Jason S. Goldstein

The Complete Development of Larval Caribbean Spiny Lobster Panulirus argus (Latreille, 1804) in Culture

The Caribbean spiny lobster (Panulirus argus) is the most widespread, commercially important, and extensively studied spiny lobster in the western hemisphere, yet until now it has never been successfully reared through all its planktonic (phyllosomal) stages from egg to early benthic juvenile. Here we describe the development of phyllosomal P. argus in culture including the growth, duration, and morphology for 10 distinct stages. Phyllosomata were cultured from egg to juvenile in two ways: 1) in individual cultures using small glass bowls (120 and 400 mL) to determine individual growth, and 2) in group culture using a 40 L elliptical tank to obtain samples for morphological descriptions. Six of the 20 phyllosomata cultured individually (at 25-278C ) metamorphosed after 18-21 molts (mean1⁄420) to the puerulus stage at 140-198 days (mean1⁄4 174 days). Body lengths of the final stage phyllosomata and pueruli ranged from 25.6 to 28.2 mm (mean1⁄4 27.0 mm) and 16.4 to 17.5 mm (mean1⁄4 17.0 mm), respectively. Of the 550 mass cultured (at 258C) phyllosomata, 146 were sampled for morphological examination and subsequently divided into 10 stages, each described and illustrated herein. This is the first of the five Panulirus species known from the Atlantic Ocean to be cultured completely from hatch to settlement. This success is crucial for future research on larval behavior and dispersal and may renew interest in aquaculture of this economically consequential species.

The Complete Larval Development of the Pronghorn Spiny Lobster Panulirus Penicillatus (Decapoda: Palinuridae) in Culture

Abstract The ability to culture larval lobsters is of paramount importance to the commercial development of effective aquaculture methods. Recently, we developed two separate laboratory culturing strategies that yielded the complete larval development from egg to puerulus (post-larva) for the commercially important and transpacific Pronghorn spiny lobster, Panulirus penicillatus (Olivier, 1791). Individual phyllosomal culture of 10 newly hatched animals was carried out in a static seawater system. Two of the 10 phyllosomata held at 24.5-26.0°C metamorphosed after 22 molts to the puerulus stage at 256 and 294 days respectively (final body lengths = 30.80 mm and 32.00 mm). Mass culture of 500 newly hatched phyllosomata was also carried out in two specialized acrylic flow-through seawater tanks. Of the 500 larval animals, 215 were randomly sampled and morphologically staged (10 distinct stages were observed and documented as well as two sub-stages). Seven phyllosomata that were mass cultured metamorphosed to the puerulus stage under a constant temperature regime of 24°C (mean days = 302.4 and mean final body length = 32.133 mm). This species is now one of eight palinurid lobsters and only the fourth Panulirus spp. to be cultured completely from hatch to settlement stage. The biological understanding of larval development for this species promotes the feasibility for aquaculture and potentially facilitates future modeling of larval dispersal and duration in the field.

Influence of Natural Inshore and Offshore Thermal Regimes on Egg Development and Time of Hatch in American lobsters, Homarus americanus

Some egg-bearing (ovigerous) American lobsters (Homarus americanus) make seasonal inshore-to-offshore movements, subjecting their eggs to different thermal regimes than those of eggs carried by lobsters that do not make these movements. Our goal was to determine if differences in thermal regimes influence the rate of egg development and the subsequent time of hatch. We subjected ovigerous lobsters to typical inshore or offshore water temperatures from September to August in the laboratory (n = 8 inshore and 8 offshore, each year) and in the field (n = 8 each, inshore and offshore), over 2 successive years. Although the rate of egg development did not differ significantly between treatments in the fall (P ∼ 0.570), eggs exposed to inshore thermal regimes developed faster in the spring (P < 0.001). “Inshore” eggs hatched about 30 days earlier (mean = 26 June) than “offshore” eggs (mean = 27 July), and their time of development from the onset of eyespot to hatch was significantly shorter (inshore = 287 ± 11 days vs. offshore: 311.5 ± 7.5 days, P = 0.034). Associated growing degree-days (GDD) did not differ significantly between inshore and offshore thermal treatments (P = 0.061). However, eggs retained by lobsters exposed to offshore thermal regimes accumulated more GDD in the winter than did eggs carried by inshore lobsters, while eggs exposed to inshore temperatures acquired them more rapidly in the spring. Results suggest that seasonal movements of ovigerous lobsters influence the time and location of hatching, and thus the transport and recruitment of larvae to coastal and offshore locations.

