Social and reproductive behavior of three mouthbrooding cardinalfishes,Apogon doederleini,A. niger and A. notatus

Synopsis Social and reproductive behavior of three paternal mouthbrooding cardinalfishes (Apogonidae) were investigated in the shallow marine waters of Shirahama, Japan. The solitary species Apogon doederleini and A. niger bred in transient pairs, in which a male and female associated for only a few hours of each afternoon on less than 5 successive days. The prespawning behavior was the same as the courtship display on days prior to spawning. After spawning, egg-incubating males were usually left alone. The gregarious species Apogon notatus formed territorial lasting pairs, which resided at given sites from dawn to dusk on each day during a period of a month or more. After spawning, the egg-incubating male either continued to stay with his mate in the territory, or left it to enter into an aggregation. In the latter case, the female continued to reside in the territory, pairing with a new male whom she brought from an aggregation. It is suggested that in paternal apogonids the prolonged pair bond and territoriality should have developed only in gregarious species as secondary adaptation for reproductive success: to avoid conspecific interference during spawning.     

Functional morphology of the luminescence system of Siphamia versicolor (Perciformes: Apogonidae), a bacterially luminous coral reef fish

Previous studies of the luminescence system of Siphamia versicolor (Perciformes: Apogonidae) identified a ventral light organ, reflector, lens, duct, and a ventral diffuser extending from the throat to the caudal peduncle. The control and function of luminescence in this and other species of Siphamia, however, have not been defined. Morphological examination of fresh and preserved specimens identified additional components of the luminescence system involved in control and ventral emission of luminescence, including a retractable shutter over the ventral face of the light organ, contiguity of the ventral diffuser from the caudal peduncle to near the chin, and transparency of the bones and other tissues of the lower jaw. The shutter halves retract laterally, allowing the ventral release of light, and relax medially, blocking ventral light emission; topical application of norepinephrine to the exposed light organ resulted in retraction of the shutter halves, which suggests that operation of the shutter is under neuromuscular control. The extension of the diffuser to near the chin and transparency of the lower jaw allow a uniform emission of luminescence over the entire ventrum of the fish. The live aquarium‐held fish were found to readily and consistently display ventral luminescence. At twilight, the fish left the protective association with their longspine sea urchin, Diadema setosum, and began to emit ventral luminescence and to feed on zooplankton. Ventral luminescence illuminated a zone below and around the fish, which typically swam close to the substrate. Shortly after complete darkness, the fish stopped feeding and emitting luminescence. These observations suggest that S. versicolor uses ventral luminescence to attract and feed on zooplankton from the reef benthos at twilight. Ventral luminescence may allow S. versicolor to exploit for feeding the gap at twilight in the presence of potential predators as the reef transitions from diurnally active to nocturnally active organisms. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc     

Fish and decapod crustaceans inhabiting drifting algae in Jervis Bay,New South Wales

Abstract This study documents the fish and decapod crustaceans inhabiting a bed of Gracilaria verrucosa that was drifting on the bottom of a temperate marine embayment in relatively deep water (15- 18m) during autumn 1991. Fauna were sampled with diver-operated enclosure nets. Relatively few species inhabited the algae at this time, and the assemblage was primarily a subset of that in adjacent Posidonia australis beds. Three fish species [Neoodax balteatus (Odacidae), Cristiceps australis (Clinidae), Siphamia cephalotes (Apogonidae)] and one species of crab [Nectocarcinus tuberculosus (Portunidae)] dominated the catches numerically. A further 14 fish and decapod species were relatively rare. Neoodax balteatus, C. australis and N. tuberculosus were caught at all life stages and appeared to be permanent residents of the Gracilaria. Few juveniles of other species were captured, which indicates that these algal wracks may not be an important nursery habitat for seasonally resident fish species. Trachurus novaezelandiae and a number of other fish species that associate with a variety of benthic habitats appeared to be transient visitors. The biomass of algae varied significantly within the bed, but algal biomass was not a good indicator of faunal abundances. The low species richness of the fish and decapod crustacean assemblage may be related to both lower recruitment in deeper water and to unfavourable characteristics of the alga.     

