The REPRODUCTION Table
|Where egg and sperm meet...||
The REPRODUCTION table contains information on the reproductive mode, the frequency of spawning, whether a species is a batch spawner or not, and the type of reproductive guild to which each species belongs. Descriptions of the life cycle, and of the mating and spawning behavior are also presented in this table.
The Mode of reproduction is classified into the following choices: dioecism; protandry; protogyny; true hermaphroditism; parthenogenesis. The mode of Fertilization refers to where the egg and sperm meet, which may be: external; internal (in the oviduct); in the mouth; in a brood pouch or similar structure; or elsewhere.
The Spawning frequency is described by the following choices: one clear seasonal peak per year (i.e., the spawning season is brief, lasting a few weeks or months and little or no spawning occurs outside of it); throughout the year, but peaking once (i.e., some spawning activity occurs throughout the year, but there is one broad seasonal peak); two seasonal peaks per year (i.e., some spawning may occur throughout the year, but two peaks are clearly visible [usually one larger than the other, and separated by 5-7 months]); no obvious seasonal peak (i.e., spawning occurs throughout the year, with no well-marked seasonal peaks); variable throughout the range (i.e., spawning occurs as in the first and second choices at high latitudes, and as in the third and fourth choices at low latitudes); once in a lifetime (i.e., spawning usually occurs only once and death usually follows). Note that this field refers to the species in general and that the spawning frequency might be different for populations at the limit of the latitudinal range of a species.
The Batch spawner field states whether individuals accomplish multiple spawning during the spawning season.
|Reproductive guilds follow a classification suggested by E. Balon||
The Reproductive guild is described by the combination of two choice fields, following a classification suggested by Balon (1990). The first field pertains to the type of parental care with the choices: nonguarders; guarders; bearers. The second field refers to the pattern of care for the eggs or young, with the choices: open substratum egg scatterers (nonguarders that leave eggs after spawning in the water column or on any substrate, e.g., rocks, gravel, sand, plant, etc.); brood hiders (nonguarders that deposit eggs in inconspicuous places, e.g., caves, rock interstices, gravel depressions, inside live invertebrates, etc.); clutch tenders (non-nesters that guard eggs at the water surface, on underside of objects or any substrate, e.g., rocks, plants, etc.); nesters (fish which deposit and often guard eggs in nests, e.g., mucus bubbles, rocks, gravel, sand, holes, base of sea anemones, plants, etc.); external brooders (fish which incubate eggs externally on parental body, e.g., pouch, mouth, gill cavities, pelvic fins, etc.); internal live bearers (fish which fertilize eggs internally, with development taking place inside the maternal body).
Information on life cycle, mating and spawning behavior not included in the list of choices, and other information are accommodated in the Description of life cycle and mating behavior field.
Box 30. The latitudinal distribution of hermaphroditism.
The most common way for the gonads of fish to be distributed is for females to develop ovaries, and for males to develop testes, and to function accordingly. This is called ‘dioecism’.
However, in some groups, individuals that started off as females may turn into males (protandric hermaphroditism), or conversely (protogynous hermaphroditism); more rarely both sets of organs may simultaneously occur and function in the same individual (true hermaphroditism), known in Rivulus marmoratus.
Fish species in which either of the two common forms of hermaphroditism predominates (as opposed to occurring in a few isolated individuals) account for only a small percentage of all fish species and are concentrated in families such as the Serranidae, Labridae and Scaridae, and in lower latitudes.
Still, the percentages output by the FishBase plot of hermaphroditism by latitude (see Fig. 42) are not as reliable as may be wished, as the graph could be made to generate sensible results only by assuming that all species presently without entries in the ‘Mode’ field of the REPRODUCTION table are dioecious. Filling in this field for all species may thus still lead to changes in the shape of this graph, which presently displays a suspicious dip at the equator, where we expect the maximum will eventually be.
To date, over 3,700 records extracted from nearly 400 references have been compiled. We plan to increase drastically our coverage of modes and types of reproduction by using the classic Breder and Rosen (1966), Thresher (1984), aquaculture and aquarium literature and other compilations.
A plot of hermaphroditism by latitude (Fig. 42) can be generated (see Box 30). This graph can be accessed by clicking consecutively on the following buttons: Reports in the Main Menu, Graph in the Predefined Reports window, Reproduction and Early Stages in the Graphs window and Hermaphroditism vs. Latitude.
|How to get there||
You get to the REPRODUCTION table by clicking on the Biology button in the SPECIES window and the Reproduction button in the BIOLOGY window and REPRODUCTION in the following window.
On the Internet, you get to the REPRODUCTION table by clicking on the Reproduction link in the ‘More information’ section of the ‘Species Summary’ page. You can create a list of all species with available data by selecting the Reproduction radio button in the ‘Information by Topic’ section of the ‘Search FishBase’ page.
Balon, E.K. 1990. Epigenesis of an epigeneticist: the development of some alternative concepts on the early ontogeny and evolution of fishes. Guelph Ichthyol. Rev. (1):1-48.
Breder, C.M., Jr. and D.E. Rosen. 1966. Modes of reproduction in fishes. T.F.H. Publications, Neptune City. 941 p.
Lagler, K.F., J.E. Bardach, R.R. Miller and D.R. May-Passino. 1977. Ichthyology. 2nd ed. John Wiley and Sons, New York. 506 p.
Thresher, R.E. 1984. Reproduction in reef fishes. T.F.H. Publications, Neptune City. 399 p.