ISRAEL JOURNAL OF ZOOLOGY, Vol. 48, 2002, pp. 33–42

E-mail: achity@mail.biu.ac.ilAccepted November 2001.

OCCURRENCE OF SOLIDOBALANUS AURICOMA (CIRRIPEDIA;BALANOMORPHA) IN THE GULF OF ELAT (RED SEA)

YAIR ACHITUV

Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 52900, Israel

ABSTRACT

The presence of Solidobalanus auricoma (Cirripedia; Balanoidea) in the RedSea at a depth of 112 m is reported, and its morphology is described.S. auricoma is a relatively deep water barnacle known from the Persian Gulfthrough Malaysia, southeastern Australia, and northeastern New Zealand atdepths of 27 to 320 m. This is its first record from the Red Sea. The presentfinding of S. auricoma in the Gulf of Elat (Aqaba) extends the boundaries ofits geographic distribution farther west and north.

INTRODUCTION

The cirripede fauna of the Red Sea has received only limited scientific attention. Thereare few publications on the free-living cirripedes and even the list of species is far fromcomplete. Newman (1967) described a new chthamalid, Tetrachthamalus oblitteratus,based on specimens collected in the Gulf of Elat (Aqaba). Safriel and Lipkin (1964) andAchituv (1972) studied the zonation of rocky shores in Elat, mentioning T. oblitteratusand Tetraclita rufotincta. Achituv and Safriel (1980) described a new chthamalid,Chthamalus barnesi, from intertidal rocks of the Red Sea. Achituv (1984) described thecirripede of the hard bottom mangal of Sinai, adding Balanus amphitrite, which occursalso in lagoons, ports, and sea water fish ponds in the northern part of the Gulf of Elat, tothe above-mentioned barnacles. Ross (1999) reviewed the systematic position ofTetraclita from Elat and reported two new species, T. achituvi and T. barnesorum. Itshould be noted that the Red Sea symbiotic cirripedes are hardly known, and it is onlyrecently (Ilan et al., 1999) that the sponge-inhabiting barnacles in the Red Sea havebegun to receive scientific attention.

In June 1993 the German scientific submersible Jago retrieved two bottles coveredwith cirripedes from a depth of 112 m. These bottles had been immersed at that depthseven years earlier to serve as underwater markers. Upon examination, the barnaclesappeared to be Solidobalanus auricoma, a species not yet known from the Red Sea andnot found in any scientific collection in Israel.

34 Y. ACHITUV Isr. J. Zool.

Solidobalanus (Balanus) auricoma (Hoek, 1913)Figs. 3–6

Synonymy listed by Newman and Ross (1976) Solidobalanus (Balanus) auricoma.

MATERIAL EXAMINED

Over one hundred dried specimens on two glass bottles and about twenty specimens,fixed in ethanol, attached to the piece of rope that anchored the bottles (Fig. 1), collectedJune 1993, at 112 m depth off the H. Steinitz Marine Laboratory, Elat, Red Sea (29°28′N34°58′E). The barnacles were scattered all over the bottles, with small specimensattached to the walls of larger ones, as well as on their scuta. The material was dividedinto two samples and deposited at the Hebrew University of Jerusalem ZoologicalCollection (HUJ-Cirr219) and Tel Aviv University Zoological Museum (AR 27788 andAR 27789). The rostro-carinal diameter of specimens in two randomly chosen squaresof 3 × 3 cm was measured using vernier calipers and rounded to the nearest millimeter.Size distribution of the barnacles is presented in Fig. 2.

DESCRIPTION

Shell truncated cone (Fig. 3A), maximum carino-rostral diameter 14 mm (Fig. 2).Orifice diamond-shaped, (Fig. 3B), maximal carino-rostral diameter 8 mm. Ratio between

Fig. 1. One of two bottles covered with Solidobalanusauricoma recovered from the Red Sea (depth 112 m) offElat. Note the presence of small barnacles (arrow) onshells of bigger animals. Tel Aviv University ZoologicalMuseum (AR 27788).

Vol. 48, 2002 SOLIDOBLANUS AURICOMA IN THE RED SEA 35

02

46

81012

14

1618

20

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Rostrocarinal diameter (mm)

No.

of s

peci

men

s

Fig 2. Size distribution of Solidobalanus auricoma from Elat, Red Sea.

Fig. 3. Solidobalanus auricoma: SEM micrographs of shell and opercular valves. A—side view ofa whole specimen showing growth ridges on alae of carina and latera. B—opercular aperture andvalves in situ showing epidermal hairs along occludent margins. C—outer view of scutum andtergum. Note the epidermal hairs along occludent margins and at the apices of both plates, shortand grooved spur of tergum. D—inner view of scutum and tergum with crests for carinal depressormuscles. Scale bars: A = 1 mm; B–D = 0.5 mm.

36 Y. ACHITUV Isr. J. Zool.

orifice diameter and carino-rostral diameter ≈0.6. Wall compartments solid. Shell whitewith pink dots or strips. Radii developed with growth lines parallel to base. Exposed partof alae with growth lines similar to that seen in radii. Basis calcareous, without tubes butradially grooved.

