Phylogeography on the rocks: The contribution of current and historical factors in shaping the genetic structure of Chthamalus montagui (Crustacea, Cirripedia)

The model marine broadcast-spawner barnacle Chthamalus montagui was investigated to understand its genetic structure and quantify levels of population divergence, and to make inference on historical demography in terms of time of divergence and changes in population size. We collected specimens from rocky shores of the north-east Atlantic Ocean (4 locations), Mediterranean Sea (8) and Black Sea (1). The 312 sequences 537 bp) of the mitochondrial cytochrome c oxidase I allowed to detect 130 haplotypes. High within-location genetic variability was recorded, with haplotype diversity ranging between h = 0.750 and 0.967. Parameters of genetic divergence, haplotype network and Bayesian assignment analysis were consistent in rejecting the hypothesis of panmixia. C. montagui is genetically structured in three geographically discrete populations, which corresponded to north-eastern Atlantic Ocean, western-central Mediterranean Sea, and Aegean Sea-Black Sea. These populations are separated by two main effective barriers to gene flow located at the Almeria-Oran Front and in correspondence of the Cyclades Islands. According to the 'isolation with migration' model, adjacent population pairs diverged during the early to middle Pleistocene transition, a period in which geological events provoked significant changes in the structure and composition of palaeocommunities. Mismatch distributions, neutrality tests and Bayesian skyline plots showed past population expansions, which started approximately in the Mindel-Riss interglacial, in which ecological conditions were favourable for temperate species and calcium-uptaking marine organisms

Multiple transgressions and slow evolution shape the phylogeographic pattern of the blind cave-dwelling shrimp Typhlocaris

Background: Aquatic subterranean species often exhibit disjunct distributions, with high level of endemism and small range, shaped by vicariance, limited dispersal, and evolutionary rates. We studied the disjunct biogeographic patterns of an endangered blind cave shrimp, Typhlocaris, and identified the geological and evolutionary processes that have shaped its divergence pattern. Methods: We collected Typlocaris specimens of three species ( T. galilea, T. ayyaloni, and T. salentina), originating from subterranean groundwater caves by the Mediterranean Sea, and used three mitochondrial genes (12S, 16S, cytochrome oxygnese subunit 1 (COI)) and four nuclear genes (18S, 28S, internal transcribed spacer, Histon 3) to infer their phylogenetic relationships. Using the radiometric dating of a geological formation (Bira) as a calibration node, we estimated the divergence times of the Typhlocaris species and the molecular evolution rates. Results: The multi-locus ML/Bayesian trees of the concatenated seven gene sequences showed that T. salentina (Italy) and T. ayyaloni (Israel) are sister species, both sister to T. galilea (Israel). The divergence time of T. ayyaloni and T. salentina from T. galilea was 7.0 Ma based on Bira calibration. The divergence time of T. ayyaloni from T. salentina was 5.7 (4.4-6.9) Ma according to COI, and 5.8 (3.5-7.2) Ma according to 16S. The computed interspecific evolutionary rates were 0.0077 substitutions/Myr for COI, and 0.0046 substitutions/Myr for 16S. Discussion: Two consecutive vicariant events have shaped the phylogeographic patterns of Typhlocaris species. First, T. galilea was tectonically isolated from its siblings in the Mediterranean Sea by the arching uplift of the central mountain range of Israel ca. seven Ma. Secondly, T. ayyaloni and T. salentina were stranded and separated by a marine transgression ca. six Ma, occurring just before the Messinian Salinity Crisis. Our estimated molecular evolution rates were in one order of magnitude lower than the rates of closely related crustaceans, as well as of other stygobiont species. We suggest that this slow evolution reflects the ecological conditions prevailing in the highly isolated subterranean water bodies inhabited by Typhlocaris

Occurrence of Solidobalanus auricoma (Cirripedia; Balanomorpha) in the Gulf of Elat (Red Sea)

The presence of Solidobalanus auricoma (Cirripedia; Balanoidea) in the Red Sea 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 Gulf through Malaysia, southeastern Australia, and northeastern New Zealand at depths of 27 to 320 m. This is its first record from the Red Sea. The present finding of S. auricoma in the Gulf of Elat (Aqaba) extends the boundaries of its geographic distribution farther west and north

