A Noninvasive Method For In situ Determination of Mating Success in Female American Lobsters (Homarus americanus)

The American Lobster is an iconic fixture throughout its geographic range from Atlantic Canada to New England. It is the target of one of the largest single species fisheries in the eastern United States in many areas. The continued success of this fishery is attributed to a variety of management measures, including biological controls intended to conserve brooded stock.

These regulations include minimum and maximum size limits protection for egg bearing females, and prohibition on the harvest of v notched females that are considered proven breeders. The future of the lobster fishery depends in part on a healthy supply of new recruits that are dependent on the success of the lobster's mating system. However, the heavily exploited nature of this fishery, similar to other crustacean fisheries worldwide, may influence the reproductive dynamics of this species.

Therefore, the goal of this work was to develop a simple, non-invasive method for ascertaining the mating success of sexually mature female lobsters. The sex of a lobster is best distinguished by looking at their ventral surface seen on the left as a female characterized primarily by the first pair of PLE pods, which are flat and feathery. Females also have an oval shaped seminal receptacle in which they store the spam metaphor passed by the male.

The male is shown on the right identifiable by the first pair of pleo pods that are somewhat conical and hardened. These gono pods assist with transferring the spermatophore to the female's. Seminole receptacle.

Also shown are the male's gono pores from which this SPO metaphor is extruded. During the courtship process, male and female lobsters display complex behaviors including chemically mediated communication and den sharing. Den sharing behavior occurs both before and after the female's molt and can be interpreted as m guarding by the male mating typically occurs within an hour after the female molts and lasts only for a very short time.

The male turns the newly molted female onto her back in order to transfer the S SPM metaphor to her seminal receptacle. A female lobster is capable of storing sperm from a mating event for two years or more, after which time she extrudes her egg clutch. The eggs are attached to the female's ple pods on the underside of her abdomen.

Egg development generally takes from nine to 11 months and is highly dependent on seawater temperature. Eggs hatch as planktonic larvae in the spring and summer and progress through several larval stages before settling to the bottom as juveniles. The method we describe here provides a technique to obtain sperm samples from a large number of female lobsters while aboard commercial lobster boats or other survey platforms at sea.

A blunt tipped needle is inserted into the female seminal receptacle and a portion of the spermatophore with the associated sperm is removed. The sperm sample can then be stored and examined later in the laboratory. Due to the structure of the Seminole receptacle, we have found no mortality associated with this technique.

Supplies needed for field sampling include a cooler with ice to keep samples cold small. Two milliliter sample vials. We used plastic einor tubes, an 18 gauge blunt tipped needle fastened to a three cc syringe and cold clean sea water.

Sterile is ideal but not necessary. Also, you will need calipers for recording the lobster's morphometric features such as carpus length, abdominal width, and claw dimensions if desired. Pre-printed data sheets are used to record these metrics along with the sample tubes identification number.

The sampler should also record details such as date sampling location, and method of capture commercial trap. For example, measure each lobster the nearest millimeter using the calipers carus length should be taken dorsally from the back of the eye socket to the end of the carus. Sometimes additional measurements such as abdominal width may be useful for estimating an index of maturity.

Later on, using a pair of calipers, measure the standard carus length. Then turn the animal ventral side up to measure abdominal width. To collect the sperm sample from the seminal receptacle, hold the female lobster ventral side up with the abdomen towards you.

Insert the needle of the syringe into the seminal receptacle. If a spermatophore is present, there will be a very firm sperm plug. You will need to penetrate carefully empty the syringe into a pre-labeled tube, fill the syringe with a small amount of clean sea water and inject into the seminal receptacle.

This will assist with dissociating the sperm from the hard plug. Then raise the plunger again and deposit this additional sample into the same sample tube. The angle and depth of the needle are both critical to obtaining consistent samples.

In this image, the seminal receptacle has been dissected and split vertically. The sperm plug occupies the top portion of the receptacle while a spermatozoa are located at the bottom, the deepest point of the receptacle. The receptacle is approximately a centimeter deep, depending on the size of the female, and the needle will need to penetrate the hardened plug to collect the sperm sample.

Be careful not to push through the shell like substance at the bottom of the receptacle. We will now show the sampling process more slowly. In a laboratory setting.

We recommend anyone who wishes to use this technique practice first in the lab before attempting to collect samples in the field. Again, hold the lobster with its ventral side up and abdomen towards you. Use a blunt tipped needle starting at a 45 degree angle with a tip towards the abdomen to penetrate the seminal receptacle and test for a sperm plug.

If there is a plug, this is where the resistance will be felt applying constant pressure. Twist the needle slightly to assist with this penetration. Push through the sperm plug, inserting the needle approximately one centimeter as noted by the black reference mark on the needle shown.

Empty the syringe into a sample tube. Then fill the syringe with a very small amount of cold, fresh seawater to flush out the seminal receptacle and again, empty the contents into the sample tube between lobsters. Make sure to thoroughly wash the syringe to avoid contamination.

Wipe the needle, then fill and empty the syringe multiple times to ensure any sample material has been flushed out. Before sampling another lobster, we recommend replacing the syringe and needle after several uses for the processing and identification of sperm. You will need a 200 microliter pipette disposable pipette tips, microscope slides and cover slips.

Take a sperm sample tube and remove approximately 200 microliters of liquid material. Pipette this onto an appropriately labeled microscope slide with cover slip using a standard compound microscope at a magnification of 100 x, determine the amount of sperm present. Sperm on the microscope slide may be oriented in many different positions, including vertical and lateral views.

As seen in these sample images, we recommend using qualitative descriptions such as many, few, or none to describe the amount of sperm present. We have successfully employed this technique in many locations at sea and by sampling lobsters at ports. Results shown here are from offshore lobsters captured on George's bank, which we were able to sample at a commercial holding facility.

A total of 84%of these females had sperm in their seminal receptacles. Surprisingly, those that did not were in the middle of the size range, not at the smaller, potentially immature sizes. This technique is not intended to quantify the actual amounts of sperm in the sperm metaphor.

Rather, it provides a non-invasive method that can be utilized at sea to determine whether a female lobster has made it successfully. The more we know about the reproductive success in lobsters, the better we can understand the impacts of exploitation of this species and thus appropriately manage this valuable marine resource.