Leptocardii |
Not assigned |
Branchiostomidae
Environment: milieu / climate zone / depth range / distribution range
Ecology
Benthic; depth range 229 - ? m (Ref. 766). Deep-water
Northwest Pacific: Japan.
Length at first maturity / Size / Weight / Age
Maturity: Lm ? range ? - ? cm
Body, 14.7 mm long and up to 1.5 mm high, elongated longitudinally and much flattened laterally, tapering gradually towards both ends; preatrioporal region 10.9 mm, atriopore to anus 1 .0 mm, postanal 1.8mm, and urostyloid process 1.0 mm. Rostral fin extensive and semi-circular, clearly separable from other part by dorsal
and ventral notches. Dorsal fin very low in anterior two-thirds of body, while becoming much higher posterially. Left metapleuron terminated abruptly and markedly just behind atriopore, while the right confluent with well-developed ventral fin, followed by thin and high caudal fin, somewhat higher than dorsal fin. Urostyloid process separable from dorsal and caudal fins by its own lower dorsal and ventral fins. Dorsal fin-chambers 270, relative length to width for posterior tall ones up to 3.3; preanal fin-chambers indiscernible, but instead, an elongated vacuole detected along ventral side of rectum between atriopore and anus. Myotomes 83 in total, consisting of 58 in preatrioporal region, 9 in region from atriopore to anus, and 16 in postanal, thus giving the myotome formula of 58+9+16=83. A black pigment spot detectable in neural tube just anterior to first myotome. Tentacular ring composed of Ca. 30 tentacles (including a few dorsal-most minute ones), its anterior margin situated at level of axial (=proximal) part of 5th myotome; intertentacular membrane extremely higher in span of 6 tentacles next to much shorter midventral tentacle than elsewhere. Mid-gut coecum elongated, ranging at level from 20th to 48th myotomes. No gonad.
Life cycle and mating behavior
Maturity | Reproduction | Spawning | Eggs | Fecundity | Larvae
Members of the class Cephalochordata are gonochoric. Life cycle: Eggs develop into planktotrophic larva and later on to benthic adults.
Nishikawa, T. 2004 A new deep-water lancelet (Cephalochordata) from off Cape Nomamisaki, South West Japan, with a proposal of the revised system recovering the genus Asymmetron. Zoological Science 21:1131-1136. (Ref. 766)
IUCN Red List Status
(Ref. 130435: Version 2025-1)
CITES status (Ref. 108899)
Not Evaluated
Not Evaluated
Threat to humans
Harmless
Human uses
| FishSource |
Tools
More information
Trophic EcologyFood items (preys)
Diet composition
Food consumption
Predators
Population dynamicsGrowth
Max. ages / sizes
Length-weight rel.
Length-length rel.
Length-frequencies
Mass conversion
Abundance
Life cycleReproductionMaturityFecunditySpawningEggsEgg developmentLarvae PhysiologyOxygen consumption
Human RelatedStamps, coins, misc.
Internet sources
Estimates based on models
Price category
Unknown.
