#halimeda

Halimeda Carras: the artist

Ricci Andersen: the chemist and the motivational speaker

Kibou Akiyama: the musician

Shen Jin: the author and the doctor

These seaweeds give the appearance of small, hard plates, that look strung together; this is outwardly somewhat similar, to a prickly pear cactus (Opuntia sp.). Of course, the two clades are not related; for whereas desert cacti are obviously land plants, Halimeda sp. are, in fact, siphonous green algae, and their resemblance to certain cactuses is very superficial.

The reason why each segment is hard, is because they are impregnated with calcium carbonate, unlike the connecting tissue between them; as with the limey skeletons of the stony corals, those of Halimeda sp. degrade into sand, and Halimeda are so important in shallow marine ecosystems, that they produce vast quantities of 'Halimeda sand'; and this voluminous material contributes to the formation of atolls.

Halimeda it is one of the 'coralline algae' by some definitions - in such a sense, they are a non-phylogenetic group of macroscopic marine plants, all possessing hard skeletons. Cactus algae are unrelated altogether to the corallinale clade - the encrusting red and purple coralline algae that many reefers love; among green algae they are related to genera such as Chlorodesmis, Penicillus, Udotea, and Cauleroa.

Some Halimeda species form thickets in lagoons; but although they are obvious and easy to identify as Halimeda, there is uncertainty and confusion about the number of species, and their demarcation. To the reef aquarists, what matters primarily is that some Halimeda sp. - such as H. incrassata - are associated with sand or coral rubble.

Whereas other species in the same genus, grow attached to hard substrates, in locations with conditions of higher flow, but in relatively sheltered microhabitats. (Halimeda should not be exposed to higher than moderate currents.) Yet other members of the genus grow according to a sprawling habit. But the lagoon-associated H. incrassata is one of the sand growing species.

H. incrassata is a tropical seaweed that grows best at a temperature between 26 and 28 degrees centigrade, a little warmer than are most marine aquariums. Neither the light nor the water flow need to be strong, because this plant grows in turbid environments that are sheltered from the most severe wave action.

Some sources insist that Halimeda sp. are rather immune to the attention of herbivores. In truth, they suffer a lot of grazing, in the wild; it is just that their calcification deters ill equipped species from biting them. Around the reef, different herbivores consume different plants, either out of need or preference, just as grazers and browsers do on land.

Fish that graze on well established Halimeda often tend to have narrow diets, indicating they tend to be specialists, rather than generalists. Parrotfish and scarids bite at Halimeda much more often than do acanthurids or siganids, and these seaweeds are not preferred as food by either turf grazers, or browsers of fleshy algae.

It has been confirmed that a number of Siganus species are outright averse to eating cactus algae because it is calcified; these include S. argenteus, S. caniculata, S. radians and S. spinus. Similarly most acanthurids such as 'Acanthurus' triostegus are not Halimeda consumers at all, or they appear to consume it only incidentally or when it is newly settled, as do Ctenochaetus strigatus.

Proper feeding on Halimeda appears limited to some of the acanthurids possessing gizzard-like stomachs, such as 'Acanthurus' blochi, 'A'. cyanocheilus, and 'A.' olivaceous. These are not the species most popular among aquarists. So it is true that Halimeda will not be grazed by tangs, but it is only a rule of thumb.

A Tribute to Llewellya H. Willis

In the Sunday (5/12/2019) NYT Obituary was homage paid to Llewellya W. Hillis (1930 – 2019) — a Canadian-American trailblazer for women in the field of Science and a rock star to me for her extensive contribution in Marine Biology with a specialty in macro-algae… yes… seaweed.  Her bio is too impressive to cover here but I could tell from the obituary she had a favorite, Halimeda.  I know what…

Tagged by @fat-rolls-frictions

Araceli Faith Morandi

DEFENSIVENESS.

arms cross on chest / crossing legs / fist-like gestures / pointing index finger / karate chops / stiffening of shoulders / tense posture / curling of lip / baring of teeth

REFLECTIVE.

hand-to-face gestures / head tilted / stroking chin / peering over glasses / taking glasses off — cleaning / putting earpiece of glasses in mouth / pipe smoker gestures / putting hand to bridge of nose / pursed lips / knitted brows / looking away

SUSPICION.

arms crossed / sideways glance / touching or rubbing nose / rubbing eyes / hands resting on weapon / brows raising / lips pressing into a thin line / strict, unwavering eye contact / wrinkling of nose / narrowed eyes

CONFIDENCE.

hands behind back / hands on lapels of coat / steepled hands / baring teeth in a grin / rolling shoulders / tipping head back but maintaining eye contact / chest puffed up / shoulders back / arms folded just above navel / wide eyes / standing akimbo

INSECURITY & ANXIETY.

chewing pen or pencil / rubbing thumb over opposite thumb / biting fingernails / biting lips / hands in pockets / elbow bent / closed gestures / clearing throat  / “whew” sound / picking or pinching flesh / fidgeting in chair / hand covering mouth whilst speaking / poor eye contact / tugging at pants whilst seated / jingling money in pockets / tugging at ear / perspiring hands / playing with hair / swaying / playing with pointer/marker/cane / smacking lips / sighing / rocking on balls of feet / flexing or cracking fingers sporadically

ANGER & FRUSTRATION.

short breaths / “tsk” sounds / tightly-clenched hands / fist-like gestures / pointing index finger / rubbing hand through hair / rubbing back of neck / snarling / revealing teeth / grimacing / sharp-eye glowers / notable tension in brow / shoulders back, head up – defensive posturing / clenching of jaw / grinding teeth / nostrils flaring / heavy exhales

Cressida Philomena Rey (Halimeda)

DEFENSIVENESS.

arms cross on chest / crossing legs / fist-like gestures / pointing index finger / karate chops / stiffening of shoulders / tense posture / curling of lip / baring of teeth

REFLECTIVE.

hand-to-face gestures / head tilted / stroking chin / peering over glasses / taking glasses off — cleaning / putting earpiece of glasses in mouth / pipe smoker gestures / putting hand to bridge of nose / pursed lips / knitted brows / looking away

SUSPICION.

arms crossed / sideways glance / touching or rubbing nose / rubbing eyes / hands resting on weapon / brows raising / lips pressing into a thin line / strict, unwavering eye contact / wrinkling of nose / narrowed eyes

CONFIDENCE.

hands behind back / hands on lapels of coat / steepled hands / baring teeth in a grin / rolling shoulders / tipping head back but maintaining eye contact / chest puffed up / shoulders back / arms folded just above navel / wide eyes / standing akimbo

INSECURITY & ANXIETY.

chewing pen or pencil / rubbing thumb over opposite thumb / biting fingernails / biting lips / hands in pockets / elbow bent / closed gestures / clearing throat  / “whew” sound / picking or pinching flesh / fidgeting in chair / hand covering mouth whilst speaking / poor eye contact / tugging at pants whilst seated / jingling money in pockets / tugging at ear / perspiring hands / playing with hair / swaying / playing with pointer/marker/cane / smacking lips / sighing / rocking on balls of feet / flexing or cracking fingers sporadically

ANGER & FRUSTRATION.

short breaths / “tsk” sounds / tightly-clenched hands / fist-like gestures / pointing index finger / rubbing hand through hair / rubbing back of neck / snarling / revealing teeth / grimacing / sharp-eye glowers / notable tension in brow / shoulders back, head up – defensive posturing / clenching of jaw / grinding teeth / nostrils flaring / heavy exhales