''Leachia'' is a
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 ...
containing eight species of
glass squid
The family Cranchiidae comprises the approximately 60 species of glass squid, also known as cockatoo squid, bathyscaphoid squid, cranch squid, or simply cranchiids. The common name "glass squid" derives from the transparent bodies of most spe ...
s. The genus was formerly divided into two
subgenera
In biology, a subgenus ( subgenera) is a taxonomic rank directly below genus.
In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the ge ...
: ''Leachia'' and ''Pyrgopsis'', but is no longer.
[
Members of this genus live in tropical and sub-tropical waters worldwide.
]
Description
The mantle is up to 20 cm long in the largest species. ''Leachia'' are characterised by the presence of two parallel ridges bearing raised cartilage
Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...
spikes, which run along the underside of the body near the head. They have large round fins
A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foil (fluid mechanics), foils that produce lift (force), lift or thrust, or provide the ability to steer or stabilize motion while travelin ...
, which often constitute 20–30% of the entire mantle length. Like most glass squids, members of this genus possess a ring of light organs around their eyes. Bioluminescent
Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some fungi, microorganisms inc ...
cells produce light that cancels the shadow cast by their large eyes. Typical of cranchiid squids, juvenile ''Leachia'' species have stalked eyes. As they mature, females develop light organs on the ends of their third arm
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between ...
pairs. These are thought to be used in mating displays to attract males.
Species
* '' Leachia atlantica'' - Eastern North Atlantic
* '' Leachia cyclura -'' South Indian Ocean
* '' Leachia danae'' (Joubin, 1931) - Gulf of Panama
* '' Leachia dislocata'' (Young, 1972) - Eastern Temperate Pacific.
* '' Leachia lemur'' ''-'' Western North Atlantic
* '' Leachia pacifica'' - South Pacific
Six species are considered valid by Voss, ''et al.'' (1992), who suggests there are 5 more that remain undescribed:
* ''Leachia spp. A -'' Western South Atlantic
References
* Norman, M. 2000. ''Cephalopods: A World Guide''. Hackenheim, ConchBooks, p. 158.
External links
Cranchiinae
Bioluminescent molluscs
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