Mallacoota capricornia, Lowry & Hughes, 2009

Lowry, J. K. & Hughes, L. E., 2009, Maeridae, the Elasmopus group *, Zootaxa 2260 (1), pp. 643-702 : 673-677

Mallacoota capricornia sp. nov.

( Figs 17 , 18 )

Mallacoota insignis . — Myers, 1985: 117, figs 93, 94. — Ledoyer, 1983: 552, fig. 210 (in part).

Type material. Holotype, male, 6.5 mm (6 slides), AM P78030, Picnic Beach , Palfrey Island , Lizard Island (14°41.69’S 145°26.89’E), green alga Codium sp. , reef flat, 2 m, T. Krapp-Schickel, 27 February 2005 ( QLD 1716 ) . Paratype: female, 7.6 mm (5 slides), AM P78032 ( QLD 1716 ) .

Additional material examined. 1 unsexed, AM P75812 (75 LIZ 11-2 ) ; 1 unsexed, AM P75654 (76 LIZ A 03.12.2) ; 5 unsexed, AM P30814 ( HI-B3-11 ); 1 unsexed, AM P78035 ( QLD 1319 ); 10 unsexed, AM P78034 ( QLD 1336 ); 1 unsexed, AM P70569 ( QLD 1618 ); 5 unsexed, AM P70930 ( QLD 1698 ); 3 unsexed, AM P71078 ( QLD 1704 ); 5 unsexed, AM P71035 ( QLD 1708 ); 1 male , 6.6 mm, 1 slide, AM P78031 ( QLD 1716 ); 3 unsexed, AM P71088 ( QLD 1716 ); 7 unsexed, AM P71151 ( QLD 1732 ); 1 unsexed, AM P75653 ( QLD 1801 ); 2 unsexed AM P75620 ( QLD 1846 ); 2 unsexed, AM P75745 ( QLD 1851 ); 2 unsexed, AM P78033 ( QLD 1901 ); many unsexed, AM P75737 ( QLD 1940 ); 6 unsexed AM P75738 ( QLD 1941 ); many unsexed, AM P75849 ( QLD 1951 ); many unsexed, AM P75739 ( QLD 1967 ); many unsexed, AM P75740 ( QLD 1978 ); 6 unsexed AM P75736 ( QLD 2000 ); many unsexed, AM P75734 ( QLD 2006 ); 10+ unsexed, AM P78297 ( NT 63 ); 27 unsexed, AM P78298 ( NT 65 ); 10+ unsexed, AM P78299 ( NT 66 ) .

Type locality. Picnic Beach , Palfrey Island, Lizard Island, Queensland, Australia (14°41.69’S 145°26.89’E) .

Etymology. This species takes its name from the Capricorn area of north-eastern Australia.

Description. Based on holotype, male, 6.5 mm, AM 71078.

Head. Head eyes ovate; lateral cephalic lobe broad, truncated, anteroventral margin with notch/slit, anteroventral corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 slightly longer than article 2, with 3 robust setae along posterior margin; article 2 longer than article 3; accessory flagellum minute, with 2–3 articles; flagellum with 29–30 articles. Antenna 2 peduncular article 4 slightly longer than article 5; flagellum with 8 articles. Mandible incisor a smooth cutting edge with 2 apicomedial cusps; accessory setal row with 4 setae; palp reduced, 3-articulate; article 1 about twice as long as broad, subequal in length to article 2, inner margin article 1 not produced distally; article 2 subequal to article 3; article 3 long (more than 3 x as long as broad), rectolinear, subequal in length to article 1.

Pereon. Gnathopod 1 coxa anteroventral corner produced, rounded, anterior margin straight; merus without posterodistal tooth; carpus about 2 x as long as broad, subequal in length to propodus, setae in anterodistal bunches and along posterior margin; propodus palm acute, straight, entire, defined by posterodistal corner, with posterodistal robust setae. Gnathopod 2 coxa posteroventral corner notch absent; basis slender; merus with subquadrate distoventral corner; carpus compressed, projecting between merus and propodus, length 0.6 x breadth; propodus expanded, with slender medial setal bunch, palm acute, convex, sculptured, palm about two thirds length of propodus, with subtriangular distomedial shelf, with group of 4 robust setae on shelf, with small midmedial excavation, palmar margin with sparse 1 robust seta along palm, with 2 subacute teeth, subpalmar surface smooth, corner defined by posteroventral tooth, without posterodistal robust setae; dactylus not reaching end of palm, closing along palm, without setae on anterior margin, without posteroproximal shelf, apically blunt. Pereopod 4 coxa posteroventral lobe slightly developed, with subacute posteromedial corner. Pereopod 5 basis expanded, posterior margin straight, without long slender setae, posteroventral corner narrowly rounded; carpus and propodus without long, slender setae along anterior margin. Pereopod 6 basis posterior margin slightly convex, without long slender setae, posteroventral corner narrowly rounded; carpus and propodus without long, slender setae along anterior margin; merus and carpus broadened; propodus slightly expanded posterodistally to from a hood-like projection. Pereopod 7 basis posterior margin convex, minutely castelloserrate, without long slender setae, not produced posterodistally, posteroventral corner narrowly rounded or subquadrate; merus and carpus broadened; propodus slightly expanded posterodistally to from a hood-like projection.

