Raoulserenea pygmaea, Caldwell & Manning, 2000

Caldwell, Roy L. & Manning, Raymond B., 2000, A new dwarf pseudosquillid of the genus Raoulserenea from French Polynesia (Crustacea, Stomatopoda), Zoosystema 22 (1), pp. 101-105 : 102-104

Raoulserenea pygmaea n. sp.

( Fig. 1 )

HOLOTYPE. — French Polynesia. Moorea , Society Islands, 17°32’N, 149°50’W, 1 m, rubble, 10-

15.XI.1992, leg. R. L. Caldwell, 1 33 mm ( USNM 260953).

PARATYPES. — French Polynesia. Same data as holotype, 5 20-26 mm, 2 21 and 27 mm ( USNM 260954), 2, 1 (MNHN-St1978). — 1 m, rubble, V.1980, 1 22 mm, 2 22 and 24 mm ( USNM 260955). — 25 m, rubble, V.1980, 1 15 mm ( USNM 260956). — no date, 1 22 mm, 1 25 mm ( USNM 260957). — 1991, 1 25 mm, 1 22 mm ( USNM 260958). — Cook’s Bay, Moorea, Society Islands, 0.5 m, rubble, VII.1988, 7 18-28 mm, 2 postlarvae 17 and 18 mm, 2 19 and 21 mm, 1 postlarva 18 mm ( USNM 260959).

Tuamotu Archipelago. Monihi, low intertidal, 19°00’S, 142°00’W, rubble, V.1980, leg. R. L. Caldwell, 1 damaged 26 mm (USNM 260958). — Mataiva Atoll, 1 22 mm (MNHN-St1979).

ETYMOLOGY. — From the Latin, pygmaeus, dwarf or pygmy, alluding to the diminutive size of the species.

MEASUREMENTS. — Males (n = 18), tl 15-28 mm; male postlarvae (n = 2), tl 17 and 18 mm; females (n = 12), 19-33 mm; female postlarva (n = 1), tl 18 mm. Other measurements of holotype, in mm: carapace length 6.7; rostral plate length 1.5, width 2.2; cornea width 1.9; length of propodus of raptorial claw 8.0; fifth abdominal somite width 5.0; telson length 5.1, width 4.2.

DISTRIBUTION. — Known only from Moorea and Tahiti, Society Islands and Manihi and Mataiva Atoll, Tuamotu Archipelago, French Polynesia.

DIAGNOSIS. — Size small, maximum total length 33 mm. Rostral plate broad, lacking anterior spinule, apex obtusely pointed. Eyespots on carapace surround- ed by white ring. Propodus of raptorial claw spotted.

DESCRIPTION

Total length of adults to 33 mm. Eye large, cornea distinctly broadened, not extending beyond segment 2 of antennular peduncle. Antennal scale slender, entire margin setose. Rostral plate broader than long, obtusely pointed anteriorly, lacking apical spine. Carapace dorsum with pair of dark circles surrounded by uninterrupted white ring. Raptorial claw propodus with three movable spines proximally. Lateral margin of thoracic somite 6 broader than that of somite 7. Abdominal somite 5 only with posterolateral spine. Sternal keel acutely pointed on abdominal somites 1-3, sharper, spiniform on somites 4 and 5. Uropodal exopod with 10 graded spines, distalmost overreaching distal segment. Uropodal protopod with “step” or low prominence on inner margin proximal to base of inner spine. Endopod of male pleopod with tube process longer than hook process.

Color in life

Body fairly uniform olive green made up of tiny stellate chromatophores with only a trace of the network of light and dark spots forming the pattern seen on the rostral plate, carapace and merus and propodus of the raptorial appendages of preserved specimens. The antennules are clear with a bluish green tint and the flagella have salmon-colored spots. The antennae are clear with tiny salmon spots on each segment. The antennal scales are clear with pink to salmon margins and setae. The raptorial second maxillipeds are light green with tiny dark spots with the dactyl margins tinged with salmon. Maxillipeds 3-5 are greenish yellow with salmon setae. The margins of the thoracic and abdominal segments are dull red. The pleopods are greenish yellow with salmon setae. The telson is green with transverse white stripes and the margins of teeth and spines salmon. The uropods are blue-green with clear bands, setae salmon, and spines slightly purple.

REMARKS

Manning (1995) recognized the genus Raoulserenea for four species previously assigned to Pseudosquilla Fabricius, 1787 that are characterized by broad eyes, eyespots on the carapace, and three pairs of dorsal carinae on the telson. Raoulserenea pygmaea is the fifth species of the genus to be recognized. Four of these species have now been found in Moorea. In addition to R. pygmaea , R. komaii (Moosa, 1991) and R. ornata (Miers, 1880) are found in shallow water (depth less than 4 m) and R. hieroglyphica (Manning, 1972) is found deeper than 15 m (Caldwell personal observation). Only R. oxyrhyncha (Borradaile, 1898) has not been found in French Polynesia.

