Comparison of Larval and Adult Stages of dalli and Chthamalus fissus (Cirripedia: Thoracica) Author(s): Kristina M. Miller, Sally M. Blower, Dennis Hedgecock, Jonathan Roughgarden Source: Journal of Biology, Vol. 9, No. 2 (May, 1989), pp. 242-256 Published by: The Crustacean Society Stable URL: http://www.jstor.org/stable/1548504 Accessed: 16/02/2009 12:15

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http://www.jstor.org JOURNALOF CRUSTACEANBIOLOGY, 9(2): 242-256, 1989

COMPARISON OF LARVAL AND ADULT STAGES OF CHTHAMALUS DALLI AND CHTHAMALUS FISSUS (CIRRIPEDIA: THORACICA)

Kristina M. Miller, Sally M. Blower, Dennis Hedgecock, and Jonathan Roughgarden

ABSTRACT Adult and larval forms of Chthamalusdalli and Chthamalusfissusare comparedand distin- guishingcharacteristics described. Adult forms of these differin malate dehydrogenase enzyme allozymes, in the setae of the second cirrus,and in shell characteristics.Larval forms are morphologicallyidentical, although larvae culturedfrom adults collectedat MontereyBay differin size at naupliarstages I-III and at the cyprid stage.

Chthamalus dalli Pilsbry is a common the MDH allozymes, by the setae of the northern inhabiting the high in- second cirrus (W.A. Newman, personal tertidalzone from Alaska to San Diego and communication), and by a combination of northernJapan. ChthamalusfissusDarwin, externalfeatures. The larvaeof these species a close relative of C. dalli, is a southern appear to be morphologicallyidentical. barnacleinhabiting the high intertidalzone MATERIALSAND METHODS from San Francisco to Baja California. In the between San Francisco and San Mass CulturingTechniques.- Ripe eggswere obtained region from freshlycollected adult barnaclesand placed in 1 Luis Obispo, these species areabundant and um-filteredsea water.Newly hatchedlarvae were col- can be found in combined densities reach- lected by pipettingthem from areasof maximumlight ing 70,000 per m2in the same high intertidal intensity created by a point light source. The larvae band on the shore Newman and Abbott, were then placed in a 4-1 glass jar at a density of one (cf. larva per 2 ml sea water.The jars, each of which con- 1980). tainedfresh 1 ,m-filtered sea waterat 33.5 ppt salinity, The community structure of barnacle werekept at either 13?or 18?Cand mildly aeratedwith populationshas been studied extensively in filteredair from a 1/3hp oil-freepump. The larvaewere the studies fo- fed the Tahitianstrain of Isochrysisgalbanaat a density past twenty-fiveyears. Early x cused on the roles of and of 1 105cells per ml. competition pre- The waterin the jars was changedon alternatedays dation on adult in structuring by pouringthe contents through100-gm filters,wash- benthic communities (Connell, 1961a, b; ing the larvae in the filters (continuallyimmersed in Southward, 1976). Recent work has ex- water)with 1 gm-filteredsea water,placing the larvae the role of settlementin benthiccom- in small bowls, and pipettingactive larvaeinto beakers plored with fresh 1 um-filteredsea water.Subsamples of these munities (Gains and Roughgarden, 1985; larvae were preservedfor later use in 3% Formalin. Roughgardenet al., 1985). Currentstudies Larvaethat were inactive at the bottom of the bowls are examining factors that determine the were presumedunhealthy or dead. Such larvae were settlement rate such as currents and pre- usuallyalive but not feedingand were more prone to dation in the et bacterialinfection than the active larvae.To minimize plankton (Roughgarden al., the risk of bacterialcontamination, the unhealthylar- 1987; Roughgardenet al., 1988). Such work vae were discarded. requiresidentification of barnaclelarvae in Larvaeof Chthamalusare particularlyprone to be- mixed-species plankton samples. The pres- coming caught on debris due to their fine setulation ent was conducted to examine the and small size. Therefore,to rearthese larvaesuccess- study fully, all particulatecontaminates coming from the air morphologicaldifferences between the lar- or filterbags were removed regularlyand the alga was vae of C. fissus, not previously described, monitoredcarefully for evidence of clumping. and C. dalli, previously described from Analysis of Larvae.- Formalin-preservedlarvae were Russian materialby Korn and Osyannikova examinedunder a compoundmicroscope with a com- (1979). Electrophoreticand morphological bined phase contrast/Nomarskiattachment. Size was with shell determinedwith an ocular micrometer.Total length characterstogether distinguishing was measuredfrom the frontalmargin to the tip of the featuresare presented.We found that adult dorsalthoracic spine. Cephalicshield lengthwas mea- C. dalli and C. fissus can be separated by sured from its frontal marginto its posteriorborder,

242 MILLER ETAL.: COMPARISON OF LARVAE AND ADULTS OF CHTHAMALUS DALLI AND C. FISSUS 243 d A.: :j B

?i?2i; X r r- 4t

*, '. A

;? :eT

...I

:r- :t' is

t?1 j? ?

