Variable slime fish
| Variable slime fish | ||||||||||||
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Variable blimp ( Parablennius pilicornis ) |
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| Scientific name | ||||||||||||
| Parablennius pilicornis | ||||||||||||
| ( Cuvier , 1829) |
The variable slime fish ( Parablennius pilicornis ) is a fish that mostly lives on rocky banks and belongs to the family of slime fish (Blenniidae). Like all mucous fish it belongs to the class of ray fins (Actinopterygii), in which most bony fish are classified. The species was first described in 1829 by the French zoologist Frédéric Cuvier under the name Blennius pilicornis .
features
Parablennius pilocornis can reach a maximum length of 13 cm, whereby no sexual dimorphism is recognizable in relation to the size . Its body is scaly, elongated and laterally flattened, this shape can be found in all species of slimy fish. Since the body has no scales, the slimy fish protects itself from dehydration with mucous cells. Like most bottom-living fish, this species does not have a swim bladder .
The color-variable slimy fish has a blunt mouth with a noticeably large upper lip. Above each eye are five filamentous tentacles, which are among other things a characteristic of the family of slime fish. The lateral line organ is present in the head area through numerous rows of pores. Two run between the eyes and one circles the eye. More are usually also available but individually different.
The species has 11 to 12 hard rays in the dorsal fin and then 18 to 24 soft rays. Both sections of the dorsal fin are not separated from one another by a notch. Two hard rays and 20 to 25 soft rays can be seen in the anal fin. The common name of the fish is "Variable Schleimfisch". The reason for this is that its body color can vary greatly. You often see him with a beige or brownish body, which is covered with dark brown spots. The upper part of the body can have up to nine dark bands and the lower part is characterized by dark spots, some of which are pale and have darker features. On the underside of the head there are two equally dark bands. There are also golden-yellow individuals, which are mostly still marked with orange-red dots. On the head, these points are small and close together. On the rest of the body they are larger and usually arranged in rows above the anal fin. What is striking about the eyes is that the iris is colored red. This variation can only be found in females, however, and increasingly after the end of the breeding season (from July). Males exhibit secondary sexual characteristics, such as enlarged supra-orbital tentacles and glands on the anal fin near the urogenital opening. Their color changes to black before and during the breeding season (see reproduction).
Way of life
nutrition
The diet of Parablennius pilicornis is very varied and covers a wide range of different food sources. These also vary in the different seasons. In January the main food source are polychaetes , in April bivalvia is preferred. In the summer months there is no noticeable preference for a food source, where the variable slime fish feeds on polychaetes , gastropods , bivalvia or algae . Towards the end of the year it mainly gets its food from the sand and also eats polychaetes and hydrozoa . The variable mucous fish takes its food, among other things, by grazing on algae and sponges. In this way he gets the small invertebrates living or crawling on it. Compared to other slimy fish , Parablennius pilicornis is noticeably omnivorous in its diet.
Habitat and behavior
Parablennius pilicornis occurs in the Eastern Atlantic, in Spain, Portugal, south to the Möweucht in Namibia, also in the Mediterranean Sea, along the coast of Spain, Morocco and Algeria. In the southwestern Atlantic, it is found on the coasts of Brazil, Argentina and Patagonia. In the western Indian Ocean it occurs from Natal to Knysna in South Africa. The maximum depth at which the species occurs is around 25 meters. The male prefers to live on rocky banks and often on steep walls that are exposed to the surf. During the breeding season, it is territorial and feels responsible for its den. This is cleaned regularly by spitting the disturbing particles out of its cavity with its mouth. With a floating swimming style Parablennius pilicornis makes its territory clear. This is supposed to scare off other males and attract the females. Since most of the males are in their burrows during the breeding season, fighting rarely occurs. If another male gets too close to another cave, the territory will be defended. This starts with a slight nod of the head, followed by a sideways shake of the body. His mouth is opened strongly, he swims out of his cave and positions himself spreading rivers and sideways in front of the cave entrance. The enemy is ultimately chased away by snapping and biting movements. Females are more likely to be observed alone, swimming on the open ground. Nevertheless, you can call them local. If they perceive a danger, they find shelter under stones or in rock niches. If two females get closer than 50 cm, the weaker female will be driven away. This happens because they first meet with their fins spread and their mouths wide. Then one of the two swims vertically towards the other. The weaker individual usually moves away without a great struggle.
