title for learn-about sections for chitons in A SNAIL'S ODYSSEY
  Reproduction
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  Brooding
 

Topics on chiton reproduction include brooding, considered here, and GONADAL GROWTH & SPAWNING, MORPHOLOGY OF EGGS & LARVAE, and SETTLEMENT & METAMORPHOSIS considered in other sections.

 
Research study 0
 

An early review of chiton reproduction includes a reference to brooding in Ischnochiton (Lepidozona) asthenes collected at White’s Point near Los Angeles.  Several adult specimens are noted to have metamorphosed young adhering to their girdle regions tucked in amongst the ctenidia.  The author notes that brooding has been described in several other world species, but with no particular taxonomic pattern.  Smith 1966 Proc Calif Acad Sci 32 (15): 433.

 
Research study 1
 

photograph of chiton Lepidochitona dentiens courtesy Rian Dickson and the Royal British Columbia Museum, Victoriaphotograph of a trochophore of a chiton Lepidochitona hartwegiA comparison of 6 species of chitons Lepidochitona from San Juan Island, WA and Santa Cruz, CA shows that half brood their young to crawl-away juveniles (L. thomasi, L. caverna, L. fernaldi), while the other half are free-spawners (L. dentiens, L. hartwegii, L. berryana).  Eggs of all species are yolky, and larvae of the spawners are lecithotrophic. The brooding species are smaller than the spawning species (means of 1.6 and 2.9cm length, respectively), and their eggs are somewhat larger (250µm vs. 220µm).  Eggs of the of the spawners hatch at 36h to swimming trochophore larvae (see photo upper Right) while eggs of the brooders hatch at 8-12d to crawl-away juveniles (see photo lower Right). The brooders tend to be reproductively active for most of the year, while the spawners are more seasonal (Feb-May).  Eggs are brooded in the pallial grooves on either side of the body.  Eernisse 1988 Biol Bull 174: 287. Photograph of Leptidochitona dentiens courtesy Rian Dickson and Royal British Columbia Museum, Victoria.

photograph of a 7-d pre-hatch trochophore larva of a chiton Lepidochitona cavernaNOTE  6 of 20 (30%) species in the genus Lepidochitona brood while, worldwide, only 30 out of 800 (4%) species of chitons brood.  Two of the local brooding species L. caverna and L. fernaldi are uniquely simultaneous hermaphrodites, and are the only known chiton species capable of self-fertilisation. 

NOTE interestingly, although some species of Lepidochitona are considered to be brooding species, if the eggs are cultured separately from the parents they hatch to a free-swimming larval stage

 

 

 

 

 

 

 

The photos below show eggs of several species of Lepidochitona. The scale bar roughly applies to all eggs:

 

photograph of egg of chiton Lepidochitona berryanna
Lipidochitona berryanna: spawner

photograph of egg of chiton Leptidochitona caverna
Lepidochitona caverna: brooder
photograph of egg of chiton Lepidochitona dentiens
Lepidochitona dentiens: spawner
photograph of egg of chiton Lepidochitona thomasii
Leptidochitona thomasi: brooder
 
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