Petersenaspis narisarae, Plathong & Plathong & Salazar-Vallejo, 2021

Plathong, Jintana, Plathong, Sakanan & Salazar-Vallejo, Sergio I., 2021, Three new species of Sternaspidae (Annelida: Sedentaria) from Thailand, Zootaxa 5081 (3), pp. 373-388 : 380-382

Petersenaspis narisarae sp. nov.

LSID urn:lsid:zoobank.org:act:9862A44C-9251-43C9-A85C-9827D8E081C0

Fig. 5

Material examined. Seven specimens from the Songkhla Sea, Gulf of Thailand, Western Pacific, from muddy sediments mixed with sand and shells; coll. Marine Ecosearch Management Company ( MEM). All specimens were collected from sampling site S03 (7°21’02 ” N, 100°31’45 ” E), at 9 m. Holotype : PSUZC - POL - 0291 (1 spec.), 21 May 2015 . Paratypes: S03, PSUZC - POL - 0292 (2 specs., 1 juvenile), 30 Jan 2012 ; PSUZC - POL - 0293 (1 spec., juvenile), 24 May 2012 ; PSUZC - POL - 0294 (1 spec., juvenile), 11 Oct 2012 ; PSUZC - POL - 0295 (1 spec., juvenile), 17 May 2016 ; AM W.52925 (1 spec.), 1 Oct 2012 .

Description. A small species, holotype complete, body whitish without sediment particles; anterior part not exposed, branchiae whitish, coiled, long straight filaments orange brown. Body 5.3 mm long, 3.5 mm wide, and abdomen 4.3 mm long ( Fig. 5A – B ). Paratypes, two large specimens, introvert invaginated; body 5.2 – 6.2 mm long, 3.6 – 4.3 mm wide. Others juvenile, two specimens with anterior region not exposed but with golden chaetae visible through body wall ( Fig. 5D ), 2.3–2.9 mm long, 1.2–1.7 mm wide, and abdomen 1.8–1.9 mm long; two specimens introvert exposed 1.3–4.3 mm long, 1.2–1.3 mm wide, and abdomen 0.7–2.7 mm long.

Prostomium, peristomium and mouth not exposed, prostomium and middle of body fragile.

First three chaetigers not visible in holotype or paratypes. In small paratypes, golden spatulate hooks visible through body wall ( Fig. 5D ); one juvenile had introvert exposed showing golden spatulate hooks.

Pre - shield region with eight segments, oval shape ( Fig. 5A, C ) with single lateral bundles of 2 – 3 short, thin capillary chaetae, protruding from body wall along segments 9 – 13 in both holotype and paratypes. Body papillae at the dorsal and ventral surfaces small, minute; lateral body papillae long, thin.

Ventro - caudal shield yellow - orange - reddish, butterfly wing - shaped with three colored bands; outer band yellow - orange, middle band reddish and widest, inner band darker and narrowest. Ventro - caudal shield plate with anterior, lateral and posterior margins rounded, fan with a deep median notch, margins smooth. Few papillae on shield surface and integument, without ciliary clumps. Radial ribs distinct, no concentric lines; posterior shield margin round ( Fig. 5A, C, E, F ).

Marginal shield chaetae fascicles include 9 – 10 lateral fascicles in oval arrangement with offset and parallel fascicles, and 12 posterior fascicles, each with 2 – 3 chaetae: 1 long and strong; and 1 to 2 short and thin.

Branchial filaments abundant, comprising two types: coiled, whitish; and straight, brown to golden. Each branchia starts from the branchial plate, the anterior part of the branchia is the base to which the branchia curls back leaving the long filament exposed. Branchiae in paratypes easily detached from branchial plates. Branchial plates wide, parallel distally, divergent basally; interbranchial papillae long, abundant ( Fig. 5A, B, E, H ).

Variation. Juveniles have shields with barely defined colored bands ( Fig. 5D ).

Etymology. The species name honors Ms. Narisara Kongcharoenkit, Mr. Sakanan Plathong’s secretary, who has helped with coastal and marine resources management for many years.

Habitat. Found at 9 m depth, in muddy sediments mixed with sand and shells, Gulf of Thailand.

Distribution. Only known from the Songkhla Sea, Gulf of Thailand ( Figs 1 , 2 ).

Remarks. Petersenaspis narisarae sp. nov. belongs to the group of Petersenaspis species that present both a median notch and two lateral notches. It closely resembles P. palpallatoci Sendall & Salazar-Vallejo, 2013 , P. apinyae sp. nov., and P. pakbaraensis sp. nov. However, P. narisarae sp. nov. differs from all these species in having 2–3 colored bands and an oval abdominal region that is also wider than the abdominal region of other species. These features are unique among all currently described Petersenaspis species. P. narisarae sp. nov., also has a shield that is anteriorly wider than that of P. palpallatoci and a lateral shield and genital papillae that are smaller than those of P. palpallatoci .

Furthermore, P. narisarae sp. nov. differs from P. palpallatoci by the color of the introvert hooks, which are golden rather than bright bronze. P. narisarae sp. nov. also has a shield which is anteriorly wider, and a lateral shield that is more strongly curved than P. palpallatoci and exhibits yellow - orange - red bands. In P. palpallatoci , the shield is not anteriorly wider, and the lateral shield is rounded and lacking colored bands. Moreover, P. narisarae sp. nov. has 12 fascicles of posterior shield chaetae and 3 capillary chaetae per bundle at the lateral pre - shield rather than 10 fascicles and 2 capillary chaetae per bundle as occurs in P. palpallatoci ( Sendall & Salazar-Vallejo 2013) .

Petersenaspis narisarae sp. nov. differs from P. apinyae sp. nov. and P. pakbaraensis sp. nov. in the morphology of the lateral and posterior shields and their margins. In P. narisarae sp. nov. these characters are more rounded, whereas the lateral shield in P. apinyae sp. nov. is strongly curved with a very expanded anterior region and the posterior shield is straighter. In P. pakbaraensis sp. nov. the lateral shield is expanded anteriorly, and the posterior shield is expanded laterally. Moreover, P. narisarae sp. nov. presents 2 posterior shield chaetae per fascicle, while P. apinyae and P. pakbaraensis both present 3–4 chaetae per fascicle. The abdominal region in P. narisarae sp. nov. is more expanded into an oval shape than in P. apinyae sp. nov. and P. pakbaraensis sp. nov., which both have a narrower abdomen. The genital papillae in P. narisarae sp. nov. are smaller than they are in P. apinyae sp. nov. and P. pakbaraensis sp. nov..

Figures

FIGURE 1. Type localities of the accepted species of Petersenaspis Sendall & Salazar-Vallejo, 2013.

FIGURE 2. Sampling sites in the Gulf of Thailand and Andaman Sea where specimens of P. apinyae sp. nov. (triangles), P. narisarae sp. nov. (stars), and P. pakbaraensis sp. nov. (circles) were collected.

FIGURE 5. Petersenaspis narisarae sp. nov. Light photographs (A–B, H. Holotype, PSUZC-POL-0291; C, G. PSUZC-POL- 0292; D. PSUZC-POL-0295; E, F. AM W.52925). A. Complete specimen, dorsal view; B. Same, lateral view; C. Complete specimens with introvert invaginated, dorsal view; D. Golden hooks inside the body wall, lateral view; E. Branchial filaments, ventral view; F. Branchial plate after removal of branchiae and longer interbranchial filaments, ventral view; G–H. Ventro-caudal shield, dorsal view. Abbreviations: inner shield 1, medial shield 2, outer shield 3, interbranchial filaments ibf, branchiae br, genital papilla gp, straight filament hd, suture st.