Ofer Gon

Conserving pattern and process in the Southern Ocean: designing a Marine Protected Area for the Prince Edward Islands

South Africa is currently proclaiming a Marine Protected Area (MPA) in the Exclusive Economic Zone (EEZ) of its sub-Antarctic Prince Edward Islands. The objectives of the MPA are to: 1) contribute to a national and global representative system of MPAs, 2) serve as a scientific reference point to inform future management, 3) contribute to the recovery of the Patagonian toothfish (Dissostichus eleginoides), and 4) reduce the bird bycatch of the toothfish fishery, particularly of albatrosses and petrels. This study employs systematic conservation planning methods to delineate a MPA within the EEZ that will conserve biodiversity patterns and processes within sensible management boundaries, while minimizing conflict with the legal toothfish fishery. After collating all available distributional data on species, benthic habitats and ecosystem processes, we used C-Plan software to delineate a MPA with three management zones: four IUCN Category Ia reserves (13% of EEZ); two Conservation Zones (21% of EEZ); and three Category IV reserves (remainder of EEZ). Compromises between conservation target achievement and the area required by the MPA are apparent in the final reserve design. The proposed MPA boundaries are expected to change over time as new data become available and as impacts of climate change become more evident.

Comparative spermatogenesis, spermatocytogenesis, and spermatozeugmata formation in males of viviparous species of clinid fishes (Teleostei: Clinidae, Blennioidei)

Spermatogenesis and spermatocytogenesis in 16 species of viviparous clinid fishes (Clinidae, Blennioidei) from various localities were followed for the first time by means of light and electron microscopy. The testes of the studied species are of the lobular type, with germinal stem cells situated at the apical ends of the lobules and a vas efferens along the internal margin. Maturation of the spermatides takes place in spermatocysts formed by Sertoli cells around the B‐spermatogonia. The gradual condensation and relocation of the chromosomes along the nuclei membranes are highly prominent in this process, which can be divided into several stages. Anisodiametric and slightly flattened sperm heads are eventually formed, 0.4–0.5 μm in diameter and 7.5 ± 1 μm long, bearing 80 ± 15 μm long flagella. The sperms are packed into spermatozeugmata within the spermatocysts, enveloped and penetrated by the mucotic material of the Sertoli cells. With division of the germ cells and maturation of the spermatids, the spermatocyst dimensions increase, attaining 40 ± 8 μm in diameter in the smaller species of Heteroclinus, and up to 90 ± 10 μm in the larger males of Clinus superciliosus and C. cottoides. Accordingly, the volume of the maturing spermatocysts attains ca. 1,300 ± 100 μm3 in the smaller species, and ca. 6,500 ± 300 μm3 in the larger ones. As sperm head volume is ca. 2.24 μm3, the number of sperm in the smallest mature spermatocysts reaches ca. 440 and in the largest over 2,900. Upon release from the cysts, the spermatozeugmata are transported along the sperm ducts to the posterior ampullae where they are stored in the epididymis. During copulation, the sperms are transported from there to the female via the intromittent organ. The sperm formation parameters and their structure and numbers are discussed. Anat Rec Part A, 2007.

Comparative oogenesis in cardinal fishes (Apogonidae, Perciformes), with special focus on the adaptive structures of the egg envelopes

The present study compares gonad structure and oogenesis in 30 species of cardinal fish (Apogonidae) from the Indo-Pacific region. In all of the species studied the ovaries are bilobed, with each lobe possessing ovigerous lamellae whose numbers and dimensions increase concomitantly with growth of the fish and reproductive stage, and correlate with the total dimensions of the particular species. In species of the genus Siphamia, the ovarian lobes are associated with a fat body that is not found in species of the other genera studied. Some of the species studied (Siphamia spp.; Archamia spp.) demonstrate group-synchronized maturation of eggs, possibly with only one spawn per reproduction season. However, most of the Apogon spp., and other genera, have unsynchronized cycles, a characteristic of multiple spawners. The various stages of previtellogenic and vitellogenic development are similar in the different species, but differ in timing and dimensions of the oocytes around which the morphogenesis of the egg envelope (chorion) and follicle begins. Differentiation of the egg envelope and follicle cells parallels the vitellogenic stages of egg development. The number of eggs was found to correlate positively with the length of the body and ovary of the fish, whereas egg diameter was found to correlate negatively with body length. The surface of the egg envelope bears ridges that form patterns of various types, whose structures and dimensions seem to be species-specific, and which in most species converge upon the single micropyle on the animal pole. The exposed ridge mazes include a special fibrous web that anchors in the micropyle. The production and importance of these ridges, as well as the correlations between egg numbers per spawn, egg dimensions, and the oral dimensions of the paternal male, are discussed.

