Capitella ambonensis, Pamungkas, Joko, 2017

Pamungkas, Joko, 2017, Capitella ambonensis: a new polychaete species (Annelida: Capitellidae) collected from a mangrove habitat on Ambon Island, Indonesia, Zootaxa 4227 (4), pp. 573-582 : 575-580

Capitella ambonensis sp. nov.

Material examined. Holotype: 1 male ( MZB. Pol 00182), Poka Village , Ambon Island, 03˚38′45.3″S, 128˚11′31.6″E, coll. J. Pamungkas, August 28th, 2015 . Paratypes: 5 males ( MZB. Pol. 00183), 1 male ( MZB. Pol. 00184), 10 females (?) ( MZB. Pol. 00185), 2 females (?) ( MZB. Pol. 00186), 1 female (?) ( MZB. Pol. 00187), 1 female (?) ( MZB. Pol. 00188), 3 males ( RCLA. Ann. 176), 2 females (?) ( RCLA. Ann. 196), all from Poka Village , Ambon Island, 03˚38′45.3″S, 128˚11′31.6″E, coll. J. Pamungkas, August 28th, 2015 .

Description. Holotype complete but with broken pygidium, with about 179 chaetigers, 54 mm long, 0.9 mm wide in anterior abdomen. Paratypes complete or anterior fragments (mostly), ranging from 17 mm long by 0.7 mm wide (49 chaetigers) to 57 mm long, 1.0 mm wide (about 208 chaetigers). Color in alcohol whitish, except abdominal dorsum pigmented dark brown. Prostomium conical, somewhat flattened dorsoventrally, eyes absent. Peristomium distinct, a single achaetous ring.

Thorax with 9 segments, all chaetigerous. Chaetigers 1–7 with capillary chaetae only in both rami ( Figs 2A & B; 5A). Chaetigers 8 and 9 with neurohooks only; notopodia achaetous, but with genital spines in male (i.e., on chaetigers 8 and 9) and some female (?) specimens (i.e., on chaetiger 9 only); thoracic chaetal formula = c/c (1–7), gs/h (8–9) for males, and c/c (1–7), a/h (8–9) or c/c (1–7), a/h (8), gs/h (1 9) for females (?). Thoracic region with two distinct parts, i.e. (1) striated uni-annulate segments (starting from peristomium to chaetiger 7), and (2) smoother multi-annulate segments (chaetigers 8 and 9). First six chaetigers gradually increasing in size with chaetiger 6 largest. From chaetigers 7–9, size gradually decreasing ( Fig. 2A & B). Shallow lateral line from chaetigers 5 or 6 continuing to posterior end ( Figs 2A & 5A ). Ventral groove present from chaetiger 7 to posterior end ( Fig. 4 C & D). Genital pore, when seen, between chaetigers 7 and 8 ( Fig. 5A ).

In males, genital spines of each chaetiger in two bundles. Spines of both chaetigers pointed toward each other with larger spines of chaetiger 9 directed anteriorly and smaller, less conspicous spines of chaetiger 8 directed posteriorly. Color of genital spines of chaetiger 8 light brown with those of chaetiger 9 blackish brown ( Fig. 2 C). In most females (?), genital spines not seen ( Fig. 2 D), often hidden in intersegmental groove between chaetigers 8 and 9. Some female specimens with minute genital spines in chaetiger 9 only (size of spines much smaller than those of males). Dorsal region around genital spines of chaetiger 9 of male specimens inflated ( Fig. 2A , B & C), perhaps due to the presence of copulatory organ; chaetiger 9 of females not inflated. Holotype male with three obvious pairs of genital spines in chaetiger 9, but hidden spines in intra-annular groove of chaetiger 8. Paratype MZB Pol. 0 0 184 male with six and three pairs of obvious genital spines in chaetigers 8 and 9, respectively ( Fig. 2 C). Most male paratypes with spines not visible, or with slightly visible spines in chaetiger 8 and obvious spines in chaetiger 9.

