Cerapus brevirostris, 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 : 383-386

Cerapus brevirostris sp. nov.

urn:lsid:zoobank.org:act:CFB4B46E-D166-46BD-A2A4-FA5FE218D2C7

Figs 1–3

Holotype: Male, 2.4 mm, AM P.106325, Penneshaw, Kangaroo Island , South Australia, Australia, 35°43'S 137°56'E, in Caulerpa sp. on jetty piles, 5 m, I. Loch, 9 March 1978. Paratypes: 1 female, ovigerous, 2.7 mm, AM P.106326; 1 female, ovigerous, 2.5mm, AM P.106327; all with same data as holotype. 1 male, 2.8 mm, AM P.106328; 14 specimens, AM P.106329; 1 male, 2.2 mm, AM P.106330; Stokes Bay, Kangaroo Island, South Australia, Australia, 35°37'S 137°12'E, algae on vertical rock face, 7 m, I. Loch, 4 March 1978. 6 specimens, SAM C14774, Sellicks Beach, South Australia, Australia, 35°20'06"S 138°26'44"E, K. Sheard & H. M. Hale, 16 January 1937; 10 specimens, MV J.13186, north of False Island, King George Sound, Western Australia, Australia, 35°00.702'S 118°10.08'E, 27 m, scuba, SWA-57 G. C. Poore & H. M. Lew Ton, 15 April 1984.

Additional material examined. 2 specimens, SAM C14775, Sellicks Beach, South Australia,Australia, 35°20'06"S 138°26'44"E, dead low tide, outer edge, K. Sheard, April 1939; 43 specimens, MV J.13190, north of False Island, King George Sound, Western Australia,Australia, 35°01.002'S 117°25.02'E, scuba, 25 m, SWA-56, G. C. B. Poore & H. M. Lew Ton, 15 April 1984; 2 specimens, MV J.13187, south side off Eden Road, Wilson Inlet, Western Australia,Australia, 35°00.702'S 1188°10.08'E, by hand, 0.1 m, SWA-58, G. C. B. Poore & H. M. Lew Ton, 16 April 1984; 5 specimens, AM P.106331, Ningaloo Reef,Western Australia, 21°55'41"S 113°55'11"E, brown algae on rocks under jetty, 13 m, MI WA 979, N. L. Bruce & M. Blazewicz-Paszkowycz, 17 June 2008; 1 male, 6 females,several juveniles, AM P.106332, same data as holotype; 7 specimens, AM P.106333, Red Bluff, Kalbarri, Western Australia, Australia, 27°42'S 114°09'E, rocky shore, mixed coralline algae, 3–4 m, MI WA-480, R. T. Springthorpe, 10 January 1984; 1 female, ovigerous, 2 juveniles, AM P.106334, 500 m off Chinamans Rock, Kalbarri, Western Australia,Australia, 27°42'S 114°09'E, rocky bottom, brown algae with epiphytic coralline algae, 6 m, MI WA-462, J. K. Lowry, 10 January 1984; 1 male, 6 females, AM P.106335, 500 m off Chinaman’s Rock, Kalbarri,WesternAustralia,Australia, 27°42'S 114°09'E, brown alga Padina sp. , 6 m, MI WA-465, J. K. Lowry, 10 January 1984; 1 specimen, AM P.106336, 500 m off Chinamans Rock, Kalbarri, Western Australia,Australia, 27°42'S 114°09'E, 6 m, MI WA-460, R.T.Springthorpe, 10 January 1984; 2 females, AM P.106337, Stokes Bay, Kangaroo Island, South Australia, Australia, 35°37'S 137°12'E, 7 m, I. Loch, 4 March 1978; 1 specimen,AM P.106338, 500 m off Chinaman’s Rock, Kalbarri, Western Australia, Australia, 27°42'S 114°09'E, rocky bottom, brown and coralline algae, 6 m, MI WA-459, J. K. Lowry, 10 January 1984; 20 specimens, AM P.106339, Thompsons Bay, Rottnest Island, Western Australia, Australia, 32°00'S 115°32'30"E, airlift sample from Posidonia sp. , 3 m, MI WA-221, J. K. Lowry & R. T. Springthorpe, 20 December 1983; 3 specimens, MV J.75812, The Hotspot Reef, 9.3 km west of north end of Flinders Island, South Australia, Australia, 33°40'48"S 134°22'30"E, scuba, 21 m, SA 70, G. C. B. Poore, 20 April 1985; 1 specimen, MV J.75813, The Hotspot Reef, 9.3 km west of north end of Flinders Island, South Australia, Australia, 33°40'30"S 134°22'1"E, scuba, 17 m, SA 62, G. C. B. Poore, 19 April 1985; 1 male, AM P.106340, reef west of groyne, 2 km south of Cape Peron, Western Australia, Australia, 32°16'S 115°41'E, deep channels in limestone reef, sand from pocket in reef, 6 m, MI WA-292, J. K. Lowry, 26 December 1983; 1 male, 3 juveniles, MV J.75814, north-east side of Topgallant Island, Investigator Group, South Australia,Australia,33°43'0"S 134°36'36"E, scuba, 12 m, SA 83, S. Shepherd & G. C. B. Poore, 22 April 1985; 1 female, ovigerous, 4 juveniles, MV J.75815, The Hotspot Reef, 9.3 km west of north end of Flinders Island, South Australia, Australia, 33°40'30"S 134°22'1"E, scuba, 7 m, SA 64, S. Shepherd, 19 April 1985.

