Summarization of Copepods
Table of Contents:
Introduction Page 3
What is Labidocera Pages 3-4
What makes Copepods Important Pages 4-6
Anatomy of Copepods Pages 6-10
Cephalosome region Pages 7-8
Metasome region Pages 8-9
Urosome region Page 10
Developmental stages Page 11
Current research Pages 11-12
References Pages 13-15
The planet Earth has an incredible level of biodiversity across its surface, amongst the most diverse regions is that of the oceans. One of the many creatures within this vast region is a group of Copepods called Labidocera. Labidocera is genus of living organisms within the phylogenic tree. More specifically it is classified by the following branches of the phylogenic tree: Kingdom-Animalia, Phylum-Arthropoda, Class-Hexanauplia, (Subclass-Copepoda), Order-Calanoida, Family-Pontellidae, and Genus-Labidocera (Walter, 2021). This being just a Genus, there are several species within Labidocera. Labidocera are found in water ways across the planet. One specific type of waterway in which samples can be found for research are estuaries. Estuaries are where rivers or streams reach a large body of water, likely an ocean. This area is a good site for samples, because it is the area in which concentrated nutrients are delivered to the ocean. This is beneficial for the lower-level organisms within the food web of an ecosystem.
What is a Labidocera?
Labidocera can be classified using the taxonomic system as previously stated. This is great for the classification of types of organisms but can still be vague if someone is not familiar with what separated each classification. First it is important to understand what a copepod is before knowing the genus. Copepods are, named from the Copepoda-subclass, are small crustaceans found within fresh and salt water. They can function as “free-living organisms, symbionts, or as parasites” (Anderson, 2021). Copepods can then be further divided into either bethic or planktonic forms (Anderson, 2021). Labidocera are categorized within the planktonic category, meaning it drifts between water columns and can use its’ appendages to swim. Labidocera has nearly a hundred species across the world, (Walter, 2021). These Labidocera also grow in large numbers making them easy to harvest. Within the United States there is not currently a set of regulations dictating what researchers cannot do with regards to copepods. This makes the Genus Labidocera an ideal sample organism for research, especially that of this course which is designed around the techniques and skills of microscopes.
What Makes Copepods Important?
As previously stated, Copepods are a crucial organism within the aquatic ecological community. They are amongst the basal layer, meaning that collectively they contain more energy and are responsible for the distribution of energy from plants into predators. Further illustrating the point that copepods are a good source of energy, researchers state “[t]hey Copepods (Crustacea: Arthropoda) are the most abundant and probably the most ecologically significant zooplanktonic animals of the first consumer level of the marine food-chain. They are considered to be “nutritionally superior live feeds” for commercially important cultivable species, as they are valuable source of proteins, lipids, carbohydrates and enzymes all of which play an important role in digestion…” (P, Rajkumar. M, Santhanam. 2009). This quote by the researchers shows that not only are the copepods a good source of energy, but they are concentrated sources of macronutrients. Labidocera not only are an important transporter of energy within the ecosystem, they also eat the underdeveloped members of their own subclass. This helps maintain the fitness of their population as well as keep it in check. Labidocera help self-regulate the population of fellow copepods, maintaining their populations through feeding on nauplii and other vulnerable stages of copepod developments. This self-regulation allows them to maintain stable populations within their ecosystems (Conley & Turner 1985).
Beyond levels of energy transfer and biodiversity Copepods can also be an important indicator of ocean acidification. This is important for tracking levels of carbon in the water as a result of the air saturation. The ocean uses a similar buffer system to that of the human body which uses the flow of carbon dioxide, oxygen, bicarbonate and carbonic acid to modulate the concentration of free hydrogen atoms. This is relevant to Copepods because they have calcareous shells (Perumal. P, Rajkumar. M, Santhanam. 2009), which means their exoskeletons are at least partially composed of calcium carbonate. Like other hard-shell organisms, such as clams, snails, and mussels, Copepods are vulnerable to low pH levels. This is because under acidic conditions the increased amounts of hydrogen can outcompete the calcium in calcium carbonate needed to create or maintain their’ calcareous shells. Sampling of Copepods and their shells can show not just the direct pH of the environment, but their daily movement patterns alter when exposed to higher concentrations of hydrogen (Smith. J, Richter. C, Fabricius. K, and Cornilis. A, 2017). This also adds to the evidence supporting the claim for the climate change theory.
