The short and sweet of horseshoe crab spawning

You may have heard about the phenomena of horseshoe crab spawning … but, do you really know what’s going on? It’s when hundreds of thousands of these ancient arthropods (dating back 400 million years!) make the journey to low-energy sandy beaches along the Atlantic coast, predominately along the Mid-Atlantic region (highest concentration found along the Delaware Bay), around the time of the full and new moons of May and early June to spawn. Here’s the distilled version of the horseshoe crab spawning saga complete with the words you need to know (i.e., “pedipalps” and “satellite” male) if you want to be considered a horseshoe crab expert. Who doesn’t?

https://www.flickr.com/photos/beachchairscientist/

https://www.flickr.com/photos/beachchairscientist/

  1. Journeying from intertidal and deeper waters, male horseshoe crabs arrive near the beach waiting for females.
  2. As the females come closer to shore, males attach to the female’s abdomen. The extra claw, or “pedipalps”, is what the male uses to attach itself to the females.
  3. Not just the one … but, many “satellite” males follow the conjoined pair.
  4. The females dig a depression about 5 to 30 centimeters deep in the upper part of the beach and deposit the clusters of eggs.
  5. External fertilization occurs – Allows for a little extra competition from the “satellite” males!
  6. Repeat steps 1 through 5 multiple times per season, laying 3,650 to 4,000 eggs in a cluster (usually an estimated 88,000 eggs annually!).
  7. In 2 to 4 weeks after fertilization, planktonic larvae hatch from the eggs. Some slow moving larvae may even winter within the nests and hatch out the following spring.
  8. After hatching, larvae swim for about six days before they relax in shallow waters to molt into their first juvenile stage in approximately 20 days.
  9. For the first two to three years of life horseshoe crabs molt many times over, growing a quarter of their size each time. Once sexual maturity is reached they slowdown their molting to once per year.
  10. Horseshoe crabs mature around 10 years of age (or 17 molts) and are known to live to be approximately 20 years of age.

For more information on horseshoe crabs and “99 reasons I am in Limulus Love” check out my horseshoe crab page here.

Why you should never walk on dunes

It might seem nonsensical since the dunes look calm and peaceful, but it’s not a good idea to explore dunes. In addition to being illegal in many coastal towns, here are six other reasons why you should stay off the dunes:

1) Dunes store sand that help diminish potential shoreline erosion.
2) Dunes absorb the impact of storm surge and high waves.
3) Dunes prevent water from flooding coastal towns.
4) Dunes provide habitat and crucial nesting area for threatened and endangered species.
5) Dunes create a relaxing backdrop to any beach.
6) Dunes buffer the full force of the ocean and protect property.

BCS_Dunes

For more on dunes, their importance and role in beach ecology, check out the post “From Sandy, coastal towns learn ‘dune’ diligence. Is it enough?” written immediately after Hurricane Sandy.

17 facts about the wee sea potatoes

In honor of St. Patrick’s Day, and my Irish heritage, here’s a post on the humble and charming sea potato.

  1. The dried shell (also known as the test) of this urchin resembles a potato, hence the common name – sea potato.
  2. The sea potato, Echinocardium cordatum, is a common echinoderm found along beaches on all coasts of Britain and Ireland.
  3. The sea potato is related to sea urchins, heart urchins, and sand dollars.
  4. Most sea urchins live in rocky areas, but the sea potato prefers sand, particularly muddy sand.
  5. The spines of this echinoderm are thin and flattened.
  6. On the underside of the urchin are special spoon-shaped spines that help it to dig.
  7. There are longer spines of the back of the sea potato which aid in helping to breathe while it is burrowing.
  8. The sea potato can survive to depths of 650 feet.
  9. Unlike regular urchins, the sea potato has a distinct front end (i.e., not circular).
  10. The sea potato can grow up to 3 inches.
  11. The sea potato is very fragile and rarely survives collection.
  12. While alive the sea potato is deep yellow in color and covered in fine spines.
  13. The sea potato prefers sub-tidal regions in temperate seas.
  14. The sea potato are a type of heart-shaped urchin.
  15. Sea potato are deposit feeders and tube feet on its underside the sea urchin pick up sediment from the front of its mouth.
  16. The sea potato has no conservation concerns.
  17. The sea potato often has a commensal symbiotic relationship with the bivalve Tellimya feringuosa attached to its anal spines.
ocean313seapot_003_oceana

A sea potato, commonly found along the shore of Ireland

seapotatotest_images

The test of the sea potato

seaPotatounderside_theseashoreorguk

The underside of the sea potato

Ho, ho, ho! Look who’s coming to town … it’s the bearded seal!