Two Methods for Determining the Fertility Status of Early-Stage American Lobster, Homarus americanus, Eggs

Abstract The American lobster (Homarus americanus Milne Edwards, 1837) is the focus of the most important commercial fishery in New England, which relies on a variety of biological monitoring programs and surveys to guide the development of appropriate management plans. One key piece of information provided by these surveys is the number of females that are carrying eggs (ovigerous) that will subsequently contribute new recruits to the fishery. A major assumption is that all eggs carried by ovigerous females are fertilized and will thus result in viable recruits. However, because some lobsters extrude, and briefly carry, unfertilized eggs, this assumption needs to be re-evaluated. In particular, it is important to determine the approximate proportion of newly extruded eggs that are either fertilized, or not. The major goal of this project was to develop reliable methods for determining if early-stage lobster eggs (live and preserved) were in fact fertilized. One method involved using a nucleic acid stain to visualize egg DNA, after pretreatment of eggs with a proteolytic and collagenolytic enzyme solution to facilitate stain penetration through the egg membrane. With this method multi-nucleated (fertilized) eggs could be clearly distinguished from unfertilized eggs. A total of 20 egg clutches were tested to determine their fertility status using this method. Of these, 16 clutches (80%) were fertilized while 4 were not fertilized (20%). Of the 16 clutches with fertilized eggs, two had a mix of both fertilized and unfertilized eggs. A second method, using fluorometry to obtain measurements of total egg DNA, was also developed. There was a significant difference between the total DNA concentration in unfertilized control oöcytes and early-stage fertilized eggs (P < 0.001), and the total amount of DNA gradually increased as eggs developed (r  =  0.961, P < 0.0001). Both of these methods will make it possible to make a more accurate assessment of the proportion of female lobsters that will actually contribute new recruits to the fishery.

Biochemical changes throughout early- and middle-stage of embryogenesis in lobsters (Homarus americanus) under varying thermal regimes

Most marine crustacean eggs contain a full complement of nutritional resources that fuel the growth and metabolic processes over the course of their development. In terms of biochemical constituents, lipids and proteins play pivotal and central roles in these processes and, accordingly, have been studied extensively in crustaceans. Given the propensity of some ovigerous (egg-bearing) American lobsters (Homarus americanus) to undergo seasonal inshore-to-offshore migrations, thereby exposing their eggs to varying thermal regimes, this study’s goal was to assess egg quality over their course of development by documenting changes in total lipids, proteins, and egg size (volume) in lobsters subjected to one of three simulated thermal regimes (inshore, offshore, constant (12°C), N = 5/trt, 15 total) in the laboratory and sampled at five discrete time intervals. Total egg lipids showed a marked decrease over time (r2adj = 0.85, P < 0.0001), early in the fall (average = -26%) and late spring (-62%), compared with stark increases in proteins over the same period (r2adj = 0.63, P < 0.0001, averages = 60%, 34%, fall and spring). Although there were no significant differences in total lipid or protein values (or egg sizes) between eggs exposed to inshore and offshore temperatures (P > 0.05), differences occurred in eggs exposed to a constant temperature, and they hatched almost three months sooner than inshore or offshore ones. Seasonal temperature fluctuations also appear to control the rates of biochemical processes in lobster eggs but may be confounded by other variables.

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

Despite being one of the most productive fisheries in the Northwest Atlantic, much remains unknown about the natural reproductive dynamics of American lobsters. Recent work in exploited crustacean populations (crabs and lobsters) suggests that there are circumstances where mature females are unable to achieve their full reproductive potential due to sperm limitation. To examine this possibility in different regions of the American lobster fishery, a reliable and noninvasive method was developed for sampling large numbers of female lobsters at sea. This method involves inserting a blunt-tipped needle into the females seminal receptacle to determine the presence or absence of a sperm plug and to withdraw a sample that can be examined for the presence of sperm. A series of control studies were conducted at the dock and in the laboratory to test the reliability of this technique. These efforts entailed sampling 294 female lobsters to confirm that the presence of a sperm plug was a reliable indicator of sperm within the receptacle and thus, mating. This paper details the methodology and the results obtained from a subset of the total females sampled. Of the 230 female lobsters sampled from Georges Bank and Cape Ann, MA (size range = 71-145 mm in carapace length), 90.3% were positive for sperm. Potential explanations for the absence of sperm in some females include: immaturity (lack of physiological maturity), breakdown of the sperm plug after being used to fertilize a clutch of eggs, and lack of mating activity. The surveys indicate that this technique for examining the mating success of female lobsters is a reliable proxy that can be used in the field to document reproductive activity in natural populations.