''Macrochlaena winckworthi'', Winckworth's octopus, is a little known species of

octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...

, it is the only species in the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Macrochlaena'', in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Octopodidae The Octopodidae comprise the family containing the majority of known octopus species (about 175 species). Genera The World Register of Marine Species lists these 23 genera: *'' Abdopus'' Norman & Finn, 2001 (7 species) *'' Ameloctopus'' Norman, ...

. It was described by the British

malacologist Malacology, from Ancient Greek μαλακός (''malakós''), meaning "soft", and λόγος (''lógos''), meaning "study", is the branch of invertebrate zoology that deals with the study of the Mollusca (molluscs or mollusks), the second-largest ...

Guy Coburn Robson Guy Coburn Robson (1888–1945) was a British zoologist, specializing in Mollusca, who first named and described '' Mesonychoteuthis hamiltoni'', the colossal squid. Robson studied at the marine biological station in Naples, and joined the staff ...

in 1926, the

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

s having been collected in the

Gulf of Mannar The Gulf of Mannar ( ) (; ) is a large shallow bay forming part of the Laccadive Sea in the Indian Ocean with an average depth of .Thoothukudi Thoothukudi (formerly called Tuticorin) is a port city, port industrial city in Thoothukudi district in the Indian state of Tamil Nadu. It lies on the Coromandel Coast of the Bay of Bengal. The city is capital and headquarters of the di ...

Tamil Nadu Tamil Nadu (; , TN) is the southernmost States and union territories of India, state of India. The List of states and union territories of India by area, tenth largest Indian state by area and the List of states and union territories of Indi ...

, southeastern India.

Description

''Macrochlaena winckworthi'' is a small species of octopus with relatively short arms, the arms being 1.5-2.5 times longer than the mantle with the lateral arms being slightly longer. The web is relatively deep, being one third the length of the arms, and the web is slightly deeper between the lateral arms. There are no pouches between the arms. Each arm has two rows of small suckers n its underside, with each arm having around 65 suckers. The funnel organ has a shape described as "UU" and the gills have 8 to 10 lamellae per demibranch. The

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

has 9 elements, 7 teeth rows and marginal plates and the rachidian tooth has a single lateral cusp in a symmetrical series. It possesses a small

ink sac An ink sac is an anatomical feature that is found in many cephalopod mollusks used to produce the defensive cephalopod ink. With the exception of nocturnal and very deep water cephalopods, all Coleoidea (squid, octopus and cuttlefish) which dwell ...

. In the males the third right arm is

hectocotylised A hectocotylus (: hectocotyli) is one of the cephalopod limb, arms of male cephalopods that is specialized to store and transfer spermatophores to the female. Structurally, hectocotyli are muscular hydrostats. Depending on the species, the male ma ...

being approximately 80% of the length of the opposite arm and having 35 to 40 suckers. The terminal organ is linear and the

diverticulum In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, t ...

is simple in form with a slightly swollen shape. It has small

spermatophores A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially ...

each being 8 to 10 mm in length, roughly one third of the length of the mantle. The head is now dsitnguished much from the mantle and the eyes are rather small. The skin is smooth and overall the animal is red-brown to purple in colour with a marbling of darker mottles. The total length of an adult is at least 93mm, the mantle length is 33mm.

Habitat and distribution

''Macrochlaena winckworthi'' was originally collected from

pearl oyster ''Pinctada'' is a genus of saltwater oysters, marine bivalve mollusks in the family Pteriidae. These pearl oysters have a strong inner shell layer composed of nacre, also known as "mother of pearl". Pearl oysters are not closely related to ...

beds in shallow water off the coast of Tamil Nadu in the Gulf of Mannar. It has also been collected off

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

and it has been inferred that its distribution extends from India east to the

Malay Archipelago The Malay Archipelago is the archipelago between Mainland Southeast Asia and Australia, and is also called Insulindia or the Indo-Australian Archipelago. The name was taken from the 19th-century European concept of a Malay race, later based ...

in shallow waters of less than 20m in depth. It seems to have some convergent adaptations with other species of octopods which live in muddy habitats. This is a little known species and its biology and behaviour are unknown, as is its importance in any fisheries.

References

{{Taxonbar, from=Q18579970 Octopuses Cephalopod genera Cephalopods described in 1926