Jesús Matallanas

Feeding strategies of deep-water morids on the western Mediterranean slope

Abstract This study examines the feeding habits of Lepidion lepidion , the dominant species of fish and the most abundant morid inhabiting the deep slope of the Catalan Sea, and presents some data on the diet of the other two deep-water morids inhabiting this zone. Samples were obtained at depths between 1000 and 2200 m. The diet of L. lepidion was analysed in two size-classes and for three bathymetric strata. The feeding habits of L. lepidion included a broad range of benthic and pelagic prey. The planktonic prey are most abundant at 1000–1400 m and are almost entirelt absent at 1800–2200 m. Suprabenthos increases with depth. This difference may be the consequence of a change in available resources. There are ontogenetic differences in the diet of L. lepidion that are basically determined by the depth (below 1600 m only adult specimens are found). Lepidion guentheri and Mora moro were active predators of suprabenthic and epibenthic fauna. The bathymetric distribution of morids is also discussed in relation to a possible competitive interaction for similar resources.

Ecomorphological trends and phylogenetic inertia of otolith sagittae in Nototheniidae

A quantitative ecomorphological study was carried out on the sagitta otoliths of Antarctic and Subantarctic nototheniids, a particularly interesting family due to its fast adaptive radiation into different life strategies. We analyzed the otolith shape and size of 18 nototheniids to test the relationship between phylogeny, otolith characters and trophic niche. Relative size (area, length, width, perimeter and weight) and shape (biometric warp analysis based on homologous and pseudo-homologous landmarks) measurements were compared with phylogenic, habitat dwelling and food composition analyses. The results of the multivariate analysis of these factors indicate that there is a weak relationship between otolith shape of nototheniids and phylogeny; however, there is a clear correspondence between relative otolith size and shape and their trophic niche. The most benthic feeders of the family had the largest sagittae in relation to body size, and pelagic species had smaller and rounder shaped sagittae than benthic species. Consequently, in ecomorphological studies, it is useful to analyze the size and shape of sagittae. The discoidal shape of pelagic species, such as Pleuragrama antracticum, can be considered as a paedomorphic characteristic, converging to the juvenile sagittae of many species, which exhibit round sagittae that become elongated as they grow.

Feeding habits of Alepocephalus rostratus (Pisces : Alepocephalidae) in the western Mediterranean sea

The present study examines the feeding habits of Alepocephalus rostratus , the only species of the family Alepocephalidae in the Mediterranean Sea and the second most important fish species, in terms of biomass, inhabiting the deep slope of the Catalan Sea. Samples were obtained at depths between 1000–2250 m. Diet was analysed for two different size-classes (immature and mature specimens) at three different bathymetric strata during two different seasons. The feeding habits of A. rostratus included a narrow range of mobile macroplanktonic organisms (e.g. Pyrosoma atlanticum and Chelophyes appendiculata) and some material of benthic origin. Pyrosoma atlanticum was the preferred prey item in spring at 1000–1425 m, being very scarce in summer at the same depth as a consequence of its scarcity in the environment during this season. There were some ontogenic differences in the diet of A. rostratus at 1425–2250 m. Adults ingested more and larger prey than juvenile specimens. The scarcity of resources below 1200–1400 m fostered a more diversified diet, as well as passive predation of sedimented material.

The Food of Seriola Dumerili (Pisces: Carangidae) in the Catalan Sea (Western Mediterranean)

Stomachs of 385 specimens of Seriola dumerili (Risso, 1810) have been analysed. Their coefficient of repletion is 50·8% in juveniles and 90·3% in adults. Juveniles feed almost exclusively on Teleostei with Engraulis encrasicholus and Sardina pilchardus as the main food; Cephalopoda ( Loligo vulgaris and Sepiola sp.) and Crustacea (Squilla mantis) are also eaten. Adults feed on a great diversity of Teleostei headed by S. pilchardus and Merluccius merluccius. According to Smith-Vaniz (1986) Seriola dumerili is both epibenthic and pelagic, occurring at 18–72 m in small to moderate schools. Juveniles are associated with flotsam in oceanic or offshore neritic waters. Adults often live near reefs or at deep off-shore holes or drop-offs. It is found from the Mediterranean and the Bay of Biscay to South Africa, from Nova Scotia to Brazil, and also in the Arabian Gulf, Australia, Japan and the Hawaiian Islands.

Description of two new genera, Santelmoa and Bentartia and two new species of Zoarcidae (Teleostei, Perciformes) from the Southern Ocean

Two new genera of lycodine zoarcid fish, Santelmoa and Bentartia, and two new species, Santelmoa carmenae and Bentartia cinerea, are described from 13 specimens collected from the Gerlache Strait, Southern Ocean, at 1,056-m depth. Santelmoa can be distinguished from all other lycodine genera by the combination of the following characters: anterior portion of frontals fused; scapular foramen open; ceratohyal–epihyal articulation interdigitating; cranium narrowed; supratemporal commissure and occipital pores absent; intercalar reaching the prootic; parasphenoid wing well developed; palatal arch well developed; posterior hyomandibular ramus short; post-temporal ventral ramus well developed; six branchiostegal rays; vertebrae asymmetrical; pelvic fin rays ensheathed; scales, lateral line, pyloric caeca, palatine and vomerine teeth present. Bentartia differs from the remaining lycodine genera by the following combination of characters: basioccipital and exoccipitals fused; supraoccipital–exoccipital articulation broadly contacting; ceratohyal–epihyal articulation interdigitating; post-temporal ventral ramus weak; two posterior nasal pores; cranium narrowed; supratemporal commissure and occipital pores absent; intercalar set posteriorly; palatal arch well developed; posterior hyomandibular ramus not elongate; parasphenoid wing high; six branchiostegal rays; vertebrae asymmetrical; pelvic fin rays ensheathed; scales, lateral line, pyloric caeca, palatine and vomerine teeth present. The relationships of the two new genera are discussed.

