Marbled sand goby
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Marbled sand goby ( Pomatoschistus marmoratus ) |
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| ( Risso , 1810) |
The marbled sand goby ( Pomatoschistus marmoratus ) is a small benthic single-sex fish of the genus Pomatoschistus from the family of Oxudercidae .
General
P. marmoratus was first described in 1810 by the French naturalist Joseph Antoine Risso . Synonyms are Atherina marmorata (A. Risso, 1810), Gobius marmoratus (A. Risso, 1810), Gobius reticulatus (Valenciennes, 1837), Gobius leopardinus (Nordmann, 1840), Pomatoschistus microps leopardinus (Nordmann, 1840), Gobius rhodopterus ( Günther, 1861), Gobius ferrugineus (Kolombatović, 1891) and Syrrhothonus charrieri (Chabanaud, 1933).
features
The marbled sand goby is 6 to 6.5 centimeters long and is brown-gray in color. The first dorsal fin ( dorsalis ) is supported by six to eight fin rays, the second, separated from the first by a gap, by eight to eleven soft rays. The anal fin ( analis ) has one hard and seven to ten soft rays. The number of vertebrae is 30 to 32. There are 40 to 46 scales along the sideline, with the back of the fish only being scaled from the base of the first dorsal fin. The caudal fin ( caudalis ) is rounded.
P. marmoratus can hardly be distinguished from the related beach goby ( Pomatoschistus microps ) due to the lack of distinguishing features . The only distinguishing feature mentioned in the literature is the scales on the chest of P. marmoratus . These are absent in P. microps . However, since a real distinction between P. microps and P. marmoratus is only possible through special staining of the dermal papillae or through molecular analyzes (e.g. mtDNA), both types are also referred to as cryptic .
The males can be distinguished from the females by a spot behind the first dorsal fin, while the females have a black spot under the chin and the underside of the head is light. In general, however, it can be said that the twelve species of the genus Pomatoschistus can only be determined very poorly or not at all in open water, as they all have the same uniform sand color.
Geographical occurrence and habitat
P. marmoratus is native to the eastern Atlantic , the Bay of Biscay , along the Iberian Peninsula , the Mediterranean , the Black Sea and the Sea of Azov , but can also be found in the Suez Canal and the Qarun Sea in northeastern Egypt. The species prefers sandy soils of shallow waters close to the coast at a depth of one to 20 m. The marbled sea bottom is a euryhaline fish that is very robust against fluctuations in salinity and therefore copes well with fluctuating salt levels in brackish water, at estuaries and hypersaline waters. In the sandy, flat habitats of many river mouths and lagoons of the Mediterranean, the marbled sand goby is the dominant benthic fish species.
P. marmoratus is a species that is true to its location and, unlike migratory species, spends its entire life in a bay. Preferably it is found in deep salty lagoons with minimal salt fluctuation. Due to the transformation of the pelvic fin into a suction disk, adults are considered to be rather poor swimmers. It is therefore believed that the spread and distribution takes place during the brief pelagic stage of the larvae.
nutrition
The prey of P. marmoratus consists of small crustaceans ( Crustacea ), especially copepods (Copepoda), but also polychaetes , mosquito larvae (Chironomidae) and other zoobenthos such as mollusks , nematodes and foraminifera . The diet of the young consists mainly of copepods . With increasing age and size is preferred larger prey such as amphipods (amphipods), eaten.
Reproduction
P. marmoratus reproduces in spring and summer and ranges from April to October, although there may be regional differences. For example, Atlantic populations have a shorter reproductive period than their counterparts in the significantly warmer Mediterranean.
As with all gobies, the male takes care of the brood. During the mating season, the males build nests by cleaning the inside of empty mussel shells and completely covering the outside with sand. The male can modulate the water flow and thus the oxygen concentration in the nest via the size of the entrance. When choosing a mussel, they do not show any clear preferences for a specific type of mussel. Once the males have finished building their nests and a female has been convinced to lay her eggs, the female spawns her eggs on the upper clamshell in a single layer. It is more common that males simultaneously nursed the clutch of several females in their nest, which suggests that these are polygynous. The larger the mussel surface, the more eggs can be placed there.
