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Volume 24, Issue 1 – 05 June 2018

Volume 24, Issue 1 – 05 June 2018
New Scientific publication – started delivery on July 25, 2018

Full Text | PDF (1,8 MB)

Joseph C. Waddell and William G. R. Crampton: A simple procedure for assessing sex and gonadal maturation in gymnotiform electric fish, pp. 1-8


Studies of the reproductive life history of fish populations typically require a reliable assessment of sex and gonadal maturation stage. Some recently published methodologies for describing gonadal maturation involve time-consuming histological analyses. However, histological procedures can be impractical in studies involving large sample sizes of fishes. Here we describe a robust methodology for staging gonadal maturation in gymnotiform fish based on readily identifiable features of gross morphology from dissected gonads. We unify previously published gonadal maturation schemes to describe five gonadal maturation stages in females (1. Immature or Resting; 2. Maturing; 3. Mature; 4. Pre-spawning; 5. Spent) and four stages in males (1. Immature or Resting; 2. Maturing or Spent; 3. Mature;
4. Pre-spawning). The procedure described here permits discrimination of all major gonadal stages (with the exception of some early and late male maturational stages that can only be discriminated using histological techniques) and provides similar levels of subjectivity for separating successive early maturational stages relative to histology-based procedures, but is far less time consuming.

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Line drawing of approximate position and size of developing gonads for each maturational stage in Brachyhypopomus beebei. L = liver. S = stomach. G = gas bladder…


Natascha Wosnick, Bianca de Sousa Rangel, André Sucena Afonso, Hugo Bornatowski, Fábio Hissa Vieira Hazin, Renata Guimarães Moreira and Carolina Arruda Freire: Hormones and migration in tiger sharks (Galeocerdo cuvier): can they be related?, pp. 9-14


Behaviors associated with reproduction, territorial defense and hierarchical position within a population are strongly shaped by the endocrine system and may influence breeding, feeding, and migratory patterns. This study examined the link between endocrine reproductive parameters [plasma Testosterone (T), Progesterone (P4) and 17β-estradiol (E2)], total cholesterol and movement behavior of three juvenile males of similar size tagged with a satellite transmitter off Fernando de Noronha Archipelago (FEN), Brazil. The results suggested a possible link between the parameters and the movement pattern observed. This preliminary analysis indicates that hormonal profile might thus be, at least partially, related to the habitat shift observed, being consistent to the regulating role of the endocrine system as an evolutionary adaptation molded to e.g. avoid interspecific competition or to optimize foraging efficiency in species which move through wide-ranging home-ranges such as the tiger shark.

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Tiger shark soon after capture, being lead to the sampling platform. Photo by R. Snow, OCEARCH.


Gerald R. Allen: Chromis torquata, a new species of damselfish (Pomacentridae) from Mauritius and Réunion, pp. 15-22


A new species of pomacentrid fish, Chromis torquata, is described from six specimens, 22.0-91.9 mm SL collected in 30 m at Mauritius in the southwestern Indian Ocean. It also occurs at nearby Réunion, based on photographic evidence. The new species belongs to the C. xanthura complex, which also contains C. anadema (Japan and Micronesia to Marquesas and Pitcairn Island), C. opercularis (East Africa to Christmas Island, Indian Ocean), and C. xanthura (Indonesia to Japan, eastward to Fiji and Tonga). Diagnostic features for the new species include usual counts of XIII, 11 dorsal rays, II, 11 anal rays, 19 pectoral rays, 3 spiniform caudal rays, 17-19 tubed lateral-line scales, and a distinctive colour pattern that includes a broad dark band immediately behind the head, extending downward to the body side of the pectoral-fin axil. The maximum width of the dark band is equal to or greater than the horizontal eye diameter in C. torquata, but the similarly-positioned band of the other species in the complex is clearly less than the eye diameter. The new species also differs in having the entire iris orange-yellow compared with a narrow rim of yellow around the pupil in the other three species.

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Chromis torquata, preserved holotype, 87.4 mm SL, off Grand Baie, Mauritus. Photo by G. R. Allen.


Fabio Origuela de Lira, Dalton Tavares Bressane Nielsen and Luciano Medeiros de Araujo: First record of Laimosemion xiphidius (Huber 1979) (Cyprinodontiformes: Rivulidae) in Brazil, pp. 23-26


The first record for the rivulid killifish Laimosemion xiphidius (Huber) for Brazil is presented. The species was recorded in a small tributary of the Oyapock River (Rio Oiapoque in Brazil), Amapá state, at the border with French Guyana. The potential occuurence of the species in other sites in Brazil is remarked.

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Chromis torquata, preserved holotype, 87.4 mm SL, off Grand Baie, Mauritus. Photo by G. R. Allen.


Hiroki Iwatsubo and Hiroyuki Motomura: Chromis katoi, a new species of damselfish from the Izu Islands, Japan, with a key to species in the Chromis notata species complex (Perciforms: Pomacentridae), pp. 27-34


Chromis katoi n. sp., a new damselfish (Pomacentridae) belonging to the Chromis notata species complex, is described on the basis of 11 specimens collected at a depth of 18 m off Hachijo Island, Izu Islands, Japan. The new species is similar to C. notata in having an indistinct white blotch at the end of the dorsal-fin base, and 4 or 5 and 11 or 12 scale rows above and below the lateral line, respectively, but differs in having the spinous portion of the dorsal fin yellowish in adults (vs. entire dorsal fin brownish in the latter), the caudal fin dusky yellow in adults (vs. each caudal-fin lobe with a broad horizontal dark band), the body entirely yellow in juveniles (vs. grayish to brownish throughout life), fewer dorsal-fin soft rays, more tubed lateral-line scales, pectoral-fin rays and gill rakers, and greater body depth and pre-anal-fin length. A key to species in the C. notata species complex is provided.

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Underwater photographs of Chromis katoi n. sp. of Hachijo Island, Izu Islands, Japan. Left Mature male; right Spawning of C. katoi


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