Heteromastus namhaensis, Jeong, Man-Ki, Soh, Ho Young & Suh, Hae-Lip, 2019

Jeong, Man-Ki, Soh, Ho Young & Suh, Hae-Lip, 2019, Three new species of Heteromastus (Annelida, Capitellidae) from Korean waters, with genetic evidence based on two gene markers, ZooKeys 869, pp. 1-18 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.869.34380
publication LSID	lsid:zoobank.org:pub:50D49A54-A386-4738-AE1F-393B77EC652C
persistent identifier	https://treatment.plazi.org/id/D41E7B49-B712-42A7-8095-94E906ABB121
taxon LSID	lsid:zoobank.org:act:D41E7B49-B712-42A7-8095-94E906ABB121
treatment provided by	ZooKeys by Pensoft
scientific name	Heteromastus namhaensis
status	sp. nov.

Treatment

Heteromastus namhaensis sp. nov. Figures 2 A–G View Figure 2 , 5A, B View Figure 5 , 6A View Figure 6

Material examined.

Holotype: MABIKNA00155558, sex uncertain, Cheongsando, 34°1.662'N, 127°4.272'E, subtidal, sandy mud bottom, 34 m depth, March 2016, coll. Man-Ki Jeong. Paratypes (two specimens): MABIKNA00155560, Yeosu, 34°41.569'N, 127°51.848'E, subtidal, sandy mud bottom, 15 m depth, June 2018; MABIK NA00155559, Jejudo, 33°16.699'N, 127°16.230'E, subtidal, sandy mud bottom, 54 m depth, April 2018. Additional 6 specimens from type locality on SEM stub.

Diagnosis.

Abdominal hooks with four rows of teeth, three teeth in basal row, three in second and third row, and four to six in superior row. Genital pores present in intersegmental furrows between chaetigers 7-8, 8-9, 9-10, and 10-11. Hemispheric notopodial lobes present on posterior abdominal segments.

Description.

Holotype entire, about 60 mm long, 0.9 mm wide for 98 chaetigers (terminal part missing). Paratypes range from 19-41 mm in length, 0.5-0.8 mm width for 41-95 chaetigers. Body thread-like, rounded dorsally, flattened ventrally, widest in anterior thoracic chaetigers, and tapering from abdomen to pygidium. Color brownish yellow in alcohol.

Prostomium conical, with short and hemispherical palpode; nuchal organs not seen, eyespots absent ( Fig. 2A, B View Figure 2 ). Everted proboscis with numerous small papillae ( Fig. 2A View Figure 2 ). Peristomium uni-annulated and slightly longer than first thoracic chaetiger ( Fig. 2A, B View Figure 2 ).

Thorax with 11 chaetigers ( Fig. 2A, B View Figure 2 ). Thoracic segments biannulated, with shallow intra- and intersegmental grooves ( Fig. 2A, B View Figure 2 ). Anterior five thoracic segments slightly expanded ( Fig. 2A, B View Figure 2 ). First chaetiger biramous, with three or four bi-limbated capillaries; chaetigers 2-5 with six to 14 capillaries per fascicle in both parapodia; chaetigers 6-11 with five to 12 long-shafted hooded hooks per fascicle ( Fig. 2A, B, F View Figure 2 ); thoracic hooks with indistinct node on shaft and at least six teeth in three rows above the main fang ( Fig. 2F View Figure 2 ). Notopodia located dorso-laterally, dorsally located in last few thoracic segments; neuropodia located in lateral positions ( Fig. 2A, B View Figure 2 ). Lateral organs present between noto- and neuropodia of all thoracic chaetigers, nearer to notopodia in chaetigers 5-11; sometimes indistinct on first thoracic chaetigers ( Fig. 2A View Figure 2 ). Genital pores present in intersegmental furrows of between chaetigers 7-8, 8-9, 9-10, and 10-11 ( Fig. 2A View Figure 2 ).

Transition between thorax and abdomen distinguished by changes in ultrastructure of chaetae and shape of segment ( Fig. 2A, B View Figure 2 ); abdominal segments multi-annulated, gradually longer posteriorly, with short-shafted hooded hooks in posterior parapodial lobes; thoracic chaetigers usually bi-annulated, wider than long, with long-shafted hooded hooks in center of segment ( Fig. 2A, B View Figure 2 ).

Abdominal parapodial lobes located in posterior end of each segment, well separated from each other, and gradually developed posteriorly ( Fig. 2 A–D View Figure 2 ). Abdominal notopodia separated, mid-dorsal on anterior few segments, becoming dorsolateral in following abdominal region, with six to eight hooded hooks per fascicle, having dorso-posteriorly protruded and hemispheric lobes from chaetiger 90 to end of body ( Figs 2 A–D View Figure 2 , 5B View Figure 5 ). Abdominal neuropodia well separated, with 10-12 hooded hooks per fascicle, having slightly protruded lobes in posterior abdomen; neuropodial lobes less developed than notopodial lobes ( Figs 2C, D View Figure 2 , 5B View Figure 5 ).

Hooded hooks with main fang extending slightly beyond hoods. Abdominal hooks with distinct node on shaft and four rows of small teeth above main fang; three teeth in basal row, three in second and third row, and four to six in superior row ( Figs 2E, G View Figure 2 , 5A View Figure 5 ). Pygidium with digitate anal cirrus ( Figs 2D View Figure 2 , 5B View Figure 5 ).

Methyl green staining pattern.

Prostomium, peristomium and thoracic chaetigers 1-2 not stained ( Fig. 6A View Figure 6 ). Thoracic chaetigers 3-11 stained blue; chaetigers 3-8 stained dark blue; chaetigers 9-11 stained light blue; post-chaetal region of chaetiger 11 not stained ( Fig. 6A View Figure 6 ). Abdominal region without any distinct staining pattern.

Etymology.

The species is named for its wide distribution in Namhae (=Korean name of southern sea of Korea).

Distribution.

Subtidal areas (15-54 m) near southern part of Korea ( Fig. 1 View Figure 1 ).

Ecology.

Heteromastus namhaensis was sampled from soft sediments in March of 2016 (10 ind./m2), April of 2018 (40 ind./m2), and June of 2018 (20 ind./m2). The most well-developed individual (having over 100 segments) was obtained in March and eggs in the coelom were 87-94 μm in diameter. Surface sediment of the station was mainly composed of sandy mud with fragmented shells. Leiochrides yokjidoensis Jeong, Wi & Suh, 2017 co-occurred in Jejudo of Korea ( Jeong et al. 2017a; Fig. 1 View Figure 1 ). The salinity range among sampling locations was about 31-32.5 PSU.

Remarks.

Heteromastus namhaensis resembles H. filiformis sensu Hutchings & Rainer, 1982 in the absence of distinct eyespots on prostomium, three teeth in basal row above the main fang of abdominal hooks, and the presence of posteriorly extended abdominal notopodial lobes (Table 2). However, they differ in the shape of notopodial lobes in posterior abdomen (hemispheric protrusion in H. namhaensis vs broadly-based and rounded lamellae in H. filiformis sensu Hutchings & Rainer, 1982), the different dental structure of abdominal hooks (Table 2). Heteromastus namhaensis is also easily distinguished from Korean former record of H. filiformis ( Choi and Yoon 2016) by the presence of hemispheric abdominal parapodial lobes and the absence of eyespots in H. namhaensis . In particular, the hemispheric notopodial lobe of H. namhaensis is a unique feature in the genus.