Pyrgopsella Zullo 1867

Pyrgopsella Zullo 1867 Pyrgopsis Gruvel 1907 Pyrgopsella Zullo 1967 Diagnosis: Walls sub­conical, totally concrescent. Basis membranous with short peduncle. Opercular plates separate, scutum transversally elongated, tergum triangular. Type species: Pyrgopsella annandalei Gruvel 1907.Published as part of Achituv, Yair & Simon-Blecher, Noa, 2006, Pyrgopsella (Cirripedia: Balanomorpha: Pyrgomatidae) is not a sponge­inhabiting barnacle, pp. 29-42 in Zootaxa 1319 on page 31, DOI: 10.5281/zenodo.27355

Pyrgospongia Achituv & Simon-Blecher, 2006, gen. nov.

Pyrgospongia gen. nov. Diagnosis: Wall concrescent, thin, made of radiating rods connected by chitinous material, elliptical in outline; ribs on shell absent; heath absent. Basis membranous. Scutum and tergum not fused, scutum transversally elongated, tergum triangular. Type species: Pyrgopsella stellula Rosell, 1973. Etymology: From the Greek pyrgos (tower), found in the family name Pyrgomatidae of the coral­inhabiting barnacles, and the Latin (from Greek) spongia (sponge), referring to the host group. Remarks: Based on the morphology of the shell and the opercular valves, Ross & Newman (1973) suggested that Pyrgopsella annandalei is an offshot of the “ Savignium line” of pyrgomatids. Anderson (1992) suggested that P. annandalei is a specialized member of the line of Savignium crenatum (Sowerby). However, the opercular valves of our material, as well of the material depicted by Gruvel (1907), are closer in form to those of Trevathana dentata (Darwin); a tergal tooth and a thin, pointed, inward­projecting tooth located on the spur are characteristic of T. dentata but missing in Savignium crenatum. The position of Pyrgospongia is more ambiguous. The opercular valves, elongated scutum, and especially the tergum of Pyrgospongia stellula, without any sign of an internal tooth, appear to be more similar to those of a different pyrgomatid line comprising those species of Cantellius with transversally elongated scuta, such as C. brevitergum (Hiro) or C. transversalis (Nilsson­Cantell). It might be supposed that Pyrgospongia was derived from within Cantellius. On the other hand, being a sponge­inhabiting rather than coralinhabiting barnacle and having rather pleisomorphic opercular valves, the Philippine and Japanese P. stellula may not be a pyrgomatid at all. Molecular analysis using DNA sequences may shed light on this enigma.Published as part of Achituv, Yair & Simon-Blecher, Noa, 2006, Pyrgopsella (Cirripedia: Balanomorpha: Pyrgomatidae) is not a sponge­inhabiting barnacle, pp. 29-42 in Zootaxa 1319 on page 39, DOI: 10.5281/zenodo.27355

Pyrgopsella youngi Achituv & Simon-Blecher, 2006, sp. nov.