100 jum I I Fig. 1. Photographs of the characteristic setae of the second cirrus of adult Chthamalus dalli and C. fissus. Setae of C. dalli (A) are finely bipectinate, while setae of C. fissus (B) are coarsely bipectinate and have a pair of basal guards (see arrow).

and its width measured behind the frontolateral horns. dalli appear finely bipectinate (Fig. 1A), In addition, drawings were made with a camera lucida while the setae of C. are bi- attachment. At least 50 larvae of each species at each fissus coarsely stage were examined for the drawings. pectinate and have a pair of basal guards this setal characteristic to Adult Descriptions. -Adult C. dalli and C. fissus were (Fig. 1B). Using collected from the field to examine and to photograph separate the species initially, electrophore- the characteristic differences in the second cirrus, a sis showed that C. fissus and C. dalli can be feature noted by W. A. Newman (personal commu- clearly distinguished on the basis of their nication). In addition, shell features that might be used malate to separate the species in the field were quantified. dehydrogenase (MDH) enzymes (Fig. 2A). Chthamalus has two loci encoding Electrophoresis. -Adult barnacles, Chthamalus spp., malate and were collected, dissected, and identified to species by dehydrogenase (Mdh- Mdh-2, the second cirrus characteristic. Sixty barnacles of each see Figs. 2A, B); both enzymes are dimers, species (the sample of C. fissus included all three oper- so that the single-banded phenotypes rep- cular morphs) were then placed in individual wells in resent homozygotes and triple-banded phe- a and covered with a few of 0.5M plastic tray drops notypes represent Tris-HCL buffer, pH 7.1. Each barnacle was homog- heterozygotes. Although enized within the well with a glass pestle and the bar- both Mdh-1 and Mdh-2 are highly poly- nacle extract was absorbed with a filter-paper wick. morphic loci, the two species have different Horizontal starch-gel electrophoresis and enzyme- alleles (further work with larger samples has staining were carried out on the samples as described led to the identification of at least six alleles The by Hedgecock (1979). samples were then stained at each locus and un- for malate dehydrogenase enzyme. (Blower Hedgecock, published observations)). The difference in RESULTS the alleles is particularly clear for the Mdh- I Adult Descriptions locus (Fig. 2A), and served to confirm the Under microscopic observation (400 x), species classification using the setae on the the setae on the second cirri of Chthamalus second cirri. 244 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 9, NO. 2, 1989

A

Mdh-2 (113) Mdh-2 - * (114) Mdh-1 (108) (100) Mdh-1 --

C. daill C. fissus B

Mdh-2 *9::000000,00 0 }Mdh-2 { 0 ??0 S@0 000 ???*@ go??0* 0 0.... 0 0 0 Mdh-1 { 00 910,99 0 000000 }Mdh-1 i C.C dallida C. fissus Fig. 2. Results of gel electrophoresis on Chthamalus dalli and C. fissus. A. Horizontal starch gels stained for malate dehydrogenase (MDH) enzyme. The characteristic migration distances are different for C. fissus and C. dalli and hence this assay can be used for species identification. The single bands at both the Mdh-1 and Mdh-2 loci of both species indicates homozygosity. B. A drawing of a horizontal starch gel stained for malate dehy- drogenase (MDH) enzyme. Both species are extremely polymorphic at both loci (Mdh-l and Mdh-2). Both heterozygotes (3 bands) and homozygotes (1 band) at each locus are shown.

