''Sunamphitoe femorata'' is a species of

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

in the family

Ampithoidae Ampithoidae is a family of amphipod crustaceans. The family has a worldwide distribution as algal dwellers. They commonly create tube-shaped nests on their host plants or algae which serve as both shelter and food. Young ampithoids develop from ...

. It is a herbivore and constructs a tubular nest-like home on a blade of the

sporophyte A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote pr ...

of the giant kelp ''

Macrocystis pyrifera ''Macrocystis pyrifera'', commonly known as giant kelp or bladder kelp, is a species of kelp (large brown algae), and one of four species in the genus ''Macrocystis''. Despite its appearance, it is not a plant; it is a heterokont. Giant kelp is ...

''. This home is made by rolling the sides of the blade together and securing them with silk. As the kelp blade grows, so the nest is advanced down the blade towards the base, approximately keeping pace with the algal growth.

Taxonomy

The species was originally described in 1845 as ''Ampithoe femorata'' by

Henrik Nikolai Krøyer Henrik Nikolai Krøyer (22 March 1799 – 14 November 1870) was a Denmark, Danish zoologist. Born in Copenhagen, he was a brother of the composer Hans Ernst Krøyer. He started studying medicine at the University of Copenhagen in 1817, which he ...

and moved to ''Peramphithoe femorata in 1982. Following a phylogenetic analysis that found neither ''Peramphithoe'' nor ''Sunamphitoe'' monophyletic, with the species intermingled within a clade, the two genera were synonymised and ''Peramphithoe femorata'' renamed ''Sunamphitoe femorata''.

Distribution

''Sunamphitoe femorata'' has been reported from the Caribbean Sea, Venezuela and the Southern Ocean.

Behaviour

''Sunamphitoe femorata'' is a tubicolous (tube-forming) amphipod that feeds and makes its home on the giant kelp ''

''. This

brown alga Brown algae (singular: alga), comprising the class (biology), class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the ...

is found in shallow water and can grow to a length of in a single season. It is attached to the substrate by a holdfast from which grow several long slender stems. These are clad in numerous small leaf-like blades growing from

pneumatocyst In phycology, a pneumatocyst is a floating structure that contains gas found on brown seaweed. A seaweed's thallus may have more than one. They provide buoyancy to lift the blades toward the surface, allowing them to receive more sunlight for ph ...

s (gas-filled bladders) and it is on these blades that the amphipod lives. The blades grow continuously from near their bases and the amphipod chooses a position some way along a blade, rolling the edges together to form a tube. It first deposits a mass of silk on the blade and grips this with its 5th, 6th and 7th

pereopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s. It then secures the edges of the blade to each other with a silken thread, produced from glands on the third and fourth pairs of pereopods, manipulating the thread with the first and second pairs. The weaving process continues rhythmically at the rate of about 24 silk attachments per minute, alternately on the left and right sides of the blade, and a tube is formed. The

meristem The meristem is a type of tissue found in plants. It consists of undifferentiated cells (meristematic cells) capable of cell division. Cells in the meristem can develop into all the other tissues and organs that occur in plants. These cells conti ...

from which the blade grows is just above the junction with the pneumatocyst. The rate of elongation of the blade decreases over time and for about six days the nest is extended towards the base of the blade at about the same rate as the blade is growing. After that the rate of growth of the blade slows down further and the rate of nest advancement becomes more variable. At the entrance of the nest (the end nearest the base of the blade) the surface layer of the blade is grazed by the amphipod while at the other end of the nest the central tissue of the blade is also consumed. The oldest part of the blade becomes senescent and sloughs off. The amphipod does not occupy the nest continuously but sometimes moves elsewhere on the host kelp, leaving a small grazing scar to show where it has foraged. Sometimes the nest is abandoned and a new nest may be built in a different location. Researchers studying this amphipod (Cerda, Hinojosa & Thiel, 2012) hypothesised that the position chosen for the nest might be a location where the maximum nutritional value of the tissue coincided with a decrease in production of defensive chemicals by the alga.

References

{{Taxonbar, from=Q63724790 , from2=Q7842454 Corophiidea Crustaceans of the Atlantic Ocean Crustaceans described in 1845 Taxa named by Henrik Nikolai Krøyer