EARLY ZOEAL STAGES OF PLACETRON WOSNESSENSKII AND RHINOLITHODES WOSNESSENSKII (DECAPODA, ANOMURA, LITHODIDAE) AND REVIEW OF LITHODID LARVAE OF THE NORTHERN NORTH PACIFIC OCEAN EVAN B. HAYNES I ABSTRACT Stage I zoeae of Placetron wosnessenskii. and Stage I and Stage II zoeae of Rhinolithooes ",osnes­ senskii. which were reared in the laboratory. can be distinguished from other described zoeae of Lithodidae: P. wosnessenskii have long. blunt spines on posterior margins of abdominal somites 2-5 and sinuate curvature of long, blunt. posterolateral spines on abdominal somite 5; R. l<YJsnessenskii zoeae have a spine in the middorsal. posterior portion of the carapace. Zoeae of Lithodidae can be distinguished from zoeae of Pagurinae by body shape. size of the eyes. spines on the carapace. devel­ opment of uropods, and presence or absence of the anal spine. Stages of Iithodid zoeae can be distin­ guished by eye attachment. number of natatory setae on maxillipeds, and development of pleopods. uropods. and telson. Keys, based on spination of the carapace. rostrum. abdomen. and telson. distin­ guish between zoeae and glaucothoe of each described species of Lithodidae from the northern North Pacific Ocean. Crabs of the family Lithodidae constitute a major METHODS AND RESULTS component of the reptant decapod fauna of the northern North Pacific Ocean. Ofabout 25 species In March 1982, ovigerous females of Placetron ofLithodidae in the northern North Pacific Ocean. wosnessenskii and Rhinolithodes wosnessenskii larvae have been described. at least in part, were collected near Auke Bay, Alaska. in traps for eight species: Dermaturus mandtii Brandt, and by divers using scuba. The females were Cryptolithodes typicus Brandt. Hapalogaster transported to the laboratory and kept in filtered grebnitzkii Schalfeew, H. mertensii Brandt, Lith­ seawater (about 6e Cl until the zoeae hatched odes aequispina Benedict, Paralithodes brel'ipes about 1 wk later. After hatching, about 50 zoeae of (Milne Edwards and Lucas). P. camtschatica each species were transferred to each of four 4 I (Tilesius), and P. platypus Brandt. Most descrip­ glassjars containing about 2,500 ml ofseawater at tions are scattered in foreign scientific journals. 6.1e C. Seawater in the jars was changed about however, and published reviews of the larvae are every other day. Zoeae were fed live plankton limited in species and scope. This report describes strained through a 0.333 mm mesh. About 10 ml of and illustrates Stage I zoeae of Placetron ll'osnes­ live plankton was added to each jar every other senskii Schalfeew and Stages I and II zoeae of day. The live plankton consisted mostly of phyto­ Rhinolithodes wosnessenskii Brandt reared in the plankton and barnacle nauplii. A more detailed laboratory from ovigerous females. I characterize description of the rearing system and type and the morphological differences between zoeae of duration of illumination is given in Haynes and the Lithodidae and subfamily Pagurinae (family Ignell (19831. Paguridae), compare the morphology of lithodid Zoeae of Placetron wosnessenskii hatched at larvae of the northern North Pacific Ocean, and night, and samples ofzoeae were taken the follow­ provide keys for identifying the described larvae ing morning. No prezoeae of P. wosnessenskii to species and stage. were seen. Rhinolithodes wosnessenskii zoeae hatched at night and during the day, and those examined about 10 min after hatching had rem­ nants ofprezoeal exuviae attached to the cephalo­ 'Northwest and Alaska Fisheries Center Auke Bay Labora­ tory, National Marine Fisheries Service. NOAA. P.O. Box thorax and telson. The remnant exuviae are not 210155. Auke Bay. AK 99821. described in this paper. 315 Manuscript accepted October 1983. FISHERY BULLETIN: VOL. 82. NO.2. 1984. FISHERY BULLETIN: VOL. 82. NO.2 Although food was seen in the guts of some their appendages, techniques of illustration, and Placetron wosnessenskii zoeae, none molted to nomenclatureofappendagesfollow Haynes(1979). Stage II. Zoeae ofRhinolithodes wosnessenskii fed Carapace length refers to the straight-line dis­ actively and molted to Stage II about 20 dafter tance from posterior margin of eye orbit to mid­ hatching. Failure to change the seawater on dorsal posterior margin ofcarapace, excluding the schedule prevented rearing the zoeae of R. wos­ middorsal spine. Spines on the telson are num­ nessenskii beyond Stage II. bered from the outermost to innermost (medial) pair. Setation formulae are the number of setae DESCRIPTION OF ZOEAE per segment from the distal segment to the proxi­ mal segment. For clarity in the illustrations, Terminology, methods of measuring zoeae and. setules on plumose setae are usually omitted, but A 1.0 mm ·O.S mm RIGHT E O.S mm O.S mm FIGURE I.-Stage I zoea of Place/ron wosnessenskii: A, whole animal, right side; B. carapace, dorsal; C. antennule, ventral; D. antenna, ventral; E, mandibles (\ef!; and right>. posterior; F. maxillule, ventral; G, maxilla. dorsal; H. first maxilliped, lateral; 316 HAYNES: EARLY ZOEAL STAGES OF L1THODID CRABS spinulose setae are shown. Five zoeae were used to mm (range 5.90-6.70 mm, 10 specimens) (Fig. lA, verify segmentation and setation; 10 zoeae were B). Live zoeae orange throughout except for color­ usedfor measurements. Only those morphological less appendages and posterolateral spines on characteristics useful for readily identifying each carapace and abdomen. Carapace with medially stage are given. curved, long (>114 carapace lengthl, posterolat­ eral spines; markedly pronounced lateral ridges Placetro1J ·u'ostlessemkii-Stage I Zoeae and dorsoventral ridge; and two middorsal angu­ lar prominences: one near center of carapace and Mean carapace length, 2.12 mm (range 2.08­ other at posterior edge. No supraorbital spines. 2.21 mm, 10 specimens); mean total length, 6.22 Eyes sessile. II 0.5 mm 1.0 mm J \\ \ \ 'W 1.0 mm 1.0 mm K 1.0 mm I, second maxilliped, lateral: J. third maxilliped, lateral; K. pereopods 1-5. lateral: L. abdomen and telson, dorsal. 317 FISHERY BULLETIN: VOL. 82. NO.2 Antennule (Fig. 1C).-First antenna (antennule) segmented with four natatory setae. Endopodite with unsegmented tubular basal portion (pedun­ slightly longer than exopodite and distinctly five cle) and distal conical projection. Peduncle with segmented; setation formula 5. 3, I, 2, 3. Protopo­ ventral plumose seta. Conical projection with sev­ dite unsegmented with 10 setae. en aesthetascs and two simple setae terminally. Second maxilliped (Fig. 11l.-Similar to first Antenna <Fig. 1D).-Second antenna (antenna) maxilliped except endopodite slightly shorter with inner flagellum (endopodite) and outer an­ than exopodite. Endopodite four segmented, seta­ tennal scale (exopodite). Flagellum unsegmented. tion formula 5. 2, 2, 2. Protopodite with three shorter than scale, and tipped with two simple lateral setae. setae. Antennal scale without distal joint. has fringe oflO heavily plumose setae along terminal Third maxilliped iFig. lJl.-Exopodite and en­ inner margin and prominent spine on distal outer dopodite undeveloped. Exopodite partially seg­ margin. Ventral surface of protopodite with spin­ mented, with three undeveloped setae terminally. ulose spine atbase offlagellum and naked spine at Endopodite with undeveloped seta terminally. base ofantennal scale. Pereopods (Fig. 1Kl.-Poorly developed, without Mandible (Fig. 1E).-Incisor process of right exopodites. First pereopod bilobed. Fifth pereo­ mandible a tooth; left mandible with biserrate in­ pod arises medially between first and second cisor process. Anterior margins of each mandible pereopods. with premolar denticles. Mandibles without sub­ terminal processes or movable premolar denticle Abdomenand te/son (Fig. lA, Ll.-Abdomen with (lacinia mobilis). five somites and telson (somite 6 fused with telson). Somites 2-5 have six bluntly tipped spines Maxillule (Fig. IF).-First maxilla (maxillule) on posterior margin and two minute dorsal setae. with coxopodite. basipodite, and endopodite. Cox­ Outer pair ofposterior spines on somite 5 are long opodite (proximal lobe) unsegmented with four (about 1.2 times somite width). blunt. and some­ large spinulose spines and three simple spines what sinuate. Thlson with medial invagination terminally. Basipodite (median lobe) with three posteriorly and 6 + 6 spines. Third pair oftelsonic spines terminally (each spine with several spin­ spines longest (about 3/4 maximum telson width/. ulesl and two simple spines subterminally. Three­ All spines jointed with telson. Minute seta be­ segmented endopodite originates from lateral tween spinal pairs 1 and 2 originates from ventral margin ofbasipodite. Endopodite with three setae surface; seta often without setules: spinules on terminally, a long distal seta on second segment, spinal pairs 2-6. No uropods or anal spine. and a short distal seta on first segment. Fine hairs on inner and outer margins of exopodite, outer Rhblo/ithodes u'osnessenskii margin ofendopodite. both lobes ofbasipodite, and distal lobe ofcoxopodite. Stage I Zoeae Maxilla lFig. 1G).-Second maxilla (maxilla) Mean carapace length, 1.29 mm (range 1.21-1.34 with platelike exopodite (scaphognathite). Exo­ mm, 10 specimens); mean total length, 4.45 mm podite with three long plumose setae terminally (range 4.02-4.62 mm. 10 specimens) (Fig. 2A, B). and a subterminal plumose seta on outer margin; Cephalothorax and base of maxillipeds orange; no proximal expansion of exopodite. Endopodite remainder ofmaxillipeds. most ofrostrum, and all unsegmented,