Cerapus dildilgang, Berents, 2023

Berents, Penelope B., 2023, New Species of Cerapus from Australian Waters (Amphipoda: Senticaudata: Ischyroceridae), Records of the Australian Museum (Rec. Aust. Mus.) 75 (4), pp. 381-403 : 391-394

Cerapus dildilgang sp. nov.

urn:lsid:zoobank.org:act:A77CB54F-06C6-4341-88EF-F12E510EA71E

Figs 9–13

Holotype: Male, 3.8 mm, AM P.26097, off Sow and Pigs Reef, Port Jackson , New South Wales, Australia, 33°50'S 151°16'E, Smith-McIntyre benthic grab, shell and sandy mud, 5 m, J. K. Lowry & A. R. Jones, 30 September 1976. Paratypes: 1 female, ovigerous, 3.2 mm, AM P.106356; 1 male, 3.3 mm, AM P.106357; 1 male, 2.3 mm, AM P.106358; all with same data as holotype. 6 males, 3 females, 4 juveniles, AM P.10659, Store Beach, Port Jackson, New South Wales, Australia, 33°48'48"S 151°17'12"E, sand, detritus, and fine shell fragments, Halodule sp. and other algae, hand dredge on scuba, 3 m, AU 59, J. Just, P. B. Berents & R. T. Springthorpe, 26 September 1984.

Additional material examined. Many specimens,AM P.106360, same data as holotype; 157 specimens, AM P.106362, 200 m south-east of Croppy Point, Hawkesbury River, New South Wales, Australia, 33°33'S 151°14'E, sandy mud, Smith-McIntyre benthic grab, 12 m, HRS 2-3-2 Feb 84, A. R. Jones & A. Murray, 9 February 1984; many specimens,AM P.106361, just beyond beach flats, off Bagnalls Beach, Port Stephens, New South Wales, Australia, 32°43'17"S 152°7'17"E, 3 m, benthic sled, W.F.Ponder & J. Hall, 25 October 1980; 5 specimens, AM P.106363, Store Beach, Port Jackson, New South Wales, Australia, 33°48'48"S 151°17'12"E, sand, detritus, and fine shell fragments, Halodule sp. and other algae, hand dredge on scuba, 3 m, AU 59, J. Just, P. B. Berents & R. T. Springthorpe, 26 September 1984; 5 specimens, AM P.106364, Quarantine Beach, Port Jackson, New South Wales, Australia, 33°49'S 151°17'E, hand dredge on scuba, 2 m, J. Just, P. B. Berents & P. M. Berents, 1 March 1986; 2 males & 1 female, ovigerous, AM P.73726, Outer Latitude Rock, Forster, New South Wales, Australia, 32°12'39"S 152°34'06"E, sediment from rock face, hand collected on scuba, 16 m, NSW 2154, Australian Museum party, 18 March 2003; 1 male, AM P.106365, north of Moon Island, Swansea Heads, New South Wales, Australia, 33°05'08"S 151°40'25"E, rocky reef with barnacles, turf algae, and shelly sediment, airlift on scuba, 10 m, MI NSW 3458, R. T. Springthorpe, 5 May 2009.

Type locality. Off Sow and Pigs Reef, Port Jackson, New South Wales, Australia, 33°50'S 151°16'E.

Etymology. The species epithet means “little prawn” (prawn “dildil”; little “gang”) in the language of the Dharawal people of Port Jackson. Used as a noun in apposition.

Description. Male (based on holotype, 3.8 mm, AM P.26097).

Head. Rostrum short, length 0.2 × head, evenly tapered, apically subacute; lateral cephalic lobe with ventral corner rounded, subocular margin deeply recessed, reaching beyond eye, anteroventral corner rounded, ventral margin sloping, posterior margin sloping. Antenna 1 long, length 0.6 × body length; peduncle without scales; peduncular article 1 shorter than article 3, length 0.8 × peduncular article 3, not produced anterodistally and anteromedially, swollen along posterior margin, posterodistal corner not produced; peduncular article 2 anterodistal corner without distal projection; flagellum 4-articulate; article 1 long. Antenna 2 length equal to antenna 1; flagellum 3-articulate.

Pereon. Pereonite 1 with lateral keel, without sternal keel. Pereonite 5 length 1.5 × depth.