Pyrgopsella youngi sp. nov. Achituv (Figs 1–6) Material examined: Fifteen specimens, six with soft parts, were obtained from a partly bleached colony of Symphyllia radians Milne­Edwards and Haime, found in a tropical fish shop in Israel. The source of the coral was Sulawesi, Indonesia, exact location unknown. The barnacles were suspended in the coral tissue and easily detached from the coral. Part of the host coral (catalogue number RMNH Coel. 33023) and the barnacle holotype (RMNH C. 2602: two slides with cirri and mouth parts, SEM stubs of shell and opercular valves) and two paratypes (RMNH C 2603 and RMNH C 2604: shell and opercular valves, and SEM stubs with shell and opercular valves, respectively) have been deposited in the RMNH. The other part of the host coral (catalogue number TAU Co 32349), the remaining paratypes, shell and opercular valves of four specimens prepared for SEM analysis, slides of two specimens with cirri and mouth parts, are deposited in the TAU (catalogue number TAU Ar 27804). Two specimens were used for DNA extraction. Etymology: The specific epithet honors the late Paulo Young in recognition of his contribution to our knowledge of cirripede biology. Diagnosis: Wall concrescent, ribs on shell absent. Basis, membranous, with inferior end calcareous. Scutum and tergum not fused, scutum transversally elongated, tergum triangular with internally directed tooth. Description: Shell (Fig. 1 C, 2 A, 3 A, B) white but nearly transparent, concrescent, low­conical, thin, oval, maximum carino­rostral diameter 8 mm, maximum lateral diameter 4 mm. Radiating rib absent; shallow, concentric growth lines on outer surface. Shell tubiferous, tubes wide, penetrating 2 / 3 of shell; inner shell white; sheath with concentric growth lines, reaching margins of shell; short spines on sheath perimeter located at margins of lateral septa, number of spines equal to number of septa, with no denticulation on margins of septa. Orifice oval, located at carinal end of shell; carinorostral diameter 1 / 3 carino­rostral diameter. Tergoscutal flaps banded purple on white cream ground. Basis (Fig. 1 B) membranous, sometimes with basal part elongated and peduncle­like, basal tip connected to small, white, calcareous disc, latter usually attached to septum of coral calyx (Fig. 3 A,B). Scutum and tergum white, separate. Scutum (Fig. 2 C, E) transversally elongated, thin, total length (including tergal tooth) ~five times maximal width; basal margins slightly sinusoidal; adductor muscle pit shallow, distinct; adductor ridge small, low; lateral depressor muscle pit indistinct; width of tergal tooth ~ 1 / 2 width tergal margin, located closer to occuludent margin then to basal margin; growth lines on outer surface; narrow, oblique furrow beginning at tergal margin halfway between tergal tooth and occludent margin, ending near occludent basal angle. Tergum (Fig. 2 D, F) triangular, growth lines on outer surface; short, spur barely distinct; external groove running from middle of scutal margin to basi­carinal apex; small notch in middle of scutal margin; basi­scutal angle pointed; thin, pointed, inward­projecting tooth on spur; notch in middle of carinal margin; inner side with depression accommoding tergal tooth of scutum; growth lines visible inside depression. Labrum (Fig. 4 A, E) rounded with deep median notch, very short, fine setae on margins and outer surface; palps (Fig. 4 A) elongate, oval with upper margins straight, long setae on outer surface, longest at distal end, inner margins with shorter setae. Mandible (Fig. 4 C) with five teeth along cutting edge, distances between teeth unequal, upper two teeth occupying 1 / 2 length cutting edge, second and fourth teeth bifid, lower angle with short spines; face and margins of mandible bearing setae, lower margins with combs, conical spines on lower angle. Maxillule (Fig. 4 D) with cutting edge unnotched, armed with row of ~ten unequal spines, tuft of smaller, hair­like setae at distal angle; setae scattered along upper part of maxillule, row of dense setae on lower part; some combs of hairs on face of maxillule projecting beyond cutting edge. Maxilla (Fig. 4 B) oval­elongate, long setae distally, short setae on inner side, few simple setae on upper and lower margins, distal surface with two rows of short, sharp setae; lower angle with two to three spines. Number of articles of cirri of three randomly selected individuals given in Table 1. Cirrus I (Fig. 5 A) highly setose; anterior ramus ~twice length of posterior ramus; proximal articles of anterior ramus and all segments of posterior ramus with protuberances bearing setae. Cirrus II (Fig. 5 B) with rami ~equal length; articles slightly protuberant, bearing long setae. Cirrus III with anterior ramus somewhat longer than posterior ramus; articles with protuberances bearing tufts of long, plumose setae (Fig. 5 C). Cirri IV (Fig. 5 D) to VI (Fig. 6 A) long and slender; each article with four pairs of setae of different lengths arranged along anterior margin, generally each pair accompanied by short, proximal seta; setae at distal end of articles longer, ~three times article width; two or three short setae at posterior articulation of each article (Fig. 6 B); basal articles with a row of pairs of setae. Penis (Fig. 6 A) long, annulated, scattered thin setae along length; distal end modified, more slender then rest of penis, not annulated, few setae (Fig. 6 C). Remarks: The barnacles from Symphyllia radians differ from those described by Gruvel (1907) in two striking aspects: the tergum as depicted and described by Gruvel carries a truncate internal tooth, whereas the inward projecting tooth found in our specimens is thin and pointed and located on the short spur. The second difference concerns the distal end of the penis. In Pyrgopsella annandalei it is