Perspective Chapter: Crustaceans Taxonomy

Abstract

Crustaceans are one of the organisms living on the earth that is important to know forms (e.g., larvae, morphs, adults, sexes) and units. In the current era, crustaceans (crab, shrimp, and lobster) emerge as one of the most demanding seafood than other types of seafood, and therefore, natural implication of worldwide fisheries is more dominated by crustaceans. Because a large number of crustaceans taxa have been identified and described, it is necessary to definite groups. Crustaceans are one of the world’s oldest and most diversified arthropods, as well as one of the most successful invertebrate groups, with an assessed 40,000 living species and more than 150,000 identified. The names “shrimp” and “prawn” do not relate to any specific taxonomic groups. Although “shrimp” is often used to refer to smaller species and “prawn” is more commonly used to refer to larger ones, there is no clear distinction between the two terms, and their usages are sometimes misunderstood or even reversed in various regions. This chapter aims to focus on the taxonomy of the crustacean and their contribution and importance in fisheries.

1. Introduction

Crustaceans are a varied group of arthropods (phylum Arthropoda) that includes Brine shrimp, copepods, ostracods, Sand hoppers, crayfish, crabs, lobsters, barnacles, prawns, krill, and mantis shrimp (see Figure 1) [1]. Crustaceans have branched (biramous) appendages, chitin and calcium exoskeleton, two pairs of antennae projecting in front of the mouth, and paired appendages that function as jaws with three pairs of biting mouthparts. Carcinologists have long argued the taxonomic classification of crustaceans, with five, six, or even 10 classes sometimes assigned to the group at the phylum, subphylum, or superclass level [2]. The Crustacean has been classified as a class by others [3].

Figure 1.

Illustration of the major groups of freshwater crustaceans [1].

2. Taxonomy, systematic, and classification

The term taxonomy is derived from the Greek taxis (it means “order” or “arrangement”) and nomos (it means “law” or “science”) (A.P. de Cadolle, 1813). Taxonomy is the rehearsal and application of classification and can be used ass taxonomic units also familiar as taxa. It originally can be denoted only to the classification of organisms but up-to-date it is used in a fuller sense to the principle fundamental such as a classification. Taxonomy essentially copes with the naming and classification of taxa and forms only a part of biological systematics known as biodiversity. In taxonomy, the smallest unit of classification is called species, which consists of classification and nomenclature. Based on the relation of the organisms, it can be grouped or placed known as classification [4]. The system of classification is developed and used by Carl Linne, 1735, the term systematic can be used in taxonomy.

Crustaceans are divided into six categories (see Table 1).

1. Ostracoda—tiny animals with bivalve shells [5, 6].

2. Branchiopoda—clam shrimp.

3. Cephalocarida-horseshoe shrimp.

4. Maxillopoda—include barnacles.

5. Malacostraca—great diversity.

6. Remipedia—blind crustaceans.

Class Branchiopoda	Class Ostracoda	Class Maxillopoda	Class Remipedia
Subclass Phyllopoda	Subclass Myodocopa	Subclass Tantulocarida	Order Nectiopoda
Order Diplostraca	Order Myodocopida	SubclassMystacocarida	Family Godzilliidae
Suborder Cladocera	Order Halocyprida	Subclass Copepoda	Family Micropacteridae
Family Daphniidae	Subclass Podocopa	Order Platycopioida	Family Speleonectidae
Family Moinidae	Order Platycopida	Order Calanoida
Family Bosminidae	Order Podocopida	Order Misophrioida
Family Macrothridicae	Subclass Mystacocarida	Order Cyclopoida

Table 1.

Crustacean taxonomy is constantly being revised and reevaluated, and the classification system utilized herein is no exception (generally based on [3]).

Crustaceans are sometimes separated into two groups: entomostracans, which include copepods, barnacles, and fairy shrimp, and malacostaceans, which include lobsters, crabs, and shrimp (Figure 2).

Figure 2.

Crustaceans groups.

