DOI: 10.5061/dryad.hqbzkh1cn
title: Description of two new species of Paraonidae (Annelida) from the Gulf of Thailand, Western Pacific

description: Two new species of Aricidea Webster, 1879 (Paraonidae), Aricidea (Acmira)
 anusakdii sp. nov. and Aricidea (Aricidea) thammapinanae sp. nov. were
 collected from 10–26.5 m depth, in shallow soft bottoms with mud mixed
 with sand and shell substrates at Songkhla Sea, the Gulf of Thailand
 between 2011–2018. Aricidea (Acmira) anusakdii sp. nov. is clearly
 distinguished from other species of the subgenus Acmira by having a
 rounded bilobed prostomium divided by a slight notch on the anterior
 margin; red pigments on the subdistal to the tip of each branchia (new
 character); two prebranchial chaetigers; 48–68 pairs of branchiae; and
 modified neurochaetae as strong curved spines with blunt shafts surrounded
 by pubescence from chaetigers 19–44. On the other hand, Aricidea
 (Aricidea) thammapinanae sp. nov. can be separated from other members of
 the subgenus Aricidea by the presence of a biarticulated median antenna;
 distinctive notopodial lobes as broad triangular with short distal
 protuberances on chaetiger 3, 4–8 pairs of branchiae; and modified
 neurochaetae as bidentate neurochaetae with a long pubescent subterminal
 arista on the concave side.
description: Specimens were collected between 2011
 and 2018 in the southern Gulf of Thailand
 (7°14'21"–7°49'21"N;
 100°24'42"–100°49'0"E) (Fig. 1), with a Van Veen grab
 (0.1 m<sup>2</sup>) at depths ranging from 10 to 26.5 m. The
 collected samples were sieved with 2.0 mm, 1.0 mm and 0.5 mm mesh screens
 in the field. Later, water and sediment from the sieved grab samples were
 passed through a 300 µm filter bag. Specimens retained by both separation
 methods were separately fixed with a 4% formaldehyde in seawater solution.
 In the laboratory, samples were washed with fresh water and transferred to
 70% ethanol. The polychaetes were sorted into taxonomic groups using a
 stereomicroscope and those belonging to the proposed new species were
 examined under dissection and compound light microscopes. SEM images were
 produced with a JEOL JSM-5800LV microscope and Apreo-Field Emission
 Scanning Electron Microscope (FESEM) at the Office of Scientific
 Instrument and Testing (OSIT), Prince of Songkla University, Hatyai,
 Thailand. Light microscope photographs were taken with a Leica digital
 camera in the SEC, Prince of Songkla University. The morphological
 measurements of the holotype are indicated in the taxonomic description.
 Information on character variability found in the paratypes is included in
 parentheses. The confirmation of the taxonomic status of the new species
 was based on the excellent revision and compilation of the diagnostic
 characteristics of all recognized species of the subgenera
 <i>Aricidea (Acmira)</i> and <i>Aricidea
 (Aricidea)</i> by Blake (1996), Lovell (2002) and Arriaga-Hernández
 et al. (2013). For comparative purposes, a table with the main diagnostic
 characters of the new species and closely related species was also
 included.             The
 type material was deposited in the Princess Maha Chakri Sirindhorn Natural
 History Museum, Prince of Songkla University (PSUZC) and the Australian
 Museum (AM). Additional material is maintained in the personal collections
 of Jintana and Sakanan Plathong at MEM (Marine Ecosearch Management Co.,
 Ltd.).