ornamented with short spines, which are missing in our material, and the modified end of the penis in Gruvel’s material is pear­like, while in the present material this part of the penis is elongate. On the basis of these differences, we conclude that our material is not referable to P. annandalei, but should be assigned to a new species, named by us as P. youngi. In most coral­barnacles the shell is overgrown by the coral and calcareous material is deposited on the barnacle surface. In many cases the coral forms spines or perturbations over the surface of the shell plates and in some cases even an entire corallite. However, in Pyrgopsella, soft coral tissue covers the shell with no deposition of calcareous material over it and the barnacle comes to be suspended in the coral tissue. A more remarkable difference between Pyrgopsella and other pyrgomatids is the membranous basis with a vestigial, calcareous part. In all other coral­inhabiting barnacles the basis is calcareous and, in most cases, it is cone­like and tapered, embedded in the coral skeleton. A particular feature of the coral Symphyllia radians is the thick, fleshy tissue in which the barnacles are embedded. This thick tissue supports the barnacles, thus making a calcareous basis superfluous. Rosell (1973; 1975) reported the existence of a barnacle similar to Pyrgopsella annandalei embedded in a sponge collected in the Philippines. He described this barnacle as a new species, P. stellula. Grygier (1992) reported the occurrence of P. stellula in Japan, extending the geographical distribution of this species, and noted an additional species of Pyrgopsella in a sponge from Indonesia. Rosell (1973; 1975) suggested that the genus Pyrgopsella consists of sponge inhabiting barnacles and assumed that the host of P. annandalei was also a sponge. This view has been widely accepted, but our new find suggests that Pyrgopsella is a coral­barnacle and that Gruvel’s species, which is similar to ours, most probably was detached somehow from a coral. It is surprising that for a century, ever since its description by Gruvel (1907), Pyrgopsella was never reported from corals. Both P. annandalei and P. youngi are rather large pyrgomatids, reaching a carino­rostral diameter of 8 mm, and can hardly be missed. The lack of records until now can be explained by the way in which coral­inhabiting barnacles are studied. Mostly, the barnacles are extracted from dry corals kept in museum collections. Moreover, since identification of corals is based on the structure of the calices and septa, in many cases biologists remove the coral tissue using household bleach or an alkali solution, whereby Pyrgopsella with its membranous basis would be lost. Examination of the dried and bleached skeleton of the coral from which the present sample was removed showed no conspicuous evidence of the presence of the barnacles. Only detection of the vestigial calcareous basis could show that barnacles had formerly lived on the coral. In the collection of Naturalis, Leiden, there is a colony of Symphyllia radiance from S.W. Sulawesi (RMNH Coel 24745) with vestigial calcareous basis. Our new findings underline the importance of examining live corals, or corals preserved with their tissue, for the presence of barnacles, a technique that might reveal additional kinds of coral­inhabiting barnacle. The main feature that Pyrgopsella stellula (Figs. 1 C; 7 A, B), P. annandalei (Pl. 2 Fig. 7 b in Gruvel, 1907) and P. youngi (Fig. 2 A, B) share is a single­plate shell, but otherwise it is difficult to accept that these species all belong to the same genus. In addition to being symbionts of hosts from different phyla, there are striking morphological differences between these species. Pyrgopsella stellula lacks the peduncle that is present in P. annandalei (Pl. 2 Fig. 7 a in Gruvel, 1907) and in P. youngi (Fig. 1 B, D). In our material, and one may perhaps assume also in P. annandalei, the basal tip of the peduncle anchors the barnacle to the septa of a coral calyx. The shell of P. stellula is thin and flexible and only partly calcified (Fig. 7 A, B) The calcareous area is in the form of thin spokes radiating from the operculum and a flexible membrane connects those spokes. In P. youngi and P. annandalei, the shell is totally calcified. In P. stellula there is no distinct sheath, whereas it is distinct in P. annandalei and P. youngi (Fig. 2 B). The sickle­shaped, barbed bristles and star­like spines (Fig. 7 G) that are arranged in concentric rows over the outer shell membrane in P. stellula are absent in P. youngi. The shape of the opercular valves of P. stellula (Fig. 7 C, D, E, F) and those of P. annandalei (Pl. 2 Figs 9,10 in Gruvel, 1907) and P. youngi (Fig. 2 C, D, E, F) are different. The scutum of P. stellula is elongated, rather big and lacks a tergal tooth (Fig. 7 D); in situ it projects beyond the rostral margins of the shell (Fig. 1 D; see also Rosell 1975: Fig. 2 c). The tergum is missing the internal tooth that is found in the other species of Pyrgopsella (Figs 2 D, 7 C). Cirrus III of P. stellula carries small conical spines that are not found in P. youngi and cirrus IV of P. stellula is armed with diagonally arranged conical spines (Rosell 1975: Fig. 2 n) that are absent in P. youngi. On the basis of these differences we suggest that P. youngi sp. nov. and P. annandalei do not share the same evolutionary line as P. stellula and that the latter should be assigned to a different genus. Therefore, we propose a new genus, Pyrgospongia, to accommodate the sponge­inhabiting pyrgomatid Pyrgospongia stellula (Rosell 1973).Published as part of Achituv, Yair & Simon-Blecher, Noa, 2006, Pyrgopsella (Cirripedia: Balanomorpha: Pyrgomatidae) is not a sponge­inhabiting barnacle, pp. 29-42 in Zootaxa 1319 on pages 32-38, DOI: 10.5281/zenodo.27355