External characters allow an approximate and a dark brown band at the base are C. distinction of C. dalli from C. fissus to be fissus (Fig. 3C-E). However, we found that made in the field. We have found that the 12% of adult Chthamalus spp. with oval two species can be identified in the field with orifices possessed a mixture of these char- approximately 90% accuracy, measured acteristics (19/156 of C. dalli and C. fissus against the setal characteristics, using a combined; Table 1). In C. dalli, 4% of the combination of shell features including adults had brown bases and 2% possessed shape of orifice, color at the base, and rel- corrugated shells. Alternatively, of adults of ative degree of corrugation of the shell (see C. fissus, 6% had even coloration and 31% Table 1 and Fig. 3). The orifice of C. dalli had relatively smooth shells (individuals is always broad and oval (Fig. 3A, B), while with slit or overhanging orifices showed that of C. fissus varies from slitlike, over- slightly less variability). In the case of mixed hanging, or oval (Pilsbry, 1916; Fig. 3C-E). characteristics, the second cirrus should be Therefore, individuals with slitlike or over- examined before a definite identification can hanging orifices can be immediately clas- be made. sified as C. fissus. Moreover, individuals with oval orifices that have smooth shells Larval Descriptions with even, light brown coloration are C. dal- In the laboratory, C. dalli and C. fissus li (Fig. 3A, B); those with corrugated shells developed at approximately the same rate MILLER ETAL.: COMPARISON OF LARVAE AND ADULTS OF CHTHAMALUS DALLI AND C. FISSUS 245 when rearedat 18?C(Fig. 4) and both species Table 1. Externalfeatures of adult Chthamalusdalli took 17-18 days for the first cyprids to ap- and C.fissus. Percentagesand sample numbers(N) are shown. For each charactertype, the total number of pear. They spent an average of 3-4 days at individuals examined is equal to the sum of the N's. each of the six naupliarstages, excluding the Color and rugositycharacters were scored only on in- first which lasted less than a day. At the dividuals with oval orifices.Color indicates the color lower temperature(13?C), however, the de- of the basal regionof the shell, while rugosityindicates time to for C. dalli was the roughnessof the base of the shell. The symbol O-H velopmental cyprid stands for overhanging. extendedby about five days (to 22-23 days), while C. fissus ceased to develop past the Percentage third stage. Character C. dalli N C. fissus N The nauplii of C. dalli and C. fissus have the same features of other Orifice morphological Oval 100 122 29 36 species so far described in the genus Slit 0 0 61 76 Chthamalus (C. malayensis Pilsbry (see O-H 0 0 10 12 Karande and Thomas, 1976); C. fragilis Color Darwin (see Lang, 1979); C. stellatus Poli Even 96 116 6 2 (see Bassindale, 1936; Daniel, 1958)), and Brown 4 6 94 34 in a species of Euraphia (E. aestuariiStub- Rugosity bings, originally classified in the genus Smooth 98 119 31 11 Chthamalus; see Sandison, 1967). In ad- Corrugated 2 3 69 25 dition, the present descriptions of C. dalli and C. fissus are similar to Korn and Os- yannikova's (1979) descriptionof larvae of considered to be close to the stem of the C. dalli with the exception of four setae and sessile barnacles(Darwin, 1854). slightdifferences in generalshape. The shape All of these characteristicscan be used in of the larvae describedin the present paper making distinctions between nauplii of differsfrom that describedby Korn and Os- Chthamalus and nauplii of other species, yannikova (1979) in that the cephalic shield but by farthe easiestdistinction is theirsmall in naupliarstages I-V is slightlyless round- relative size at all stages. With this distinc- ed, the anterior portion of the labrum is tion alone, a separation can be made be- rounded,and the anteriorand posteriorends tween most larvaeof Chthamalusand those of the cyprid carapaceare less pointed. of other barnaclespecies thus far described In general, the convex dorsal shield of on the CaliforniaCoast, with the exception nauplii of Chthamalus is round, with the of Pollicipespolymerus (see Discussion). width nearly equalingthe length. When the In this study, no morphological differ- cephalic shield differentiatesfrom the trunk ences were found between the larvae of C. in stages IV-VI, it has no paired posterior dalli and C.fissus. The only possible distin- spines as often found in other genera. The guishingcharacteristic (at least in the vicin- labrum of nauplii of Chthamalusis unilo- ity of Monterey Bay) is the size of the two bate and the sequenceof spine formationin species at same stages, althoughsize should successivestages is similarin all species thus be used as a characterwith caution (Barnes, far described. The successive formation of 1953). At 18?C,Chthamalus dalli startsout spines on the thorax is also similar in all in the first stage as the larger of the two species of Chthamalus described. The de- species at 248 ? 4 jm in length and 138 ? creasingratio of the dorsal thoracicspine to 3 ,umin width (Table 2). Chthamalusfissus the trunkis similarin species of Chthamalus is only slightly smaller at 206 ? 3 ,um x and Euraphia (Sandison, 1967). Further- 124 ? 5 ium.These size differencescontinue more, nauplii of Chthamalusgenerally have to diverge through the third stage, after highlysetulose appendages, often with many which the larvae of both species become plumose or featherysetae. Sandison (1967) indistinguishablein size. However, at the cited the presenceof"hispid" setae as unique cypridstage, the larvaeof C.fissus are slight- to the family .However, these ly largerthan those of C. dalli (493 ? 3 gm setae have since been found by Lewis (1975) x 246 ? 3 gm versus 448 ? 10 Am x 229 on the naupliarappendages of Pollicipespo- ? 5 gAm;Table 2). Sizes of larvae grown at lymerus Sowerby, a pedunculate barnacle 13?Care similar (Table 2). Fig. 3. Photographsshowing a rangeof externalshell featuresof Chthamalusdalli (rows A, B) and C. fissus (rows C-E). An oval orificialopening, smooth shell, and even colorationat the base of the shell are featuresof

246 C. dalli C. fissus Day11 Day Day11

W Day5 Day15 Day5 Day15 C, 100. ^5 12 14 2 I-- 80- Z 60- 40- cc 20- IL 0 Day7 Day17 2

I II mIV V C I 1nmIV v I c I IImIIV VI C I I mI vIv c STAGE Fig. 4. Developmental timetable for Chthamalus dalli and C. fissus. Histograms indicate the percentage of jars with stages present on the indicated day. Since jars often contain more than one stage on a given day, these percentages do not add up to 100, nor do they give the actual proportion of stages present for a given day. They indicate only the presence of a given stage on a given day. Numbers in the upper left corner (under day) indicate the number of jars examined.

C. dalli (A, B). Alternatively, C. fissus is characterized by corrugation of the shell, a dark brown band at the base of the shell, and variability in the shape of the orifice including oval (C), slit (D), and overhanging (E) forms. Scale bar equals 2 mm.

