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Hogfish - Lachnolaimus maximus
Topic Started: Mar 13 2018, 03:28 PM (323 Views)
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Hogfish - Lachnolaimus maximus

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Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Labridae
Genus: Lachnolaimus G. Cuvier, 1829
Species: Lachnolaimus maximus (Walbaum, 1792)

The hogfish (Lachnolaimus maximus), is a species of wrasse native to the western Atlantic Ocean, with a range from Nova Scotia, Canada to northern South America, including the Gulf of Mexico. This species occurs around reefs, especially preferring areas with plentiful gorgonians. This species is currently the only known member of its genus.

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The hogfish is characterized by a large, laterally compressed body shape. It possesses a very elongated snout which it uses to search for crustaceans buried in the sediment. This very long "pig-like" snout and its rooting behavior give the hogfish its name. The caudal or tail fin is somewhat lunate and the pectoral fins are along the lateral sides of the body with the paired pelvic fins directly below. A prominent black spot behind the pectoral fins differentiates males from females. The dorsal fin usually is composed of three or four long dorsal spines followed by a series of shorter dorsal spines. It is a carnivore. It mainly feeds on small crustaseans.

Like many wrasses, the hogfish is a sequential hermaphrodite, which means it changes sex during different life stages. The hogfish is a protogynous, "first female" hermaphrodite: juvenile hogfish start out as female and then mature to become male. The change usually occurs around three years of age and about 14 inches in length. Females and juveniles will usually start out as pale gray, brown, or reddish brown in color, with a paler underside and no distinct patterns. Males are distinguished by a deep, dark band spanning from the snout to the first dorsal spine, as well as by a lateral black spot behind the pectoral fins. Hogfish reach a maximum of 91 cm (36 in) in total length and about 11 kg (24 lb) and have been recorded to live up to 11 years. Spawning in South Florida occurs from November through June. Hogfish social groups are organized into harems where one male will mate and protect a group of females in his territory.

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Economic importance
Hogfish, is a commonly targeted species for many spear and reef fisherman and is regarded highly by many for its taste and food value. In 2007, the Florida landings of hogfish totaled 306,953 pounds. The fish stocks are regulated by the South Atlantic Fishery Management Council and Florida Fish and Wildlife Conservation Commission. Bag, size, and gear limits all have been placed on this species to ensure a healthy stock and to protect it from overfishing.

How the color-changing hogfish 'sees' with its skin

March 12, 2018 by Robin A. Smith, Duke University

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A pointy-snouted reef fish called the hogfish can change from white to spotted brown to reddish depending on its surroundings. Credit: Dean Kimberly and Lori Schweikert

Some animals are quick-change artists. Take the hogfish, a pointy-snouted reef fish that can go from pearly white to mottled brown to reddish in a matter of milliseconds as it adjusts to shifting conditions on the ocean floor.

Scientists have long suspected that animals with quick-changing colors don't just rely on their eyes to tune their appearance to their surroundings—they also sense light with their skin. But exactly how "skin vision" works remains a mystery.

Now, genetic analysis of hogfish reveals new evidence to explain how they do it. In a new study, Duke University researchers show that hogfish skin senses light differently from eyes.

The results suggest that light-sensing evolved separately in the two tissues, said Lori Schweikert, a postdoctoral scholar with Sönke Johnsen, biology professor at Duke.

With "dermal photoreception," as it is called, the skin doesn't enable animals to perceive details like they do with their eyes, Schweikert said. But it may be sensitive to changes in brightness or wavelength, such as moving shadows cast by approaching predators, or light fluctuations associated with different times of day.

Schweikert, Johnsen and Duke postdoctoral associate Bob Fitak focused on the hogfish, or Lachnolaimus maximus, which spends its time in shallow waters and coral reefs in the western Atlantic Ocean, from Nova Scotia to northern South America. It can make its skin whitish to blend in with the sandy bottom of the ocean floor and hide from predators or ambush prey. Or it can take on a bright, contrasting pattern to look threatening or attract a mate.

The key to these makeovers are special pigment-containing cells called chromatophores, which, when activated by light, can spread their pigments out or bunch them up to change the skin's overall color or pattern.

The researchers took pieces of skin and retina from a single female hogfish caught off the Florida Keys and analyzed all of its gene readouts, or RNA transcripts, to see which genes were switched on in each tissue.

Previous studies of other color-changing animals including cuttlefish and octopuses suggest the same molecular pathway that detects light in eyes may have been co-opted to sense light in the skin.

But Schweikert and colleagues found that hogfish skin works differently. Almost none of the genes involved in light detection in the hogfish's eyes were activated in the skin. Instead, the data suggest that hogfish skin relies on an alternative molecular pathway to sense light, a chain reaction involving a molecule called cyclic AMP.

Just how the hogfish's "skin vision" supplements input from the eyes to monitor light in their surroundings and bring about a color change remains unclear, Schweikert said. Light-sensing skin could provide information about conditions beyond the animal's field of view, or outside the range of wavelengths that the eye can pick up.

Together with previous studies, "the results suggest that fish have found a new way to 'see' with their skin and change color quickly," Schweikert said.


Journal Reference:
Lorian E. Schweikert et al, De novo transcriptomics reveal distinct phototransduction signaling components in the retina and skin of a color-changing vertebrate, the hogfish (Lachnolaimus maximus), Journal of Comparative Physiology A (2018). DOI: 10.1007/s00359-018-1254-4

Across diverse taxa, an increasing number of photoreceptive systems are being discovered in tissues outside of the eye, such as in the skin. Dermal photoreception is believed to serve a variety of functions, including rapid color change via specialized cells called chromatophores. In vitro studies of this system among color-changing fish have suggested the use of a phototransduction signaling cascade that fundamentally differs from that of the retina. Thus, the goal of this study was to identify phototransduction genes and compare their expression in the retina and skin of a color-changing fish, the hogfish Lachnolaimus maximus. De novo transcriptomics revealed the expression of genes that may underlie distinct, yet complete phototransduction cascades in L. maximus retina and skin. In contrast to the five visual opsin genes and cGMP-dependent phototransduction components expressed in the retina of L. maximus, only a single short-wavelength sensitive opsin (SWS1) and putative cAMP-dependent phototransduction components were expressed in the skin. These data suggest a separate evolutionary history of phototransduction in the retina and skin of certain vertebrates and, for the first time, indicate an expression repertoire of genes that underlie a non-retinal phototransduction pathway in the skin of a color-changing fish.

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