Category: fish

Male pipefish who get pregnant reduce investment in their offspring if they see a sexy female

August 22, 2018 • 11:45 am

This new paper in the Proceedings of the Royal Society B caught my eye because of its title (abstract here but paper behind a paywall; judicious inquiry might yield you a pdf).  Check out the title and the abstract, and I’ll explain a bit of the results below (I read the paper quickly):

First, a bit of biology. Many species of pipefish and seahorses have a reproductive system in which males become pregnant. What happens is that females produce their eggs and stick them into the brood pouches of males, who fertilize them and then protect them, control the salinity, and even nourish the eggs using materials from the male’s body.  Since there is a shortage of available male brood pouches compared to the number of females who want their eggs fertilized, there’s competition between females for male pouches—the reverse of the usual competition by males for access to female eggs when females get pregnant or lay eggs. (Don’t believe Richard Prum’s new book about this, in which he implies that there really isn’t male competition by males for females, even in humans where the data on male profligacy vs. female choosiness are clear.)

Since sexual selection is reversed in these species, you find reverse ornamentation as well: it is the females who are ornate compared to the drabber males. And males in tests prefer both larger and more ornate females above smaller or less showy females. Here is the difference in seahorse anatomy and a male giving birth:

Look at all those babies!

In the new paper, authors M. Cunha et al did three sets of studies:

  1. They gave pregnant males of black-striped pipefish the sight (in a divided aquarium) of new females, some larger, some smaller, and some about the same size as females who had already “impregnanted” the males. In the first study, those males who got to see larger females produced smaller offspring. This may be because they’re reducing their investment in past pregnancies in hopes of remating to a “fitter” or more attractive female and producing more and better offspring.
  2. The authors measured the incidence of aborted embryos in pregnant male pipefish, and showed that the presence of very large females on the other side of the divider increased the percentage of aborted embryos in the male (they didn’t test females of different size, but used large females vs no females). This suggests that males can somehow reduce their investment when seeing another attractive female, though they didn’t use females of different size (attractiveness), which would have been a marked improvement of the design.
  3. They looked at wild pipefish males whose embryos were at different stages of development, and found that the heterogeneity of embryo size within a male decreased as pregnancy proceeded, and this was correlated with marked reduction in brood size. This was not due to random culling of embryos, but to culling of either the smallest or largest embryos (they couldn’t determine which were culled), which the authors see as a a form of selective abortion.

Overall, although the data aren’t terribly strong, this suggests a form of post-fertilization sexual selection, in which males decide to abort or reduce investment in embryos if they see a better mating opportunity. To quote from the paper:

Male pipefish, triggered to invest less in ongoing pregnancies by the sight of a very large, sexy female, hence produced smaller and more heterogeneous offspring, while also reducing brood size. As in pipefish resources derived from aborted embryos are captured by the father, instead of being directly distributed among developing embryos [14], males stricken by a sexier female not only save energy reserves for a presumably more auspicious future reproductive event, but they also potentially seize resources from a less rewarding brood.

As I lacked the time to read this paper as closely as usual, readers may find problems with the paper or errors in my summary.

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Cunha, M., A. Berglund, S. Mendes, and N. Monteiro. 2018. The ‘Woman in Red’ effect: pipefish males curb pregnancies at the sight of an attractive female. Proc. Roy. Soc. B. 285:20181335. Published online.

Readers’ wildlife photos

July 11, 2018 • 8:00 am

Stephen Barnard from Idaho has sent some diverse photos, including an unusual montage. His notes are indented.

Boris (the male American kestral [Falco sparverius] who bred in Stephen’s nestbox):

A female fledgling:

There are at least three kestrel fledglings, and probably at least four. I think that’s Natasha [the mother] up high and the other four are chicks. They’re being harassed by barn swallows.

An HDR combination of two photos, one focused on the fledgling and one focused on the moon. Weird effect. I had to add an eye.

