CRUSTACEAN RESEARCH, NO. 39: 3736 - 5352, 2010 37 Larval stages of the crinoid-associated squat lobster, Allogalathea elegans (Adams & White, 1848) (Decapoda: Anomura: Galatheidae) described from laboratory- reared material Yoshihisa Fujita Abstract.– T h e c o m p l e t e l a r v a l of Lauriea gardineri (Laurie, 1926) and development of Allogalathea elegans Phylladiorhynchus integrirostris (Dana, 1853) (Adams & White, 1848) is described (see Fujita & Shokita, 2005; Fujita, 2007), all and illustrated from laboratory-reared from coral reefs of the Ryukyu Islands. material. This species has four zoeal T his paper describes the larval stages and one megalop. Diagnostic zoeal development of Allogalathea elegans for characters of the genus Allogalathea are the first time. Diagnostic zoeal characters of compared with those of the other galatheid the genus Allogalathea are compared with genera for which the larval morphology those of the other galatheid genera for which is known. Zoeas of A. elegans are readily the larval morphology is known. Megalopal distinguished from those of other morphology of A. elegans is also compared galatheids by the combination of setation with those of the two sympatric galatheids, of the maxillular and maxillar endopods. Galathea amboinensis and G. inflata. Megalopal morphology of A. elegans is remarkably different from those of the two Materials and Methods sympatric galatheids, Galathea amboinensis and G. inflata, in dentition on the lateral Spent female margins of the rostrum and carapace. An ovigerous female of Allogalathea elegans was found solitarily on the host crinoid, Oxycomanthus bennetti (Müller, Introduction 1841), on the Onna coast (Udui) of Okinawa Allogalathea elegans (Adams & White, Island, Ryukyu Islands, on 27 September 1848) is one of the well-known crinoid- 2000. However, this identification is associated squat lobsters, inhabiting shallow provisional, because Cabezas et al. (in press) waters in the Indo-West Pacific from the are revising the genus, in which three new eastern coast of Africa to Fiji Islands and species are described, along with A. elegans. from Japan to southern Australia (Baba et al., Three of the four species are being reported 2008, 2009). This species is also common in from Japan, so diagnostic characters of the the Ryukyu Islands, Japan where four other spent female used in this study are given crinoid-symbiotic squat lobsters, all belonging in order to allow correct identification of to the genus Galathea, are sympatric, often the present material after the revisional sharing the same crinoid hosts (Baba & work has been published: (1) body orange Fujita, 2008). During my current studies on in base colour, with broad, yellow median the biology of the Ryukyuan galatheids, I longitudinal stripe flanked by one dark brown have reported crinoid-galatheid associations and one white stripe on each side; (2) rostrum and larval development of G. amboinensis 2.1 times longer than broad; (3) pereopod De Man, 1888 and G. inflata Potts, 1915 1 palm 1.6 times longer than dactylus; (4) (see Fujita & Baba, 1999; Fujita et al., 2001, pereopod 2 merus lacking distinct spines on 2003). Meanwhile, I have also reported the dorsal margin, length 2.7 times breadth; and larval development of Sadayoshia edwardsii (5) epipods present on pereopods 1-2 . (Miers, 1884), and the zoeal morphology 38 LARVAL STAGES OF ALLOGALATHEA ELEGANS 37 Rearing methods and descriptions of larvae between 13 and 16 days. Hatching of larvae occurred on 6 October 2000, and 45 zoeas were recorded. Almost Description of larvae all of the hatched zoeas were mass-cultured Allogalathea elegans (Adams & White, 1848) in a circular plastic tank (30 cm in diameter) Figs. 1–10, Tables 1–2 containing 8-liter of filtered, UV treated First Zoea seawater. In addition, five zoeas were kept Size. CL 1.18-1.25 mm, TL 2.64-2.68 mm. individually in 50 ml glass beakers in order to Carapace (Figs. 1a, 2a, 2f). Typical determine the normal number of their larval galatheid larval form, with posteriorly stages and duration. The salinity and water produced acute spine on each side; temperatures of the seawater were 34.0–35.0 posterodorsal margin with 17-18 small teeth, ‰ and 25.5–27.5 ºC, respectively. Food given posteroventral margin with 18-25 small teeth; throughout all the larval stages was freshly rostrum spiniform, covered with denticle- hatched Artemia sp. nauplii. Approximately like small spines, extending to level of tip of one-third of the water in the tank was changed antennal scaphocerite; eyes sessile. daily. Antennule (Fig. 3a). Elongated, slightly The zoeal and megalopal specimens were swollen medially and narrowing distally, fixed and preserved in 50 % ethylene glycol terminally bearing 3 aesthetascs and 3 setae for morphological observations. Dissections (comprising 2 simple and 1 plumose setae); and measurements were carried out under one long plumose seta on future endopod bud. a Nikon SMZ-10 binocular