As the spawning season progresses, the average egg size of 1.0 × 0.6 mm in P. marmoratus decreases significantly. As the water temperature increases over the summer, the oxygen concentration in the water decreases. Because large eggs have a poor surface-to-volume ratio, smaller eggs have a better chance of survival at low oxygen concentrations. As a consequence, the production of small eggs is often preferred. However, this does not seem to be the only decisive factor for the marbled sand goby. The egg size of P. marmoratus seems to correlate with the size of males and females, which indicates assortative mating . In addition, one suspects an influence of temperature on processes of vitellogenesis . Despite all seasonal influences, the size of the female is and will remain the decisive influencing factor.
rearing
Until the offspring hatch, the male protects the nest and takes care of the eggs by cleaning the nest and fanning the clutch with fresh, oxygen-rich water. From observations one deduces that the marbled sand goby, like many other Gobi species, selects their nests according to their body size, even if mussels (nesting facilities) of various sizes are available. The size of the males thus correlates positively with the number of eggs and the size of the clutch. This could be related to the ability to defend the nest against enemies in an emergency. A small male would not be able to defend a large nest, even if it strives for the largest possible clutch in order to guarantee a high successful reproduction .
During brood care, males show a typical color with four dark stripes on the side, a blue point on the first dorsal fin and a black color on the ventral fin and on the edge of the anal fin.
Branch cannibalism
As in the case of many fish Pomacentriden active filialer cannibalism observed. Males of P. marmoratus occasionally attack their own clutch. There are several hypotheses that explain this behavior. The energy -based hypothesis states that the eggs serve as an alternative source of energy for the males who care for the brood. This behavior is explained as an adaptation to the high energetic costs of brood care and the limited possibilities of foraging. A male eating some of his eggs can draw enough energy to complete the current incubation cycle and possibly initiate another. This creates a trade-off between current reproductive success and expected future success. Poor environmental conditions such as low oxygen content in the water, poor food supply or poor physical condition of the male increase the costs for the male and could lead to increased cannibalism.
Another explanation is given by the selective cannibalism hypothesis , which states that those eggs are eaten that do not develop properly, are unfertilized or infected with pathogens and may infect the other eggs. In this case, branch cannibalism would be a real act of brood care. But it could also be that males also recognize cross-fertilized eggs from satellite males (sneakers) and eat them. Another reason for intraspecific cannibalism could be the time pressure that the males are under when caring for the brood. Since there are clutches of different females in the nests, which were laid at different times, there are age differences in the eggs. Observations show that larger, more slowly developing eggs are eaten from the second clutch. Males who are busy with brood care are under pressure to get ready as quickly as possible in order to be able to start a new breeding cycle. For this reason, those eggs are preferred to be eaten that are young, i.e. that take a relatively long time to hatch.
In the event of an environmental decrease in the oxygen concentration in the water, partial cannibalism could increase the probability of survival of the eggs, which are usually tightly packed, since more oxygen is available to the remaining eggs after thinning.
Larval development
The larvae hatch after four to five days, depending on the temperature. They initially live pelagic in open water. The juvenile fish move to bottom life at a size of 11 to 12 millimeters and reach sexual maturity from a size of 2.4 to 4.8 centimeters. Since the life span of P. marmoratus is only two years, and sexual maturity is usually reached in one year, P. marmoratus has only one breeding season.