Scutum (Fig. 3C,D) triangular, occuldent margins longer than lateral, long, but notconspicuous articular ridge. A line of red dots along occuldent margins of scuta. Tergum(Fig. 3C,D) with short spur protruding beyond basiscutal angle. Externally there aregrowth lines; a shallow, but conspicuous, groove along the spur, 4–7 crests for carinaldepressor muscles at the basicarinal angle. Epidermal hairs along occludent edges ofboth scuta and terga, and mainly at apices (Fig. 3B–D).

Trophi (Fig. 4): Labrum (Fig. 4E,F) almost straight, divided by a moderate fissure, onboth sides of the fissure three to four stout teeth, teeth sometimes bifid (Fig. 4E). Palps:(Fig. 4B), elongated oval, upper margins straight, long setae on outer surface, longestsetae on distal end, inner margins with shorter setae. Mandible (Fig. 4A) with 4 teeth,

Fig. 4. Solidobalanus auricoma: Photomicrographs of trophi. A—mandible, B—palp, C—maxillae,D—maxillule, E,F—labrum. Scale bars: A–F = 100 µ.

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first one the biggest; second one located in the middle of the mandible, at the lower tipone or two spines. Short setae on surface parallel to cutting edge, setae outcrop from thecutting edge in the gap between the first and the second tooth. Few long setae at the distalpart of the mandible. Maxillule: (Fig. 3D) small and shallow notch below two upperstrong spines, group of setae arranges as a small brush in it. Cutting edge armed withabout ten smaller spines, arranged in a row. A brush of smaller, hair-like setae at thedistal angle of maxilla. Some setae scattered along the upper part of the maxillules, a rowof dense setae at the lower part. Some setae on the face of maxillule project beyond thecutting edge. Maxilla (Fig. 4C) elongated oval long setae on inner side.

Cirri: number of articles of cirri is given in Table 1. Number of articles depends onsize of barnacle, data given in table are of counts of randomly chosen barnacles.

Table 1Cirral counts of Solidobalanus auricoma Hoek 1913 from the Gulf of Elat (Aqaba); number ofarticles of anterior (A) and posterior (P) rami. + indicates a broken ramus. For comparison, cirral

counts of Hoek (1913) and Foster (1978) are presented

C–Rdiameter Cirrus I II III IV V VImm A P A P A P A P A P A P

4 Left 10–6 6–8 9–10 18+–20 20–8+ 18+–24Right 10–6 7–8 10–10 20–18+ 22–26 26–24

6.5 Left 14–7 10–8 11–9 18–19 19–20 21–20Right 13–7 9–8 12–12 18–18 21–20 21–21

7 Left 13–7 10–9 13–12 20–22 21–24 24–24Right 11–7 10–10 12–12 22–20 24–24 25–23

7 Left 12–7 9–8 12–11 21+–26 – 26–25Right 11–7 9–8 12–11 19–22 23–24 26–24

7.5 Left 13–8 9–10 12–13 26–22 25–25+ 23–24Right + –9 9–9 12–13 26–19 23–26 24–28

10 Left 13–7 9–9 13–12 21–23 26–26 27–29Right 14–8 10–10 12–12 22–22 26–25 27–29

Hoek (1913) 10–6 6–7 9–8 15–13 – 18–17

Foster (1978)2.2 8–6 7–7 9–9 12–13 15–16 16–17

2.5 10–6 7–7 9–8 13–15 – 17–18

6.5 15–8 10–10 10+–10 21–21 20–21 22–23

16 15–10 11–11 15–14 21–22 22–23 24–23

38 Y. ACHITUV Isr. J. Zool.

Fig. 5. Solidobalanus auricoma: Photomicrographs of cirri. A—cirrus I; B—cirrus II; C—cirrusIII; D—part of cirrus IV; E—distal end of penis; F—basal region of penis with basidorsal horn.Scale bars: A–D = 100 µ; E = 250 µ; F = 50 µ.

Cirrus I: (Fig. 5A) highly setose, anterior ramus about twice length of posterior.Proximal segments of anterior ramus and all segments of posterior ramus with protuber-ances bearing setae. Cirrus II: (Fig. 5B) rami of more or less equal length. Segmentsslightly protuberant, bear long setae. Cirrus III: (Fig. 5C) outer ramus somewhat longerthan inner ramus, segments with protuberances that bear tufts of long setae (Fig. 6A), onprotuberances short lateral denticles, not always conspicuous. Denticles on proximalsegments of posterior ramus more prominent. Setae plumose. Examination of denticleswith SEM reveals that on proximal segments there are several short stout denticles,while on the more distal segments the spines are gradually replaced by combs of variabledenticles (Fig. 6B–D).

Cirri IV–VI: long and slender, five pairs of setae of different length arranged alonganterior margins of each segment, distal one is the longer, about five times article width,at posterior articulation of each segment one to two pairs of setae, usually one long andshort pair (Fig. 5D). A row of pair of setae on basis.