microscope Antenna (Fig. 3f). Protopod with spinulose by using fine entomological needles. distal process; endopod fused to protopod, Measurements of carapace length (CL), as long as distal process of protopod, distally total length (TL), and postorbital carapace bearing one terminal seta; scaphocerite length (PCL, measured only in megalops) posteriorly produced into an acute spine, follow Fujita et al. (2001). Drawings were covered with small spines, and mesial margin made using a Nikon Optiphot-2 microscope. with 10 plumose setae, ventral surface heavily Descriptions were based on two specimens dentate. of each zoeal stage and one specimen of Mandibles (Fig. 4a). Asymmetrically the megalop. Body somites are described dentate; without palp. from anterior to posterior, appendages from Maxillule (Fig. 5a). Coxal endite with 7 endopod to exopod, and segments and plumodenticulate setae; basial endite with setae from proximal to distal. Terminology 2 cuspidate and 3 plumodenticulate setae; generally follows Gore (1979) and Ingle endopod unsegmented, with 1 short seta (1991). proximally and 1+4 setae distally (setal The spent female and complete larval formula, 1+1+4). series (undissected samples) are deposited Maxilla (Fig. 6a). Coxal and basial endites in the Ryukyu University Museum, Fujukan, bilobed, with 8+4 and 5+4 plumodenticulate Okinawa, Japan (RUMF) under the following setae, respectively; endopod unsegmented, registration numbers: RUMF-ZC-01174 for with 3 subdistomesial, 2 distomesial, and the spent female, RUMF-ZC-1175-1178 for 4 distolateral setae (setal formula, 3+2+4); first to fourth zoeas, RUMF-ZC-1179 for the scaphognathite with 4 marginal plumose megalop. setae, posteriorly ending in elongate plumose process. First Maxilliped (Fig. 7a). Coxa with 2 Results terminal setae; basis with 12 ventral setae Allogalathea elegans passed through four arranged 3+3+3+3; endopod 5-segmented, zoeal stages before attaining the megalopal with setation of 3, 2, 1, 2, 4 +I (I=dorsal (decapodid) stage. However, all the megalops plumose seta); exopod medially constricted, could not metamorphose to the first juvenile with 4 natatory plumose setae terminally. stage. The duration of the zoeal stages from Second Maxilliped (Fig. 8a). Coxa naked; hatching to the end of the fourth stage ranged basis with 1+2 setae on distoventral margin; 38 Y. FUJITA 39 Fig. 1. Allogalathea elegans (Adams & White, 1848): a, first zoea, lateral; b, second zoea, lateral; c, third zoea, lateral; d, fourth zoea, lateral. Scale bars = 0.5 mm. endopod 4-segmented, with 2, 2, 2, 4+I setae; short plumose seta (=anomuran hair), third to exopod as in first maxilliped. seventh articulated, long and stout plumose Third Maxilliped (Fig. 9a). Small setae with small spines. biramous bud. Pereopods. Not visible. Second Zoea Abdomen (Figs. 1a, 10a). Five somites; Size. CL 1.48-1.51 mm, TL 2.97-3.04 mm. each somites covered with numerous small Carapace (Figs. 1b, 2b, 2g). Posterodorsal spines; posterodorsal margins without distinct and posteroventral margin of carapace with teeth; pair of posterolateral spines on somites 3-14 and 16-19 teeth, respectively; dorsal 4-5; pair of short setae on posterodorsal surface of carapace with 3 pairs of short margin of somites 2-5; pleopods absent. setae, one pair at midpoint of carapace, two Telson (Fig. 10a, 10b). Trigonal form, pairs between eyes; rostrum depressed, lateral deeply concave on median part of posterior margin with 23-27 teeth; eyes now stalked. margin, dorsal surface covered with numerous Antennule (Fig. 3b). Protopod with small spines, posterior margin with 7 + 7 3 plumose setae on distal one-fourth, 4 processes (telsonal formula; I +ii + 3-7), first aesthetascs plus 4 setae on distal end; (lateralmost) spines fused to telson, second endopodal bud slightly developed, with a 40 LARVAL STAGES OF ALLOGALATHEA ELEGANS 39 Fig. 2. Allogalathea elegans (Adams & White, 1848): a-d, carapace, first to fourth zoeas, dorsal; e, megalop, dorsal; f, rostrum, first zoea, dorsal; g, same, second zoea, dorsal; h, same, megalop, dorsal. Scale bars: a-e = 0.5 mm, f-g = 0.1 mm. terminal plumose seta. absent; scaphocerite similar to first zoea. Antenna (Fig. 3g). Protopod with Mandibles (Fig. 4b). As in first zoea; additional robust spine at ventrodistal end; without palp. endopod developed, slightly longer than in Maxillule (Fig. 5b). Coxal endite the previous stage, distal plumose seta now unchanged; basial endite with 4 cuspidate 40 Y. FUJITA 41 Fig. 3. Allogalathea elegans (Adams & White, 1848), antennule (a–e) and antenna (f–j): a, f, first zoea; b, g, second zoea; c, h, third zoea; d, i, fourth zoea; e, j, megalop, middle segments of antenna omitted. Scale bars = 0.1 mm. and 3 plumodenticulate setae; endopod First Maxilliped (Fig. 7b). Coxa, basis and unchanged. endopod unchanged; exopod with 7 plumose Maxilla (Fig. 6b). C o x a l e n d i t e natatory setae. unchanged; proximal lobe of basial endite Second Maxilliped (Fig. 8b).