247 248 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 9, NO. 2, 1989

Table 2. Sizes of larvae of Chthamalus dalli and C. issus grown at 18? and 13?C. Total length was measured from the frontal margin to the tip of the dorsal thoracic spine. Cephalic shield length was measured from the frontal margin to the posterior border of the cephalic shield. Width was measured as the maximum cephalic shield width. Means are given, with standard errors in parentheses.

Chthamalus dalli Chthamalus fissus Tempera- Carapace Carapace Stage ture Total length Width length N Total length Width length N I 18?C 248 (4) 138 (3) - 22 206 (3) 124 (5) - 22 II 18?C 309 (3) 175 (3) - 13 271(3) 156 (7) - 5 13?C 318(2) 191(2) - 35 264 (2) 162 (2) - 31 III 18?C 361(5) 219(6) - 7 305 (2) 193 (3) - 13 13?C 353 (3) 209 (2) - 16 309 (3) 194 (3) - 16 IV 18?C 383 (2) 257 (3) 285 (3) 20 346 (7) 248 (3) 270 (4) 26 13?C 379 (3) 250 (3) 293 (2) 15 - - - - V 18?C 414(3) 303 (3) 348 (3) 24 416(5) 316(6) 348 (4) 20 13?C 421(7) 307 (4) 357 (5) 5 - - - - VI 18?C 470 (10) 354 (8) 404 (8) 14 465 (7) 380 (4) 423 (4) 27 C 18?C 448 (10) 229 (5) - 7 493 (3) 246 (3) - 14

Since the larvae of C. dalli and C. issus of this paper. The ventral views of the larvae are similar in all other aspects except size, are illustrated in Fig. 5, while lateral views their morphological features will be de- of the posterior portion of the body are pre- scribed together throughout the remainder sented in Fig. 6. In addition, drawings of

I

II III

IV

V C 100pm VI Fig. 5. Body forms of larvae of Chthamalus dalli and C. fissus. The six naupliar stages, indicated by Roman numerals, are drawn from their ventral aspect, while the cyprid stage, indicated by "C," is a lateral view. The spines on the thorax are labeled, in order of appearance, with Arabic numerals. The abbreviations Thor and Abd labeled on stage V stand for Thorax and Abdomen, respectively. MILLER ETAL.: COMPARISON OF LARVAE AND ADULTS OF CHTHAMALUS DALLI AND C. FISSUS 249

I II III IV

I?"^ 1 e .- \\\

1 2 I 100 jJm

V VI

Fig. 6. Lateral view of the posterior portion of the body of the six naupliar stages of Chthamalus dalli and C. fissus. Spines on the trunk are labeled in order of appearance with Arabic numerals. Naupliar stages are indicated with Roman numerals. Abbreviations include: Abd = Abdomen, Thor = Thorax, DTS = Dorsal Thoracic Spine, FR = Furcal Rami, and mx = Maxillae.

the antennules (Fig. 7), the antennae (Fig. row of five to seven spinules on its lower 8), and the mandibles (Fig. 9) are referred margin. The dorsal thoracic spine becomes to in the following descriptions. A presen- longer than the trunk, giving these a ratio tation of the setation formulae (following of 1.2:1. There is one pair of spines 17 ,um Newman, 1965) is given in Table 3. long with spinules on the lower margin as Stage I larvae are wineglass-shaped with well as three rows of fine spinules on the horns 30 um long (Fig. 5). The dorsal tho- thorax (Fig. 5). The dorsal thoracic spine racic spine and trunk are approximately and furcal rami are covered with small spines equal in length at 24 Aum.The labrum is from this stage forward. In addition, many smooth and rounded at the distal margin, of the setae of the appendages develop fine the setae on the appendages are all simple, setules, giving them a plumose or feathery and no frontal filaments are apparent at this appearance in this and subsequent stages stage. The exopodite of the antenna has only (Figs. 7-9). The exopodite of the antenna five simple setae (Fig. 8), while that of the receives two more setae, but the antennule mandible shows four (Fig. 9). The antennule still has no preaxial setae at this stage. setation formula is 00042110 (Fig. 7, Table Stage III larvae appear around the third 3). day and are characterized by a loss of three Stage II nauplii appear sometime during to five spines on the pubescent labrum, leav- the first day after the hatching of stage I ing two spines 11 ,m long on the postero- nauplii. The characteristic feature of stage lateral margin (Fig. 5). It should be noted II is the seven to nine spines 8.5 ,m long that, in some instances, the larvae of C. fis- on the lower margin of the pubescent la- sus retain a fine row of spines 2 ,m long brum (Fig. 5). At this stage, the broad and between the paired 11-m spines. The nau- somewhat rounded cephalic shield has a fine plii in stage III are otherwise similar to those 250 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 9, NO. 2, 1989

I II III

100 um I I Fig. 7. Antennules of the nauplii of Chthamalus dalli and C. fissus. Naupliar stages are indicated by Roman numerals.