Gnathopod 1 coxa not fused to pereonite 1, length 1.3 × depth, without anteroventral lobe; basis length twice depth; carpus broad, length 1.5 × depth with setose posterior lobe; propodus palm extremely acute, robust setae present. Gnathopod 2 carpochelate; coxa not fused to pereonite 2, length twice depth, without anteroventral lobe or cusp; basis short, broad, length 1.7 × breadth, without anteroproximal group of long slender setae; carpus very long, length 1.9 × breadth, slender, posterior margin without teeth, palm straight, anterodistal tooth small, located near articulation with propodus, posterodistal tooth poorly defined; propodus slender, curved, length 4.8 × width, without tooth on posterior margin, posterodistal corner smooth, without teeth; dactylus length 0.5 × propodus.

Pereopod 3 coxa with narrow anteroventral lobe, not fused to pereonite 3, length 1.9 × depth; basis length 1.7 × breadth, anterior margin evenly rounded with simple setae, without denticles along anterior margin; ischium long, length 1.8 × breadth; merus length 1.1 × breadth; short; without ridges. Pereopod 4 coxa not fused to pereonite 4, with anterior lobe separated from an anteroventral lobe; basis length 1.3 × breadth, with simple setal group midway along anterior margin; ischium long, length 2.2 × breadth; merus long, length 1.6 × breadth. Pereopod 5 coxa length 1.5 × depth, without patches of small setae, with setae along ventral margin few or absent; merus with anterior lobe not extending beyond anterior margin of carpus, posterior lobe with 2 plumose setae; propodus with 1 seta along posterior margin; dactylus short, uncinate with 1 accessory hook. Pereopod 6 coxa with setal fringe ventrally, without patches of small setae near margins; basis without patch of small setae near anterior margin; merus length 1.5 × breadth; dactylus short, uncinate, with 1 accessory hook. Pereopod 7 coxa with posterodorsal lobe, without patch of small setae; merus length 1.4 × breadth; dactylus short, uncinate, with 1 accessory hook.

Pleon. Pleopods 1–3 biramous, decreasing in size. Pleopod 1 inner ramus 7-articulate; outer ramus 4-articulate, article 1 evenly swollen; Pleopod 2 inner ramus reduced, 1-articulate; outer ramus, broad, 3-articulate. Pleopod 3 inner ramus reduced, 1-articulate; outer ramus broad, 1-articulate. Uropod 1 biramous; peduncle, length 1.5 × outer ramus; rami with distoventral fan of robust setae; outer ramus with lateral row of denticles, without medial setae, with 5 lateral setae, with large apical robust seta and smaller slender setae; inner ramus, length 0.6 × outer ramus, without medial and with 1 lateral seta, with large apical robust seta. Uropod 2 uniramous, peduncle, length 3.6 × breadth, 5.9 × length of ramus; ramus small with 2 denticles and 1 slender apical seta. Uropod 3 uniramous, peduncle length 1.3 × breadth; ramus with 2 curved hooks. Telson broader than long, length 0.4 × breadth, cleft to base, each lobe with 12 anteriorly directed recurved spines in 2 rows.

Female (sexually dimorphic characters). Based on paratype female, 3.1 mm, AM P.106356. Antenna 1 peduncle without scales; flagellum 3-articulate. Antenna 2 flagellum 3-articulate. Pereonite 1 without lateral keel. Pereonite 2–3 without sternal keel. Gnathopod 1 coxa length 1.5 × depth; basis length 2.6 × depth; carpus length 1.2 × depth, with setose posterior lobe. Gnathopod 2 subchelate; coxa length 1.2 × depth; basis length 1.6 × depth, without medial line of setae; palm extremely acute Pereopod 5 coxa length 1.6 × depth. Oostegites from gnathopod 2 to pereopod 5.

Tube. Fine grained smooth tube with light and dark rings.

Habitat. Marine, 2 – 16 m.

Remarks. The shape of gnathopod 2 propodus and carpus in C. dildilgang changes as males grow, with the propodus becoming curved and slender in larger males. The carpus comes more elongate in larger males with the length to breadth ratio increasing from 1.1:1 in males less than 3 mm, 1.2:1 in males up to 3.5 mm and 1.9:1 in the holotype (3.8 mm in length). On the carpus, the anterodistal tooth near the articulation with the propodus becomes more prominent in larger males. In males less than 3 mm in length the tooth is absent, and poorly defined in males up to 3.5 mm. The tooth is small but well defined in the holotype. The palm of gnathopod 2 is straight rather than excavate as in most species of Cerapus .

Distribution. New South Wales: Port Jackson to Port Stephens.