Pleon. Pleonites 1–3 dorsally smooth, without setae, spines or carinae. Epimeron 1 posteroventral corner with small acute or subacute spine. Epimeron 2 posteroventral corner acute. Epimeron 3 ventral margin smooth, posteroventral margin smooth, posteroventral corner with small acute spine. Urosomite 1 bicarinate, subtriangular. Urosomites 2–3 dorsally smooth, without setae, spines or carinae. Uropod 1 peduncle with basofacial robust seta. Uropod 3 rami distally truncated, apical robust setae long or short; inner ramus subequal in length to outer ramus, long (length 2 to 2.5 x breadth); outer ramus short (length 1.9 x breadth), longer than peduncle, 1-articulate. Telson moderately cleft (30 to 65%), broader than long, short, lobes apically truncated, apical conical extension reaching scarcely one third along longest seta, without dorsal robust setae, each lobe with 3 apical long and short robust setae, without robust setae on inner and outer margins.

Female (sexually dimorphic characters). Based on paratype female, 7.6 mm, AM P78032. Gnathopod 2 carpus long, length 1.6 x breadth, not enclosed by merus and propodus; propodus subrectangular, half length of propodus, smooth, without distomedial shelf, without teeth along margin, without posteroventral corner, with posterodistal robust setae .

Habitat. Marine, epibenthic, among algae, coral rubble and sponges.

Remarks. Pirlot (1936) considered that Gammarus indicus Dana, 1853 (described from the Balabac Strait, Sabah) might be a female of the species now known as Mallacoota insignis ( Chevreux, 1901) . Dana’s (1853) whole animal illustration (pl. 66, fig. 4) shows a female with a bicarinate urosomite 1, but other details are lacking or misleading. For instance the lateral cephalic lobe is not notched. Based on the available evidence Dana’s taxon could be in the genus Mallacoota or Parelasmopus and the species in indeterminable.

The Australian material of Mallacoota capricornia sp. nov. compares well with the descriptions of Mallacoota insignis ( Chevreux, 1901) , J.L. Barnard (1970), Ledoyer (1983), Myers (1985). One difference is pereopods 5–7 which are much broader in Chevreux’s material from the Seychelles. As males of some Mallacoota species mature the distal articles (merus and carpus) of these pereopods become immensely broadened.

A more significant difference is the structure of the palm in male gnathopod 2. In the current material of M. capricornia from the GBR (6.5 mm) and the material of Myers (1985) from Fiji (8 mm) there is a small cusp defining the end of the palm which is not apparent in the illustrations of Chevreux 1901 (no size), J.L. Barnard 1970 (7.7 mm), Ledoyer 1983 (8 mm) and Appadoo et al., 2002 (7.2 mm). Myers (1985) stated that the lack of a cusp occurs in juveniles, which is true in his material, but Chevreux, Barnard, Ledoyer and Appadoo et al. have all illustrated fully mature specimens. Ledoyer (1983) also showed an individual with the cusp (5.5 mm) which indicates that he had two species in his samples.

It is difficult to assess the records of M. insignis studied by Schellenberg (1938). Although there were large males in his study material, Schellenberg illustrated the second gnathopod of two juveniles (3 mm and 4.5 mm) from unnamed localities. The illustrations do not compare well with juvenile second gnathopods illustrated by Ledoyer 1983 and Myers 1985, and leave his records suspect. This is unfortunate because Schellenberg reported on material from a number of Pacific localities – Kiribati ( Gilbert Islands), Tuvalu ( Ellice Islands), Fiji, Hawaii and the Philippine Islands.

Mallacoota capricornia aligns with species in which the male gnathopod 2 palm is defined by a tooth. On the GBR the only other species with a tooth defining the palm is M. chandaniae which differs from M. capricornia by its massive, tranverse male second gnathopod.

Distribution. Australia. Northern Territory: New Year Island (current study). Queensland: Hawkesbury Island, Horn Island, Torres Strait; Heron Island; One Tree Island (current study). Fiji. Momi Bay, Malevu, Votualailai, Nukumbutho Island, Makuluva Island, Mburelevu ( Myers 1985). Madagascar. Tuléar ( Ledoyer 1979 b, 1983).

Figures

FIGURE 17. Mallacoota capricornia sp. nov., holotype, male, 6.5 mm, AM P71078, Lizard Island, Great Barrier Reef.

FIGURE 18. Mallacoota capricornia sp. nov., holotype, male, 6.5 mm, AM P71078, paratype, female, 7.6 mm, AM P78032, Lizard Island, Great Barrier Reef.