in stage II in that the cephalic shield has yet of fine spinules on the thorax (Fig. 5). The to differentiate from the body, there are still dorsal thoracic spine and furcal rami are five pairs of spines 17 ,m long with spinules covered with small spines from this stage on the lower margin as well as three rows forward. The exopodite of the antenna re- MILLER ETAL.: COMPARISON OF LARVAE AND ADULTS OF CHTHAMALUS DALLI AND C. FISSUS 251

I 100 umr I Fig. 8. Antennae of the nauplii of Chthamalusdalli and C. fissus. Naupliar stages are indicatedby Roman numerals. ceives two more setae, but the antennule 5, 6). The abdominal spines 32 ,m long, the still has no preaxial setae at this stage. third pair, located directly above the furcal Stage IV individuals appear on the sev- rami (46 ,um), are the most prominent of enth day (Fig. 4). In stage IV, the cephalic the three pairs of trunk spines, while the shield further differentiates from the body, second pair of spines 10 ,um long, located becoming more shieldlike with a smooth anterior to the first and more towards the lower margin. The dorsal thoracic spine is center of the thorax, are less visible. In ad- approximately equal in length to the trunk dition, the thorax possesses six rows of fine (90 ,um each). The characteristic feature of spinules and appears more segmented. From this stage is the appearance of two more this stage forward, the highly pubescent la- pairs of trunk spines (one thoracic, one ab- brum possesses two pairs of spines, the first dominal) with lower margin spinules (Figs. on the lower margin, the second on the lat- 252 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 9, NO. 2, 1989

100 .um I

Fig. 9. Mandibles of the nauplii of Chthamalus dalli and C. fissus. Naupliar stages are indicated by Roman numerals.

eral margin. The exopodite of the antenna phalic shield becomes much rounder in ap- of stage IV individuals has nine setae, while pearance and the dorsal thoracic spine is the endopodite of both the antenna and the slightly shorter than the trunk with a ratio mandible receive two to three new setae of 0.7: 1. The exopodite of the antenna has (Figs. 8, 9). The antennule bears two preax- 1 1 setae in this stage, while that of the man- ial setae (Fig. 7). dible bears six setae (previously 5). In ad- Stage V individuals appear between days dition, the endopodites of both the man- nine (C. fissus) to thirteen (C. dalli; Fig. 4). dible and the antenna receive more simple The trunk in stage V is much more prom- setae and there is a third preaxial seta on inent and segmented than in previous stages. the antennule (Figs. 7-9). The abdominal portion bears a fourth pair Stage VI larvae appear on days 13 and 15 of 14-,um spines located between the first (Fig. 4). The trunk in this stage bulges and and third pair (Fig. 5). In addition, a fifth protrudes forward, and is clearly segmented pair of trunk spines, on the thoracic portion, with six new paired spines spread out in a is visible next to the first (Fig. 6). The ce- V-shaped pattern on the ventral surface of MILLER ETAL.: COMPARISON OF LARVAE AND ADULTS OF CHTHAMALUS DALLI AND C. FISSUS 253 the thorax (Figs. 5, 6). These are the pre- cursors of the six pairs of swimming limbs of the cyprid larva, which in turn become ,3 the cirri of the adult. All other spines except 0 the third and fourth are lost. Late stage VI nauplii possess paired compound lateral eyes u alongside the unpaired median eye present 01 0o in all stages. The cephalic shield is broad 0 Cd) V) r and even rounder than in previous stages w PU P U4P U 1) C) and the horns, which become harder to dis- II I Cd) C) C) A a4 - Cl Cl ( / 2 Cd Ci ( tinguish, are directed sideways. The exopo- Cen C#) Cen C dite of the antenna of stage VI individuals cce bears 12 setae and the antennule gains one postaxial seta (Figs. 7, 8). B- The cyprid larvae appear on days 17 and 18 (Fig. 4). The cyprids retain both the me- 0 dian and lateral eyes (Fig. 5). The dorsal U .i curvature of the carapace is greater than the * I0a ventral curvature, and the posterior margin is broad and evenly curved, while the an- terior margin is pointed. 'o 0. DISCUSSION CC) ) Cd) Cd) rC')A Chthamalidae are a taxonomically diffi- cult group with many species being recog- 0 o a o nized, and while most tend to be allopatric TUt.1aa 41 or of Chthamalus are fre- L; allotopic, species I I quently sympatric over part of their range c Cd pa p CdACd) Cd (Southward, 1976; Hedgecock, 1979; Dan- 0 PUPUPU do et al., 1979; Dando and Southward, 1980, r. PUPUPU 1981; Achituv and Mizrahi, 1987). The ge- nus Chthamalus underwent a apparently 01 rapid radiation in the late Cenozoic (Stanley and Newman, 1980), and often the only re- liable characteristics are separating species dO a U 0 P4 0 P-4 0 found internally, by dissecting reproductive 0 "I' f) ) - t- 00 l..""*l c\ \ cc or feeding structures. An example is the morphologically different setae of the sec- [-,0., ond cirri of C. dalli and C. fissus (W. A. Newman, personal communication). Using m C#3 (C #v) the MDH allozyme analysis, the cirral char- acteristic separating the species was vali- s -iF0 dated with total the m &^ at Pc Fi (3H reliability. Moreover, cO C d) Cd() ^ specimens for this study were collected at Cd CQ) the same site Marine m yA0 maCd a CQaCd) (Hopkins Station), 0 ) Z va ..a *a which indicates that the species differences c. -i. .o 11 v ciq(. between C. dalli and C. fissus are observed u (/ at sites where both are sympatric. However, C3k 1 when species identifications must be made on live in the field, a combination of external characteristics must be em- Cd It ployed. The shape of the orifice of Chtha- -"r r % malus fissus, for example, can be slitlike (originally classified as C. microtretus Corn- wall, 1937), overhanging, or oval. The pro- 254 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 9, NO. 2, 1989

