocarina Rota, Erséus & Wang, 2003 , the latter existing in Western Australian waters. Grania novacaledonia is different from G. ocarina and G. v a r i o - chaeta in its chaetal shape ( G. ocarina has no distinct heel; G. variochaeta has upturned tips on the ental “feet”) and the presence of ectal glands at the spermathecal pores. The lack of penial stylets also distinguishes G. novacaledonia from G. ocarina . Ectal glands by the spermathecal pores have also been recorded in Western Australian species [G. e r s e i Coates, 1990 and G. darwinensis ( Coates & Stacey, 1997) ], as well as in North Pacific waters [ G. paucispina (Eisen, 1904) and G. americana Kennedy, 1966 ]. Grania novacaledonia differs from all of these, however, in its chaetal distribution.

The bilobed vesicle present anterior to the brain in this and two other species described herein is peculiar, as it has the same apparent structure as the “head organ” recently described in a number of Grania species ( Rota & Erséus, 1996; Rota & Erséus, 1997; Locke & Coates, 1999; Rota & Erséus, 2000, 2003), yet it contains no inclusions. This has previously been noted in descriptions of only two species: G. aquitana Rota & Erséus, 2003 and G. monochaeta (Michaelsen, 1888) (see Rota & Erséus, 1997). Rota et al. (1999), however, noted that some other species (e.g. G. m a r i c o l a Southern, 1913) also possess this feature. Upon re-examination, it seems as if this could be the case in a considerable number of species of the genus (De Wit, personal observation) (see Discussion).

Another feature worth noting is the apparent lack of coelomocytes in this and several other species from New Caledonia. This has also been reported for G. algida Rota & Erséus, 1996 and in G. carchinii Rota & Erséus, 1996 , both inhabiting Antarctic waters. This could, possibly, be an artifact caused by the fixation or staining procedure. However, the presence or lack of coelomocytes has frequently been omitted in literature, which might justify further investigation and re-examination of poorly described species.

Distribution and habitat: Touho and Nouméa areas, New Caledonia, lower intertidal and subtidal (to 21 m), heterogeneous sand.

Figures

FIGURE 2. Grania novacaledonia sp. n.. A: Chaetae. B: Clitellar cell pattern. C: Overview of I – VII. D: Penial apparatus. E: Spermatheca.