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aqua International Journal 15-4



Volume 15, Issue 4

15 October 2009

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Volume 15, Issue 4 – 15 October 2009

John E. Randall and Jennifer K. Schultz: Pictichromis dinar, a new dottyback (Perciformes: Pseudochromidae) from Indonesia, pp. 169-176

A new pseudochromid fish species, Pictichromis dinar, is described from five specimens from the western side of the Gulf of Tomini, Sulawesi, Indonesia, where it occurred on a drop-off in 15 to 25 m. It is bright purple anteriorly and abruptly bright yellow posteriorly in life, hence remarkably similar to P. paccagnellae (range from Bali and Sulawesi to Vanuatu), and to P. coralensis (range from Queensland to New Caledonia). The demarcation of purple and yellow is generally more anterior and more slanting in P. dinar. The caudal fin of P. paccagnellae and P. coralensis varies from slightly rounded to slightly emarginate, compared to distinctly emarginate in P. dinar, the caudal concavity is 9.9-11.2% SL. Also, P. dinar has modally one more gill raker. Thirty specimens of Pictichromis dinar and 28 of Pictichromis paccagnellae were assessed at 628 base pairs of the mitochondrial cytochrome c oxidase I gene. No haplotypes are shared between the species, and within species sequence divergence (d = 0.003) is an order of magnitude lower than sequence divergence between the two species d = 0.06). This is consistent with reproductive isolation and species-level designation.

John E. Randall: A review of the gobiid fishes of Easter Island, with description of a new species, pp. 177-190

Only 129 species of fishes are known for Easter Island from the shore to a depth of 200 m. Six of these are gobies: Gnatholepis pascuensis, first considered as a new subspecies of G. cauerensis, here given species rank; Kelloggella disalvoi, a new species from the highest tide pools, previously identified as the Hawaiian K. oligolepis; the endemic Pascua caudilinea, a common species from tide pools to at least 40 m, never seen while diving; Priolepis psygomophilia, also cryptic, with the same unusual depth range for a goby, described from two small specimens from the Kermadec Islands and regarded as the same species at Rapa and Easter Island; Priolepis squamogena, conspicuously marked with dark-edged brown bars, described from French Polynesia and the Line Islands, and reported here as a first record for Easter Island from two juvenile specimens; and Trimma unisquamis, a wide-ranging insular species represented by 25 specimens collected from depths of 16.5-40 m. A key is provided for the Easter Island species of Gobiidae.

Shnoudy A. Bakhoum: Biometric characteristics and some biological features of natural hybrids between Nile tilapia Oreochromis niloticus and blue tilapia Oreochromis aureus in Lake Edku, Egypt, pp. 191-204

Oreochromis niloticus, O. aureus and specimens with an external appearance intermediate between these putative parents were sampled from Lake Edku and examined to determine the hybrid nature of the intermediate specimens. The results of hybrid index, principal component analysis, discriminant function analysis and the Mann-Whitney U-test indicated the hybrid nature of these specimens and determined the most suitable biometric characters to distinguish different hybrid types from the parent species. Hybrid specimens represented about 28% of the total catch of Lake Edku. Hybrids have a higher percentage of males than females. Hybrids become mature at a smaller size and their reproductive activity is lower than that of the parent species. The natural mortality of hybrids is higher than that of the parent species.

José I. Castro: Observations on the reproductive cycles of some viviparous North American sharks, pp. 205-222

The reproductive cycle of sharks is defined by how often a species breeds and consists of two periods: vitellogenesis and gestation. These two periods can run concurrently or consecutively, and the duration of each period is variable. Together, the periods of vitellogenesis and gestation determine the length of the reproductive cycle. The genera Rhizoprionodon, Mustelus, and some Sphyrna exhibit annual cycles with concurrent vitellogenesis and gestation, and thus, they produce one brood each year. Carcharias taurus females apparently have a biennial reproductive cycle with discontinuous ovulation. Alopias spp. exhibit an annual cycle with concurrent vitellogenesis and gestation, and have continuous ovulation. Squalus acanthias has a squaloid biennial cycle with concurrent vitellogenesis and gestation. Sharks of the genera Carcharhinus, some Sphyrna, and Ginglymostoma have a biennial cycle with consecutive vitellogenesis and gestation. Galeocerdo cuvier has a 12-month gestation period in the western Atlantic, its reproductive cycle may be biennial. Carcharhinus obscurus has an 18-month gestation period and probably a three-year reproductive cycle. The biennial cycle, with all its variations, is found in sharks of different phyletic origins such as carcharhinoid, squaloid, and orectoloboid sharks, reflecting their common physiological processes that require a long time to accumulate sufficient energy to produce a brood.

Friedhelm Krupp, Uwe Zajonz, Maroof A. Khalaf: A new species of the deepwater cardinalfish genus Epigonus (Perciformes: Epigonidae) from the Gulf of Aqaba, Red Sea, pp. 223-227

A new species of epigonid fish, Epigonus marisrubri, is described, based on two specimens (134 mm and 136 mm SL), which were collected over a reef area at a depth of 52 m at the northern tip of the Gulf of Aqaba, Red Sea, Jordan. The new species differs from its congeners by the following combination of characters: dorsal rays VII + I,10; anal rays II,9; pored lateral line scales 48 or 49; gill rakers 29 or 30; pyloric caeca 10; two pterygiophores between neural spines 9 and 10; pectoral fins long, reaching level of second dorsal-fin origin; tongue with a band of teeth on glossohyal; opercle with a short, poorly ossified spine and 1-2 spinelets; otolith (sagitta) oval, elongate, with smooth rims; sulcus and cristae weakly developed. This is the first record of the family Epigonidae from the Red Sea.

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Dimensions 26.6 × 20.3 × 0.3 cm
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