Topics on chiton reproduction include settlement & metamorphosis, considered here, and GONADAL GROWTH & SPAWNING, MORPHOLOGY OF EGGS & LARVAE, and BROODING, considered in other sections.

Laboratory development of Mopalia ciliata in southern California follows the schedule:

0h               fertilisation
10-12h       gastrulation
24-48h       larvae break free of egg capsule and begin swimming
5-8d           end of free-swimming stage
8-16d         adult features begin to appear

The larvae exhibit photonegative behaviour when swimming. The author could not rear the larvae through metamorphosis.  Thorpe 1961 Veliger 4: 202. Photograph courtesy Lovell & Libby Langstroth, California and calphotos.

Chiton Mopalia ciliata 1.4X

Studies in the Pacific Grove area of California on Mopalia lignosa and M. muscosa show patterns of larval development similar to that described for M. ciliata above.   A swimming trochophore larva hatches within a day.  Dorsal ridges that are prelude to the shell plates and foot rudiment appear 4d after hatching.  The ciliated foot-flap is present at 5d, and settlement occurs within a day.  Metamorphosis, defined by appearance of shell plates and loss of the apical tuft, occurs at 7-8d.  The eyespots, so prominant in the larva, disappear completely about 8wk after fertilisation.  By 21d after metamorphosis the authors note radular movement, although feeding is likely to have commenced much earlier than this. Watanabe & Cox 1975 Veliger 18 (Suppl): 18. Photograph of Mopalia lignosa courtesy Linda Schroeder and Pacific Northwest Shell Club, Seattle, Washington PNWSC.

NOTE only the pattern for M. lignosa is shown here.  Mopalia muscosa differs in having a longer free-swimming period before settling and metamorphosing (13d s as compared with 7d for M. lignosa at 13-16^oC)

Mopalia lignosa

Experiments on temperature effects on the development of metamorphic competency  in chitons Mopalia muscosa at Friday Harbor Laboratories involve rearing of the lecithotrophic larvae at different temperatures.  Best metamorphic performance (50%) is attained with larvae reared for 17d at 11^oC, then switched to 16^oC.  Growth is most rapid at the warmer temperature, but survival is poor.  In fact, the author notes that most larvae in the experiments die before metamorphosing, so the results should be considered with this in mind.  Pechenik 1984 Int J Invert Repr Dev 7: 3. Photograph of Mopalia lignosa courtesy Linda Schroeder and Pacific Northwest Shell Club, Seattle, Washington PNWSC.

NOTE  metamorphosis, when it occurs in the experiments, is “spontaneous”, that is, it takes place in the absence of an inducer

Recruitment of Katharina tunicata in areas around Trinidad in northern California is mainly through late summer/autumn, suggesting that larval settlement is in spring/summer.  Stebbins 1988 Veliger 30: 351. Photograph courtesy Russ Markel, Bamfield Marine Sciences Centre.

Black-leather chitons Katharina tunicata in
Barkley Sound, British Columbia 0.5X

A research study at the Oregon Institute of Marine Biology, Charleston provides detail on larval growth and metamorphosis, and on post-settlement growth of gumboot chitons Cryptochiton stelleri.  Lecithotrophic larvae hatch at 2d post-fertilisation (11-12^oC) and 3d later begin to develop shell plates (see photo series below).  The larvae are competent to metamorphose 3d from hatching (5d post-fertilisation), and can be induced to settle by exposure to aqueous extracts of coralline algae.  In the absence of an appropriate cue, metamorphosis can be delayed for at least 2mo in the laboratory. In culture the post-metamorphic juveniles eat diatoms and cyanobacteria off the bottoms of the culture vessels, as evidenced by grazing trails and presence of these food organisms in their fecal pellets. The author provides 8mo of growth data for 4 juveniles collected from red algae Cryptopleura sp. in the field, and fed in the laboratory on diets of Cryptopleura sp., green algae Ulva lactuca and, later at 1yr of age, on red algae Mazzaella splendens, a common food of the adults.  Lord 2011 J Molluscan Studies 77: 182.

NOTE  the species is not provided by the author