Complex behaviour by coral-reef fish larvae in open-water and near-reef pelagic environments

We present the first in situ observations of the pelagic larvae of coral-reef fishes feeding, schooling and being preyed upon. In addition, we report on their behavioural interactions with adult and juvenile fishes. Observations on over 500 larvae of over 50 species (mostly from four families) near the end of their pelagic interval were made in both open water (> 1 km offshore) and near-reef environments. Nearly 10% of larvae were seen to feed in open water, but < 1% fed near the reef. Presettlement schooling was observed in five species of four families. We observed no predation upon larvae in open water except near the bottom. Near the reef, 8.5% of larvae were eaten. The main predators near and on the reef were a species of wrasse and lizardfishes. Rates of predation seem to differ among genera of pomacentrids, perhaps related to differences in behaviour when settling. When confronted with adult fishes, which happened largely near the reef, larvae reacted with a limited range of behaviours, including sheltering near the observer, swimming to the surface, slowing or stopping, or swimming offshore. The frequency of these behaviours differed among larvae of three pomacentrid genera. Interactions with reef residents, particularly pomacentrids, were common, and usually involved aggression by the resident toward settling larvae. This may act to discourage settlement during the day when such residents are active. These data show that behaviour of late larvae of coral-reef fishes is complex and can greatly influence survival and recruitment. Further, behaviour differs among taxa, showing that not only are larvae not passive, but also that a generalised behaviour of larvae does not exist.     

Seasonal pattern of filial cannibalism by Apogon doederleini mouthbrooding males

In temperate waters of southern Japan, mouthbrooding males of the cardinal fish Apogon doederleini sometimes ate their entire brood within a day of spawning. In spite of annual variation in age structure and length of the breeding season, however, the annual cannibalism rate (broods cannibalized to total broods spawned) was nearly constant, 12–16%. Fish 1 year old frequently cannibalized early broods of the season, especially the first brood, whereas the cannibalism rate by 2 year-old fish did not vary within the season. In contrast, the cannibalism by older males increased late in the season. This tendency was attributed to their different allocation patterns to growth and reproduction. For 1 year-old fish, which can enhance future reproductive success by growth and cannibalizing on early broods instead of mouthbrooding (at relatively low temperatures), this may be a tactic for investing energy in growth. For fish 3 years, which have more breeding cycles and grow little, cannibalizing late broods may be energetic compensation for their poor somatic condition. No seasonal variation of cannibalism by 2 year-old fish can be explained by their intermediate nature of growth and reproduction. Multiple mate availability is one factor facilitating the cannibalism by 2 and 3 + year-old fish whose operational sex ratio is female-biased.     

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.     

Filial cannibalism by mouthbrooding males of the cardinal fish,Apogon doederleini, in relation to their physical condition

Synopsis Paternal brood cannibalism was observed in a population ofApogon doederleini in Shikoku Island, Japan. Of 361 egg masses mouthbrooded by males, 47 disappeared within a day of spawning. A stomach check with a syringe ascertained that they had been consumed by the males. The frequency of this cannibalism increased as the breeding season advanced. As males completed 4–7 breeding cycles in a breeding season and spent 80% of the time mouthbrooding without taking ordinary food, their physical condition deteriorated greatly late in the breeding season. We concluded that parental physical condition is an important factor in the occurrence of brood cannibalism.     

Homing is not for everyone: displaced cardinalfish find a new place to live

It was tested whether the pajama cardinalfish Sphaeramia nematoptera (Apogonidae) could home by displacing individuals up to 250 m within and among isolated reefs. Contrary to expectations, only two of 37 (5·4%) displaced S. nematoptera returned home and another 16 (43·2%) were found to have joined other social groups and did not home after 26 months of observations; while over the same period, 94% of control S. nematoptera remained associated with home corals, demonstrating strong site attachment. Hence, while this species has the potential to return home, being able to do so may not be as critical as previously assumed.     

Chorion microstructure for identifying five fish eggs of Apogonidae

The chorion microstructure of the eggs of apogonids including Apogon lateralis , A. aureus , A. nitidus , A. cookii and A. guamensis was studied by scanning electron microscopy. In Apogonidae, egg chorion microstructures, especially those in the micropyle region, are useful characters for egg identification.     

First record of Apogon queketti Gilchrist (Osteichthyes: Apogonidae) in the Mediterranean Sea

The spotfin cardinalfish Apogon queketti is recorded for the first time in the north-eastern Mediterranean Sea (Iskenderun Bay, Turkey). Two specimens of this species, 111 and 102 mm total length were caught by a commercial trawler at depths of 55 and 60 m on 14 October 2004 and 23 April 2005, respectively. The occurrence of this species in the Mediterranean Sea is the result of migration from the Red Sea via the Suez Canal.