portions of these three morphs can be spa- found variations in egg sizes and showed a tially variable in the field, and possibly decrease in egg size from north to south related to environmental conditions. For along both coasts of the North Atlantic. Pa- example, Lively (1986) found that the ov- tel and Crisp (1960) examined differences erhanging(bent) form of Chthamalusani- in egg size due to temperatureand showed sopoma Pilsbrywas an environmentallyin- that egg size was larger at lower tempera- duced developmental response elicited by tures (hence, in the north) possibly due to the presenceof a carnivorousgastropod. He slower development rates. The findings in furtherdemonstrated that the overhanging this study support the notion of slower de- form of this barnaclewas more resistentto velopment rates at lower temperaturesand predatoryattack by these snails. A similar similar development rates of southern and situation could be happeningin the case of northernbarnacle larvae grown at the same C. fissus. Alternatively, the orifice of temperature(within their temperaturetol- Chthamalus dalli is always oval (Pilsbry, erancerange). However, no intraspecificdif- 1916; Newman and Abbott, 1980). There- ferencesin size wereshown for naupliigrown fore, with the orifice characteristicalone, at low (13?C)or high (18?C)temperatures. many, but not all C. fissus can be identified. In addition, the sizes of C. dalli measured For those individuals with an oval orifice, in this study coincided with those measured the presence of a dark brown band at the by Korn and Ovsyannikova (1979) in the base of the shell and a high degree of cor- sea of Japan. However, since sizes of larvae rugationof the shell are good indicatorsfor of C. fissus and C. dalli were measured on C. fissus. However, since these shell features a limited number of laboratory-reared are measuredrelative to C. dalli, and there broods collected in MontereyBay, and dif- can be variabilityamong individuals, up to ferencesin size have not been substantiated 10% of Chthamalus spp. cannot be posi- by planktonic comparisons, the size crite- tively identifiedusing even all three of these rion for separatingthe speciesshould be used external characteristics. with caution. Chthamalus dalli and C. fissus are even The known larvae of other sessile bar- more similar in their larval forms. No mor- nacles on the central coast of California phological differenceswere detected in the (north of Point Conception), namely Bala- larvae of the two species (except in about nus glandula Darwin, B. crenatus Bru- 5% of the stage II nauplii where the spines guiere,B. nubilusDarwin, and Semibalanus on the labrumdiffered). However, slight size cariosus Pallas, are 100-200 tumgreater in divergencebetween the two species in nau- lengththan C. dalli and C.fissus (Herz, 1933; pliar stages I-III and in the cyprid larvae Barnes and Barnes, 1959; Standing, 1981; was apparent. In this study, the nauplii of Branscomband Vedder, 1982; Brown and C. dalli were larger than those of C. fissus Roughgarden, 1985). They also differ in in the first three stages, but due to a faster having paired dorsal spines on the cephalic growth rate at 18?C(in size, not stage), C. shield in stages IV-VI, a trilobate labrum, fissus surpassedC. dalli in size at the cyprid lack of hispid and featherysetae, and a nar- stage. In addition, both species developed rower shape of their cephalic shield. Tetra- (in stage) at similar rates at 18?C,a tem- clita, represented by T. squamosa rubescens peraturewithin the range both species ex- Darwin on the central Californiacoast, fol- perience.However, C. dalli developed more lows a similar pattern(Barnes and Achituv, slowlyat a temperatureof 13?Cand the more 1981). southernbarnacle, C. fissus, did not develop A more difficult distinction is found be- at this colder temperature.The inability of tween chthamalidsand lepadidswhen com- larvae of C. fissus to grow at temperatures paring C. fissus and C. dalli to Pollicipes of 13?Cor less could be a factor affecting polymerus(noted by Lewis, 1975). The nau- the northernmostlimit of their distribution. plii of these barnaclesdo not differ mark- Barnes (1953) found that there was vari- edly in size (althoughP. polymerusis closer ation in cyprid size within a single species to the size of C. dalli in stages I-III than C. and subsequentlyargued that size is not a fissus)and are similar in their lack of paired valid characteristicwith which to separate posterior spines on their cephalic shield, species in the plankton. Crisp (1959) also presence of a unilobate labrum, and pres- MILLER ETAL.: COMPARISON OF LARVAE AND ADULTS OF CHTHAMALUS DALLI AND C. FISSUS 255 ence of hispid and feathery setae. In addi- Barnes, H. 1953. Size variations in the cyprids of tion, the setation of their appendagesis re- some common barnacles.-Journal of the Marine Biological Association of the United Kingdom 32: markablysimilar. Even the increasingratio 297-304. of the trunk to dorsal thoracic spines with ,and M. Barnes. 