Armandia amakusaensis, Saito & Tamaki & Imajima, 2000

Saito, Hidetoshi, Tamaki, Akio & Imajima, Minoru, 2000, Description of a new species of Armandia (Polychaeta: Opheliidae) from western Kyushu, Japan, with character variations, Journal of Natural History 34 (11), pp. 2029-2043 : 2032-2036

Armandia amakusaensis sp. nov. (®gure 3)

Material

HOLOTYPE (NSMT-Pol.H-360): complete specimen, collected from an intertidal sandāt facing Tomioka Bay on the north-western corner of Amakusa-Shimoshim a Island in western Kyushu, Japan (®gure 1) in August 1988 . PARATYPES (NSMT- Pol. P-361 to P-369): 312 complete specimens, collected from the type locality and a nearby boulder beach with sand patches on a sand spit during March 1988 to March 1992. All specimens have been deposited in the National Science Museum , Tokyo under accession numbers NSMT-Pol.H-360 (1 specimen: holotype); paratypes: NSMT-Pol.P-361 (59 specimens) , NSMT-Pol.P-362 (73 specimens), NSMT-Pol.P- 363 (36 specimens), NSMT-Pol.P-364 (63 specimens), NSMT-Pol.P-365 (15 specimens), NSMT-Pol.P-366 (47 specimens), NSMT-Pol.P-367 (9 specimens), NSMT- Pol.P-368 (8 specimens) and NSMT-Pol.P-369 (2 specimens).

Description of holotype

Holotype 13.14 mm long, 0.87 mm high and 0.56 mm wide, with 32 setigers (®gures 2A, C, D, 3A). Sex not clear. Body slender, slightly tapering toward anterior and posterior ends. Prostomium conical, 0.78 mm long, with a ball-shaped palpode, three eyes, a pair of ring-shaped nuchal organs, and an eversible pharynx (®gures 2B, 3B, C). Three ®laments on each side of base of pharynx (®gure 3B). Body surface smooth, with three faint annulations in each setiger (®gure 3D). Ventral groove from setiger 2 to last. Branchiae on setigers 2 to second from last (®gure 3A). Eleven pairs of lateral eyes on setigers 7±17, diameter of anterior four pairs increasing progressively and that of posterior seven pairs decreasing gradually (®gure 3A). Parapodia biramous, with presetal lobe and ventral cirrus on each parapodium (®gure 3E, F, G). Presetal lobes decreasing gradually in size toward anterior and posterior setigers, with small semicircular projection present on setigers 2 to second from last (®gure 3E, F, G). Simple capillary setae in two bundles, notosetae generally longer than neurosetae (®gure 3E, F, G), and longest setae of median setigers slightly longer than those of anterior and posterior ones. Anal funnel with V-shaped incision mid-dorsally and mid-ventrally (®gure 3J, K); funnel 0.27 mm long ventrally, slightly shorter dorsally (0.23 mm) and slightly shorter than last three setigers (0.28 mm) (®gures 2E, F, G, 3I). Opening of anal funnel directed posterodorsally, funnel thus appearing obliquely truncate in lateral view (®gure 3I). Anal funnel fringed with 11 tapering columnar, papillae measuring 0.03±0.28 mm long; lower-most ventral pair of papillae sandwiching a long unpaired cirrus of same shape as others (®gures 2I, 3I, K). Long unpaired cirrus 1.29 mm long, with constrictions at intervals, originating mid-ventrally from inside of anal funnel (®gures 2J, 3I, K).

Variations in selected characters in holotype and paratypes

In the following description, N and n refer to the number of all specimens (i.e. 313) and that of a part of the specimens, respectively. The body-size (total body length) frequency distribution of all specimens is shown in ®gure 4A. The total body length ranges from 4.76 to 26.73 mm, with the mean Ô SD being 12.81 Ô 4.67 mm (N 5 313). Three major groups are recognized, centring around 11, 20 and 25 mm. Most members of the two largest size-classes were derived from the overwintering populations ( Tamaki, 1985b). The relationship between the total number of setigers and total body length is shown in ®gure 4B. The total number of setigers ranges from 27 to 34, generally increasing with total body length (N 5 313, r 5 0.72, p <0.0001). In the frequency distribution of the total number of setigers (indicated by n s; see also ®gure 5A), there are distinct peaks at setigers 29 and 33, comprising 38.0% and 27.2% of all specimens, respectively. The much lower frequencies at setigers 30 and 31 suggest that the polychaete grows swiftly through these setiger stages.

