Octomeris brunnea Darwin, 1854

Chan, Benny K. K., Tsao, Yao Feng & Ganmanee, Monthon, 2020, Morphological and molecular evidence support the intertidal barnacle Octomeris intermedia Nilsson-Cantell, 1921 (Thoracica, Chthamalidae) as a valid species in Indo-Pacific waters, ZooKeys 914, pp. 1-31 : 1

Octomeris brunnea Darwin, 1854 Figures 2G , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 15D-F , 16D-F

Octomeris brunnea Darwin, 1854: 484, pl 20, figs 3a, b; Weltner 1897: 274; Gruvel 1905: 197, fig. 217; Nilsson-Cantell 1921: 299, figs 58, 59, pl 3, fig. 7; -1931: 108; - 1932, 14; Hiro 1939: 252, figs 3-4, 6a, b; Utinomi 1949: 25; -1958: 307; Endean, Kenny and Stephenson 1956: 122, 127, tab. 1; Endean, Stephenson and Kenny 1956: 332, 336, app II; Pope 1965: 20, figs 1c, 2b, pl 1: figs 3, 6; Newman and Ross 1976: 40; Poltarukha 1996: 992; Liu and Ren 2007: 283, fig. 123; Chan et al. 2009: 153: figs 128-130; Jones 2012: tabs 1, 2.

Materials examined.

ASIZCR-000431. Intertidal rocks at General Rock, Green Island, Taiwan (22°40.35'N, 121°29.45E, 16 August 2019, 1 specimen). CEL-Octm_GI_01. Intertidal rocks at General Rock, Green Island, Taiwan (22°40.35'N, 121°29.45'E, 16 August 2019, 5 specimens). CEL-KT-131. Intertidal rocks at Hai Kou, Kenting, Taiwan (22°06.06'N, 120°42.56'E, 4 Dec 2007, 7 specimens). CEL-LAN-178. Intertidal rocks at southern Lanyu, Lanyu, Taiwan (22°00.82'N, 121°33.94E, 19 June 2019, 2 specimens). CEL-Octm_sp_01. Intertidal rocks at Shi-Ti-Ping, Hualien, Taiwan (23°28.56'N, 121°30.41E, 13 May 2009, 1 specimen). CEL-Octm-G05. Intertidal rocks at Puerto Galera, Philippines (02 June 2009, 20 specimens). CEL-Octm-G23. Intertidal rocks at Varadaro Point, Puerto Galrea, Philippines (02 June 2009, 1 specimen).

Diagnosis.

Shell eight plated, conically depressed. Shell brown, surface with longitudinal furrows and tergo-scutal junction straight in young and uneroded specimens. Shell gray, surface smooth and tergo-scutal junction sinuous in old and eroded specimens. Maxillule with deep notch at upper 1/3 of cutting edge, lower 1/3 strongly protruded, cutting edge clearly divided into upper, middle, and lower region by the clear notch and protrusion of lower margin.

Description.

Shell 8 plated, composed of piece of rostrum (R), carina (C), paired rostro-lateral (RL), carino-lateral (CL) and lateral (L) (Figs 2G , 4A, B ). Shell conically depressed. Shell brown, surface with longitudinal furrows and tergo-scutal junction straight in young and uneroded specimens (Figs 3 , 4A ). Shell grey, smooth, tergo-scutal junction sinuous in old and eroded specimens (Figs 3 , 4B ). Sutures of shell plates serrated (Figs 2G , 4A, B ). In young and uneroded specimens, scutum triangular, outer surface with horizontal growth lines (Fig. 4A ). Scutum inner surface brown, tergal and occludent margins straight in young specimens, basal margin slightly convex (Fig. 4A ). Tergal margin straight, with conspicuous articular ridge. Adductor muscle scar shallow (Fig. 4A ). In older and eroded specimens, tergal margin of scutum strongly sinuous, adductor muscle scar deep (Fig. 4B ). Tergum with basal margin strongly bended in an angle, scutal margin straight with deep articular ridge in young specimens, depressor muscle distinct, muscle crests prominent and extended slightly out of the carinal margin of tergum (Fig. 4A ). In older and eroded specimens, the scutal margin strongly concaved (Fig. 4B ).

Cirrus I rami unequal (Fig. 5A ). Posterior ramus short, six-segmented. Anterior ramus seven-segmented. All segments height greater than width (Fig. 5A ). Bidentate serrate setae and simple setae present. Bidentate serrate setae appear up to seven segments in anterior ramus and present up to first three distal segment in posterior ramus (Fig. 5B-D ). Cirrus II, posterior ramus seven-segmented, anterior ramus eight-segmented. Bidentate serrate setae present up to seven segments in anterior ramus and up to first four distal segments in posterior ramus (Fig. 5E-H ). Cirri III to VI similar in morphology, long and slender (Figs 6 , 7 ). Cirrus III, posterior and anterior rami 12 segmented (Fig. 6A-D ). Cirri IV and V, posterior and anterior rami 15-segmented (Figs 6E-H , 7A-C ). Dorsal surface of cirri IV- VI has small spines (Figs 6G , 7F ). Cirrus VI with 16 segmented rami (Fig. 7D-E ). Intermediate segments of cirri III and VI with three pairs of long and one pair of short simple setae (Figs 6B, F , 7B, E ). Distal segments of cirrus III bear two pairs of long and one pair of short setae (Figs 6C, D, H , 7C ). Caudal appendage absent. Penis short, tip with a few simple setae (Fig. 7G, H ).