REVIEW OF THE SOLES OF THE GENUS ASERAGGODES OF THE WESTERN INDIAN OCEAN, WITH DESCRIPTIONS OF THREE NEW SPECIES

The Indo-Pacific soleid fish genus Aseraggodes is represented by eight species in the western Indian Ocean and Red Sea: A. brevirostris, n. sp., described from two specimens from the Comoro Islands; A. diringeri Quero, type locality, Reunion, recorded here from Mauritius, Seychelles, Comoro Islands, KwaZulu-Natal, and Kenya; A. guttulatus Kaup, the type species of the genus, known from one specimen from Reunion; A. heemstrai, n. sp., described from 16 specimens from KwaZulu-Natal; A. jenny, n. sp., described from one specimen from Mauritius; A. sinusarabici Chabanaud, known from 9 adult syntypes taken by trawling in 35–68 m the Gulf of Suez (one designated as lectotype); A. steinitzi Joglekar, described from three small specimens from the southern Red Sea (none available for study); and A. umbratilis (Alcock), described from five specimens (one designated as lectotype) taken by trawling at depths of 70–271 m in the Bay of Bengal and later reported from the Arabian Sea.

Descriptions of three new species of Marcusenius Gill, 1862 (Teleostei: Mormyridae) from South Africa and Mozambique

Morphological and genetic studies of mormyrid fishes belonging to the genus Marcusenius from South Africa and Mozambique revealed four species of which three are described as new. Marcusenius pongolensis is widespread throughout the Incomati, Pongola and Kosi river systems, and sparsely represented in the Limpopo River system in South Africa. Marcusenius krameri sp. nov. is endemic to the Limpopo River system, and is the sister taxon of M. caudisquamatus sp. nov. from the Nseleni and Mhlatuze river systems in the KwaZulu-Natal Province of South Africa. The Ruvuma specimens were well differentiated from all southern and eastern African species of Marcusenius, and are therefore recognised as M. lucombesi sp. nov. Phylogenetic analysis of the mitochondrial cytochrome b gene showed that the three new species and M. altisambesi form a monophyletic lineage that is sister to a group containing M. pongolensis and M. macrolepidotus. Marcusenius krameri and M. lucombesi seems to prefer slow flowing reaches of rivers, whereas M. pongolensis and M. caudisquamatus seems to mainly inhabit rapid flowing sections of rivers with a rocky substrate. A key to the southern African species of Marcusenius is provided.

Comparative morphology of the oropharyngeal cavity of clinid fish (Perciformes: Clinidae), with particular attention to the form, number and distribution of taste buds, and dentition

The present study compares the form, number and distribution of taste buds (TB) in the oropharyngeal cavity (OC) of 17 species of clinid fish (Perciformes, Blennioidei, Clinidae) from different geographical regions (Australia, Taiwan, South Africa), and includes observations on dentition. Larger juveniles and adult clinids possess the three types of TB described in teleost fish: Type I, protruding on papillae, dominate the anterior OC, often together with the less protruding Type II, whereas Type III, whose apical parts are level with the oral epithelium, dominate the posterior OC, closer to the pharynx. The average surface diameter of a TB is approx. 4μm, but some TB of 1.5μm were also observed. High numbers of TB are situated on and around the toothed epipharyngeal and hypopharyngeal bones, possibly serving as the final checkpoint of food items. The total number of TB in the various species ranges from 648 in Heteroclinus wilsoni of 35mm SL and 977 in a 54mm SL adult Muraenoclinus dorsalis, to 2 526 in Heteroclinus heptaeolus of 74mm SL and 4 050 in a 118mm SL Clinus superciliosus. In specimens of the same species the number of TB is positively correlated with fish size, but there appears to be no such correlation between different taxa. The highest density of TB (216 mm−2) was observed on the hypopharyngeal bones of Clinus superciliosus, and the lowest (8.4 mm−2) on the upper valve of Clinus cottoides. The number and distribution of TB in clinids are compared with data from other fish taxa.