1959. The naupliar stages of stage is similar. The only noticeable differ- Balanus nubilus Darwin. -Canadian Journal of Zo- ences between these species are the patterns ology 37: 15-23. of spine formation on the labrum and the Barnes, M. and Y. Achituv. 1981. The nauplius stages of the cirripede Tetraclita squamosa rufotincta Pils- overall goblet shape of P. polymerus. bry.-Journal of Experimental Marine Biology and The similarity between larvae of pollici- Ecology 54: 149-165. poids and chthamaloids accords with the Bassindale, R. 1936. The developmental stages of similarityof the adultstage. As earlyas 1854, three English barnacles, Balanus balanoides (Linn.), resemblances the (Poli), and Verruca stroemia Darwin noted between (O. F. Muller). -Proceedings of the Zoological So- shell of chthamaloid and the capitulum of ciety of London 106: 57-74. pollicipoid adults and hypothesized a tran- Branscomb, E. S., and K. Vedder. 1982. A descrip- sitional link. Other similarities exist be- tion of the naupliar stages of the barnacles Balanus tween these such as a thick and glandula Darwin, Balanus cariosus Pallas, and Bal- families, anus crenatus Bruguiere (Cirripedia, Thoracica).- bullate labrum and the use of the first and Crustaceana 42: 83-95. second cirri for cleaning and transferring Brown, S. K., and J. Roughgarden. 1985. Growth, food to the mouth. These similarities sup- morphology, and laboratory culture of larvae of Bal- port the phylogenetic hypothesis that the anus glandula (Cirripedia: Thoracica).-Journal of Crustacean Biology 5: 574-590. Chthamalidaedescended from a pollicipoid Connell, J. H. 196 la. Effects of competition, preda- lepadomorph, possibly with an intermedi- tion by Thais lapillus, and other factors on natural ate brachylepadomorphan-like ancestor, populations of the barnacle Balanus balanoides. - and that it is morphologically as well as Ecological Monographs 31: 61-104. older than the Balanidae 196 lb. The influence of interspecific com- stratigraphically petition and other factors on the distribution of the (Zullo, 1963; Newman and Ross, 1976; barnacle Chthamalus stellatus.- Ecology 42: 710- Newman, 1987). 723. In conclusion, this study has confirmed Cornwall, I. E. 1937. A new species of baracle from that C. dalli and C. fissus are two distinct the coast of California.-Annals and Magazine of elec- Natural History, series 10, 20: 232-235. species. The adults can be separated Crisp, D. J. 1959. The rate of development of Bal- trophoretically, by malate dehydrogenase anus balanoides (L.) embryos in vitro.-Journal of enzyme allozymes, and morphologicallyby Ecology 28: 119-132. the setae on the second cirri and by certain Dando, P. R., and A. J. Southward. 1980. A new shell features. The could species of Chthamalus (Crustacea:Cirripedia) char- larvae, however, acterized by enzyme electrophoresis and shell mor- not be separated morphologically,but the phology: with a revision of other species of Chtha- size differencesin naupliarstages I-III and malus from the western shores of the Atlantic the cyprid stage may be useful in making Ocean.-Journal of the Marine Biological Associa- distinctionsin the of tion of the United Kingdom 60: 787-831. vicinity MontereyBay. ,and . 1981. Existence of "Atlantic" Furtherwork is now in progressusing im- and "Mediterranean" forms of Chthamalus mon- munologicalassays to separatethese species tagui (Crustacea: Cirripedia) in the western Medi- in the plankton. terranean.-Marine Biology Letters 2: 239-248. , and D. J. Crisp. 1979. Enzyme vari- ACKNOWLEDGEMENTS ation in Chthamalus montagui (Crustacea: Cirripe- dia): evidence for the presence of C. montagui in the We gratefully acknowledge the photographic skill of Adriatic.-Journal of the Marine Biological Asso- C. Patton, discussions and technical assistance by S. ciation of the United Kingdom 59: 307-320. Gaines, B. Miller, G. Ruiz, R. Saunders, and F. Sly. Daniel, A. 1958. The development and metamor- In addition, we thank Granite Canyon Laboratory for phosis of three species of sessile barnacles.--Journal supplying algal cultures. Support was provided by the of the Madras University 28,B: 23-47. Division of Ecological Research, Department of En- Darwin, C. 1854. A monograph on the sub-class Cir- ergy (Contract EV10108). ripedia with figures of all the species. The Balanidae, Verrucidae, etc.-Ray Society, London. Pp. 1-684. LITERATURECITED Gaines, S. D., and J. Roughgarden. 1985. Larval set- tlement rate: a leading determinant of structure in Achituv, Y., and L. Mizrahi. 1987. Allozyme differ- an ecological community of the marine intertidal ences between tidal levels in Tetraclita squamosa zone. - Proceedings of the National Academy of Sci- Pilsbry from the Red Sea. -Journal of Experimental ence 82: 3707-3111. Marine Biology and Ecology 108: 181-189. Hedgecock, D. 1979. Biochemical genetic variation 256 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 9, NO. 2, 1989