A rare insect photo from me: a Western Tiger Swallowtail (Papilio rutulus):

 

Here’s another insect photo. These are trico spinners. Tricos are tiny mayflies that mate in the morning in huge swarms and then fall dead into the water. The trout go bananas, abandoning their territoriality to gather in pods at the optimal places to slurp tricos. It makes for very good fishing. I’ve attached a couple of photos of a rainbow trout [Oncorhynchus mykiss] in the act of eating a trico. Also, a pretty big rainbow trout (21″) that took a trico imitation. Finally, a closeup of the trout’s eye, showing a reflection of the sky and the creek bank.

 

 

Readers’ wildlife photos (and a video)

June 6, 2018 • 7:45 am

Stephen Barnard has sent us a batch of lovely photos from Idaho. Among his many great pictures, this first one, of the female American kestrel (Falco sparverius) roosting in Stephen’s nestbox, has to be one of my favorites: Stephen sent some technical info:

Natasha. This photo is with my Canon 5D4 and 700mm lens.

 

And a video; the pair are being severely harassed by Brewer’s blackbirds:

While being harassed by blackbirds, Boris brings a vole to the nest box, Natasha arrives, he hands it off to her, and she takes it inside.

We also have pelicans; Stephen’s notes are indented.

First, a few photos of American White Pelicans (Pelecanus erythrorhynchos). These are magnificent birds, but whenever I see them on the creek I chase them away, and so does every other fisherman and landowner with water. They can do a great deal of damage to the trout fishery in a short time.  For the second and third photos I’d sneaked up very closely. (They’re very easily spooked because everyone chases them.) I watched them doing their typical feeding behavior — working as a coordinated group, pushing schools of small fish into the shallows where they chow down.


Here is a Barn Swallow (Hirundo rustica). This is one of the swallows that build mud nests on my front porch every year.

This Sandhill Crane (Grus canadensis) wasn’t happy about me passing by in the truck. This is a male, one of a pair, and I suspect they have a colt or an egg nearby, because they were luring/threatening me into another direction (which wasn’t wasn’t an option).

And a brown trout (Salmo trutta):

 I caught it in one of my ponds on opening day. It took a callibaetis nymph imitation.

Reader’s wildlife photo (and a ZeFrank video)

May 13, 2018 • 8:00 am

I have a hiatus on my backlog of wildlife pictures until I return on Saturday, but here’s one sent by Stephen Barnard from Idaho: it’s Boris, one of the two American kestrels (Falco sparverius) nesting in a box on his garage. (The female’s named Natasha.) No word about whether there are chicks yet:

As lagniappe, ZeFrank has a new video: “True Facts about the Frog Fish” (h/t: Rick). There is some great footage of this amazing fish; check out the frogfish attacking a flounder.

Readers’ wildlife photos

March 29, 2018 • 8:00 am

I’m delighted to have Stephen Barnard back, who took a hiatus from photography. Here are some of his photos from Idaho, along with his captions (indented):

The weather and the lighting are improving so I’m back to taking some photos.

First, an in-flight photo of a pair of Sandhill Cranes (Grus canadensis). They breed here and have just recently shown up.

Next, a couple of photos of a female American Kestrel (Falco sparverius) that’s been hanging around. I hope she decides to use one of the nest boxes I installed.

 

Next, a bull moose (Alces alces), shed of his antlers, whom I call Blind Bob because he’s blind in his left eye—probably due to combat. I’ve seen him around for several years and he seems to be doing OK. My tenant photographed him the day before (the next two photos) when he was “grooming his honey”. The third moose photo documents that this was indeed Blind Bob. Moose aren’t known for their keen eyesight, and it isn’t a fatal injury, obviously.

Finally, a couple of trout I caught this afternoon, a Brown Trout (Salmo trutta) and a Rainbow Trout (Oncorhynchus mykiss). They’re skinny from the winter, and hungry.

Also, some Green-winged Teal (Anas carolinensis).

