Macroctopus

Macroctopus was first proposed as a new subgenus of Octopus in 1928 by Guy Coburn Robson with Octopus maorum as its type species. This species was first formally described in 1880 by Frederick Hutton with its type locality given as Dunedin. This taxon is regarded, by some authorities, as being regarded as conspecific with Pinnoctopus cordiformis, with M. maorum being treated as the junior synonym of P. cordiformis. Yet other authorities do not regard P. cordiformis as conspecific with M. maorum and suggest that P. cordiformis is a synonym of Enteroctopus zealandicus. ==Identification==

Macroctopus maorum is a large octopus and it is regularly described as a ‘robust’ species, it is a member of the Octopus macropus species complex. The morphological traits characteristic of this complex are a high number of gill lamellae, a robust conical copulatory organ and arms of varying length with long unequal dorsal arms generally four to six times longer than the mantle. Although being unequal, their arms are said to be long and evenly tapering and Macroctopus maorum are even known to regrow arms when one has been lost. Being the largest member of its complex arm span is said to exceed . They have four to six suckers on the first and second arm pairs which are usually about in size. Suckers are arranged in two rows down the arm length. There is thought to be no correlation between sexes and size of suckers; however, there was an increase in sucker size with body mass increase. Coloration of this species can vary Macroctopus maorum can be distinguished from other species by the colour, they will be either orange-brown or dark purple-grey. The octopus has numerous small iridescent white spots on the web, arms and dorsal arm crown but there are no spots present on the mantle. Macroctopus maorum has 12–14 gill lamella per demibranch, the mantle is described as broadly ovoid and exhibits a skin pattern of longitudinal ridges. Along the dorsum there are five rows of unbranched papillae and two more papillae appear individually above the eyes. Octopus papillae are camouflage specialised with the ability to change shape, such as by extending in and out from the body. Male M. maorum have a small ligula, the ligula is a specialised arm tip on the hectocotylized arm which grips to allow the transfer of spermatophores. Within the complex O. macropus, Macroctopus maorum is thought to be the largest member. In a study estimating M. maorum size based on a sample of 90 beaks, the largest individual found had a body length of and body mass of . Macroctopus maorum has an upper beak and lower beak, the upper beak can be used to differentiate Macroctopus maorum and Enteroctpus zealandicus as it has a lack of overlap in the ratio of upper hood length and upper chest length. Macroctopus maorum hatchlings are usually about in size, they have 7–8 suckers per arm and each dorsal arm will have 6–11 chromatophores. ==Life cycle/Phenology==

Sexual maturity Female Grubert and Wadley assigned 5 maturity stages for the egg development of Macroctopus maorum: • Newly formed primary oogonia which has a small, distinct nucleus is visible and Follucular cells attach to the ovum and forming follicular epithelium. • Follicular epithelium has completely filled the ova and nucleus is no longer visible. There are no yolk present and cuboidal follicular cells become distinct and closely packed. • First granular yolk appears in the ova. Epithelial convolution still occupying much of the interval volume. • Only periphery of the ova found and been forced out by the expanding yolk. Nuclei of epithelium has now become indistinct. • Mature ova which have thin walls and are replete with yolk. Follicular epithelium produced the chorion and degenerated. Ova is free in the ovary, oviduct or oviducal glands. Female that undergoes stage 4 oocytes were caught throughout the month of April to October, while those females that undergo stage 3 were caught only in April and July. However, females with stage 5 oocytes were caught every month except May and August. The position of testis moved backward until it reached the final position at the hinder end of the body during the adult stage. Male octopus will then become senescent and die after mating. Octopus maorum swept across the eggs sheet with one or more tentacles to keep the eggs well oxygenated, clean and safe from predators. During brooding period female Macroctopus maorum will stop feeding so that it produce less wastes and ensure the water quality is good for the eggs. When the eggs are about to hatch Macroctopus maorum will frequently squirt water on the eggs using siphon until the eggs hatched. After the eggs hatch, the female Macroctopus maorum will swim away and might die as she has been weakened from guarding the eggs. The hatchlings are planktonic and have 7 to 8 suckers per arm. If the hatchling manages to survive, the life cycle will be repeated. == Global distribution and habitat ==

Global distribution M. maorum is commonly found in the waters of New Zealand and South Australia, M. maorum is also common in the waters of the islands surrounding New Zealand including Campbell, Chatham and Auckland Islands. In Southeast Tasmania, at Eaglehawk Bay the site of a commercial fishery is the only known inshore location where the M. maorum have been known to gather in large numbers year round. Habitat M. maorum lives in the benthic zone in soft-sediment and rubble habitats with depths of and will sometimes forage in nearby hard-reef habitats and are less common at the fringes between reefal and soft sediment habitats. Rather than settling in a specific location, M. maorum uses temporary shelters. In Tasmania, young M. maorum have been observed settling in intertidal rock pools. Similar sightings of M. maorum in intertidal rock pools have been reported during the summer months in Kaikoura and Banks Peninsula. ==Diet/Predators==

Diet and Foraging A study of M. maorum off the coast of southeastern Tasmania found evidence of 12 different species in the stomachs of sampled octopuses with the dominant prey being the crab P. gaimardii and other M. maorum. This is a low number of prey species compared to other species of octopus and it is assumed that the diet of M. maorum in Southeastern Tasmania is more diverse than results indicated in the study. When executing different hunting methods colour and texture are adjusted, often by darkening and erection of papillae. Penguins such as yellow-eyed, fiordland crested and little blue penguin might prey on Macroctopus maorum as well. M. maorum hosts dicyemid mesozoans and digenetic trematodes as parasites. A more recent study of the species adds wobbegongs, school and gummy sharks, mulloway, queen snapper and dolphins to the list of predators. Sea slugs will often feed on M. maorum eggs. ==Other information==

While research was being carried out the behavior of M. maorum was monitored and results showed that while being in the aquarium they showed a variety of behaviors such as fighting, flamboyant postures and defensive up-turning of arms, withdrawing and cleaning. Small M. maorum would often take on larger octopuses such as O. tetricus such as a M. maorum fought and started to eat a 1 kg O. tetricus. M. maorum has a significant economic effect on rock lobster fisheries in New Zealand and Southern Australia. M. maorum will prey on trapped southern rock lobster killing many and leaving some lobster missing limbs making them unsaleable. This also means that M. maorum is being caught as bycatch. The South Australian rock lobster fisheries report that since 1983 octopus bycatch has ranged from 38,000 to 119,000 octopus a year. M. maorum are fished commercially in Eaglehawk Bay Tasmania where they congregate throughout the year in large numbers (as many as 70 octopuses). ==References==