Different settlement strategies explain intertidal zonation of barnacles in the Eastern Mediterranean

The Mediterranean mid-littoral zone is inhabited by two sympatric chthamalid barnacles: Chthamalus stellatus and Euraphia depressa, C. stellatus extends from the high midtidal zone, above the algal belt, to the supra-littoral fringe, E. depressa is restricted to the uppermost intertidal levels in wave-beaten places and to cryptic habitats lower on the shore within the belt of C. stellatus. Previous studies have suggested that the reason for the fragmented distribution pattern of E. depressa is competitive displacement by the sympatric C. stellatus, following random settlement. This hypothesis is in agreement with the common model of zonation suggested by Connell that lower distribution limits are determined by biotic factors (competition and predation), while upper limits are set by physical factors. It is hard to test the validity of this model for this barnacle pair since the early ontogenetic stages of the species are morphologically indistinguishable, hindering our ability to understand distribution processes. Using 16S mtDNA as a genetic marker in a multiplex PCR system, cyprids and spats were individually identified. Settlement and recruitment rates were assessed using settlement plates, and the effect of post-settlement processes was tested with transplantation of settlers between zones. Results showed different strategies in each species: settlement of E. depressa was habitat-specific, while settlement of C. stellatus was random. Shifting individuals of C. stellatus to the high and cryptic zones resulted in high mortality; however, exposing juveniles of E. depressa that settled in artificially cryptic low shore habitat to C. stellatus presence had no effect on their survival. These finding do not agree with the formerly suggested hypothesis that zonation is mainly determined by post-settlement factors, and that the interspecies boundary is determined by interspecific competition, implying that competition model cannot be adapted to Mediterranean intertidal zonation and that other models, dominated by physical enforcement and pre-settlement recruitment-limiting factors, may prevail in this ecosystem

Boxer crabs induce asexual reproduction of their associated sea anemones by splitting and intraspecific theft

Crabs of the genus Lybia have the remarkable habit of holding a sea anemone in each of their claws. This partnership appears to be obligate, at least on the part of the crab. The present study focuses on Lybia leptochelis from the Red Sea holding anemones of the genus Alicia (family Aliciidae). These anemones have not been found free living, only in association with L. leptochelis. In an attempt to understand how the crabs acquire them, we conducted a series of behavioral experiments and molecular analyses. Laboratory observations showed that the removal of one anemone from a crab induces a “splitting” behavior, whereby the crab tears the remaining anemone into two similar parts, resulting in a complete anemone in each claw after regeneration. Furthermore, when two crabs, one holding anemones and one lacking them, are confronted, the crabs fight, almost always leading to the “theft” of a complete anemone or anemone fragment by the crab without them. Following this, crabs “split” their lone anemone into two. Individuals of Alicia sp. removed from freshly collected L. leptochelis were used for DNA analysis. By employing AFLP (Fluorescence Amplified Fragments Length Polymorphism) it was shown that each pair of anemones from a given crab is genetically identical. Furthermore, there is genetic identity between most pairs of anemone held by different crabs, with the others showing slight genetic differences. This is a unique case in which one animal induces asexual reproduction of another, consequently also affecting its genetic diversity