The rather short snout with thick, long, white whiskers gives this true seal it’s appropriate common name. The bearded seal (Erignathus barbatus) can be as long 8 feet and weigh up to 800 pounds. I guess now we know what idiom they use under the sea instead of “the 800 pound gorilla in the room …”. These seals tend not to be seen in packs like their more social counterparts we view along harbors.

Bearded seals spend most of their lives in the Arctic waters, although one was recently found in southeast Florida. They enjoy feasting on arctic cod, shrimp, clams, crabs, and octopus and have been known to live up to 25 years. For more information on the conservation efforts and status of the bearded seal population please check out this page created by the NOAA Fisheries Service Office of Protected Resources.

Adult bearded seal by by wildlife photographer Paul Souders

Adult bearded seal by by wildlife photographer Paul Souders

Image (c)  www.telegraph.co.uk

What happens if the tide leaves a horseshoe crab stranded?

HSC_BCS

It’s not often you stumble across this on the beach. I asked horseshoe crab expert Danielle Chesky, Fishery Management Plan Coordinator with the Atlantic States Marine Fisheries Commission, what was happening in this picture and she said that “they’re dug in for the day after spawning until the high tide comes and they can get back out to sea”. For more posts on horseshoe crabs check out the Limulus Love page. Thank you to a colleague’s in-laws for sending along this picture.

 

Getting to know three … Bivalve edition

Ever know instinctively that some animals are ‘related’ and just can’t pinpoint their similarities? On the third day of every month I explain three features that are common among three animals of a certain group. Of course, generally each group has more than three representatives and even  many more similarities and then even more differences, but I am going to choose three similarities that link threes to keep it simplified. This month is focused the mussel, scallop, and clam. These three animals are all part of the bivalve group which is the second largest group of mollusks. The largest group of mollusks are the gastropods. Mollusks are well-known for their soft, unsegmented bodies and shell covering (although cephalopods do not have this feature). Check out the image below to learn what the featured animals all have in common.

 

Finned foliage

I wanted to share this image of anthias swimming in the Red Sea to usher in the briskness of autumn! As you know it’s my favorite time to beachcomb, but it’s also my favorite time to be surrounded by the brilliant-colored leaves of trees. The reds, yellows, and oranges are as vibrant as a coral reef

These schooling anthias are interesting because they are born one sex, but then change to another. In fact, all anthias are born female and only change to male if the male in their school dies. Most anthias remain female their entire life. This type of hermaphrodite is known as protogynous (proh-TAH-guh-nus). If it were the other way (beginning their life as male and changing to female) it would be known as protandrous (pro–TAN-dur-us).

RedseaAnthiasThe image is from Free Underwater Images, a new favorite resource. This website “promotes increased awareness of the marine environment by allowing users to download free, high quality underwater photos.  All images are in the public domain and free for any use without prior written permission and without fee or obligation. Images can be used for any non commercial purpose”.

Myth debunked: Delaware Bay not an annual pit stop for all shark species

A fan of Beach Chair Scientist on Facebook recently asked me to demystify a rumor she had heard. This is what she wanted to know: “I was told that over the course of a year, at least one of every species of shark can be found in the Delaware Bay. Do you know if this is true?” I asked Jim Wharton, frequent BCS guest blogger and shark expert, to tackle this one. This is his response.

Sadly, it is not true. There are at least 500 species of sharks in the ocean. They range in size from six inches to sixty feet. They can be found in water ankle deep to the abyssal depths … from the tropics to polar ice caps. To find a nexus point like this anywhere in the ocean would miraculous. Sharks are just too diverse.

Still, there are sharks in Delaware Bay. Anglers might encounter sand tigers, sandbar (brown) sharks, smooth dogfish, and spiny dogfish with other occasional visitors (including at least one record of a juvenile white shark). In fact, the National Marine Fisheries Service has identified the Bay as ‘Essential Fish Habitat’ for several species of Federally protected ‘Highly Migratory Species’ including sandbar sharks, sand tigers, and smooth dogfish. This designation recognizes the critical foraging and nursery habitat the Bay provides for these important species.

