Four genes, morphology and ecology: distinguishing a new species of Acesta (Mollusca; Bivalvia) from the Gulf of Mexico

Morphological and genetic variation in North Atlantic giant file clams, Acesta spp. (Bivalvia: Limidae), with description of a new cryptic species in the northwest Atlantic

“…These recent findings, however, prompted the examination of a more extensive sample of North Atlantic material to determine whether the eastern Canadian specimens are part of a much broader distribution of the European giant file clam, A. excavata, or whether they constitute a distinct species. A cursory examination of a Nova Scotian specimen revealed a shell morphology closer to that of Acesta bullisi (Vokes, 1963), one of two species found in the Gulf of Mexico (Järnegren et al 2007), than to that of A. excavata. This may have been due to the fact that all of those specimens had a very thin white to semi-translucent shell with a narrower hinge line and smaller v-shaped ligament compared to previously examined A. excavata.…”

“…However, a quantitative comparison with sufficient sample size was necessary in order to draw any firm conclusions. We have obtained thirteen specimens from different localities along the continental slope of eastern Canada, allowing for a better comparison of the shell morphology of the northwestern Atlantic specimens with the European giant file clam and other Acesta species such as the two found in the Gulf of Mexico (Järnegren et al 2007).…”

“…3,4). Other than the rather unusually shaped Acesta oophaga Järnegren, Schander & Young, 2007, the second species from the Gulf of Mexico (Fig. 3F), most species are characterized by the presence or absence of radial ribs (and their prominence when present) on the external side of the valves, the shape and size of the hinge ligament (particularly the oblique v-shaped ligament) and the general shape and profile of the shell.…”

“…There is little information available, however, on the larval shell morphology or the mode of larval development for the genus Acesta. Järnegren et al (2007) reported a larval shell length of 217 µm for one specimen of A. excavata. When present, we also examined the general morphology and size of the larval shell of the Acesta specimens used in this study.…”

Molecular Phylogeny and Morphological Distinctions of Two Popular Bivalves,Ctenoides scaberandCtenoides mitis

“…Numerous studies have been conducted on their behavior [11][12][13][14][15][16], morphology [17][18][19], habitat [20][21][22], reproduction [23,24], physiology [25], and vision [26][27][28][29][30][31]. However, systematics studies have only been done on a small number of species in this family [10,19,[32][33][34][35]. It is also noted that conchological traits alone are not always sufficient to establish clear boundaries between taxa [36].…”