Our last field trip of the semester, an optional one in the early morning to Surf Beach.
Later, in the afternoon at our normal class meeting time, we had the required "field trip" at high tide with a class potluck followed by final taxon presentations
by the 23 students. I will miss Friday afternoons with these talented students. This juvenile or very small adult was the only Aplysia californica
(California sea hare) that I saw. Instead, we saw lots of black sea hares (A. vaccaria).
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Doriopsilla albopunctata (white-spotted sea goddess)
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Tentative: Ophiopteris papillosa (flat-spined brittle stars) with very swollen bursa.
This species has small (0.1 mm diameter) eggs that develop into planktonic larvae and they have seasonal reproduction. These were the only two I saw. In contrast,
Ophionereis annulata (banded brittle stars) were under most rocks.
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elegant terns
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Embryos of Octopus bimaculoides ("lesser" two-spotted octopus; is there a better common name?).
This species is more common in intertidal than the larger and mostly subtidal two-spot octopus species, O. bimaculatus. O. bimaculoides spawns much
larger eggs that are released as benthic juveniles, so the species is holobenthic. In contrast, O. bimaculatus females brood many more and smaller embryos
that are planktonic after hatching.
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The mother of these Octopus bimaculoides was lurking nearby, not seen at first.
We tried our best to return the rock so she could resume her parental care.
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An Ophionereis annuala (banded brittle star) that also had swollen bursa,
apparently ready to spawn.
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We saw perhaps six Octopus bimaculoides ("lesser" two-spot octopuses).
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A still-small and quite adorable Aplysia vaccaria (black sea hare)
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Stenoplax conspicua (conspicuous chitons)
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ventral side of S. conspicua
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decorator crab
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juvenile Haliotis fulgens (green abalone)
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adult Haliotis fulgens (green abalone)
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We saw hundreds of mostly quite large Megastraea undosa (wavy turban snail),
and more than half had a pair of quite large Crepidula onyx (onyx slipper limpet) on their underside. This one had instead a pair of Crepipatella lingulata
(half slipper limpets), which is a little unusual, but this species is quite common in diverse intertidal and subtidal microhabitats
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Fissurella volcano (volcano keyhole limpet) was another extremely common species
that was on the underside of the abundant rocks at a low tide level; which stretch for about a mile without interruption along Surf Beach.
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Ceratostoma nuttalli (Nuttall's hornmouth) is a common muricid snail.
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Lepidozona pectinulata (pectinated Lepidozona)
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This Lepidozona pectinulata was on the underside of a Megastraea undosa
(wavy turban snail) which is an unusual place to see one. This species is the most common species seen under rocks in southern California.
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Navanax inermis (California aglaja) is a voracious cephalaspidean sea slug predator that feeds
on a variety of species, but mostly other sea slugs (including other N. inermis).
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My favorite study on the variety of species eaten by Navanax inermis (California aglaja)
was published in 1963
by a marine ecologist, Dr. Robert Paine (see linked source 1). You might recall that Dr. Paine
later performed a famous study, published in 1966 (source 1), demonstrating that ochre sea stars (Pisaster ochraceus) have a much more important impact on the community
structure and diversity of species in the mid-intertidal, than one would predict based on their relatively minor contribution
to the overall biomass
of the community.
The sea stars move up to feed in that zone when the tide is high. They especially prefer California mussels (Mytilus californianus, and their consumption of
mussels allows a variety of other animals and algae to coexist with the competitively dominant mussels.
He coined the phrase keystone species for these sea stars, which soon became a well known concept in the community ecology of intertidal habitats.
But few know that he studied the diet of Navanax inermis earlier. I recommend that you click on the first link to appreciate the incredible variety of species
they slurp up, documented with extensive observations by Paine.
- (Paine, 1963 and 1966).
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Cyanoplax keepiana (Keep's chiton);the following illustrate a few of their color variants.
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One of the juvenile Octopus bimaculoides ("lesser" two-spot octopus) that students found.
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Tentative: a nemertean
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There are multiple species of limpets on the abundant Tegula gallina,
including Lottia asmi, known as the "black" limpet. However, L. asmi can be greenish and lower profile when found on rocks.
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Lottia fenestrata (chocolate or fenestrate limpet)
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Mopalia muscosa (mossy chiton)
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Neotrypaea biffari (tidepool ghost shrimp)
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Under Construction!