This week’s fascination with brooding shrimp in Lembeh caused us to look a bit more closely into shrimp relationships. It all started with one simple question from a guest: are female shrimp bigger than the males? According to our Tropical Pacific Reef Creature Identification guide (Humann and Deloach), you can often times distinguish the gender of a shrimp based on its living arrangement, but not necessarily by its size. For example, if you happen upon a single set of shrimp, such as the beautiful Coleman’s Shrimp pictured above, you can assume that the larger of the two shrimp is the female.

This is due to the fact that Coleman Shrimp are “monogamous”, which means that the male Coleman Shrimp doesn’t have to grow large in order to fend off his reproductive competitors. Over time, small males are just as reproductively successful as larger ones, allowing the “small trait” to remain present in the population. Meanwhile, large female Coleman Shrimp produce more and more successfully brood their eggs (which takes a lot of energy). This leads to a higher reproductive success rate amongst larger females.

Skeleton Shrimp, on the other hand, are an example of a non-monogamous shrimp: Due to the fact that the males have to fend off competitive males every time they reproduce, males grow larger than females in this population. In a nut shell, two shrimp living side by side tend to put more energy into successful egg production and brooding which makes for larger females, whereas “communally-living” shrimp tend to produce larger, highly competitive males.

Along with doing a bit of gender identification on shrimp this week in Lembeh, we were also witness to quite the amazing Solar Eclipse! We skipped the first morning boat-dive in order to witness the event via a variety of devices: return guests from England brought “black-out glasses” that allowed us to directly view the eclipse, and our homemade “pin-hole box projector” projected the image of the eclipse amazingly well onto a small viewing screen. At the resort, old nail holes in the roof of the café acted as larger “pin-hole projectors” as they projected images of the eclipse all across the concrete floor of the café! It was yet another rare and amazing site to behold at Two Fish Lembeh!