A new species of the cardinalfish genus Gymnapogon (Perciformes, Apogonidae) from the Red Sea

Abstract A new cardinalfish species, Gymnapogon melanogaster, is described from two specimens collected at night in the Gulf of Aqaba, Eilat, Israel. This species is characterized by having 9 dorsal and 8 anal fin soft rays; 14–15 pectoral fin rays; 2 + 11 gill rakers; a flat, bifurcated preopercular spine; a naked body without a papillae network; black pelvic fins; and a black stomach. It is similar to Gymnapogon vanderbilti (Fowler, 1938) that is known only from the Line Islands of the Central Pacific Ocean.

Rhinobatos austini n. sp., a new species of guitarfish (Rhinopristiformes: Rhinobatidae) from the Southwestern Indian Ocean

Rhinobatos austini sp. n. is described from the southwestern Indian Ocean based on four specimens collected from the KwaZulu-Natal Province, South Africa and from Mozambique. The new species, with one exception, can be distinguished from all other members of this genus by a prominent teardrop-shaped dark blotch on the ventral surface of its snout. Its closest congener, R. holcorhynchus, also has a prominent teardrop-shaped blotch on its snout, but the new species differs from it by a lack of prominent thorns and tubercles on it dorsal disc surface and a very striking dorsal surface colour pattern of paired spots, some forming darker transverse bands across its back. Geographically, these two species broadly overlap, but R. austini appears to be a shallow, more coastal species (<1-107 m) compared to R. holcorhynchus that has a mostly offshore (75-254 m) depth distribution.

A new species of Neobathyclupea from the northern Indian Ocean with comments on N. malayana (Teleostei, Perciformes, Bathyclupeidae)

A new species of Neobathyclupea is described from two specimens collected off Myanmar and off Socotra Island. The new species is most similar to N. malayana, but differs from it and other congeners in having jet-black coloured fins, larger pseudobranch, dorsal-pterygiophore pattern and some body proportions. Neobathyclupea malayana is re-diagnosed. Individual variations in armament of the preopercle and in the dorsal-pterygiophore patterns within Bathyclupeidae are discussed.

Comparative embryogenesis of Australian and South African viviparous clinid fishes (Blennioidei, Teleostei)

The study follows the embryogenesis of 16 species of viviparous clinid fishes (Clinidae, Teleostei), from the Cape south coast of South Africa and from Australia, with comparative remarks on the development of juveniles in oviparous species. The sperm intromitted into the female duct fertilise the eggs within the follicles. The embryos then develop in individual follicles, nourished by nutrients derived from the mother, until they are mature for release. During the reproductive season in the South African genera Clinus and Muraenoclinus, the females ovaries harbour eggs and embryos at various stages of development, whereas in species of the Australian genera Heteroclinus and Cristiceps, most embryos in each ovary are at an approximately equal stage of development. The ovaries of the studied species fall into two groups: species of Heteroclinus and Cristiceps that produce numerous small eggs, and species of Clinus and Blennophis that produce fewer, larger eggs. As a consequence, Heteroclinus spp. and Cristiceps spp. bear and release high numbers of smaller embryos, of c. 10-13 mm long, whereas others (e.g. Clinus superciliosus, C. cottoides) bear fewer embryos, of up to 22 mm long. The organogenesis of various organs is described, with particular emphasis on chondrification and ossification. The onset of gut, sensory organ and skeletal development in Heteroclinus and related species occurs in embryos of 2.5-3.0 mm, whereas in Clinus spp. organ development starts in 5.0-6.0 mm embryos, and occurs in parallel both in the head capsule and at the caudal ends. Consequently, the pace of embryogenesis in the studied Australian small-egg species is faster in several aspects, and their embryos at the time of release are smaller than those of the large-egg species. The developmental sequences and related phenomena are discussed.