Boltenia yossiloya Shenkar & Lambert 2010, n. sp.

Boltenia yossiloya n. sp.

Figs. 2–6

Material examined: Israel, Eilat, Gulf of Aqaba (Fig.1 29°30' N, 34°56' E). Holotype: AS25420, paratype: AS 25231, The National Collections of Natural History at Tel Aviv University, Israel.

External appearance. Individuals have a somewhat spherical body with long siphons, up to 3 cm in diameter. The test is thick and hard with embedded sand, shell fragments and rubble, grayish in living specimens (Fig. 2). The tunic is unusually thin on both left and right sides of the body of the holotype because it was in the middle of a clump of other stolidobranchs and tightly adherent to them, with only the siphons and upper part of the body extending above the clump.

Internal appearance. Both siphons are long, with 4 lobes, and directed anteriorly. The body wall is tightly attached to the whitish tunic lining. The bright orange–red siphons retain their color in formalin. The body musculature is well developed, the predominant pattern consisting of strong circular muscles around the siphons and body wall, overlying numerous wide longitudinal muscles covering the entire body wall (Fig. 3A, 3B). About 37 longitudinal muscle bands originate from each siphon and extend ventrally and posteriorly, while numerous bands circle the base of each siphon. The longitudinal muscles cross each other and interweave over the body forming a meshwork; posteriorly there are also numerous narrower muscles also interweaving to form a third irregular layer of musculature (Fig. 3C).

There are about 20 branchial tentacles sparsely branched in two orders (Fig. 3D); there are no atrial tentacles. A large velum is present at the base of both siphons and the siphonal lining is thick, white and irregularly ridged (Fig. 3E), without any siphonal spines. The stigmata, diagnostic of the genus, are transversely oriented in longitudinal rows and the longitudinal vessels cross them (Fig. 3F). The branchial sac has six high folds on each side with 12–21 longitudinal vessels on the folds and 4–10 between the folds. The branchial formula of the holotype specimen (approximately 3.2 cm in width) is:

DL 5(20)8(21)8(16)9(16)6(16)6(12)5 E Left side

E 5(18)8(20)9(17)9(20)10(18)5(16)4 DL Right side

Paratype specimen (3 cm in width) is:

DL 4(17)4(24)6(22)8(19)8(17)5(12)4 E

The dorsal lamina is composed of numerous short languets; the dorsal tubercle is C-shaped opening to the left (Fig. 4A) inside a large V with brown pigments (in preserved material) in the peribranchial area. The stomach is short, with numerous longitudinal folds. The liver, about equal in size to the stomach, consists of a large mass of glandular yellowish tubules (Fig. 4B). On the secondary intestinal curve there are 2 very small endocarps, one on the outer side and one on the inner side opposite the liver. The short rectum is attached directly and firmly to the branchial sac (as in B. transversaria). The anus is somewhat flattened into two halves, the rim with about 12 very small lobes and 4 slightly larger lobes (Fig. 5). There is one gonad on each side comprised of 5 large overlapping blocks of tissue closely but narrowly connected (Fig. 6). The left gonad lies diagonally above the secondary gut loop with the last lobe close to the rectum (Figs. 3A, 6). The right gonad lies diagonal to the ventral line (Fig. 3B). A short oviduct and sperm duct, with small brown pigmented spots on them, terminate from the distal end of each gonad, opening close together near the base of the atrial siphon.

Remarks. This new species has some characters in common with Boltenia transversaria (Sluiter, 1904), from Indonesian waters: the body tightly attached to the tunic (not actually a valid feature distinguishing species), the number of branchial folds, and the dorsal lamina description. However, the branchial formulas are quite different. According to Sluiter (1904), his B. transversaria type specimen of 3 cm (similar in size to our B. yossiloya type) had 5 broad branchial folds per side each with 10 longitudinal vessels and a smaller fold on each side of the endostyle with only 4 longitudinal vessels, and 4–7 vessels between the folds, a much different and smaller formula than for B. yossiloya. The formulas given by Tokioka (1960) and Nishikawa (1991) are not really comparable because the animals they examined were much smaller.

Boltenia yossiloya has strongly developed musculature (Fig. 3A, B, C) similar to Tokioka’s description but in contrast to Sluiter’s remark on the weak musculature of B. transversaria except on the siphons. B. yossiloya has a C-shaped dorsal tubercle opening to the left in contrast to the longitudinally ovate slit described for B. transversaria by Sluiter (1904), Herdman (1906) and Tokioka (1960); Nishikawa (1991) did not include a description of this character. Boltenia echinata (Linnaeus, 1767) which is a cold water species has eight branchial folds and long bushy tunic spines (Van Name 1945, Nishikawa 1991). Boltenia hirta Monniot and Monniot, 1977 is an abyssal Indian Ocean species that has recently been assigned to the genus Hemistyela (Sanamyan and Sanamyan 2006).

The most closely related species to B. yossiloya appears to be Boltenia africana (Millar, 1962) described from the southern coasts of South Africa, which has a similar tunic, dorsal tubercle, number of folds and longitudinal vessels, and musculature arrangement. We were not allowed to borrow the holotype of B. africana (SAM A25620) from the South African Museum but Dr. M. Rius from the University of Cape Town kindly examined and photographed it for us, and they are clearly separate species. The holotype measures 4.5 cm in the tunic. The gonads of the two species have a very dissimilar appearance (compare Fig. 7 with Fig. 6); indeed, the flattened undulating gonads of B. africana resemble those illustrated for B. transversaria by Tokioka (1960). B. africana has a much more closed and narrow gut loop with the left gonad lying very close to the secondary loop. In B. yossiloya the gut loop is broadly open until the rectal region which lies very close to the esophagus (Fig. 6), and the left gonad does not lie closely in the secondary gut loop as described for B. africana (and also clearly visible in Fig. 7) but is rather above it and diagonal (Fig. 3A). There are two small endocarps on the secondary intestinal loop in B. yossiloya (Fig. 6) which are apparently not present in B. africana. In B. yossiloya the anus has lobed margins versus the apparently plain margin of B. africana mentioned by Millar (1962) and Rius (pers. comm.). In B. africana the largest oral tentacles are tripinnate (Millar 1962) while in B. yossiloya there is only secondary branching (those of the holotype were not described by Rius). B. africana also has not been recorded from tropical coral reefs.

These specimens were collected only from artificial substrates which makes it difficult to determine whether the species is endemic to the Gulf of Eilat. However, due to its external camouflaged appearance it may be very difficult to spot this animal in the natural environment.