Penis: (Fig. 5E) long, annulated, thin setae scattered along the penis, density of setaeincreases toward distal end, tip with a tuft of setae. A prominent basidorsal horn withminute setae (Fig. 5F).

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DISCUSSION

Our material was identified as Solidobalanus auricoma. The specimens exhibit thediagnostic characters of this species: The solid poreless parietes, calcareous basis, thewhite and pink coloration of the wall plates, the epidermal hairs on the scuta and terga,and the lateral denticles on the segments of the rami of cirrus III are informative andunmistakable (Hoek, 1913; Pilsbry, 1916). Cirral counts are higher than those found byHoek (1913) and by Foster (1978) (Table 1). This may be related to the size of thespecimens. Southward (1995) mentioned that in S. fallax the number of articles dependson age. The specimens examined by Hoek (1913) were small, up to 2.5 mm rostro-carinal diameter, two of the specimens examined by Foster (1978) were rather small (2.2and 2.5 mm), and the other two were bigger, 6.5 and 16 mm, even though the number ofarticles was smaller than that of the Red Sea specimens.

Solidobalanus auricoma is a relatively deep water barnacle known from the PersianGulf through Malaysia, southeast Australia, and northeastern New Zealand (Fig. 7), atdepths of 27 to 320 m (Hoek, 1913; Broch, 1922, 1931; Nillson-Cantell, 1938; Newman

Fig. 6. Solidobalanus auricoma: A—Photomicrograph of part of cirrus III showing denticles.B–D—SEM micrographs of segments of cirrus II showing spines and combs. Scale bars: A = 100 µ;B–D = 10 µ.

40 Y. ACHITUV Isr. J. Zool.

and Ross, 1976; Foster, 1978; Jones et al., 1990). The present finding of S. auricoma inthe Gulf of Elat extends the boundaries of its geographic distribution farther west andnorth.

Recently, Southward (1995) found the warm-water Solidobalanus fallax in theEnglish Channel. He raised several possibilities for the discovery of this barnacle in thiswell-studied area. One possibility is that due to its resemblance to Balanus crenatus,S. fallax was overlooked and regarded as the former. Another possibility is that thepresence of S. fallax indicates a rise in sea temperature and the invasion of warm-waterspecies into cooler areas. However, the case of the discovery of S. auricoma in the RedSea is different, and cannot be linked either to a rise in sea temperature or to confusionwith another species. The presence is not an episodic event. The high number ofbarnacles found on the bottles indicates that S. auricoma is most probably common onhard substrata at that depth. The size distribution of the barnacles, ranging from 2 to 14

Fig. 7. Known geographic distribution of Solidobalanus auricoma, 1. Elat, Red Sea; 112 m(present study). 2. Persian Gulf; 27–303 m (Nillson-Cantell, 1938). 3. Moluccas; 27–90 m (Hoek,1913) & Ambon; 50–260 m (Broch, 1931). 4. North and North West Coast, Australia; sublittoral-deep (Jones et al., 1990). 5. South West, sublittoral-deep (Jones et al., 1990). 6. Bass Strait,Australia; 183–293 m (Broch, 1922) sublittoral-deep (Jones et al., 1990). 7. South East, Australia;sublittoral-deep (Jones et al., 1990). 8. New Zealand, North Island; 62–376 m (Foster, 1978).

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mm (Fig. 2), shows that settlement occurred more than once. Moreover small barnacleswere found on the shells and on the opercular valves of bigger ones (Fig. 1), indicatingthe occurrence of more than one recruitment event. The occurrence of animals of a widesize range suggests that this depth of the Gulf of Elat hosts a population of S. auricomathat is the origin of the samples found on the bottles retrieved from this depth. Thepresence of S. auricoma in the Red Sea shows the Indo-West-Pacific or Indo-Malayanaffinities of the Red Sea fauna. The absence of samples of S. auricoma from the Red Seain scientific collections does not necessarily indicate its rarity in the Red Sea, but ratherour lack of knowledge of the deep-sea fauna of this area. This lack emphasizes the needfor further study of the deep sea.

ACKNOWLEDGMENTS

Thanks are due to Dr. H. Fricke for collection of the samples of Solidobalanus during adive off Jago. Dr. D. Jones of the Western Australian Museum, Perth, Western Austra-lia, examined samples and confirmed their identification.

REFERENCES

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Achituv, Y. 1984. Cirripedes of the mangal ecosystem with emphasis on the hard bottom mangalof Sinai. In: Por, F.D., Dor, I., eds. Hydrobiology of the mangal. Dr W. Junk, The Hague, pp.71–78.

Achituv, Y., Safriel, U.N. 1980. A new Chthamalus (Crustacea: Cirripedia) from intertidal rocksof the Red Sea. Isr. J. Zool. 29: 99–109.

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Hoek, P.P.C. 1913. The Cirripedia of the Siboga expedition B. Cirripedia sessilia. Siboga Exped.Monogr. 31b: 129–235

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Jones D.S., Anderson, J.T., Anderson, D.T. 1990. Checklist of the Australian Cirripedia. Tech.Rep. Aust. Mus. 3:1–38.

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