Sand tiger shark at the Georgia Aquarium. Image (c) Underwater Times

Dr Dewayne Fox’s lab at Delaware State University is working to create a conservation plan for the sand tiger sharks in the Bay. These distinctive, snaggletoothed sharks are very popular in public aquariums. Despite their fearsome appearance, they rarely interact with people. Sand tigers are top predators and represent a critical keystone species in the ecology of Delaware Bay. Dr. Fox and his students are implanting passive acoustic transmitters inside sharks to better understand their movement patterns. The transmitters emit an identifiable ‘ping’ that is collected by strategically located listening stations to help researchers track the animals in the Bay. Understanding how the sharks use the Delaware Bay is essential to identifying critical habitat for protection. You can learn more about Dr. Fox’s work here.

Sand tigers, by way, are freakish and fantastic creatures that are well-worth saving. No sharks have swim bladders, but sand tigers gulp air at the surface to make themselves neutrally buoyant. Sand tigers are one of many species that explode the myth of the shark in constant motion, frequently found lying near-motionless on the sandy bottom. Sand tigers are fish-specialists, with more-than-a-mouthful of narrow, prong-shaped teeth for grabbing slippery prey. They like to hang-out in large aggregations and may actively cooperate to herd schools of fish. Most fantastic of all…baby sand tigers are “embryonic cannibals.” Sand tiger embryos quickly exhaust their meager yolk sacs and start in on the undeveloped eggs…but they don’t stop there. The largest embryo in each uterus (yes, sharks have two) attacks and consumes its brothers and sisters in the ultimate form of sibling rivalry.

Good references for more on sand tigers:

  • Castro, J. I. (2011). The sharks of North America. Oxford: Oxford University Press.
  • Compagno, L. J. V., Dando, M., & Fowler, S. L. (2005). Sharks of the world. Princeton: Princeton University Press.

Thanks for sharing you knowledge, Jim! Check out his other BCS posts on sharks here.

The flight of swallows

That’s a great title for a song if someone wants to use it. In any event, have you ever been to the beach or walking along the marsh and felt the gloom and doom of darkness approach even though it’s a bright and sunny day? Have you ever looked up into the sky to witness the emergence of a feathered tornado? What you’re watching is the flight of the swallows – which can be up to several thousand birds approaching in one flight!

These no-more-than-14-centimeter-in-length birds are commonly seen swarming along the mid-Atlantic coast in September, the tail end of their breeding season. However, they are found throughout central and northern North America during their entire breeding season from May to September. These very social birds winter in Florida and the Caribbean. They’re rarely seen on land and spend the majority of their life in trees, maybe coming down to earth just to graze their wings along the surface of a body of water for a quick bath.

Why are they found along the mid-Atlantic coast in September? Well, they congregate in large flocks to roost among groves of small trees and cattails away threats (e.g., lots of people). They also prefer to make the nest for their eggs in the holes of dead trees away from threats. Male and female swallows are very territorial when it comes to their nest and will stand guard even from approaching fellow swallows.

Swallows produce one brood per year, averaging 5 eggs. These birds prove it takes a village as they make a nest for their eggs using the feathers of other birds to keep the eggs warm. The eggs typically hatch in about two weeks and are able to fly from the nest after three weeks. In one year the young swallow will be mature enough to breed!

And, in case you’re not familiar with the phenomenon – check out this well done amateur video I found on YouTube of a swarm of swallows (set to classical music no less!). It’s quite to spectacular sight.

Other great bird resources:

 

10 tips for a successful beachcombing trip

It’s my favorite time of year. This is the best time to explore the beach. It’s still sunny and warm, there are frequent storms (you’ll see why that matters later), and there are few people on the beach. For another six weeks along the mid-Atlantic (before it gets too cold), I encourage you to spend some time getting to know your local shoreline. Here are 10 tips for a successful beachcombing trip.

