Melita ophiocola, Lowry & Springthorpe, 2005

Melita ophiocola View in CoL n.sp.

Figs. 58–61 View Fig View Fig View Fig View Fig

Type material. HOLOTYPE, ♀, 9.6 mm, AM P55192 , west side , Bottle and Glass Rocks , Port Jackson , 33°50.9'S 151°16.15'E, 4 m, J.K. Lowry & R.T. Springthorpe, 23 March 1982, stn NSW-100. GoogleMaps PARATYPES (114): 1 paratype, ♂, AM P46263 ; 1 paratype, ♀, AM P46264 , type locality, 10 m, J.K. Lowry & R.T. Springthorpe, 21 January 1982, stn NSW-97; 8 paratypes, AM P25456 , type locality, 9 m, G.D. Fenwick, 29 August 1977; 1 paratype, AM P55193 ; 1 paratype, AM P55194 ; 4 paratypes, AM P55199 ; 9 paratypes, AM P55200 , type locality; 27 paratypes, AM P55195 ; 5 paratypes, AM P55196 ; 4 paratypes, AM P55197 ; 1 paratype, AM P55198 , type locality, 4 m, 23 April 1982, stn NSW-101; 2 paratypes, AM P55236 , type locality, 26 Feb 1982, stn NSW-99; 18 paratypes, AM P55241 ; 18, AM paratypes, AM P55242 , type locality, 4 m, 26 November 1982, stn NSW-177; 11 paratypes, AM P55245 , type locality, 4 m, R.T. Springthorpe & P.N. Weber, 24 December 1982, stn NSW-267; 3 paratypes, AM P55240 , south of Vaucluse Point , Port Jackson , New South Wales, Australia, 33°52'S 151°17'E, under rocks, shelley substrate, in association with ophiurid Ophionereis schayeri , 2 m, J.K. Lowry & R.T. Springthorpe, 22 June 1982, stn NSW-107. GoogleMaps

Additional material examined. New South Wales: 1♀, AM P62903, northern cove of Boondelbah Island, Port Stephens, 32°42.28'S 152°13.47'E, under small boulders, 19.6 m, airlift, R.T. Springthorpe, P.B. Berents & A. Murray, 28 May 1998, stn NSW-1401. 92 specimens,

AM P31161 (4); AM P31162 (3); AM P31163 (1); AM P31164 (1); AM P31165 (2); AM P31166 (15); AM P31167 (14); AM P31168 (2); AM P31169 (1); AM P31170 (1); AM P31171 (4); AM P31172 (2); AM P31173 (11); AM P31174 (7); AM P31175 (8); AM P31176 (12); AM P31177 (2); AM P31178 (2), Little Box Head, Broken Bay, [approx. 33°33'S 151°16'E], sandy-muddy, very fine silt, 13 m, S. Arnam & R. Springthorpe, 18 November 1980. 68 specimens,AM P31142 (7); AM P31143 (5); AM P31144 (2); AM P31145 (2); AM P31146 (1); AM P31147 (3); AM P31148 (5); AM P31149 (1); AM P31150 (2); AM P31151 (3); AM P31153 (1); AM P31154 (2); AM P31155 (1); AM P31156 (10); AM P31157 (5); AM P31158 (8); AM P31159 (4); AM P31160 (6), 90 m south of Fairlight Pool, Port Jackson, 33°48.1'S 151°16.3'E, under stones, muddy sand, shell, in association with ophiuroid Ophionereis schayeri , 10 m, S. Arnam & R. Springthorpe, 13 October 1980. 2♀♀, AM P45267, 50 m north of Cannae Point, Port Jackson, 33°49'S 151°, on brittle star: Ophionereis schayeri , 5 m, P.B. Berents, P. Castro, G. Towner, 21 June 1995, stn NSW-1138. 67 specimens, AM P31134 (8); AM P31135 (2); AM P31136 (47); AM P31137 (1); AM P31138 (1); AM P31139 (5); AM P31140 (1); AM P31141 (2), type locality, 0.5 m, S. Arnam, J.K. Lowry & R.T. Springthorpe, 29 September 1980. 19 specimens, AM P55243 (17); AM P55244 (2), south of Vaucluse Point, Port Jackson, 33°50.9'S 151°16.15'E, rocky with sediment patches, in association with ophiuroid Ophionereis schayeri , 2 m, J.K. Lowry & R.T. Springthorpe, 27 May 1982, stn NSW-105. 7 specimens, AM P55234 (4); AM P55235 (3), South of Vaucluse Point, Port Jackson, 33°52'S 151°17'E, under rocks on soft substrate, in association with ophiuroid Ophionereis schayeri , 4 m, R.T. Springthorpe & A. Murray, 30 September 1982, stn NSW-156. 1♂, AM P55233, type locality. 2 specimens, AM P55237, type locality, 26 February 1982, stn NSW-99. 4 specimens, AM P55238 (2); AM P55239 (2), type locality, 10 m, 21 January 1982, stn NSW-97. 6 specimens, AM P55246, type locality, 4 m, R.T. Springthorpe & P.N. Weber, 24 December 1982, stn NSW-267. 6 specimens, AM P36648, Murrumbulga Point, Twofold Bay, 37°04.7'S 149°53.1'E, subtidal rock platform, 3 m, S. Keable, 9 October 1984, stn Q2. 1♂, AM P55117, Munganno Point, Twofold Bay, 37°06'S 149°56'E, subtidal rock platform, 6 m, S.J. Keable, 10 October 1984, stn M6.

