Malacoceros indicus ( Fauvel, 1928 )

Götting, Miriam, 2015, Spionidae (Annelida: ‘ Polychaeta’: Canalipalpata) from Lizard Island, Great Barrier Reef, Australia: the genera Malacoceros, Scolelepis, Spio, Microspio, and Spiophanes, Zootaxa 4019 (1), pp. 378-413 : 383-386

Malacoceros indicus ( Fauvel, 1928)

(Fig. 1)

Scolelepis indica Fauvel, 1928: 93 , figs 2g –m.— Fauvel 1930: 35, figs 7g –m; Fauvel 1953: 313 –314, figs 165g –m; Monro 1931: 25; Berkeley & Berkeley 1941: 21; Reish 1961: 277.

Malacoceros indicus .— Pettibone 1963: 99; Day 1967: 477, figs 18.5.p–u; Blake & Kudenov 1978: 195; Blake 1983: 219; Blake 1996: 105 –107, fig. 4.4; Ben-Eliahu et al. 1984: 96; Dauer & Ewing 1991: 395 –400, fig. 1; Imajima 1991: 6 –9, figs 2a–g, 3a–j.

Malacoceros (Malacoceros) indicus .— Foster 1971a: 50 –53, figs 93–99; Foster 1971b: 1455 –1457, figs 1–6.

Spio punctata .— Hartman 1961: 89 –90, plate 11, figs1–3; Hartman, 1969: 175, figs 1–3; fide Blake, 1996.

[Synonymy fide Williams 2007]

Material examined. AM W.44376, MI QLD 2376 (2 af), formalin; AM W.44384, MI QLD 2376, af, formalin; AM W.44377, MI QLD 2376, af, formalin; AM W.44378, MI QLD 2376, af, mf, palps, 96% ethanol; AM W.44565, MI QLD 2422, af, formalin; AM W.44835, MI QLD 2422, af, formalin; AM W.44834, MI QLD 2422, af, formalin; AM W.44838, MI QLD 2422, af, formalin; AM W.44834.001, MI QLD 2422, mf, no longer extant; AM W.44858, MI QLD 2439, af, formalin; AM W.44858.001, MI QLD 2439, mf, ethanol; AM W.44859, MI QLD 2438, af, formalin.

Diagnosis. Prostomium with distinct anterolateral horns or with anterolateral projections; prostomium posteriorly extended into short caruncle which terminates at the end of chaetiger 1. Branchiae present from chaetiger 1 for most of body length; cirriform with elongate, slender tip, separate from notopodial lamellae; first pair of branchiae usually about same length or longer than notopodial lamellae; branchiae often overlapping at midline in anterior mid-body region. Neuropodial postchaetal lamellae rounded, with small medial nipple-like projection in chaetigers of middle body region. Neuropodial bi-, tri-, or quadridentate hooded hooks present from chaetigers 28–115, 3–11 hooks per fascicle.

Description. (based on specimens examined in the course of the present study). All specimens incomplete; longest specimen 154 chaetigers, 2.2 mm wide and 41 mm long; other specimens 0.8–3.8 mm wide and 11.2–27 mm long. Prostomium bell-shaped to sub-triangular, larger specimens with distinct anterolateral horns (Fig. 1A, B), smaller specimens with anterolateral projections; prostomium posteriorly extended into short protuberant caruncle which terminates at the end of chaetiger 1 (Fig. 1B). Prostomium usually with two groups of black eyes positioned on posterior half at maximal width of prostomium is reached, up to six eyes in one group, arranged in irregular patches or vertical rows (Fig. 1B). Occipital antenna absent. Peristomium not well developed. Palps detached, but scars of palp insertion discernable laterally to beginning of caruncle anterior to first chaetiger. Nuchal organs not unambiguously discernable, probably as small elongate grooves laterally to the posterior tip of the prostomium. Metameric dorsal ciliated organs not discernable. Dorsal crests absent but transverse ciliary bands across dorsum in well-preserved specimens present until posterior chaetigers.

FIGURE 1. Malacoceros indicus ( Fauvel, 1928) , MI QLD 2429 (A, B); AM W.44838, MI QLD 2422 (C). A. Anterior end of live specimen, palps removed; B. Enlargement of detail from A, prostomium and anteriormost chaetigers, note protuberant caruncle and anterolateral horns; C. Left parapodium from 23rd chaetiger; note rounded shape of neuropodial postchaetal lamella with small (very indistinct) pointed tip and interramal bulge indicated by arrow. Scale bars: A, B no scale available, specimens are at least 3 mm wide, C = 100 µm. Photo: A, B—A. Semenov.

Dorsal branchiae present from chaetiger 1 until the end of fragment; cirriform with elongate, slender tip, separate from notopodial lamellae throughout (Fig. 1A–C); first branchiae either slightly shorter, about same length or even longer than notopodial lamellae, from about third chaetiger reaching full length and often reaching dorsal midline or branchiae from both sides overlapping at midline (Fig. 1A); after first third of fragment (from about chaetiger 50) branchiae becoming thinner and shorter, but still distinctly longer than notopodial lamellae. Interparapodial lateral pouches absent.