10. What to bring. Here is a list of some items you may want to remember so you’re prepared for any situation.

  • Often the beach is considerably cooler than inland so bring layers. You may want to wear hiking pants and bring a zippered sweatshirt so you’re equipped with lots of pockets for some other items that might be essential.
  • Make sure to have some appropriate soles. Sure it’s our instinct to be barefoot, however if you want to venture out along the jetties or rocks make sure you have some old sneakers or those water shoes with some decent grip (After all, you don’t want to ruin your adventure with a puncture to some sharp object). Also, the water might be a little cooler than you’d prefer and some good foot cover will allow you to wade into a tide pool.
  • Make sure to have a watch.
  • Even during the off-season the sun is shining and is strong enough to give you a burn. Make sure to bring along a hat, sunglasses, and sunscreen.
  • It’s always a good idea to bring a shovel, grabber sick, or even a metal detector so you can gently investigate inside crevices and below the sand.
  • You are going to want to cherish the moments so find that camera and try to make a neck strap so it’s always handy. You can take pictures of items you find and want to learn about later. You’ll also want to catalog those smiles in the sun.
  • Take along a small (i.e., not heavy) identification book so you can learn more about what you find while on your outing.

9. Be hands free. One more item that you’re going to love me for suggesting is a backpack. This way you can investigate a little bit further from your base and your items are quickly at your disposal.

8. Leave important items behind. Don’t ruin the day by losing a credit card or your phone. If you’re active and in the moment you might lose something and it’s going to be difficult to retrace your steps. I won’t say “I told you so”. On the same note it’s important to leave animals, plants, rocks, and seashells where you find them. If you want to have a little bit of the beach in your home check out these great books by Josie Iselin.

7. When to go. To get the optimum experience for beachcombing you’ll want to check on when low tide is at your beach spot. The best time to go beachcombing is 2-3 hours prior to low tide or an hour or so after (This is why a watch is important, you don’t want to get stuck on  shoal during high tide). Many intertidal animals live under the water in the sand during high tide, but come out to play (and seek out food) during low tide. If you can time it so you get to check out the beach after a big storm you’ll be in for a real treat. The strong wind and wave action of storms will wash up a fossils, bones, seaweed, and lot of other interesting treasures from the ocean floor. Also, keep in mind that dawn and dusk are difficult times to identify beach treasures. Although this is a great time to spot birds as many fish tend to come up to the surface at these times.

6. Where to go. My favorite spot to beachcomb is the Stone Harbor Point in NJ, but it’s not always easy for me to get there these days. I like to remind myself from time to time that I don’t need an ocean to beachcomb. There is a lake and creek in my neighborhood and these spots are a great place to spend the afternoon. After all, these waterways eventually lead to the ocean.  No matter where I decide to spend some time beachcombing I always make sure to note the general water quality.

5. Be careful. This is just a reminder to not tamper with obviously dangerous items. Fish hooks, metal canisters, and needles often wash up on the beach. While I am going to also suggest doing your part and picking up marine debris it’s also a good idea to err on the side of caution and when poking around. Also, some rocks look very steady but it’s important to be aware of your surroundings. If you are feeling like having an adventurous day it’s might be a good idea to make sure you have someone else with you. One last thing about being careful,even though the dunes might look like an interesting place to check out – it’s important to know that those grasses are incredibly brittle and can crack easily. It’s also against the law to walk on the dunes. The dunes are an important part of the beach ecosystem as they protect our homes from storm surge.

4. Leave it be. Each rock that you turn over is part of an ecosystem. A rock might be an essential part of an animal’s home as it helps pool water during high tide. Rocks also protect them from predator as well as the sun. It’s important to always remember to not take animals out of their natural setting – especially if you see them in a tide pool. Many animals are naturally attached to rocks for survival and you could be risking their survival.

3. Play. You might not want to go home, but you also might be in the company of some people that just don’t have a very long attention span. Even more frustrating is repeating the phrase, “No, you cannot go in the water today” over and over again. Build a sandcastle. Look to the horizon for dolphins or porpoises. Make a sand angel. Look up to the sky for cloud animals. Check out my ebook for other beachcombing adventures.

Image (c) Marine Debris Tracker

2. Bag it and track it. It’s always nice to be prepared to be able to do your part. I prefer to take along a hefty canvas bag that can fit in a backpack so I can tote marine debris back to a garbage can. You might even try to acquire one of these nifty bags with holes for sand to percolate through from the Green Bag Lady. When you head back to the car you can even do some citizen science and log your marine debris on the Marine Debris Tracker.

1. Don’t expect too much. It’s important to remember to relax and respect the area you are exploring. All of the ideas above are simply suggestions and ideas to ensure you get the most out of  a beachcombing adventure. Please don’t hesitate to share your favorite stories, spots, and other ideas for a great day. You can comment below of email me at info@beachchairscientist.com.