Copepods and climate change sound like two unrelated subjects. When in fact copepods add further evidence to support that climate change is not only real but is exasperated by the actions of mankind. The first part of this is due to the compositions of their exoskeleton changing as a result of limiting resources, which occurs during periods of excessive carbon in the air being precipitated into the ocean. The second part is due to the behavioral changes observed by the copepods as a result of the growing inhospitable environment that occurs within the physical composition of the ecosystem (A, Vehmaa. H, Hogfors. E, Gorojhova A, Brutemark T. Holmborn. & J, Engstrom-ost. 2013). The final aspect of climate change that is directly affecting the populations of these copepods are the increasing temperatures which are “…decreased egg viability, nauplii development, and oxidative status” (A, Vehmaa. H, Hogfors. E, Gorojhova A, Brutemark T, Holmborn. & J, Engstrom-ost. 2013 p. 1). This study also goes further into detail relating that the increased temperature and pH are not causing a change in the eggs being produced but this means the resources being placed into the attempt of reproduction are being wasted in comparison to copepods in ideal conditions. This does illustrate how the change in climate is already affecting a phylum subclass that is very valuable to the health of an ecosystem.
Anatomy of Copepods:
Copepods being spread across the world and being such a numerous group of organisms has led to the thorough studying of their anatomy. There are several physical differences between the genus’ and species’ that make each one unique. This being said, the generalized anatomy of the phylum subclass Copepod is as follows and will be based upon (J. Mauchline, 1998). Copepods have segments of their body that can be broken down by order from the cephalic to caudal regions, cephalosome, metasoma, and urosome. To be more concise they can also be labeled as head, thorax and abdominal regions. In these categories the cephalosome or head regions are where feeding, and sight are primarily controlled. This region contains several appendages such as, antennule, antenna, mandible, maxilla and maxilliped. These are for sensations and the externals processes of eating. The next segment down includes primarily the swimming appendages as well as some possible mating appendages. These swimming appendages are currently being studied by graduate students at Lincoln Memorial University. They are attempting to shed light upon the biomechanics of the swimming appendages of Copepods, specifically the genus Labidocera. The final region contains segments of genital and anal somites.
The Cephalosome region of Copepods:
The Cephalosome region has the most complex external morphology of the three regions. This is due to the far more numerous appendages that serve several different purposes. As illustrated by (J. Mauchline, 1998) this segment has the following appendages, rostrum, antennule, labrum, antenna, labium, mandible, maxillule, maxilla, and maxilliped. The rostrum functions a beak and may be a form of protection according to (J. Kennedy, 2018). The antennules are highly segmented and are bilaterally symmetrical according to (J. Mauchline, 1998), who also states that the antennules have setae or aesthetascs. The setae are microscopic projects which increase the surface area of the antennules helping the copepod maintain its place within the water column. The aesthetascs work as the sensory appendages, which as (J. Mauchline, 1998) says “…detect food, water disturbance and predators.” The labrum is loosely paired with the labium since they form the area of the mouth. Together these two can help feed, by manipulating food, harming the prey, and the release of secretions to modify the food for better digestion (J. Mauchline, 1998). The paired antenna works as a feeding appendage that has microscopic projections which help bring food into eating orifice. The mandible of copepods is similar to that of people, since in both organisms the mandible is responsible for the mastication of food. Within the mandible of the Copepods, (J. Mauchline, 1998) says they can grow spines which are nearly homologs to teeth in humanoids. These spines have a protective layer of silica which functions similar to enamel. The maxillule and maxilla are sequential appendages which are functionally the names for “first and second maxillae” according to (Lewis, 1969). These two appendages, according to (Lewis, 1969) contain motor neurons but do not contain muscles. Which (Lewis, 1969) claims must mean the motor neurons send signals for the projections at the ends to assist with the movement of food towards the mouth. The maxillipeds are paired appendages which are among the most variable sections within different copepods. According to (F. Ferrari, H. Dahms, 1998) the maxillipeds can differ in number of segments, length, projections and branches. These differences occur across different species as well as between male and females. These appendages are a more complex form of feeding appendage than those previously stated. This is because some are used to funnel food towards the mouth, which is like the other feeding appendages, but some are used as grasping appendages with as (F. Ferrari, H. Dahms, 1998) say “claw like structures.” To summarize these external structures of the cephalosome region are primarily used for the feeding of the copepod, by the detection, movement and grasping of food.