Cerapus moonamoona, 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 : 399-402

Cerapus moonamoona sp. nov.

urn:lsid:zoobank.org:act:1D29E8FB-BF85-4DE8-BF77-BFC11132031C

Figs 19–20

Holotype: Male, 5.0 mm, AM P.106377, off Moona Moona Creek , Jervis Bay , New South Wales, Australia, 35°02'54"S 150°41'12"E, airlift on scuba, 8 m, P. B. Berents, 17 November 1981. Paratypes: 1 female, ovigerous, 5.7 mm, AM P.106378, same data as holotype; 1 male, 3.7 mm, AM P.26872, north-east Botany Bay, New South Wales, Australia, 33°58'39"S 151°12'21"E, sandy mud, 7.5 m, State Pollution Control Commission, SPCC Stn. 29, 7 December 1976; 1 male, 4.2 mm, AM P.26875, east Botany Bay, New South Wales, Australia, 34°00'S 151°12'E, 11.6 m, State Pollution Control Commission, SPCC Stn.74, 27 January 1977; 1 male, 4.8 mm, AM P.106380, 1 male 4.5 mm, AM P.106381, off Moona Moona Creek, Jervis Bay, New South Wales, Australia, 35°03'S 150°40'E, silty sand with fine shell fragments, hand dredge on scuba, AU 76, J. Just, P. B. Berents & R. T. Springthorpe, 18 November 1984.

Additional material examined. 5 females, AM P.106379, same data as holotype; 1 female, 6 juveniles, AM P.106382, off Moona Moona Creek, Jervis Bay, New South Wales, Australia, 35°03'S 150°40'E, silty sand with fine shell fragments, hand dredge on scuba, AU 76, J. Just, P. B. Berents & R. T. Springthorpe, 18 November 1984.

Type locality. Off Moona Moona Creek, Jervis Bay, New South Wales, Australia, 35°2'54"S 150°41'12"E.

Etymology. Named for the type locality. Used as a noun in apposition.

Description. Male (based on holotype, 5.0 mm, AM P.106377).

Head. Rostrum short, length 0.2 × head, evenly tapered, apically subacute; lateral cephalic lobe with ventral corner subacute, subocular margin deeply recessed, reaching beyond eye, anteroventral corner acute, ventral margin horizontal, posterior margin vertical. Antenna 1 long, length 0.5 × body length; peduncle without scales; peduncular article 1 longer than article 3, length 1.3 × peduncular article 3, slightly swollen, posterodistal corner not produced; peduncular article 2 anterodistal corner without distal projection; flagellum 5-articulate; article 1 long. Antenna 2 1.3 × length antenna 1; flagellum 5-articulate.

Pereon. Pereonite 1 without lateral keel, without sternal keel. Pereonite 2 with sternal keel. Pereonite 3 without sternal keel.

Gnathopod 1 coxa not fused to pereonite 1, length 1.4 × depth, without anteroventral lobe; basis length 1.7 × depth; carpus broad, length 1.3 × depth with setose posterior lobe; propodus palm extremely acute, with barbed robust setae. Gnathopod 2 carpochelate; coxa not fused to pereonite 2, length 1.7 × depth, without anteroventral lobe or cusp; basis short, broad, length 1.6 × breadth, without anteroproximal group of long slender setae; carpus long, length 1.6 × breadth, broad, palm shallowly excavate, with 2 apical robust setae, anterodistal tooth tiny, located near articulation with propodus, posterodistal tooth long, well defined, length 1.6 × width; propodus slender, curved, length 5.4 × width, without tooth on posterior margin, posterodistal corner smooth, without teeth; dactylus length 0.4 × propodus.

Pereopod 3 coxa with broad anteroventral lobe, not fused to pereonite 3, length 2.7 × depth; basis, length 1.8 × breadth, with proximal, subquadrate anterodorsal corner, with simple setae along anterior margin, without denticles along anterior margin; ischium long, length 1.9 × breadth; merus length 1.1 × breadth, short, with ridges. Pereopod 4 coxa with anteroventral lobe, not fused to pereonite 4, length 2.2 × depth; basis length 1.3 × breadth, with simple setal group midway along anterior margin; ischium long, length 2.3 × breadth; merus long, length 1.3 × 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 extending beyond anterior margin of carpus, posterior lobe with 3 plumose setae; propodus with 2 setae 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 1.7 × breadth; dactylus short, uncinate, with 1 accessory hook. Pereopod 7 coxa with posterodorsal lobe, without patch of small setae; merus length 1.6 × breadth; dactylus short, uncinate, with 1 accessory hook,

Pleon. Pleopods 1–3 biramous, decreasing in size. Pleopod 1 inner ramus 8-articulate; outer ramus 3-articulate, article 1 evenly swollen; 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 1.5 × outer ramus; rami with distoventral fan of robust setae; outer ramus with lateral row of denticles, without medial setae, with 6 lateral setae, with large apical robust seta, without smaller slender setae; inner ramus, length 0.7 × outer ramus, with 7 medial and no lateral setae, with large apical robust seta. Uropod 2 uniramous, peduncle, length 2.5 × breadth, 4.2 × length of ramus; ramus small with 2 denticles and 1 slender apical seta. Uropod 3 uniramous, peduncle length 1.4 × breadth; ramus with 2 curved hooks. Telson length 0.8 × breadth, cleft to base, each lobe with 11 or 12 anteriorly directed recurved spines in 2 rows.

Female (sexually dimorphic characters). Based on paratype female, 5.7 mm, AM P.106378. Antenna 1 peduncle without scales; flagellum 4-articulate. Antenna 2 flagellum 2-articulate. Pereonite 1 without lateral keel. Pereonite 2–3 without sternal keel. Gnathopod 1, coxa, length 1.4 × depth; basis, length 1.7 × depth; carpus, length 1.3 × depth with setose posterior lobe. Gnathopod 2 subchelate; coxa, length 1.7 × depth; basis, length 1.8 × depth, without medial line of setae; palm extremely acute. Pereopod 5 coxa, length 1.1 × depth. Oostegites from gnathopod 2 to pereopod 5.

Tube. Composed of fine sediment.

Habitat. Marine, 7 – 12 m.

Remarks. Cerapus moonamoona is the only Australian species with peduncular article 1 longer than peduncular article 3 on antenna 1. Cerapus moonamoona and C. alquirta are the only Australian species with the male second antenna 2 longer than antenna 1 and both species have a sternal keel on pereonite 2. Cerapus moonamoona differs from C. alquirta in having 11 or 12 recurved spines on the telson whereas C. alquirta has 8 recurved spines on the telson; C. alquirta lacks a setal fringe on coxa 6; the posterior margin of the carpus and propodus of female gnathopod 2 is more densely setose in C. moonamoona and male coxa 5 is twice as long as wide in C. alquirta compared with 1.5 times longer than wide in C. moonamoona . The tube of C. alquirta is broader at one end and the tube of C. moonamoona is straight.

The male gnathopod 2 of C. moonamoona changes in shape as the male matures. The propodus is curved and slender in males longer than 4.5 mm. The posterodistal tooth of the carpus of gnathopod 2 becomes longer and more strongly defined in males of 5.0 mm. The carpus of gnathopod 2 is more elongate in mature males with the ratio of length to width 1:1.2 – 1:1.3 in males of 3.7 – 4.5 mm and 1:1.6 in males of 5.0 mm. Mature males have 2 apical robust setae on the palm, which is unique to C. moonamoona .

Distribution. New South Wales: Botany Bay and Jervis Bay.