Cuspidaria trosaetes Dall, 1925

Kolpakov, Eugeny, Boyko, Maksim, Safonova, Lyudmila & Кrylova, Elena, 2024, New records of Cuspidaria trosaetes Dall, 1925 (Bivalvia: Anomalodesmata: Cuspidariidae) in the Sea of Japan with notes on the genus Nordoneaera, Ruthenica, Russian Malacological Journal 34 (3), pp. 117-126 : 119-121

Cuspidaria trosaetes Dall, 1925

Cuspidaria trosaetes Dall, 1925: 16 , pl. 29, fig. 5; Furukawa, Kubota, 1947: 34; Kuroda, 1948: 9, pl. 1, fig. 6; Kuroda, Habe, 1952: 18; Ito, 1967: 70 pl. 10, fig. 13; Okutani, 1975: 75; Okutani, 1985: 147; Kafanov, 1991: 108; Higo et al., 2001: 185, fig. B1447.

Cuspidaria glacialis trosaetes – Habe, 1977: 21; Ito et al., 1986: 36, pl. 56, fig. 3.

Cuspidaria (Nordoneaera) glacialis trosaetes – Higo, Goto, 1993: 682.

Cuspidaria (Cuspidaria) obtusirostris – Lee, Kim, 2002: 173, fig. 351.

Cuspidaria glacialis – Belan, Belan, 2008: 118.

Cuspidaria (Nordoneaera) trosaetes – Tsuchida, Hayashi, 1994: 101, pl. 9, fig. 12; Poutiers, Bernard, 1995: 168; Higo et al., 1999: 529; Okutani, 2000: 1045, pl. 520, fig. 17; Lutaenko, 2009: 27, figs 1, 2; Okutani, Saito, 2017: 47, fig. 4H.

Type material. Holotype USNM 110770 ; 2 dry valves of the same specimen; https://collections. nmnh.si.edu/search/iz/?ark=ark:/65665/3affd314c1 aef4050854d0e7cf36f60da ( Fig. 2 A−E).

Type locality. Sea of Japan, north-west of Hokkaido, 45°40′00 N, 140°81′94 E, 594 m; mud, 22 September 1906, RV “ Albatross ”, St. 4992 [ Dall, 1925] .

Shell description ( Fig. 2 F–J ). Shell to 35 mm long, relatively high (H/L = 0.62−0.67), thin-shelled, strong, inequilateral ( Table 2): anterior side rounded, posterior side with broad and relatively short ( R /L = 0.18−0.21) rostrum. Umbo prominent, inflated, beaks orthogyrate; situated slightly in front of midline of shell (P/L = 0.57 − 0.60). Anterodorsal margin very short, straight, meeting rounded anterior margin at an obtuse angle. Ventral margin rounded, becoming sinuous posteriorly. Posterodorsal margin nearly straight. Rostrum set off from disk by radial depres- sion running from umbo to posteroventral corner of shell. Sculpture consists of coarse growth lines. Periostracum adherent, brownish, thin and glossy on the umbo, thicker and wrinkled on rostrum and in marginal region.

Internal ligament in oblique chondrophore located under beak. Left valve edentulous, right valve with posterior lateral long triangular tooth located just behind chondrophore. Interior white, glossy. Septal muscle scars look like two arcuate nearly parallel each other rows in upper region of shell.

Табл. 2. РаЗмеры правых створок Cuspidaria trosaetes .

Near-umbonal row shorter and consists of larger scars. Pallial line inconspicuous. Anterior adductor scar large, bean-shaped, elongated in dorso-ventral direction; posterior adductor scar smaller, triangular, situated at base of rostrum.

Variability. Variability can be seen in height of umbo, in length and broadness of rostrum, and in the size of posteroventral margin sinus [ Dall, 1925; Ito, 1967; Okutani et al., 1988; Lutaenko, 2009; Okutani, Saito, 2017]. Specimens from the Tatarsky Strait correspond to the holotype very well and differ from it only by a slightly higher umbo and slightly deeper pallial sinus. Some valves from the Sea of Okhotsk have shorter rostrums, maybe because the valves were weared [ Lutaenko, 2009]. The most constant characters of C. trosaetes are the straight postero-dorsal margin, short antero-dorsal margin and oblique chondrophor.

Anatomy. Septum thick, well developed; lateral septal muscles continuous, not divided into two parts; there are five pairs of septal pores, located at the same distance from each other ( Fig. 3 ). Anterior labial palps short, posterior palps longer and narrower. On the common siphonal sheath below the ring of papillae on inside rim, there is additional ring of small irregular transparent processes ( Fig. 4). There are no additional papillae between siphonal tentacles of exhalant siphon.

Remarks. Cuspidaria trosaetes is similar to C. glacialis ( Fig. 5) and differs from it by a shorter and higher right lateral tooth and a lower umbo. Ana- tomically, C. trosaetes and C. glacialis are similar in the presence of 5 pairs of septal pores, continuous lateral septal muscles, labial palps of the type II [ Allen, Morgan, 1981] and the presence of an additional ring of small irregular processes below the ring of papillae on the rim of the common siphonal sheath.

Ecology. C. trosaetes with the shell length of more than 30 mm is one of the largest species of the family. The species inhabits muddy and muddysandy sediments in the Sea of Japan near the Japanese archipelago [ Dall, 1925; Okutani, Saito, 2017] and muddy sediments with admixture of pebbles in the Tatarsky Strait (this paper). We examined the stomach contents of five specimens of C. trosaetes , which consist of foraminifers, copepods and rissoid gastropods Frigidoalvania asura (Yokoyama, 1926) with shell length of up to 1.5 mm. One specimen of C. trosaetes collected in the beginning of May con- tained about 2000 oocytes with maximum diameter of 0.38 mm.

Distribution. The Sea of Japan: off Hokkaido and Honshu to the south until the Tottori Prefecture, 50−794 m [ Dall, 1925; Ito, 1967, 1985, 1989; Okutani, Saito, 2017], the western part of the Tatarsky Strait, 531−589 m, probably off the south-western Sakhalin Island (46°99′N, 41°49′E), as C. glacialis [ Belan, Belan, 2008]; the Sea of Okhotsk: off the Cape Aniva, 185−417 m [ Lutaenko, 2009]; Pacific Ocean: the eastern coast of the Hokkaido and the south of the Kuril Islands [ Higo et al., 1999] ( Fig. 6). Also, we assume that C. trosaetes occurs in the Korea Strait, from where it was recorded as C. (Cuspidaria) obtusirostris ; image in [ Lee, Kim, 2002, p. 173, fig. 351].

Figures

FIG. 2. Cuspidaria trosaetes Dall, 1925:A–E, holotype, Sea of Japan, depth 594 м, L = 25.0 mm, USNM 110770;A, right valve, interior view; B, right valve, exterior view; C, right hinge margin; D, left valve, interior view; E, left valve, exterior view; F–J, Tatarsky Strait, Sea of Japan, depth 531 м, L= 27.7 mm, ZMFU no. 53068/Bv-8533 (periostracum mainly deleted); F, right valve, interior view; G, right valve, exterior view; H, right hinge margin; I, left valve, interior view; J, left valve, exterior view..

FIG. 3. Cuspidaria trosaetes Dall, 1925: ventral view of the septum with five pairs of septal pores; RV “Buhoro”, Stn. 109, L=32.1 mm, IORAS. Abbreviations: 1pp, first pair of septal pores; aa, anterior adductor; alp, anterior labial palp; f, foot; m, mouth; plp, posterior labial palp; psm, posterior septal muscle.