Maxilla subtriangular, distal lobe prominent and proximal lobe flat, shallow notch present in inner margin between the two lobes (Fig. 8A ), inner and outer margin with serrulate setae (Fig. 8B-D ). Maxillule with a deep notch on upper 1/3 and lower 1/3 of cutting edge. Cutting edge obviously divided into three distinct portions. Cutting edge above upper notch with two large and a few setae (length of setae ranges from 80-100 μm); middle portion of cutting edge has six setae; 1/3 of lower portion of cutting edge has eight short setae (Fig. 8E-H ). Mandibles with three teeth, cutting edge of first tooth smooth, second tooth with one or two spines, third tooth with a few spines on cutting edge (Fig. 9A-D ). Mandibular palp elongated, with serrulate setae on outer margin (Fig. 9E, F ). Cutting margin of labrum concave, with small fine teeth (Fig. 9G, H ).

Distribution.

Southern Japan, Taiwan, Philippines, east coast of Queensland in Australia, Santa Cruz and New Hebrides (based on specimens in Australian Museum stated in Pope, 1965).

Figures

Figure 2. A Krabi, Thailand, showing O. intermedia at the overhang of an intertidal cave (indicated by white arrow). B Hey or Coral Island, Phuket, showing that O. intermedia occur on shaded rocks. C O. intermedia can occupy up to 100 % cover under a shaded rock in Thailand. D Octomeris intermedia, showing partially eroded samples, with longitudinal furrows at the base of the shell plates. E O. intermedia, eroded samples, showing shell with a smooth surface. F O. intermedia, uneroded samples, showing longitudinal furrows on the surface. G O. brunnea on Lanyu, Taiwan. Shell is more conical than O. intermedia. Eroded sample with smooth shell plates.

Figure 3. Shape of the tergo-scutal junction (TS junction, indicated by arrows) of Octomeris brunnea (CEL-KT- 131, Hai Kou, Taiwan) and O. intermedia (CEL-Thai- 359, Krabi, Thailand) All specimens share the same scale bar.

Figure 4. Octomeris brunnea (CEL-KT- 131, Hai Kou, Taiwan) and O. intermedia (CEL-Thai- 359, Krabi, Thailand). A Octomeris brunnea, young specimens showing the straight tergo-scutal junction and the inner and outer sides of left scutum and tergum. B O. brunnea, older eroded specimen, showing the sinuous tergo-scutal junction and inner and outer sides of left scutum and tergum. C O. intermedia. Very small individual (shell length <10 mm) showing the straight tergo-scutal margin and inner and outer sides of scutum and tergum. Note only very small individuals of O. intermedia have straight tergo-scutal margin. D O. intermedia. Larger specimens, showing the sinuous tergo-scutal margin and inner and outer surfaces of scutum and tergum. Scale bars in mm.

Figure 5. Octomeris brunnea (CEL-KT- 131, Hai Kou, Taiwan). A Cirrus I. B Posterior ramus of cirrus I. C Bidentate serrate setae at tip of segment. D Bidentate serrate setae at tip of anterior ramus. E Cirrus II. F Dorsal side of posterior ramus. G, H Bidentate serrate setae at posterior ramus. Scale bars in μm.

Figure 6. Octomeris brunnea (CEL-KT- 131, Hai Kou, Taiwan). A Cirrus III. B Intermediate segments of posterior ramus of cirrus III. C Distal segments of anterior ramus of cirrus III. D. Simple type setae on anterior ramus of cirrus III. E Cirrus IV. F Intermediate segments of cirrus IV. G Dorsal surface of proximal segment of posterior ramus of cirrus IV. H Distal segments of anterior ramus of cirrus IV. Scale bars in μm.

Figure 7. Octomeris brunnea (CEL-KT- 131, Hai Kou, Taiwan). A Cirrus V. B Intermediate segments of posterior ramus of cirrus V. C Distal segments of anterior ramus of cirrus V. D Cirrus VI. E Intermediate segments of posterior ramus of cirrus VI. F Dorsal surface of proximal segments of posterior ramus of cirrus VI. G Penis. H Distal end of penis. Scale bars in μm.

Figure 8. Octomeris brunnea (CEL-KT- 131, Hai Kou, Taiwan). A Maxilla. B Magnified view of distal lobe showing serrulate setae. C Inner margin of proximal lobe of maxilla showing serrulate setae. D Outer margin of maxilla showing serrulate setae. E Maxillule; note the two deep notches on upper and lower 1 / 3 of the cutting edge. F Cutting edge above upper notch. G Middle portion of cutting edge. H Lower portion of cutting edge below lower notch. Scale bars in μm.

Figure 9. Octomeris brunnea. A Mandible. B First tooth of mandible. C Second and third teeth of mandible. D Lower margin. E Mandibular palp. F Serrulate setae at outer margin of mandibular palp. G Labrum. H Small teeth on middle part of cutting edge of labrum. Scale bars in μm.

Figure 15. Variation in the occurrence of small spines along the cutting edge of second and third teeth of mandibles in O. intermedia (A-C) (CEL-Thai- 359, Krabi, Thailand) and O. brunnea (D-F) (CEL-KT- 131, Hai Kou, Taiwan). Scale bars in μm.

Figure 16. Consistent differences in the presences of shallow and deep notches on the cutting edge of O. intermedia (A-C) CEL-Thai- 359, Krabi, Thailand) and O. brunnea (D-F) (CEL-KT- 131, Hai Kou, Taiwan), respectively. The notches in O. brunnea are much deeper, and three distinct regions can be seen along the cutting edge. Scale bars in μm.