and evidence of speciationin Chthamalusbarnacles species.- Bulletinof the United StatesNational Mu- of the tropical eastern Pacific Ocean.-Marine Bi- seum 93: 1-366. ology 54: 207-214. Roughgarden,J., S. D. Gaines,and S. W. Pacala. 1987. Herz, L. E. 1933. The morphologyof the laterstages Supply side ecology: the role of physical transport of Balanus crenatusBruguiere. -Biological Bulletin processes.- In: P. Giller and J. Gee, eds., Organi- 64: 432-442. zation of communities:past and present. Pp. 459- Karande,A. A., and M. K. Thomas. 1976. The larvae 486. Proceedingsof the BritishEcology Society Sym- of the inter-tidalbarnacle Chthamalusmalayensis posium, Aberystwyth,Wales. Pilsbry.-Proceedings of the IndianAcademy of Sci- ,and H. Possingham. 1988. Recruit- ence 83B: 210-219. ment dynamicsin complexlife cycles.-Science 241: Korn, 0. M., and I. I. Ovsyannikova. 1979. Larval 1460-1466. development of the barnacle Chthamalusdalli.-- ,Y. Iwasa,and C. Baxter. 1985. Demographic Soviet Journalof MarineBiology 5: 423-430. theory for an open marine population with space- Lang, W. H. 1979. Larval development of shallow limited recruitment.-Ecology 66: 54-67. water barnaclesof the Carolinas(Cirripedia: Tho- Sandison,E. E. 1967. The naupliarstages of Balanus racica) with keys to naupliar stages.-National pallidusstutsburi Darwin and Chthamalusaestuarii Oceanographicand Atmospheric Administration, Stubbings(Cirripedia Thoracica).-Crustaceana 13: TechnicalReport National Marine Fisheries Service 161-174. Circular421: 1-23. Southward,A. J. 1976. On the taxonomicstatus and Lewis, C. A. 1975. Development of the gooseneck distributionof Chthamalusstellatus (Cirripedia) in barnaclePollicipes polymerus (Cirripedia: Lepado- the north-eastAtlantic region: with a key to the com- morpha):fertilization through settlement. -Marine mon intertidalbarnacles of Britain.-Journal of the Biology 32: 141-153. Marine BiologicalAssociation of the United King- Lively, C. M. 1986. Predator-inducedshell dimor- dom 56: 1007-1028. phism in the acorn barnacle Chthamalus aniso- Standing,J. D. 1981. Commoninshore barnacle cyp- poma.-Evolution 40: 232-242. rids of the Oregonianfaunal province (Crustacea: Newman, W. A. 1965. Prospectuson larvalcirriped Cirripedia).-Proceedings of the Biological Society setation formulae.-Crustaceana9: 51-56. of Washington93: 1184-1203. 1987. Evolutionofcirripedes and theirmajor Stanley,S. M., and W. A. Newman. 1980. Compet- groups.-In: A. J. Southward,ed., Barnaclebiology. itive exclusion in evolutionarytime: the case of the Pp. 3-42. A. A. Balkema,Rotterdam. acorn barnacles.-Paleobiology6: 173-183. ,and D. P. Abbott. 1980. Cirripedia:the bar- Zullo, V. A. 1963. A classificationand phylogenyof nacles.-In: R. H. Morris, D. P. Abbott, and E. C. the Chthamalidae (Cirripedia: Thoracica).-Pro- Haderlie,text contributors,Intertidal invertebrates ceedings of the XVI InternationalCongress of Zo- of California.Pp. 504-535. StanfordUniversity Press, ology, Washington,D.C. 1: 190. Stanford,California. , and A. Ross. 1976. Revision of the balano- RECEIVED:19 April 1988. morph barnacles; including a catalogue of the ACCEPTED:19 November 1988. species.-Memoirs of the San Diego Societyof Nat- ural History 9: 1-108. Addresses:(KMM and JR) HopkinsMarine Station, Patel, B., and D. J. Crisp. 1960. The influence of StanfordUniversity, PacificGrove, California93950; temperatureon the breedingand the molting activ- (SMB) Parasite Epidemiology Research Group, De- ities of some warm-waterspecies of operculatebar- partmentof Pure and Applied Biology, ImperialCol- nacles.-Journal of the Marine BiologicalAssocia- lege, University of London, London SW7 2BB, En- tion of the United Kingdom 39: 667-680. gland;(DH) University of California,Bodega Marine Pilsbry,H. A. 1916. The sessilebarnacles (Cirripedia) Laboratory,P.O. Box 247, Bodega Bay, California, contained in the collections of the U.S. National 94923. Museum;including a monographof the American