Branchiae are continuously distributed from setiger 2 posteriorly in all specimens. Variation in the distribution pattern of the posterior abranchiate setigers is shown in ®gure 5A, B. In ®gure 5A, for each total number of setigers (27±34), the portions represented by specimens with diOEerent last branchiate setigers is indicated. The frequency distribution of the number of posterior abranchiate setigers (0±4; ®gure 5B, derived from ®gure 5A) indicates that the highest frequency is recorded for one (61.7%) and that the`0’ case (i.e. no posterior abranchiate setigers present) occurs in specimens with 28, 32 and 33 setigers.

The number of prostomial eyes varies from zero to three. In cases with less than three eyes, it is uncertain whether unseen eyes are invisibly embedded inside the body or actually absent.

The variation in the distribution pattern of lateral eyes per side is shown in ®gure 6A±C (in these ®gures the total number of samples is 626, as N 5 313 Ö 2). Often, lateral eyes are neither continuously present from the ®rst to last occurrence nor equally distributed on both sides. In most cases (93.4%), the ®rst lateral eyes are on setiger 7, the remainder starting on setigers 6, 8±11 and 16. Most of the last lateral eyes are on setiger 17 (67.6%), the remainder extending from setiger 14 to setiger 28. The total number of lateral eyes varies from one to 17, 11 being the most frequent (54.0%) and 10±12 accounting for 83.8% of all specimens. The most`normal’ type of specimen, de®ned as one possessing lateral eyes from setiger 7 to setiger 17 continuously on both sides, comprises 35.8% of all specimens.

The anal funnel opens dorsally in almost all specimens (98.7%), with the funnel opening in the remainder almost normal to the longitudinal central axis of the anal funnel. Three dimensions related to the anal funnel (the dorsal and ventral lengths of the anal funnel itself, the length of the anal-funnel papillae and the length of the long cirrus) against total body length are shown in ®gure 7A±C. The ventral length of the anal funnel increases with total body length (N 5 313, r 5 0.85, p <0.0001) (®gure 7A). Figure 8A ±C shows the relationships between the ventral length of the anal funnel and the length of the last three setigers (A), the length of the last four setigers (B) and the dorsal length of the anal funnel (C), respectively. The ventral length of the anal funnel is shorter than the length of the last three setigers in most specimens (82.1%, ®gure 8A) and that of the last four setigers in almost all specimens (98.7%, ®gure 8B). The ventral length of the anal funnel is generally longer than the dorsal length (67.7%, ®gure 8C).

The number of anal-funnel papillae generally increases with total body length (N 5 313, r 5 0.54, p <0.0001) (®gure 9A) and ranges from six to 27, 10 being the most frequent number (21.4%) and eight to 13 accounting for 85.0% of all specimens (®gure 9B). The mean length of the anal-funnel papillae increases with total body length up to an intermediate body length, e.g. 16.5 mm (the boundary value between the smallest and the two larger body-length groups in ®gure 4A) (open circles in ®gure 7B, n 5 250, r 5 0.73, p <0.0001), beyond which it varies around an asymptote (solid diamonds in ®gure 7B, n 5 63, r 5 Õ 0.19, p 5 0.146). Comparison of ®gures 7A and B shows a developmental allometry between the anal funnel and the analfunnel papillae. A diOEerent allometric relationship is detected for the anal funnel and the long unpaired cirrus (®gure 7A, C); the length of the long cirrus increases with total body length up to an intermediate body length, e.g. 16.5 mm (open circles in ®gure 7C, n 5 250, r 5 0.42, p <0.0001), beyond which it decreases (solid diamonds in ®gure 7C, n 5 63, r 5 Õ 0.43, p 5 0.0005). It is assumed that either with body growth or during the collection of specimens, the distal part of the long cirrus might easily be lost at a constriction (®gure 3I). This might explain the reduction in length of the long cirrus in the larger specimens.

Figures

FIG. 8. Armandia amakusaensis sp. nov. Relationships between ventral length of anal funnel and (A) length of last three setigers, (B) length of last four setigers and (C) dorsal length of anal funnel. A straight line of 45ss inclination indicates the same values of the two parameters.