Reproduction
The breeding period is between February / March and September. During the spawning season, the males that own a den will change to dark brown / dark blue or black. A bluish spot forms at the front end of the dorsal fin and the iris is very dark. The anal fin and the anal fin turn white.
The eggs are spawned in the male's cavity. For this, the female must be lured into this cave. Whether or not a female can be lured into a cave depends on several factors. On the one hand, the male shows courtship behavior, which in this case is a specific swimming style. This is characterized by nodding the head, seesaw swimming, shaking sideways and pointing flanks. On the other hand, male pheromones with different physiological origins are released from the gland on the anal fin . The pheromones that originate from the anal gland can be transported over long distances via the water. This allows the female to find the location and identity of the potential mate. In the vicinity of the male, pheromones, which were produced by the epididymis, also meet the female. These are crucial for the actual laying of the eggs.
Blenniids are polygynous , which means that they attract several females to spawn in their den. Therefore, the females are driven away again immediately after spawning. The eggs that are ultimately present in the cave can be represented in different stages of development.
Rearing and larval development
The eggs are laid below the low water zone and have a diameter of 0.7 mm. Paternal care is strong in fish living in this zone. It persists until the larvae have hatched. After this disappears, the larvae are exposed to some predators. One possible adaptation reaction to this is that the larvae transfer very quickly to plankton and develop rapidly postlarval. Their pelagic phase lasts 2.5 months. The length of the breeding season varies with the water temperature. At 20 to 21 ° C this is 9 days, at 19 ° C it lasts 14 days and at 17 to 18 ° C it is about 17 days. After hatching, the larvae are approx. 3 mm in size and already well developed. They have already defined lips, a differentiated jaw, fully pigmented eyes and small, rounded pectoral fins (pectoralis). The juvenile color occurs from the 90th day. In the year after they hatch, they become sexually mature at a length of approx. 7 cm. The maximum age of the variable mucous fish is 2.5 years.
communication
In the context of reproduction, blenniids make use of various signals and types of perception. This includes the olfactory , visual and acoustic systems. As already described under the section on reproduction, females use the olfactory system, among other things, to track down the males. Not much is known about acoustic communication at the moment. There is only one study on Parablennius parvicornis , the rock pool blenny. This makes grunting noises during the mating season. This may play a role in the female's decision about spawning. In the mucous fish family, the visual system is very pronounced, with differences between the species. Males have much more varied visual characteristics than females. In addition, there is a wide variety of body colors that differ within and outside of a species.
Individual evidence
- ↑ a b c d e f FishBase : Parablennius pilicornis summary page. Retrieved December 19, 2018 .
- ↑ Volker Neumann and Thomas Paulus: Mediterranean Atlas: Fish and their habitats. MERGUS Verlag GmbH, 2005
- ↑ a b c d e f g h i j k l m Denoix (1984). On the biology of the slimy fish Parablennius pilicornis Cuvier 1829 (Blenniidae, Perciformes) with special consideration of the secondary sexual characteristics of the male after hormone treatment.
- ↑ a b c d e f g Bergbauer, Humberg. 2017: What lives in the Mediterranean ?. Kosmos Publishing House.
- ↑ a b c d e f g Barata, EN, & Gonçalves, DM: Communication in blennies. In: The Biology of Blennies , 2009, pp. 353-378.
- ↑ a b c J. Nieder: Seasonal variation in feeding patterns and food niche overlap in the Mediterranean blennies Scartella cristata, Parablennius pilicornis and Lipophrys trigloides (Pisces: Blenniidae). In: Marine Ecology. Volume 18, Number 3, 1997, pp. 227-237.
- ↑ a b c d e C. Faria, F. Gil & VC Almada: Ontogenetic development of Parablennius pilicornis (Pisces: Blenniidae) in controlled conditions. In: Scientia Marina. Volume 70, Number 4, 2006, pp. 667-671
- ^ Gould, SJ (2002). The structure of evolutionary theory . Harvard University Press.