Ceradocus andamanensis, Wongkamhaeng, Koraon, Coleman, Charles Oliver & Pholpunthin, Pornsilp, 2013

Wongkamhaeng, Koraon, Coleman, Charles Oliver & Pholpunthin, Pornsilp, 2013, Three new species from the Aoridae and Maeridae (Crustacea, Amphipoda) from Thai Waters, Zootaxa 3693 (4), pp. 503-533 : 519-525

Ceradocus andamanensis sp. nov.

( Figs 14–18 )

Type material. Holotype, male, 7.0 mm, PSUZC-CR-0270, algae bed of Lidee Noi Island, Satun Province, 6°46'42"N 99°46'5"E, 27 November 2011, 2 m, Rodcharoen, E. Allotype: female, 7.7 mm, PSUZC-CR-0271, same station data.

Additional material. PSUZC-CR-276 1 male and 4 female, same station data.

Type locality. Lidee Noi Island, Satun Province, Thailand, Andaman Sea.

Etymology. This species is named after the region of type locality for the first record of this genus in this area.

Description. Based on holotype male, 7.0 mm, PSUZC-CR-0270.

Head. Lateral cephalic lobe notch and recessed. Antenna 1 peduncular article 1 slightly shorter than article 2, posterior margin with 2 marginal robust setae and 1 ventrodistal robust seta; flagellum with 19 articles, accessory flagellum 5 articles. Antenna 2 gland cone not reaching to the end of article 3, flagellum with 12 articles. Lower lip inner lobes well developed, outer lobes with 5 blunt stout setae on both inner margins. Maxilla 1 inner plate with marginal plumose setae and mediofacial setae. Mandibular palp article 3 subequal to article 1, article 1 distally acutely drawn out.

Pereon. Gnathopod 1 coxa anteroventral corner produced, posteroventral corner notched, ventral margin not serrate; merus posterodistrally produced; carpus suboval with two rows of plumose setae and a row of setae on mediofacial margin; propodus oblique, palm longer than hind margin with group of short and long setae, with a defining robust seta on anteroventral corner. Gnathopods 2 from left and right side symmetrical; merus posterodistal corner produced; carpus anterior margin without dense brush of long simple setae; propodus 3 × of carpus length, palmar margin oblique with 11 robust setae, posterodistal corner produced with 2 robust setae and few long fine setae; dactylus fit with palmar margin. Pereopod 3 coxa posterodistal corner notched, merus slightly anterodistally produced with a long robust seta. Pereopod 4 similar to pereopod 3. Pereopod 5 and 6 basis posterior margin rounded. Pereopod 7 basis posterior margin sigmoid.

Pleon. Epimera 1 and 2 posteroventral corner sparsely serrated. Epimera 3 posteroventral corner serrated above and below. Pleonite 1–3 dorsally serrated. Urosomite 1 and 2 evenly serrated. Urosomite 3 smooth. Uropod 1 peduncle with venterodistal spine, bearing 1 basofacial robust seta and two rows of marginal robust setae, both rami with a row of marginal robust setae, outer ramus with short setae along distofacial margin. Uropod 3 inner ramus slightly shorter than outer ramus, rami about 1.4 × peduncle length. Telson each half with 2 apical robust setae and 1 lateral seta, moderately cleft, telsonic lobe reaching more than halfway along longest spine.

Female - sexually dimorphic characters. Based on allotype female, 7.7 mm, PSUZC-CR-0271. Gnathopod 2 propodus 1.36 × carpus length, palm with 3 robust setae on anterodistal corner, not anterodistally produced. Epimera 1 and 2 posteroventral corner serration deeper than those of male.

Remarks. Sheard 1939 divided Ceradocus into 2 subgenera, i. e., Ceradocus (Ceradocus) and Ceradocus (Denticeradocus) . Our new species can be classified as Ceradocus (Denticeradocus) by the following characters: maxilla 1 inner plate setose along inner margin, uropod 3 outer ramus uniarticulate, lower lip with inner plate and pleon segments posterodorsally multidentate. There are 18 species in this subgenus. From those 18 species, only 3 species have symmetrical gnathopods 2 including, Ceradocus cotonensis Appadoo & Myers, 2006 , Ceradocus dooliba Barnard, 1972 and Ceradocus sheardi Shoemaker, 1948 . In C. cotonensis the inner plate of maxilla 1 is setose at the apex while in C. andamanensis sp. nov. it is setose along the inner margin and coxa 1 of the new species is notched on both, the anteroventral and posteroventral corner (vs. smooth in the former). Ceradocus dooliba which is a considerably larger amphipod (20 mm) is different from C. andamanensis on urosomite 1 and 2 dorsum unevenly serrated while the latter is evenly serrate. Ceradocus andamanensis is easily separated from C. sheardi by antenna 1 accessory flagellum which is 5 articulate while the latter is 9 articulate. Moreover, the palmer margin of the former is smooth while the palmer margin of C. sheardi has a broad sinus.

Type material. Holotype, male, 10.4 mm, PSUZC-CR-0272, coral reef of Samaesarn Island, Chonburi Province, 12°33'03"N 100°57'05"E, 30 September 2011, 4 m, Damrongrojwattana, P. Allotype, female, 7.7 mm, PSUZC-CR- 0 273, same station data.

Additional material. PSUZC-CR-277, 5 males and 2 females, same station data.

Type locality. Samaesarn Island, Chonburi Province, Inner Gulf of Thailand.

Etymology. This species is named after the type locality for the first record of this genus in this area.