Some not completely black dogs (an improvement) and my daughter Nora’s cat, Karen, in Menlo Park, CA.

 

Cormorant fishing off the skin of a whale shark

February 10, 2018 • 7:30 am

I had to put up this video because it’s so cool and unusual (Matthew alerted me to it). It’s a cormorant grabbing remoras affixed to the skin of a whale shark off Cabo San Lucas, and a one-off video. (Remember that the whale shark, Rhincodon typus, is the world’s largest fish.)

Now that is avian inventiveness!

Earth Touch News Network says this:

Fishing is time-consuming business, so diving birds in Mexico’s Baja California are frequenting the local “sushi conveyor” instead. That conveyor comes in the hulking shape of the region’s reigning big fish: the whale shark. The crafty cormorants have figured out that the giant sharks provide an endless supply of remora sashimi.

In the clip, a diving cormorant yanks furiously at a remora fish attached to the skin of a passing whale shark, before finally pulling its meal free. It’s a truly remarkable sighting – in fact, this footage filmed back in 2012 may be the first (and only) example of its kind. According to marine biologist Dr Simon Pierce, who has done extensive work on whale sharks, experts have been excitedly discussing the video since it started making the rounds online earlier this week.

“It’s super cool!” he says. “I don’t think it’s been documented. I’ve never seen or heard of it previously, but that particular cormorant certainly knew what it was doing. Smart bird!”

An extended clip released by Manta Scuba Diving [JAC: this clip] confirms the event was no once-off: after its initial catch, the bird – likely a Neotropic cormorant or double-crested cormorant (Phalacrocorax brasilianus or Phalacrocorax auritus) – came back for both second breakfast and elevenses.

But wait! There’s more! (My emphasis.):

Remoras attach to their host species (animals like sharks, cetaceans and sea turtles, as well as the odd ship or human diver) using a slatted sucking disc located above the eyes. Once in place, the hitchhikers cruise along effortlessly, ready to gobble up any morsels that float their way.

The immense size of whale sharks offers particularly spacious real estate for remoras – some individuals cart dozens of the freeloaders around – so it’s not entirely surprising that local birds have learned to capitalise on such an abundant food source.

Roominess aside, there’s another reason remoras cling to whale sharks in such large numbers: poop. While it was long believed that the remora diet comprised mainly of their hosts’ mealtime leftovers, scientists have since discovered that the suckerfish prefer to dine on something a bit more plentiful. And you don’t get much more abundant than a whale-shark poop cloud: the animals can drop 56,000 litres in one go.

Readers’ wildlife photos (and video)

October 29, 2017 • 7:45 am

We have photos from four readers today. The first is from Stephen Barnard, whose documentation of a brood of gadwall ducklings was posted this summer. I believe eleven were hatched, and nine survived. What took them? Maybe an Onchorhynchus mykiss:

Here’s a rainbow trout that may have been responsible for some gadwall duckling fatalities.

Urban wildlife: deer at night taken in New Jersey  by reader Liz Strahle with an iPhone:

 

Here’s a duck family sent on July 26 by reader Patrick Polan:

 I live roughly ten minutes  from Michigan State Universities campus and visit on a regular basis to walk the beautiful gardens as well as the river trail.
Attached are some photos I took of a female mallard duck, Anas platyrhynchos, and her three ducklings. The photos are taken at the Beal Botanical Garden on Michigan State Campus. I was able to get as close as I could and placed my hand by the water and sure enough the Mother and her ducklings came very close to my hand. In that moment I wish I had oatmeal or chicken feed on me. I am very grateful and fortunate to live close to my alma mater and experience nature. ​​​​​​​
I miss my ducks!

We have a new contributor, John Runnels of Louisiana, who took this video showing gazillions of migrating pelicans. Look at all those birds! His notes:

This Thursday on my way to work I took this video of migrating white pelicans (Pelecanus erythrorhynchos) in the Baton Rouge, Louisiana lakes. I have never seen so many all in one place: