DESCRIPTION OF LARVAE OF A HIPPOLYTID SHRIMP, LEBBEUS GROENLANDICUS, REARED IN SITU IN KACHEMAK BAY, ALASKA

EVAN HAYNESl

ABSTRACf

Larvae ofLebbeus groenlandicus, a hippolytid shrimp, were reared in situ in Kachemak Bay, Alaska, from the first zoea (Stage 1) through the megalopa (Stage III). Each ofthe three stages is described and illustrated, and then compared with descriptions of larvae of Lebbeus spp. given by other authors.

Information on the larval stages ofthe genus Leb­ setae are shown. The terms are defined as follows: beus is meager. Pike and Williamson (1961), in their summary of the generic characteristics of setose - set with bristles (setae) Spirontocaris and related genera, note that the spinose - bearing many spines only larva ofLebbeus known for certain is a larva spinous - spinelike of L. polaris dissected from a well-developed egg. spinulose - set with little spines. During studies on rearing larvae of pandalid shrimp for descriptive purposes (Haynes 1976, The figures are in part schematic and represent 1978), I succeeded in rearing larvae of L. groen­ typical setal counts. landicus to the megalopa stage. This report de­ scribes and illustrates each ofthe two zoeal stages STAGE I ZOEA and megalopa ofL. groenlandicus, and compares the stages obtained from rearing in situ and from Total length of Stage I (Figure 1A) 6.9 mm plankton in Kachemak Bay with provisionally (range 6.4-7.4 mm; 10 specimens). Live specimens identified larvae of L. groenlandicus reported by characterized by bright orange color extending other authors. along ventral surface of body from antennules to fourth abdominal segment, orange gut, small METHODS orange chromatophore at anus, and greenish in­ ternal thoracic organs; remainder of zoea trans­ A complete discussion of rearing technique, lucent. Rostrum slightly sinuate, without teeth, methods of measurement, techniques of illustra­ about two-thirds length of carapace. Carapace tion, and nomenclature ofgills and appendages is with dorsal rounded prominence at base of ros­ given by Haynes (1976). Briefly, the rearing trum and near posterior edge; no supraorbital technique consists ofobtaining Stage I zoeae from spines. Usually at least two minute spinules occur known parentage in the laboratory and then rear­ along ventral margin of carapace immediately ing the zoeae to postlarvae in 500-ml flasks sus­ posterior to pterygostomian spine. pended upright beneath the surface of the sea. Cast skins and larvae removed from the flasks ANTENNULE (FIGURE 1B).-First antenna, or were examined in the laboratory to determine antennule, consists ofan unsegmented cylindrical sequence and morphology of each stage. Larval basal portion and two distal conical projections; stage was also verified using larvae from plankton largest conical projection bears four aesthetascs of reared in the same manner as larvae obtained in various lengths; smallest conical projection bears the laboratory. a single heavily plumose seta. In the illustrations (Figures 1-3), for clarity, setules on setae are usually omitted but spinulose ANTENNA (FIGURE 1C).-Consists of inner flagellum (endopodite) and outer antennal scale (exopodite). Flagellum two-segmented, about INorthwest and Alaska Fisheries Center Auke Bay Labora­ tory, National Marine Fisheries Service, NOAA, P.O. Box 155, twice length of scale; distal segment styliform and Auke Bay, AK 99821. terminating in narrow projection. Two simple

Manuscript accepted November 1977. 457 FISHERY BULLETIN: VOL. 76, NO.2. 1978. FISHERY BULLETIN: VOL. 76, NO.2

1.0 mm A

B

0.5 mm

<- C l- e (

( c.. ( \, \ \ cc" , ( \ \ , ( (

LEFT RIGHT

c D

0.5 mm 0.25 mm

FIGURE l.-Stage I zoea of Lebbeus groenlandicus: A, whole animal; B, antennule; C, antenna; D, mandibles (right and left).

458 HAYNES: LEBBEUS GROENLANDlCUS LARVAE

E

0.25 mm 0.25 mm

, , 0.5 mm

H 1.0 mm

FIGURE l.-Stage I zoeaofLebbeusgroenlandicus: E, maxillule; F, scaphognathiteofmaxilla; G, firstmaxilliped; H, second maxilliped. setae occur at joint. Antennal scale distally di­ margin. Protopodite bears two simple spines ven­ vided into four segments (proximal joint often in­ trally, one at base of flagellum and one at base of complete) and fringed with 11 heavily plumose scale. setae along terminal and inner margins. A small seta often occurs proximally near lateral MANDIBLES (FIGURE ID).-Without palps; 459 FISHERY BULLETIN: VOL. 76. NO.2

J

0.5 mm

/- ..... , / \ / \ I \ / \ I \ / \ / \ / \ / " - ...... _".

L M

0.5 mm 1.0 mm

FIGURE l.-Stage I zoea ofLebbeus groenlandicus: I, third maxilliped; J, first pereopod; K, third pereopod, L, first pleopod; M, second pleopod; N, telson. well developed. Incisor process of left mandible mandibles bear well-developed denticles along bears five teeth, one ofthem located near movable terminal margin. Truncated end of molar process premolar denticle Oacinia mobilis), in contrast to ofright mandible formed into curved lip. Only left triserrate incisor process of right mandible. Both mandible bears a subterminal process. 460 HAYNES: LEBBEUS GROENLANDICUS LARVAE MAXILLULE (FIGURE lE).-First maxilla, or SECOND PEREOPOD.-Similar in shape to first maxillule, bears coxal and basial endites and an pereopod except narrower, exopodite smaller, and endopodite. Proximal lobe (coxopodite) bears 15 chela more deeply cleft. setae, most of them spinulose. Median lobe (basipodite) bears 24 spines terminally, 9 ofthem THIRD (FIGURE 1K) TO FIFTH PEREO­ spinulose; and 2 spines subterminally, 1 of them PODS.-Each pair essentially identical except plumose and the othersimple. A series offine hairs that they decrease slightly in size from third to occurs in vicinity of the simple spine. Endopodite fifth. No exopodites. originates from lateral margin of basipodite and bears three terminal and two subterminal PLEOPODS.-First pleopod (Figure 1L) slightly spinulose setae. No evidence of outer seta on cleft, without joints or setae. Second pleopod (Fig­ maxillule. ure 1M) bilobed; outer lamella segmented; inner lamella usually only partially segmented but MAXILLA (FIGURE 1F).-Bears platelike bears bud of appendix interna. Third to fifth exopodite (scaphognathite) with 33 long, plumose pleopods essentially identical to second pleopod setae along outer margin, and a longer, thick seta except both lamellae distinctly segmented. at the proximal end. Endopodite not segmented; setae spinous, setation formula 2, 2, 1,2,3. Both ABDOMEN AND TELSON (FIGURES lA, basipodite and coxopodite bilobed. Basipodite 1N).--Abdomen consists offive segments and tel­ bears 29 setae, 14 on distal lobe and 15 on proxi­ son (somite six is fused with telson in Stage n. mal lobe. Coxopodite bears 23 setae, 5 on distal Fourth and fifth abdominal segments each with lobe and 18 on proximal lobe. pair of posterolateral spines nearly as long as segments themselves. Telson slightly emar­ FIRST MAXILLIPED (FIGURE 1G).­ ginated distally; bears 19-21 densely plumose Protopodite segmented; bears 27 setae on distal setae; small spinules occur between bases of all segment and 8 on proximal segment, most ofthem setae except two outermost pairs. Enclosed spinulose. Endopodite four-segmented; setation uropods visible. Anal spine present. formula 4, 3, 3, 7. Basal segment of endopodite bears conspicuous setulose spine. Exopodite seg­ STAGE II ZOEA mented at base; bears four natatory setae. Epipo­ dite distinctly bilobed. Total length of Stage II 8.3 mm (range 8.1-8.7 SECOND MAXILLIPED (FIGURE 1H).­ mm; 8 specimens). Color similarto StageI zoea but more diffuse. Rostrum (Figure 2A) arched upward; Protopodite not segmented; bears nine setae, five of them spinulose. Endopodite five-segmented; slightly blunter than in Stage I; without teeth. fourth segment expanded somewhat laterally; Carapace bears supraorbital, antennal, and pterygostomian spines in addition to several terminal segment tipped by five setae and bears single seta subterminally; basal segment bears spinules along anteroventral margin. conspicuous setulose spine like that on basal seg­ ment of endopodite of first maxilliped; setation ANTENNULE (FIGURE 2B).-Shows considera­ formula 6, 4, 2, 3, 4. Exopodite about three times ble change from Stage 1. Largest conical projection longer than endopodite; bears five natatory setae. segmented at tip; terminal segment bears three Epipodite present but not bilobed. setae ofdifferent lengths; proximal segment bears six groups of five aesthetascs each in addition to THIRD MAXILLIPED (FIGURE 1I).­ row of four aesthetascs laterally and single seta Protopodite not segmented; bears three setae. En­ distally. Smallest conical projection bears three dopodite five-segmented; as long as exopodite; nonplumose setae, one long and two short. Pedun­ number of setae somewhat variable. Exopodite cle ofantennule rounded laterally, not segmented, bears five natatory setae. No epipodite. and bears five plumose setae that originate ven­ trally. FIRST PEREOPOD (FIGURE 1J).-Endopodite relatively short, wide, and partially segmented; ANTENNA (FIGURE 2C).-Flagellum of an­ chela partially formed; dactylopodite bears three tenna still two-segmented, but slightly stouter simple spines. Exopodite a small lobe. and projection at tip smaller than in Stage I; a few 461 FISHERY BULLETIN: VOL. 76, NO.2

0.5 mm 0.5 mm

0.5 mm 0.5 mm

FIGURE 2.-Stage II zoea of Lebbeus groenlandicus: A, carapace; B, antennule; C, antenna; D, first pereopod; E, second pereopod; F, second pleopod.

462 HAYNES, LEBBEUS GROENLANDICUS LARVAE small setae occur along lateral margin. Antennal PLEOPODS.-First pleopod slightly more de­ scale distally divided into two segments and veloped than in Stage I but still only about one­ fringed with 29 or 30 thin, plumose setae along third length ofsecond pleopod and without appen­ terminal and inner margins; distal outer projec­ dix interna. Second pleopod (Figure 2F) largerand tion a stout spine. Protopodite bears two stout narrower than in Stage I; outer lamella about spines, one atbase offlagellum and other atbase of one-fourth longer than inner lamella; both lamel­ scale. lae and appendix interna fully segmented at their bases. Third to fifth pleopods essentally identical MANDIBLES, MAXILLULE, AND MAX­ to second pleopods. ILLA.-Essentially identical to Stage I except scaphognathite of maxilla usually bears 35 setae ABDOMEN AND TELSON.-Posterolateral along outer margin, in addition to the longer and spines on fourth and fifth abdominal somites still thicker seta at proximal end, and proximal cleft present, those on fourth somite being only slightly slightly deeper. shorter in relation to length of somite than in Stage I. Telson essentially identical to Stage I MAXILLIPEDS.-Essentially identical to Stage I except segmented from sixth abdominal segment except exopodites offirst, second, and third maxil­ and bears 20 or 21 densely plumose setae. Uropods lipeds bear 5, 16, and 16 natatory setae, respec­ still enclosed. tively. STAGE III (MEGALOPA) FIRST PEREOPOD (FIGURE 2D).-Segme~ted; without exopodite; chela functional. Total length of Stage III 7.5 mm (range 7.4-7.6 mm; two specimens). Antennal spine of carapace SECOND PEREOPOD (FIGURE 2E).-Adult in larger and pterygostomian spine smaller than in shape; chela functional; ischiopodite articulates Stage II; no evidence of minute spinules along somewhatlaterally withbasipodite. No exopodite. anteroventral margin. Rostrum (Figure 3A) short; bears single tooth at base in addition to dorsal THIRD TO FIFTH PEREOPODS.-Similar to protuberance. Antennules similar in shape to Stage I except ischiopodite articulates somewhat adult; outerflagellum six-segmented; innerflagel­ laterally with meropodite and basipodite. lum five-segmented; peduncle three-segmented,

0.5 mm

FIGURE 3.-Stage III (megalopa) of Lebbeus groenlan­ dicus: A, carapace; B, telson. 0.5 mm 463 FISHERY BULLETIN: VOL. 76, NO.2 lateral spine ofproximal segment well developed. the exopodites nor the spines. My Stage I zoeae do Antennal flagellum with at least 30 segments; not bear supraorbital spines, the peduncle of the about four times length of scale. Mandibles with antennule is withoutjoints or a ventral spine, and unsegmented palps bearing four or five short there is no indication of the carpopodite of the teeth. Endopodite of maxillule reduced. Maxil­ second pereopod beingjointed; Stephensen's Stage lipeds shaped as in adult, exopodites reduced. Dac­ I zoeae bear supraorbital spines, the peduncle of tylopodites of first and second pereopods well the antennule is three-jointed and bears a distinct developed; carpopodite of second pereopod six­ ventral spine, and the carpopodite of the second (sometimes seven-) segmented. Lateral margins of pereopod is partially jointed. In addition, the pleopods fringed with setae; appendix internae chelae ofthe first and second pereopods are not as with minute cincinnuli. Posterolateral spines on well formed in my Stage I zoeae as they are in abdominal segments four and five remnant or Stephensen's Stage I zoeae. lacking. Telson (Figure 3B) rectangular in shape; Several of the morphological characteristics de­ bears two pairs of spines terminally and one pair scribed by Stephensen as pertaining to "Spiron­ laterally (one or two additional spines may occur tocaris-Iarva No. lA" are typical of later stage centrally on terminal margin). Uropods exposed; zoeae, a fact already noted by Pike and Williamson fully developed except transverse hinge not com­ (1961) in their discussion ofthe morphology ofthe plete. zoeae of L. polaris and which prompted them to suggest that Stephensen's zoeae were actually in COMPARISON OF LARVAL STAGES the second, or penultimate, zoeal stage. Even if WITH DESCRIPTIONS BY Stephensen was mistaken in identifying his zoeae OTHER AUTHORS as Stage I rather than Stage II, the morphological differences between my zoeae and his are too great Under the name "Spirontocaris-Iarva No. lA," to consider them identical species. My Stage II Stephensen (1935) included four specimens that zoeae bear spines on abdominal somites four and were morphologically identical to zoeae provi­ five and the telson is segmented from the sixth sionally identified by him as Stage I S. polaris abdominal somite, whereas Stephensen's zoeae do (= Lebbeus polaris (Sabine)) except that they dif­ not bearspines on abdominal somites four and five fered by lacking spines on abdominal segments and the telson is not segmented from the sixth four and five, exopodites on any pereopods, or free abdominal somite. Also, in my Stage II zoeae the uropods. He regarded these four zoeae as belong­ peduncle ofthe antennule does not bear a ventral ing to either Spirontocaris groenlandica (= L. spine and is unsegmented but in Stephensen's groenlandicus), S. gaimardii (= Eualus gaimar­ zoeae the peduncle bears a ventral spine and is dii (R. Milne Edwards), or S. spinus (Sowerby). segmented. Pike and Williamson (1961) have shown that the I have no further evidence on the identity of absence ofspines on abdominal segments four and Stephensen's "Spirontocaris-Iarva No. 1A." Ofthe five eliminates the zoeae from being either E. three members ofthe genus recorded from Green­ gaimardii or S. spinus. They agree with Stephen­ land waters, L. polaris, L. groenlandicus, and L. sen that his specimens of"Spirontocaris-larva No. microceros (cf. Holthuis 1947; Squires 1966), L. 1A" are closely allied to zoeae he tentatively de­ microceros was not recorded by Stephensen. Ap­ scribed earlier (Stephensen 1917, 1935) as S. parently it is rare and its larvae have not been polaris (= L. polaris). They suggest, therefore, described. Also, the advanced development of that Stephensen's "Spirontocaris-Iarva No. lA" Stephensen's "Spirontocaris-Iarva No. lA" makes probably belongs to the genus Lebbeus and spe­ it unlikely that it belongs to another genus ofthe cifically to L. groenlandicus. spirontocarid group (cf. Pike and Williamson Comparison of my zoeae of L. groenlandicus 1961). Apparently Stephensen's "Spirontocaris­ with the descriptions given by Stephensen for larva No. 1A" is either the zoea ofL. microceros or "Spirontocaris-Iarva No. 1A" shows that that ofanother species ofLebbeus not yet recorded "Spirontocaris-Iarva No. 1A" are not zoeae of L. from Greenland waters. groenlandicus. My Stage I zoeae bear remnant On the basis of descriptions of "Spirontocaris­ exopodites on the first and second pereopods and larva No. lA" by Stephensen (1935) and a late lateral spines on abdominal segments four and stage embryo ofHippolyte polaris (= L. polaris) by five, but Stephensen's Stage I zoeae bear neither Krl'lyer (1842), Pike and Williamson (1:961) 464 HA YNES: LEBBEUS GROENLANDICUS LARVAE

