Volume 17, Issue 4 - 15 October 2011

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Michel Bariche: First record of the cube boxfish Ostracion cubicus (Ostraciidae) and additional records of Champsodon vorax (Champsodontidae) from the Mediterranean, pp. 181-184

Abstract

A specimen of the Indo-Pacific cube boxfish Ostracion cubicus and two specimens of the Indo-Pacific gaper Champsodon vorax were collected from off the coast of Lebanon. This constitutes the first record of the boxfish in the region and confirms the establishment of a population of the gaper in the Mediterranean.

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The first specimen of the cube boxfish Ostracion cubicus Linnaeus, 1758, from the Mediterranean Sea. Photo by A. Finge

Xchel G. Moreno-Sánchez, Casimiro Quiñonez-Velázquez, Leonardo A. Abitia-Cárdenas and Jesús
Rodríguez-Romero: Diet of the Pacific sierra Scomberomorus sierra (Perciformes: Scombridae) in two areas of north-west Mexico coast, pp. 185-192

Abstract

We describe for the first time the trophic spectrum and diet breadth instead width of the Pacific sierra Scomberomorus sierra, in two areas of north-west Mexico. We analyzed a total of 178 stomachs, 131 from Mazatlan, Sinaloa, Mexico, and 47 from Bahia Almejas, Baja California Sur. The index of relative importance (IRI) was used to rank the main food components. The results determined that in these two areas that S. sierra is an opportunistic ichthyophagous predator, consuming mainly fish species that form dense schools (families Clupeidae and Engraulidae), as well as cephalopods as a smaller proportion of the food items for this important sport and commercial fish along the north-west Mexico coast.

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Scomberomorus sierra from the market, undergoing dissection for stomach contents. Photo by X. G. Moreno-Sanchez

Farooq A Ganai, A. R. Yousuf, N. K. Tripathi: First report on the karyological analysis of the Churru snow trout, Schizothorax esocinus (Teleostei: Cyprinidae), from the River Jhelum, Kashmir, pp. 193-198

Abstract

The karyotype and chromosomal characteristics of the Churru snow trout, Schizothorax esocinus (Heckel), from the Jhelum River, Kashmir, were investigated. The analysis of 80 metaphase plates revealed that the chromosome number of this fish was 2n = 98 and the fundamental arm number (FN) = 150. The diploid complement comprised 15 metacentric pairs, 11 submetacentric pairs, 5 subtelocentric pairs and 18 telocentric pairs (30 m + 22 Sm + 10St + 36t). Total length of the haploid complement equalled 228.8 µm with a range in the length of shortest and longest chromosome between 2.5-8.1 µm. The arm ratio and the centromeric index ranged between 1-∞ and 0-50 respectively. No heteromorphic sex chromosomes were found. The present study is the first to describe the chromosomal characteristics of Schizothorax esocinus from the Kashmir Valley.

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Schizothorax esocinus in lateral view. Photo by F. A. Ganai

Brett A. Human: Description of a unique catshark egg capsule (Chondrichthyes: Scyliorhinidae) from the North West Shelf, Western Australia, pp. 199-209

Abstract

A review of the chondrichthyan reference collection of the Western Australian Museum led to the discovery of several lots of previously undescribed catshark egg capsules (Chondrichthyes: Scyliorhinidae) that initially could not be assigned to any particular genus due to their novel morphology. These egg capsules bear unique, well-developed ridges running longitudinally along the length of the egg capsule and are T-shaped in cross section, with one of these egg capsules having an embryo inside. The egg capsules and the embryo are described in detail, and compared against other genera of Australian catsharks. It is hypothesised that the egg capsules belong to the genus Apristurus Garman based on the gross morphology of the embryo. There are two candidate species of Australian Apristurus whose egg capsule remain unknown and to which genus the egg capsules could belong. However, based on the gross morphology of the embryo, it is possible that they represent an undescribed species.

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Embryo (WAM P.30047-001; 27 mm TL) in ventral aspect with attached yolk sac. Photo by B. A. Human

Eugenie Clark, Diane R. Nelson, Mary Jane Stoll and Yasumasa Kobayashi: Swarming, diel movements,
feeding and cleaning behavior of juvenile venomous eeltail catfishes, Plotosus lineatus and P. japonicus (Siluriformes: Plotosidae), pp. 211-239

Abstract
Juveniles of the venomous striped eeltail catfishes, Plotosus lineatus and Plotosus japonicus, were studied by scuba divers in Papua New Guinea, the Solomon Islands, Indonesia, Mabul (Malaysia), Japan and the Red Sea. Dozens, up to thousands, of juveniles form swarms or “balls”, often touching each other, unlike typical fish schools where adjacent individuals swim close but not touching. Feeding swarms can move across large stretches of sand in a steamroller-like movement as fish from the rear constantly speed up and advance over those in front. Lead fish use head barbels to probe the sand for food. Over algal beds and coral reefs, catfish swim in smaller and looser formations. Swarms may be followed by other fishes: shrimpfish, Aeoliscus strigatus, barred soapfish, Diploprion bifasciatum, or the puffer, Arothron manilensis, which may enter and feed with the swarm. Pomacentrids, guarding their demersal eggs on dock pilings or rocks, may attack and chase Plotosus swarms away. At Izu Peninsula, Japan, juvenile P. japonicus clean the boxfish, Ostracion immaculatus, the zebra morwong, Goniistius zebra, and the head and inside the mouth of the moray eel, Gymnothorax kidako. Plotosus lineatus juveniles also exhibit intraspecific cleaning behavior. This facultative cleaning seems to result from accidental encounters, not at established cleaning stations. Swarms of Plotosus juveniles can move hundreds of meters in one hour while feeding over sand. Near sundown they retire for the night under a reef ledge or into an artifact (e.g. hollow log, abandoned car tire), not necessarily to the same place on consecutive nights nor into home burrows with adult fish. In appearance and swarming behavior, juvenile Pholidichthys leucotaenia are Batesian mimics of the venomous Plotosus lineatus.

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Three specimens of Plotosus lineatus from Group A, Vea Vea, Lolobau Island, PNG