Raoulserenea pygmaea could be mistaken for R. ornata and R. hieroglyphica , which share the unarmed rostral plate and eyespots on the carapace surrounded by a white ring, but differs in being much smaller than either of those species. Adults of R. pygmaea are not known to attain 35 mm in total length, whereas members of R. ornata may exceed 80 mm in length (Manning 1995) and adults of R. hieroglyphica may reach 83 mm in length (Manning 1977). The rostral plate of R. pygmaea has a broadly obtuse point on its anterior margin, as does R. hieroglyphica , whereas the rostral plate of R. ornata is evenly rounded in adults.

Raoulserenea komaii would not be confused with these three species, since it is the only one in the area that possesses a rostral plate with a median apical spinule; R. oxyrhyncha also has the apical spinule on the rostral plate. The propodus of the raptorial claw is spotted in R. pygmaea and R. hieroglyphica , not spotted in R. ornata . The background color of R. ornata is uniformly dark while those of R. hieroglyphica and R. komaii are marked with dark spots and irregular lines on a lighter background. In preserved specimens, the carapace of R. pygmaea displays a pattern of dark spots and irregular lines on a lighter background, but in live specimens the carapace color is a much more uniform olive green made up of numerous tiny dark spots.

In preservative, large specimens of R. pygmaea can be distinguished from R. hieroglyphica of similar size by the color pattern. Specimens of R. pygmaea lack distinct dark bands on thoracic somites 6-8 and abdominal somites 1-4; the fifth abdominal somite has a dark posterior margin. The abdominal plate is dark and abdominal somites 1-5 each have a dark spot posterolaterally, delimited anteriorly by a clear space. In R. hieroglyphica , thoracic somites 6-8 are crossed by a single band of dark spots. Abdominal somites 1-5 have two similar bands, one across the middle, the other posteriorly. These somites also have a dark spot on each side at the posterolateral angle. Both species have a prominent dark spot on the sternum at the base of each walking leg.

Between 1988 and 1998, one of us (R. L. C.) collected 230 adult R. pygmaea on Moorea. He also collected numerous postlarvae night-lighting in Cook’s Bay. Larvae, while still in the water column, molt to postlarvae, which settle into rubble while they are still totally clear, except for their eyes, and are 17-19 mm in total length. Within three to five days they begin to develop some body coloration in the form of tiny speckles and by seven days the two eyespots on the carapace are clearly visible. Newly settled males have partially formed gonopods and after the first postsettlement molt the female gonopores are visible. Like Pseudosquilla ciliata , adults will mate at any stage in their reproductive cycle (Hatziolos & Caldwell 1983) and there appears to be no prolonged mate-guarding by males. Courtship behavior contains several of the same elements described for P. ciliata but mating often occurs in a cavity in coral rubble (Caldwell, personal observation). One 21 mm female was found with developed sternal cement glands indicating that she was reproductive and two 22 mm females were found brooding yellow egg masses. Fourteen percent of the females 22 mm or larger were collected with eggs. Eggs generally are laid near the time of the full moon and hatch around the new moon. Upon hatching, larvae immediately enter the plankton. The largest female collected was 33 mm total length and the largest male 32 mm. The median size of all adult males collected was 21 mm and of adult females was 22 mm.

On Moorea, Raoulserenea pygmaea is found at depths between mean low water and 4 m. They are found over a wide range of habitats from the reef crest and back reef to inshore coastal beaches. Typically, R. pygmaea live in cavities and crevices in coral rubble. This species seems to be particu- larly tolerant of silt and frequently occurs in muddier bays as well as on sandy reef flats and the reef crest. Raoulserenea pygmaea is most commonly found co-occurring with the gonodactylid Gonodactylus childi Manning, 1971 (a dwarf species as well as a composite species, to be redescribed by Manning), but living in cavities in these same rubble habitats are the pseudosquillids Pseudosquilla ciliata , Raoulserenea komaii , and R. ornata ; Gonodactylellus affinis (De Man, 1902) and G. espinosus (Borradaile, 1898) ; Gonodactylus platysoma (Wood-Mason, 1895) , and the lysiosquilloid Parvisquilla multituberculata (Borradaile, 1898) .

Figures

FIG. 1. — Raoulserenea pygmaea, n. sp. Female holotype, tl 33 mm; A, anterior part of body and raptorial claw; B, sixth abdominal somite, telson, and uropod; C, endopod of first pleopod of male paratype, tl 25 mm. Scale bar: A, B,1 mm; C, 0.5 mm.