Parapodia on chaetiger 1 positioned slightly more dorsally than on following chaetigers, there in lateral position. Notopodial postchaetal lamellae lanceolate, slender, becoming shorter posteriorly; neuropodial postchaetal lamellae of first and also second chaetiger elongate and tapered, then becoming rounded (Fig. 1C), often with small pointed tip on outer margin, but nipple-like projection rarely accentuated; more posteriorly neuropodial lamellae lower. Both parapodial rami without prominent prechaetal lamellae prechaetal thickened swelling (Fig. 1C) developing from chaetiger 3, present in near interramal position until about chaetigers 30–40, thereafter inconspicuous.

Chaetae in anterior and middle chaetigers capillaries; in neuropodia with very fine granulations near tip and with narrow sheaths, arranged in two rows, chaetae in anterior row shorter than in posterior row; in notopodia chaetae alimbate and rather smooth, arranged in two rows, chaetae in anterior row shorter than in posterior row; few very long smooth capillaries present in uppermost position in notopodia. From middle body region capillaries and hooks present; in specimens up to 1.4 mm wide neuropodial hooks in neuropodia present from chaetiger 31– 39, in two very large specimens (anterior fragment 2.2 mm wide with 154 chaetigers or 3.8 mm wide with 83 chaetigers) hooks either present from chaetiger 121 or absent; hooks hooded with three apical teeth above main fang, consisting of one pair of teeth and additional minute apical tooth (difficult to observe due to size); 3–6 hooks present per fascicle; hooks accompanied by 1–3 thin smooth capillaries in superior position; notopodia with smooth capillaries without sheaths, first arranged in two irregular rows, more posteriorly bundle of capillaries of different length; very long capillaries present in notopodia in superiormost position. Capillaries in inferiormost position in neuropodia from chaetiger 2, numbering up to five (in very large specimen up to 15), chaetae arranged in a bundle; these capillaries slightly stronger and shorter than other capillaries in neuropodium; hook-bearing chaetigers with few (up to five) slightly granulated sabre chaetae with narrow sheath in inferiormost position; in more posterior chaetigers only 1–3 sabre chaetae present.

Pygidium not observed (all specimens incomplete).

Pigmentation. Pigment neither discernable in live or formalin preserved specimen.

Methyl green staining pattern. Inconspicuous. Prostomium, branchiae and postchaetal lamellae most intensely stained.

Remarks. Malacoceros indicus is, based on current knowledge, a very widespread species. Intraspecific variability is acknowledged to be large. For example, the number of secondary teeth in neuropodial hooks are observed to range from two ( Blake (1996) for specimens from California), three ( Williams (2007) for specimens from the Philippines, also this paper for Lizard Island specimens), to four ( Imajima (1991) for specimens from Japan). Foster (1971b) found tri- and quadridentate hooks in the same parapodium in specimens from the Carribean. Also the number of hooks per fascicle varies: our specimens have 3–6 hooks per fascicle, Williams (2007) reports up to 7 hooks, Foster (1971b) 7–8 hooks, Blake (1996) 7–10, Imajima (1991) up to 11. The first presence of neuropodial hooks was observed in chaetigers 31–121 (Lizard Island, present paper), chaetigers 28–62 ( Williams 2007), 30–57 ( Imajima 1991), 30–35 ( Blake 1996), and at the 37th chaetiger ( Foster 1971b). This character seems to be size-dependent in the specimens collected at Lizard Island since only the largest two individuals exhibit a very late start of neuropodial hooks (see description above). Hooks might be continously lost in middle chaetigers during ontogenesis.

The prostomial shape varies with the development of anterolateral horns. Among specimens from Lizard Island only the two large individuals (2.2 and 3.8 mm wide) have anterolateral horns whereas all other specimens (0.8–1.4 mm wide) have anterolateral projections. In the literature the species is usually illustrated having anterolateral projections and rarely short anterolateral horns (compare Foster 1971b, Imajima 1991, Blake 1996, Williams 2007). We noticed that specimens from Lizard Island have a protuberant caruncle. This is obviously also the case in specimens from the Philippines (compare illustrations provided by Williams (2007)). All other above mentioned authors have provided illustrations displaying a differently shaped caruncle and did not mention such a development in their descriptions.

Information on three different molecular markers is provided for M. indicus from Lizard Island in the course of the present study. Since data from other localities are not available from sources like GenBank or BOLD a comparative analysis could not be undertaken. The inclusion of both molecular and morphological data should be aspired too for future studies to verify the species status of M. indicus .

Habitat / Ecology. In the Lizard Island area the species was found in shallow water on sandy beaches, between seagrass and mangroves. The species was also found from sandy beaches, in the shallow subtidal (<5 m) in Boracay of the Aklan province in the Philippines ( Williams 2007). Records from Japan are from shallow water to 159 m water depth ( Imajima 1991). Foster (1971a) reported the species from the Bahamas and Puerto Rico from shallow water from sandy bottom and Thalassia beds. Records from Costa Rica (Golfo de Nicoya) account for subtidal habitats (11–18 m water depth) with muddy sand or sand ( Dean 2004). Dauer & Ewing (1991) classified the species as an indiscriminate surface deposit-feeder.

Distribution. Australia (Queensland, NSW), New Caledonia, Philippines, Japan, India, SW Africa, Caribbean, Chile, USA (southern California, Massachusetts to Georgia), Costa Rica (Golfo de Nicoya).