Transition between thorax and abdomen clearly marked by: (1) deep inter-segmental groove between chaetigers 9 and 10, (2) dark brown-pigmented abdominal dorsum, and (3) presence of abdominal hooded hooks in noto- and neuropodia ( Fig. 2A , B & C). Abdominal segments multi-annulate ( Fig. 2A & B), not narrowing posteriorly, except far posterior region slightly narrowing. Branchiae absent. Pygidium mostly broken; MZB. Pol. 0 0 188 complete; pygidium simple and without any appendages ( Fig. 2 E).

Hooded hooks with two rows of teeth above main fang, covered with short hood to shoulder. Hooks with narrow neck, relatively long anterior shaft between shoulder and node, obvious constriction and inflated node ( Fig. 5C –E). In anterior abdomen, number of notohooks within fascicle slightly fewer than neurohooks, i.e. about 13 and 18 hooks, respectively. Hooks within fascicles decrease in number posteriorly with about 7 and 10 hooks in noto- and neuropodia of posterior chaetigers, respectively.

Methylene blue staining pattern (MBSP). Thorax fully stained, including intersegmental and ventral grooves. Dorsal region of thorax stained blue with medium intensity, except in areas around notopodia and genital spines stained light blue ( Fig. 4 A & B). Ventral regions of prostomium and peristomium stained light blue; more weakly stained areas around neuropodia and ventral line. Ventrum of chaetigers 1, 2 and 4 stained blue with medium intensity; chaetiger 3 brighter. In subsequent chaetigers, ventral areas of chaetigers 5, 6 and 7 stained deeper on prechaetal annuli and darker on postchaetal annuli, whereas those of chaetigers 8 and 9 stained blue with medium intensity ( Fig. 4 C). Dorsum of anterior abdominal segments stained dark blue with slightly brighter areas around noto- and neuropodia ( Fig. 4 A & B), whereas that of mid to posterior abdominal segments stained brighter. Abdominal venter stained light greenish blue with dark blue oval patterns (ring-like) surrounding neuropodia ( Fig. 4 C & D).

Variation. Some variation was noted in the paratype MZB. Pol. 0 0 186. Whereas abdominal dorsum of other type specimens dark brown, those of two specimens of MZB Pol. 0 0 186 pale. Also, in contrast to other type specimens, posterior region of these two specimens slightly inflated.

Distribution. Capitella ambonensis sp. nov. was first discovered in a mangrove habitat adjacent to a dieselpowered electricity generator (PLTD) at the Poka Village, Ambon Island, Province of Maluku, Indonesia. To the best of the author’s knowledge, this species has not been found in any other mangrove habitats on the island, or elsewhere in Indonesia. Capitella ambonensis sp. nov. inhabits a mangrove area with loamy sand sediment, and seems to be tolerant of salinity. This species lives in an area where earthworms were also found.

Etymology. The species is named based on its locality, i.e. Ambon Island.

Remarks. The new species C. ambonensis sp. nov. most resembles five known Capitella species: C. dizonata Johnson, 1901 , C. capitata ( Fabricius, 1780) , C. perarmata ( Gravier, 1911) , C. singularis ( Fauvel, 1932) , and C. teleta Blake, Grassle & Eckelbarger, 2009 . They all have the first seven thoracic chaetigers with capillary chaetae in both rami (Table 1). Capitella ambonensis sp. nov. differs from these other Capitella species in the following features.

TABLE]. All Capitella species (neglecting the sub-species) arrangeđ in orđer of the increasing number of thoracic chaetigers bearing capillary chaetae.

• The following notations are useđ for thoracic chaetal formulas. a = absence of chaetae; as = acicular spines; c = capillary chaetae; h = hoođeđ hooks; m = mixeđ chaetae (capillaries anđ

hooks); gs = genital spines. Numbers in () inđicate the chaetiger number.

• The symbol ‘*’ inđicates that ređescription of the species can be suggesteđ for one or more of the following reasons, i.e. the đescription is too short anđ/ or lacks of clear illustrations anđ/

or not written in English without English abstract.

