Octomeris is a chthamalid intertidal barnacle with eight shell plates. There are currently two species of such barnacles: O. brunnea Darwin, 1854 (type locality in the Philippines), common in the Indo-Pacific region, and O. angulosa Sowerby, 1825, only recorded in South Africa. Octomeris intermedia Nilsson-Cantell, 1921, identified from the Mergui Archipelago in Myanmar, was considered to be conspecific with O. brunnea by Hiro (1939) based on samples collected in Taiwan. The morphological differences in shell and opercular plates between O. brunnea and O. intermedia are believed to be intra-specific variations due to different degrees of shell erosion. In the present study, the genetic and morphological differentiations of Octomeris in the Indo-Pacific region were examined. This study found two molecular clades (with inter-specific differences) based on the divergence in the COI genes, and the species also have distinct geographical distributions. The Octomeris brunnea clade covers samples collected from the Philippines and Taiwan waters and the other clade, which we argue is O. intermedia, is distributed in Phuket and Krabi, Thailand and Langkawi, Malaysia. Phuket and Krabi are located approximately 300 km south of the Mergui Archipelago, the type locality of O. intermedia. The morphology of samples collected from Thailand fits the type description of O. intermedia in Nilsson-Cantell (1921). Our study concludes that O. intermedia is a valid species based on morphological and molecular evidence.
The present study identified a new barnacle species from Malaysian waters, Chthamalus ngankeeae sp. nov., on morphological and molecular grounds. Chthamalus ngankeeae sp. nov. is an intertidal species that is abundant on high shores, above the oyster zone. Chthamalus ngankeeae sp. nov. has two morphotypes, based on shell colour. Brown morphs have brown shells with pale brown ridges and look similar to Microeuraphia withersi (Pilsbry, 1916). Chthamalus ngankeeae sp. nov. has four teeth on the mandible, while M. withersi has but three. White morphs of C. ngankeeae sp. nov. possess white shells with gray ridges. The white morph of C. ngankeeae sp. nov. is similar to C. moro Pilsbry, 1916, but a major morphological difference includes a more prominent articular ridge on the scutum of C. ngankeeae sp. nov. compared to C. moro. Molecular analyses of sequence divergence in the COI and NaK genes of C. ngankeeae sp. nov. with other chthamalids showed that it forms an individual monophyletic group and does not belong to any of the cryptic lineages of C. moro, supporting its designation as a new species.
In this work, a low-power plasma oxidation surface treatment followed by Al2O3 gate dielectric deposition technique is adopted to improve device performance of the enhancement-mode (E-mode) AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs) intended for applications at millimeter-wave frequencies. The fabricated device exhibited a threshold voltage (Vth) of 0.13 V and a maximum transconductance (gm) of 484 (mS/mm). At 38 GHz, an output power density of 3.22 W/mm with a power-added efficiency (PAE) of 34.83% were achieved. Such superior performance was mainly attributed to the high-quality Al2O3 layer with a smooth surface which also suppressed the current collapse phenomenon.