Description of Gosztonyia antarctica, a new genus and species of Zoarcidae (Teleostei: Perciformes) from the Antarctic Ocean

A new genus and species of zoarcid fish, Gosztonyia antarctica, is described on the basis of four specimens collected from the Bellingshausen Sea, Antarctic Ocean, at a depth of 615 m. Gosztonyia is placed in the subfamily Lycodinae and can be distinguished from all other zoarcid genera by the following combination of characters: seven branchiostegal rays, interdigitating ceratohyal–epihyal articulation, palatal arch reduced, posterior hyomandibular ramus longer than anterior, cranium narrowed, supratemporal commisure and occipital pores absent. A new species, Gosztonyia antarctica, is described and the relationships of the new genus are discussed.

Reproductive biology of female Antarctic spiny plunderfish Harpagifer spinosus (Notothenioidei: Harpagiferidae), from Îles Crozet

On the basis of histological examination, we present the first description of oogenesis in H. spinosus. Eight stages of oocyte development were identified using morphological and histochemical criteria. The development of the oocytes is synchronous, and two clutches grow simultaneously in the ovary. Spawning takes place during the end of summer and the beginning of autumn. Absolute fecundity is low, ranging from 787 to 1504 oocytes. The low fecundity is probably related to parental behaviour. Our data indicate that the features of the reproductive biology of H. spinosus, in spite of its unusual environment, are similar to those observed in other teleost fish.

Description of different stages of oogenesis in Ophidion barbatum (Pisces, Ophidiidae)

SynopsisOphidion barbatum is an oviparous fish species, with external fertilization. In females, a single-lobed ovary is followed by a short oviduct that opens directly out through the genital opening. Ovarian development is asynchronous. In a mature ovary and during the breeding season, oocytes in various stages of development can be observed simultaneously. Six stages are described in the oogenesis from the oogonia to the mature egg, using different histological techniques and based on differences of staining, of size and on the nucleus and cytoplasm structure, as viewed through a light microscope. Three of them correspond to the previtellogenic phase and the other three to the vitellogenic phase. Atretic degeneration of eggs is also described.

Description of two new species of Ophthalmolycus (Teleostei: Zoarcidae) from the southern Ocean and key to species of the genus

Two new species of zoarcid fish, Ophthalmolycus eastmani sp. nov., and Ophthalmolycus polylepis sp. nov. are described from specimens collected from the Bellingshausen Sea and Gerlache Strait, Southern Ocean, at depths of 1 8 37 and 105 6 m. Ophthalmolycus eastmani can be distinguished from its congeners by the following combination of characters: two posterior nasal pores; epidermal prickles on lips and snout; gill slit extending ventrally to the lower margin of the pectoral fin base; vertebrae asymmetrical 26 ― 27 + 91 ― 92 = 117 ― 118; dorsal fin rays 111 ― 113; dorsal fin origin associated with vertebra 6, with no free pterygiophores; pectoral fin rays 17 - 18; two postorbital pores; lateral line with ventral and mediolateral branches; scales extending anteriorly to just anterior to the anal fin origin; six branchiostegal rays; oral valve nearly reaching the anterior edge of vomer; palatine teeth in two rows anteriorly; 3 - 5 pseudobranch filaments; two well developed pyloric caeca; pelvic fin and vomerine teeth present. Ophthalmolycus polylepis can be distinguished from its congeners by the following combination of characters: two posterior nasal pores; epidermal prickles on lips; gill slit extending ventrally just to below mid-pectoral fin base; interorbital pore present; two postorbital pores; lateral line triple with ventral, mediolateral and dorsolateral branches; scales extending anteriorly to predorsal area, abdomen, pelvic fins base, and pectoral fins base and axil; vertebrae asymmetrical 22 + 7 6; dorsal fin origin associated with vertebra 5 ; pectoral fin rays 1 8; six branchiostegal rays; oral valve overlapping the anterior edge of vomer; two rows of palatine teeth anteriorly; two vestigial pyloric caeca and 2 pseudobranch filaments; pelvic fin and vomerine teeth present. A key to the species of Ophthalmolycus is provided.

Feeding strategies of Polyacanthonotus rissoanus (Pisces: Notacanthidae) in the deep western Mediterranean

The feeding habits of Polyacanthonotus rissoanus, the sixth most abundant species below 1000 m on the deep slope of the Catalan Sea (western Mediterranean), were studied in the Mediterranean Sea. Samples were obtained at depths between 1000 and 2250 m. Diet was analysed for two seasons (summer and autumn) and three different bathymetric strata. The most important food items found were small epibenthic and suprabenthic crustaceans and polychaetes, and occasionally other groups such as Priapulida, Gastropoda and Foraminifera. At 1000-1425 m, the mysids were preferential prey, while in summer at all depths analysed, isopods were a dominant prey Polychaetes have certain incidence in the diet only at 1000-1425 m, being a dominant prey in autumn. Individuals at the 1000-1425 m depth ingest larger numbers of prey of higher average sizes than those at 1425-2250 m. The scarcity of resources below 1200-1400 m resulted in diversification of diet and encouraged preying on deposited foraminiferans, molluscs or moving copepods.