When compared to C. dizonata , the first abdominal segment of C. ambonensis sp. nov. has hooded hooks in both rami, whereas C. dizonata has capillary chaetae in notopodia and hooded hooks in neuropodia. This is unfortunately the only obvious difference between the two species as C. dizonata was in fact described from a single, incomplete and presumably immature female specimen and the type specimen of this species is not known to exist ( Hartman, 1947).

When compared with C. capitata ( Fig. 3 A), the number of chaetigers of C. ambonensis sp. nov. is much higher than that of C. capitata . The largest specimen of C. ambonensis sp. nov. has about 208 chaetigers, whereas that of C. capitata , as described by Blake (2009), has around 60 chaetigers. Capitella ambonensis sp. nov. also has a striated thoracic epithelium with chaetiger 6 being the largest, whereas the epithelium of C. capitata is smooth with chaetiger 4 being the largest. In terms of visibility, genital spines of chaetiger 8 of C. ambonensis sp. nov. are often hidden in the intra-annular groove, whereas those of C. capitata are normally visible. In reverse, genital spines of chaetiger 9 of C. ambonensis sp. nov. are very obvious particularly in adult male specimens, whereas those of C. capitata are usually not visible (dissection is thus necessary to see the spines). The body color of C. ambonensis sp. nov. in alcohol is whitish with dark brown pigment on the abdominal dorsum, whereas C. capitata might have different color. The staining pattern between the two species, as well as the morphology of the hooded hooks, is also different.

In Capitella perarmata , the neuropodia of chaetigers 8 and 9 of males bear mixed capillaries and hooks, whereas C. ambonensis sp. nov. has hooded hooks only. This, unfortunately, is the only distinguishing character known between the two species as the original publication on C. perarmata by Gravier (1911) is relatively short and without figures.

In comparison with Capitella singularis , the genital spines of chaetiger 8 of C. ambonensis sp. nov. are much smaller than those of chaetiger 9, whereas in C. singularis spines of chaetiger 8 are more or less of the same size as those of chaetiger 9. Another clear difference between the two species is that branchiae are absent in C. ambonensis sp. nov., whereas branchiae are present in C. singularis .

When compared to C. teleta , the prostomium of C. ambonensis sp. nov. lacks eyes, a nuchal organ is not apparent, and the peristomium is distinct; whereas the prostomium of C. teleta has both eyes and nuchal organs, followed posteriorly with an indistinct peristomium. The thoracic chaetal formula of chaetigers 8 and 9 of females of the two species is also slightly different (Table 1), but the most obvious difference between the two species might be the color of their abdominal dorsum: dark brown in C. ambonensis sp. nov. and light tan in C. teleta . In addition, the morphology of the hooded hooks and the staining patterns between the two species are also different.

Figures

FIGURE 2. A, lateral view from prostomium to 5 th abdominal segment (holotype); B, dorsal view from prostomium to 5 th abdominal segment (holotype); C, genital spines of the paratype MZB. Pol. 00184; D, dorsal appearance of chaetigers 7, 8 and 9 of a female (?) specimen; E, posterior end with pygidium of the paratype MZB. Pol. 0 0 188. Pro, Prostomium; Per, Peristomium; gs, genital spines; Pyg. Pygidium; numbers indicate chaetigers. Scale bars: A – E = 1.0 mm

FIGURE 3. Morphological comparison between C. capitata (A) and C. ambonensis sp. nov. (B). Scale bars: A = 0.5 mm, B = 1.0 mm. A, modified after Blake (2009).

FIGURE 4. Methylene blue staining pattern of the holotype. A, lateral view, prostomium to 5 th abdominal segment; B, dorsal view, prostomium to 4 th abdominal segment; C, ventral view, prostomium to 4 th abdominal segment; D, mid-ventral abdomen. Scale bars: A – D = 1.0 mm.

FIGURE 5. A – D, Scanning electron micrographs of C. ambonensis sp. nov. A, lateral view, chaetigers 4 to 11; B, hooks of the second abdominal notopodia in one fascicle; C – D, hooded hooks of the anterior abdominal neuropodia; E, line drawing of the hooded hook. Scale bars: A = 0.5 mm, B = 15 µm, C – D = 5.0 µm, E = 10 µm. lp, lateral pore.