Boccardiella hamata (Webster, 1879)

Abe, Hirokazu & Sato-Okoshi, Waka, 2021, Molecular identification and larval morphology of spionid polychaetes (Annelida, Spionidae) from northeastern Japan, ZooKeys 1015, pp. 1-86 : 1

Boccardiella hamata (Webster, 1879) Fig. 7H, I

Larval morphology.

Thick and fusiform in overall shape, widest at middle part of body. Prostomium broad and anteriorly rounded, usually dusky brown anteriorly. Three pairs of black eyes present, most median pair rounded, lateral pairs usually double-eyes, occasionally divided into respective eyes. Black pigmentation usually presents ventrally on each lateral lip, occasionally absent. Dorsal pigmentation basically consists of a pair of medial bands, lateral branching melanophores, and small pigment patch at the base of notopodia in each chaetiger from chaetiger III onwards (Fig. 7H ). These melanophores undergo expansion and contraction, sometimes coalescing to cover almost the whole of the dorsal surface as ramified pigmentation (Fig. 7I ). Four transverse lines of black pigmentation sometimes fused as a single transverse band in chaetiger I. One or two pairs of lateral black pigmentation on chaetiger II. Two rows of band-shaped ventral pigmentation usually located on posterior edges of some chaetigers posterior to second chaetiger. A pair of black pigment patches on pygidium. Gastrotrochs on chaetigers III, V, VII, X, and XIII.

Remarks.

Adults of this species were non-boring and collected from mud deposits in crevices of shells of living C. gigas oysters in Sasuhama in May 2011 and February 2016. Adult morphology agrees with the description of B. hamata by Sato-Okoshi (2000). Therefore, this species was referred to B. hamata . The larvae and adults were confirmed to match (18S: 1772/1772, 16S: 480/481 bp) using molecular data (Fig. 2 ).

Planktonic larvae of this species were frequently collected from Onagawa Bay, Gobu-ura, and Sasuhama in July and August. The larval morphology of this species agrees with that of B. hamata described by Dean and Blake (1966, as Boccardia ).

Figures

Figure 2. Maximum Likelihood tree inferred from nuclear 18 S and mitochondrial 16 S rRNA gene sequences of spionids obtained from Japan in the present and previous studies (provided in Table 1). The gene sequences of adult and larval spionid polychaetes are indicated by solid squares and circles in front of each species name, respectively. SH-aLRT / approximate Bayes support / ultrafast bootstrap support values of ≥ 80 %, ≥ 0.95, ≥ 95 %, respectively are given beside the respective nodes. Nodes with red circles indicate triple high support values of SH-aLRT ≥ 80, approximate Bayes support ≥ 0.95, and ultrafast bootstrap support ≥ 95. The scale bar represents the number of substitutions per site. Sequences of Laonome sp. and Sabella pavonina Savigny, 1822 obtained from DDBJ / EMBL / GenBank were used for outgroup rooting.

Figure 7. Light micrographs showing the morphologies of living spionid larvae of genera Boccardia, Boccardiella, and Dipolydora A, B Boccardia proboscidea, dorsal view of accidentally hatched 9 - chaetiger (A) and 15 - chaetiger larvae (B) C Boccardia pseudonatrix, dorsal (left) and ventral (right) view of accidentally hatched 10 - chaetiger larvae D-F Boccardia sp. 1, dorsal view of 9 - chaetiger (D) and dorsal (E) and ventral view (F) of 17 - chaetiger larvae G Boccardia sp. 2, dorsal view of 15 - chaetiger larva H, I Boccardiella hamata, dorsal view of 16 - chaetiger (H) and 18 - chaetiger larvae (I) J, K Dipolydora bidentata, dorsal view of 13 - chaetiger (J) and 18 - chaetiger larvae (K) L Dipolydora cf. commensalis, dorsal view of 21 - chaetiger larva M, N Dipolydora giardi, dorsal view of 19 - chaetiger (M) and lateral view of 21 - chaetiger larvae (N) O Dipolydora cf. socialis, dorsal view of 18 - chaetiger larva P Dipolydora sp., dorsal view of 7 - chaetiger larva. Scale bars: 300 μm.