Description. Based on holotype male, 10.4 mm, PSUZC-CR-0272.

Head. Anteroventral margin with notch. Antenna 1 peduncular article 1 subequal to article 2, with 1 robust seta; flagellum with 38 articles; accessory flagellum with 3 articles. Antenna 2 cone gland exceeding peduncular article 3; article 4 longer than 5; flagellum with 10 articles. Mandible incisor with 3 teeth; lacinia mobilis with 5 teeth; accessory setal row with 3 setae; mandibular palp article 2 shortest, geniculate; article 3 subequal to article 1 with 2 long fine apical setae.

Pereon. Gnathopod 1 coxa ventral margin serrate, anteroventral corner produced, truncate, posteroventral corner with notch; merus not produced; carpus subequal to propodus, palm oblique, without posterodistal robust setae. Gnathopod 2 larger than gnathopod 1, coxa with notch on posteroventral margin; merus posterodistally produced; propodus distally expanded, posterior margin slightly excavated distally; palm transverse with subrectangular distomedial elevation with 6 robust setae, palmar margin with 2 robust setae; dactylus toothed on mid-posterior margin. Pereopod 3 coxa ventral margin serrate. Pereopod 4 coxa smooth. Pereopods 5–6 basis straight, posterior margin weakly serrate with short setae. Pereopod 7 basis posterior margin bulging outward, serrate with long fine setae. Pereonite 7 with dorsal teeth.

Pleon. Pleonites 1–3 with paired mid-dorsal teeth on posterior margin. Epimera 1–2 smooth. Epimeron 3 margin serrate below posteroventral margin. Urosomite 1 dorsally with paired mid-dorsal teeth on posterior margin. Uropod 1 peduncle with two rows of basofacial robust setae. Uropod 3 rami distally truncated with long and short apical setae, inner ramus 1.5 × of peduncle, subequal to outer ramus. Telson deeply cleft, as long as broad, lobes distally truncated, with 5 to 7 long apical robust setae.

Female- sexually dimorphic characters. Based on allotype female, 7.7 mm, PSUZC-CR-0273. Antenna 1 flagellum with 23 articles, accessory flagellum with 5 articles. Gnathopod 2, merus not produced, propodus not distally expanded, longer than that of male, palm oblique, dactylus without tooth on mid-posterior margin, with dorsal teeth. Pleonite 1 with dorsal teeth.

Remarks. Parelasmopus is a small genus, endemic to the Indo –West Pacific (Lowry & Hughes 2009). From 12 species of Parelasmopus , Parelasmopus siamensis sp. nov. has dorsal teeth on pereonite 7 which are of similar shape in six other species, namely Parelasmopus cymatilis Lowry & Hughes, 2009 , Parelasmopus echo Barnard, 1972 , Parelasmopus poorei Hughes, 2009 , Parelasmopus setiger Chevreux, 1901 , Parelasmopus suensis (Haswell, 1879) and Parelasmopus suluensis Dana, 1852 . Moreover, only P. poorei and P. setiger have a tooth on the midposterior margin of the dactylus of gnathopod 2 in the male sex. Parelasmopus siamensis sp. nov. can be separated from P. poorei by: - the lack of any robust setae on posterodistal corner of gnathopod 1 (vs. presence of 2 such setae), - its gnathopod 2 palm having a distomedial elevation while the latter has a posteroproximal elevation - and the basis of pereopod 7 is bulging outward (vs. sigmoidal-shaped).

Parelasmopus siamensis sp. nov. is very similar to P. setiger and shares many characters including the gnathopod 2 palmar margin with posteroproximal elevation with 6 robust setae, the midposterior toothed dactylus and the serration on coxa 1–3. However, the new species can be distinguished from P. setiger by the following characters—articulate accessory flagellum in the male (5-articulate in the female sex) while the latter has 4 articles in both sexes—the mandibular palp article 1 of the new species is subequal to article 3 (vs. article 1 longer than article 3)—merus of gnathopod 2 in females of P. siamensis sp. nov. posterodistally produced (vs. not produced) and coxa 6 posterodistally serrate (vs. smooth).

Figures

FIGURE 14. Ceradocus andamanensis sp. nov., holotype, male (PSUZC-CR- 0270), 7.7 mm, algae bed of Lidee Noi Island, Andaman Sea. All scale bars represent 0.1 mm.

FIGURE 15. Ceradocus andamanensis sp. nov., holotype, male (PSUZC-CR- 0270), 7.7 mm. algae bed of Lidee Noi Island, Andaman Sea. Scale bar for T represents 0.2 mm, for LL represents 0.2 mm, remaining represent 0.5 mm.

FIGURE 16. Ceradocus andamanensis sp. nov. ,, holotype, male (PSUZC-CR- 0270), 7.7 mm, algae bed of Lidee Noi Island, Andaman Sea. Scale bar for G 1 represents 0.2 mm, for G 2 represents 0.5 mm, remaining represent 0.1 mm.

FIGURE 17. Ceradocus andamanensis sp. nov., holotype, male (PSUZC-CR- 0270), 7.7 mm. algae bed of Lidee Noi Island, Andaman Sea. Scale bar for U 2 and U 3 represents 0.2 mm, remaining represent 0.5 mm.

FIGURE 18. Ceradocus andamanensis sp. nov., alllotype, female (PSUZC-CR- 0271), 7.7 mm. algae bed of Lidee Noi Island, Andaman Sea. All scale bars represent 0.2 mm.