Type locality. Bottle and Glass Rocks , Port Jackson , New South Wales, Australia, 33°50.9'S 151°16.15'E, living in association with the ophiuroid Ophionereis schayeri under rocks, 4 m.

Description. Based on holotype female, AM P55192 and paratype male, AM P55193.

Head. Lateral cephalic lobes broad, rounded, with anteroventral notch or slit, anteroventral corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 longer than article 2, with 4 or more robust setae along posterior margin; flagellum with about 30 articles; accessory flagellum with about 5 articles. Antenna 2 peduncular article 2 cone gland not reaching to end of peduncular article 3; article 4 subequal to article 5; flagellum with about 13 articles. Mandible palp article 3 rectolinear, setose along straight medial margin, longer than article 1; article 2 subequal to article 3; article 1 not produced, shorter than article 2. Maxilla 1 inner plate with setae mainly terminal.

Pereon. Gnathopod 1 coxa anteroventral corner produced, rounded, posteroventral corner notch absent; merus without posterodistal spine; carpus about 3× as long as broad; propodus palm acute, slightly convex, defined by posterodistal corner, defined by posterodistal robust setae. Gnathopod 2 not sexually dimorphic; subchelate; coxa posteroventral corner notch absent; merus with sharp posteroventral spine; carpus compressed; propodus without medial depression, without strong concentration of setae, palm broadly rounded, convex, smooth, with sparse small robust setae, defined by posterodistal robust setae, without posteroventral corner; dactylus apically acute/subacute.

Pereopod 5- 6 basis posterior margin straight, posteroventral corner broadly rounded; dactylus unguis anterior margin with 2 or more accessory spines. Pereopod 7 basis posterior margin slighlty convex, with posterior margin smooth or minutely castelloserrate, posteroventral corner broadly rounded; dactylus unguis anterior margin with 2 or more accessory spines.

Pleon. Epimeron 1 posteroventral corner with small acute spine. Epimera 1–2 posteroventral margin without spines above posteroventral corner. Epimeron 3 posterior margin smooth, posteroventral corner with strongly produced acute spine, posteroventral margin smooth or minutely serrate. Urosomite 1 with spines at midline, no conspicuous medial gape, with posterodorsal spine. Uropod 3 inner ramus scalelike, much shorter than outer ramus; outer ramus much longer (more than 2× length) than peduncle, 2-articulate. Telson each lobe with 3 apical/subapical robust setae, apical conical extension reaching at least halfway along longest seta.

Female (sexually dimorphic characters). Pereopod 6 coxa anterior lobe ventral margin slightly produced, rounded.

Habitat. Marine; living in association with the ophiuroid Ophionerieis schayeri under rocks.

Depth zone. Littoral (1 to 13 m).

Remarks. Melita ophiocola is an unusual and distinctive species of the genus. It is an obligate commensal of the brittle star Ophionereis schayeri (Muller & Troschel) . Preliminary results of experimental data indicate that the largest adult amphipods tend to occur in heterosexual pairs on the host and occasionally more than one pair may occur. Over 80% of individuals sampled were juveniles and there can be as many as 50 young per host. Juveniles occur throughout the year.

Mate selection experiments involving live animals showed that a significant number of large adults initially released on an overcrowded host move to another host and form heterosexual pairs (Peter Castro, pers. comm.). This apparent mobility may explain the high infection rates of over 90% observed in the field.

In a highly unusual situation for species of Melita , there is virtually no sexual dimorphism between males and females. We assume that this is because the female and male are always present together on the host and so there is no need for precopulatory amplexus and its associated morphological modifications.

Ophionereis schayeri View in CoL is found in shallow water beneath large rocks and in crevices. It is more active at night when it may forage in the open. It moves by sinuous flexing of its arms and feeds on detritus that is transported to the mouth by the tube feet. It is assumed that M. ophiocola feeds on the detritus collected by its host. Melita ophiocola has a banded colour pattern of purple and cream dorsally with purple gnathopods and pereopods tending to cream distally. This is similar to the colour pattern of the aboral surface of its host. Melita ophiocola is able to move freely over the body and arms of the brittle star but lives mostly on the oral surface of the arms between the two rows of tube feet.

Distribution. New South Wales: Boondelbah Island, Port Stephens; Broken Bay; Port Jackson; Twofold Bay (all AM).