3. Species of crustaceans

Crustaceans consisting of crabs, shrimps, and lobsters are one of the most important groups of Arthropod [7]. Now can be explained order Decapoda, for the first time about 8000 species of crustaceans dispersed among more than a thousand genera (Chace, 1951) and lately estimated a total number of extant species of 14,756 in 2725 genera (see Figure 3). This implies that in the last 50 years, the number of described species has nearly doubled. However, we are a long way from knowing the true global diversity of decapods. The number of known fossil species currently stands at 3300, and discoveries will continue as new localities are explored, more revisions are completed, and museum collections are more thoroughly studied.

Figure 3.

Illustrate the cladogram below results from analysis by [8].

According to Ernst Mayr’s description of a species was groups of essentially or hypothetically upbringing natural populations, which are reproductively isolated from other groups (see Table 2). Moreover, for accurate taxonomic species, there are numerous kinds relating to ecological and evolutionary concepts (e.g., sibling species, cryptic species, sympatric species, allopatric species, syntopic species, allotopic species, monotypic species, insular species, polytypic species, continental species).

Taxon	Extant species	Extant species are also known as fossils	Exclusively fossil species
Order Decapoda Latreille, 1802	14,335	321	2979
Suborder Dendrobranchiata Bate, 1888	540	0	98
Suborder Pleocyemata Burkenroad, 1963	13,795	321	2862
Infraorder Stenopodidea Bate, 1888	69	0	2
Infraorder Caridea Dana, 1852	3268	0	57
Infraorder Astacidea Latreille, 1802	653	5	124
Infraorder Glypheidea Winkler, 1883	2	0	256
Infraorder Gebiidea de Saint Laurent, 1979	192	4	25
Infraorder Axiidea de Saint Laurent, 1979	423	14	260
Infraorder Achelata Scholtz and Richter, 1995	140	3	72
Infraorder Polychelidea Scholtz and Richter, 1995	38	0	55
Infraorde Anomura MacLeay, 1838	2451	19	230
Infraorde Brachyura Linnaeus, 1758	6559	276	1781

Table 2.

Number of species Decapoda [9].

3.1 Taxonomy levels

There are three steps for a taxonomic study: (1) alpha-taxonomy (or classical taxonomy), which is concerned with the description of novel species and their classification into broad genera, (2) beta-taxonomy (or explorative taxonomy), which focuses on species-level relationships, and (3) gamma-taxonomy (or Encyclopedia taxonomy), which focuses on species-level relationships. Intraspecific differences and their evolutionary links are often known as speciation research (i.e. study of speciation). In reality, because of the three levels of taxonomy overlap, practice is impossible to investigate any species in isolation from each other taxonomy has only been applied to a few animal groups (e.g. birds and butterflies) the gamma level was reached. Study or work in the majority of animal groups including crustaceans is at gamma and alpha levels.

Linnaeus invented this system of naming, and the standards for naming animals are currently written forth in the International Code of Zoological Nomenclature (ICZN).

• Each species name in the binomial system has two parts: the genus name and the species name (also known as the specific epithet); for example, the scientific name of the kiddi (karikadi) shrimp is Parapeneopsis stylifera (H. Milne Edwards, 1837 in H. Milne Edwards 1834–1840).

• Even when derived from a proper noun such as a person’s or place’s name, the initial letter of the genus is always capitalized, whereas the first letter of the species is not. Every binomial scientific name is either a Latinized version of a word from another language or a Latinized version of a word from another language.

• All names of genera and lower taxa are italics (underlined while writing) by convention, while family names and higher taxa are put in plain text.

• Penaeus indicus H. Milne Edwards, 1837 is a trinomial name for a subspecies of the genus Penaeus (trinomen for animals, ternary name for plants). A species’ binomial name is also known as its Latin name. Biologists, on the other hand, prefer the term “scientific name” over “Latin name” because the words used to form these names are not always from the Latin language, even though terms from other languages are frequently Latinized to make them fit for this purpose. Species names are frequently drawn from Ancient Greek names [10, 11].