characterized larvae of the genus Lebbeus as hav­ HOLTHIUS, L. B. ing two (or three) zoeal stages, five-segmented 1947. The Decapoda ofthe Siboga Expedition. Part IX. The pereopods, and a small rostrum in Stage I, and Hippolytidae and Rhynchocinetidae collected by the Siboga and Snellius Expeditions with remarks on other species. pereopods without exopodites in the last zoeal Siboga Exped. 140, Monogr. 39a", 100 p. stage. My description oflarvae ofL. groenlandicus KR0YER. confirms the generic characteristics for Lebbeus 1842. Monografisk Fremstilling af Slaegten Hippolyte's larvae as given by Pike and Williamson. As noted nordiske Arter. Med Bidrag til Decapodernes Udvik­ lingshistorie. K. Dan. Vidensk. Selsk. Naturv. Math. by Pike and Williamson, however, larvae are de­ Alb. Kbh. 9:209-360. (This work has not been seen by the scribed for only a few species of hippolytids, in­ author.) cluding the genus Lebbeus, and further confirma­ . PIKE, R. B., AND D. I. WILLIAMSON. tion of the generic characteristics of the larvae is 1961. The larvae of Spirontocaris and related genera (De­ desirable. capoda, Hippolytidae). Crustaceana 2:187-208. SQUIRES, H. J. 1966. Distribution of decapod Crustacea in the northwest LITERATURE CITED Atlantic. Ser. Atlas Mar. Environ., Am. Geogr. Soc. Folio 12. HAYNES, E. STEPHENSEN, K. 1976. Description ofzoeae ofcoonstripe shrimp, Pandalus 1917. Zoogeographical investigation of certain fjords in hypsinotus, reared in the laboratory. Fish. Bull., U.S. Southern Greenland, with special reference to the Crus­ 74:323-342. tacea, Pycnogonida and Echinodermata, including a list of 1978. Description of larvae of the humpy shrimp, Pan­ Alcyonaria and Pisces. Medd. Grl'lnl. 53:229-378. dalus goniurus, reared in situ in Kachemak Bay, Alas­ 1935. Crustacea Decapoda. The Godthaab Expedition, ka. Fish. Bull., U.S. 76:235-248. 1928. Medd. Grllnl. 80:1-94.

465