Type locality. Penneshaw, Kangaroo Island, South Australia, Australia, 35°43'S 137°56'E.

Etymology. Named for the short rostrum of this species. Used as a noun in apposition.

Description. Male (based on holotype, 2.4 mm, AM P.106325).

Head. Rostrum short, length 0.2 × head, evenly tapered, apically subacute; lateral cephalic lobe with ventral corner acute, subocular margin weakly recessed, not reaching beyond eye, anteroventral corner subquadrate, ventral margin horizontal, posterior margin vertical.

Antenna 1 very long, length 0.9 × body length; peduncle without scales; peduncular article 1 subequal to article 3, length 0.9 × peduncular article 3, swollen along posterior margin, posterodistal corner not produced; peduncular article 2 anterodistal corner without distal projection; flagellum 5-articulate; article 1 long. Antenna 2 length equal to antenna 1; flagellum 3-articulate.

Pereon. Pereonite 1 without lateral keel or sternal keel. Pereonites 2–3 without sternal keel.

Gnathopod 1 coxa not fused to pereonite 1, length 0.9 × depth, without anteroventral lobe; basis length twice depth; carpus broad, length 1.2 × depth with setose posterior lobe; propodus palm extremely acute, with barbed robust setae. Gnathopod 2 carpochelate; coxa not fused to pereonite 2, length 1.9 × depth, without anteroventral lobe or cusp; basis short, broad, length 1.5 × breadth, without anteroproximal group of long slender setae; carpus short, length 1.3 × breadth, broad, posterior margin without teeth, palm shallowly excavate, anterodistal tooth large, located distal to articulation with propodus, posterodistal tooth well defined, medium length, length 1.4 × width; propodus very broad, slightly curved, length 2.3 × width, with small tooth on posterior margin, posterodistal corner smooth; dactylus, length 0.7 × propodus.

Pereopod 3 coxa without anteroventral lobe, not fused to pereonite 3, length 1.9 × depth; basis length 1.7 × breadth, with proximal, subquadrate anterodorsal corner, with plumose setal group along anterior margin, without denticles along anterior margin; ischium short, length 1.2 × breadth; merus length 1.2 × breadth; short, without ridges. Pereopod 4 coxa not fused to pereonite 4, with anterior lobe separated from an anteroventral lobe; basis length 1.4 × breadth, without setal group along anterior margin; ischium long, length twice breadth; merus long, length 1.8 × breadth. Pereopod 5 coxa length 1.7 × depth, without patches of small setae, with 1 seta along ventral margin; merus with anterior lobe 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 without setal fringe ventrally, without patches of small setae near margins; basis without patch of small setae near anterior margin; merus, length 1.6 × breadth; dactylus short, uncinate, with 1 accessory hook. Pereopod 7 merus length 1.3 × breadth; dactylus short, uncinate, with 1 accessory hook.

Pleon. Pleopods 1–3 biramous, decreasing in size. Pleopod 1 inner ramus 4-articulate; outer ramus 3-articulate, article 1 with straight medial margin; Pleopod 2 inner ramus reduced, 1-articulate; outer ramus, broad, 1-articulate. Pleopod 3 inner ramus reduced, 1-articulate; outer ramus broad, 1-articulate. Uropod 1 biramous; peduncle length 1.4 × outer ramus; rami with distoventral fan of robust setae; outer ramus with lateral row of denticles, without medial setae, with 4 lateral setae, with large apical robust seta, without smaller slender setae; inner ramus, length 0.8 × outer ramus, without medial and lateral setae, with large apical robust seta. Uropod 2 uniramous, peduncle, length 3.5 × breadth, 4.2 × length of ramus; ramus small with 2 denticles and 1 slender apical seta. Uropod 3 uniramous, peduncle length 1.5 × breadth; ramus with 2 curved hooks. Telson broader than long, length 0.4 × breadth, cleft to base, each lobe with 13 anteriorly directed recurved spines in 2 rows.

Female (sexually dimorphic characters). Based on paratype female, 2.7 mm, AM P.106326. Antenna 1 peduncle without scales; flagellum 4-articulate. Antenna 2 flagellum 4-articulate. Pereonite 1 without lateral keel. Pereonite 2–3 without sternal keel. Gnathopod 1 coxa, length equalling depth; basis length 2.3 × depth; carpus length 0.9 × depth with setose posterior lobe. Gnathopod 2 subchelate; coxa length 1.7 × depth; basis, length 1.4 × depth, without medial line of setae; palm extremely acute. Pereopod 5 coxa length 1.4 × depth. Oostegites from gnathopod 2 to pereopod 5.

Tube. Smooth tube of mud and fine particles with light and dark stripes, often covered by clay-coloured sponge or pale ascidian; may be swollen in the middle; tubes often bound together by the ascidian or the sponge.

Habitat. Marine, 0.1 – 27 m.

Remarks. Cerapus brevirostris sp. nov. and C. alquirta are the only Australian species lacking a setal fringe on coxa 6 and with a 4-articulate outer ramus on pleopod 1. Cerapus brevirostris differs from C. alquirta in having antenna 1 and 2 equal in length. The outer ramus of pleopod 1 in C. brevirostris has a straight medial margin whereas all other Australian species have the margin evenly swollen. Cerapus brevirostris is the only Australian species with a tooth on the posterior margin of the propodus of male gnathopod 2 and with antenna 1 very long relative to body length (0.9 × body length).

Distribution. Sellicks Beach and Kangaroo Island, South Australia to Ningaloo Reef, Western Australia.