If there are good nutrient conditions, however, it can happen that individuals born at the beginning of the spawning season (mid-April / beginning of May) are sexually mature in August and September. However, since there is a trade-off between growth and reproduction, these fish are usually very small (28–32 mm total length) in comparison to adult individuals (35–62 mm total length). If the environmental conditions are rather unfavorable, reaching sexual maturity will be delayed until the next spawning season in the coming year. Young animals that reach sexual maturity early and are not yet fully grown also lay smaller eggs. This is one approach to explaining why the eggs, on average, get smaller and smaller over the course of the reproductive period. In P. marmoratus , the egg size correlates positively with the size of the larvae, which in turn correlates with the fitness of the young animals. Larger animals have a distinct fitness advantage, as size has an impact on swimming performance and is therefore critical to the ability to escape predators . Larger young animals also have a wider range of prey available.
meaning
As the dominant species in shallow water near the coast, P. marmoratus has a major influence on the trophic organization of the local communities. In contrast , P. marmoratus is of no importance in fishing . In the Red List of Threatened Species of IUCN is P. marmoratus as "not at risk" (least concern) and the population trend listed as stable.
literature
- Louisy P .: marine fish. Western Europe Mediterranean . Stuttgart 2002: Eugen Ulmer Verlag, ISBN 3-8001-38441 .
- Miller PJ : Gobiidae. p. 1019-1085. In PJP Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen and E. Tortonese (eds.) Fishes of the North-eastern Atlantic and the Mediterranean. Volume 3. 1986. Paris: UNESCO, ISBN 92-3-002309-4 .
Web links
- Pomatoschistus marmoratus on Fishbase.org (English)
Individual evidence
- ↑ a b c d Miller PJ : Gobiidae. Pp. 1019-1085. In PJP Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen and E. Tortonese (eds.) Fishes of the North-eastern Atlantic and the Mediterranean. Volume 3. 1986. Paris: UNESCO, ISBN 92-3-002309-4 .
- ↑ Berrebi P. , Rodriguez P., Rooney C., Aloya S., Cattaneo-Berrebi G. (2009): Haplotypic confinement in two cryptic and closely-related species of sedentary gobies, Pomatoschistus microps and P. marmoratus in French Mediterranean lagoons . Folia Zool. 58: pp. 123-131.
- ↑ Louisy P .: Marine fish. Western Europe Mediterranean. Stuttgart 2002: Eugen Ulmer Verlag, ISBN 3-8001-38441 .
- ↑ a b c d e Mazzoldi, C. , Poltronieri C., Rasotto MB (2002): Egg size variability and mating system in the marbled goby Pomatoschistus marmoratus (Pisces: Gobiidae). Marine Ecology Progress Series. 233, pp. 231-239.
- ↑ a b c d e f Altin A. , Ozen O., Ayyildiz H., Daban IB (2015): Feeding habits of the marbled goby, Pomatoschistus marmoratus (Actinopterygii: Perciformes: Gobiidae), in the Çanakkale Strait, northern Aegean Sea , Turkey. Acta Ichthyol. Piscat. 45 (1): pp. 95-100.
- ↑ a b Mejri R. , Lo Brutto S., Ben Hassine OK, Arculeo M. (2010): Genetic architecture of the marbled goby Pomatoschistus marmoratus (Perciformes: Gobiidae) in the Mediterranean Sea. Molecular Phylogenetics and Evolution. 58: pp. 395-403.
- ↑ a b c d e Mazzoldi C., Rasotto MB (2001): Extended breeding season in the marbled goby, Pomatoschistus marmoratus (Teleostei: Gobiidae), in the Venetian Lagoon. Environmental Biology of Fishes. 61: pp. 175-183.
- ↑ Verdiell-Cubedo D. , Oliva-Paterna FJ, Torralva M. (2007): The effects of competitors on fitness of marbled goby Pomatoschistus marmoratus (Pisces, Gobiidae) in the Mar Menor coastal lagoon (SE Iberian Peninsula). Italian Journal of Zoology. 74 (2): pp. 169-177.
- ^ Rohwer S. (1978): Parent Cannibalism of offspring and egg raiding as a courtship strategy. The American Naturalist. Vol. 112, No. 984.
- ^ Klug H., Lindstöm K. (2008): Hurry-up and hatch: selective filial cannibalism of slower developing eggs. Biol. Lett. 4, pp. 160-162.
- ^ Payne AG , Smith C., Campbell AC (2002): Filial cannibalism improves survival and development of beaugregory damselfish embryos. The Royal Society. 269: pp. 2095-2102.