• Species names are frequently based on a person’s surname, such as a well-known scientist’s surname (e.g., Aristeus alcocki and Penaeus silasi), or a Latinized form of a relevant geographical name (e.g., A. alcocki and Penaeus silasi) (e.g., Metapenaeus kutchensis and Metapeneiopsis andamanensis) [11]. The species and generic names of binomen have opposing purposes: The species name indicates distinctness, while the generic name expresses the relationship.

• Biologists normally include the authority (Author who originally described the species) and the date (year) of the species description when using the scientific name of the species. Thus, the scientific name of the Indian shrimp species is P. indicus H. Milne Edwards, 1837, where the name “H. Milne Edwards” informs the reader of who originally characterized the species and 1837 is the year (year) of publication.

4. Binomial nomenclature’s importance

Binomial nomenclature is widely used because it prevents the ambiguity that can arise when common names are used to refer to a species. Even within a country, common names might range from one region to the next and certainly from one country to the next. The scientific name, on the other hand, can be used anywhere in the world and in any language, avoiding confusion and translation difficulties [11]. The only internationally (universally) acknowledged standard way of referring to biological creatures is by their scientific names. They make it easier for scientists as well as trading partners who speak different languages to communicate. Without their utilization and standardization, no two individuals could truly know what organism they were discussing unless they had both seen it.

The processes used to create binomial nomenclature tend to favor consistency. Even while the existing stability is far from perfect, it is nevertheless helpful, for example, when species are transferred between genera (as is frequently the case as a result of new knowledge), the species descriptor is maintained. Similarly, historical species names may be kept as infraspecific descriptors if previously assumed to be different species relegated from species to a lower rank. Animals of subgenera and above have uninominal scientific names that begin with a capital letter. The ICZN mandates defined taxonomic ends, such as superfamily (−oidea), family (−idea), subfamily (−inae), and tribe (−inae) (−ini). The classification of shrimps exemplifies this underneath (also see Tables 1 and 2):

Phylum: Arthropoda incertae sedis

Subphylum: Crustacea Brünnich, 1772

Class: Malacostraca Latreille, 1802

Subclass: Eumalacostraca Grobben, 1892

Superorder: Eucarida Calman, 1904

Suborder: Dendrobranchiata Bate, 1888

Superfamily: Penaeoidea Rafinesque, 1815

Family: Penaeidae Rafinesque, 1815

Subfamily: Penaeinae Rafinesque, 1815

5. Nomenclature rules

Typification is the process of identifying a nomenclatural type. It is the method by which taxa are given scientific names. A zoological object on which the original published description of a name is based is referred to as a “type.” Except for the plenary powers of ICZN, the “type” cannot be modified once it has been identified (not even by the original author). Even though Linnaeus never defined any specimen as a “type,” his descriptions were based on a single specimen, and he replaced old specimens with fresh ones. This method persisted throughout Europe for a long time, causing uncertainty when it came to tracing the original specimens. The entomologist Pierre Andre Latreille, who lived in the early 1800s, is thought to have started the practice of specifically defining types [10, 12]. Not all early authors kept type material, which can make later identification of species more difficult.

In 1901, the zoological code mandated typification for future work. There are 41 various type series; however, the following are the most well known [11]:

1. Holotype: A single specimen chosen by the author of a species to serve as the genuine type for the species. A holotype must be labeled with the following information: location, date, size, sex, developmental stage, the hostname (if epizoic or parasitic), and collector name. It should be deposited in a reputable museum and given a unique identification number.

2. Paratype: A specimen other than the holotype cited in the original description.

3. Allotype: An allotype is a specimen of the opposite gender as the type.

4. Syntype: Specimens used to determine the principal type (holotype or neotype).

5. Topotypes: Specimens that have been identified as having a unique origin.

6. Apotype: A specimen rather than the type on which a subsequent or supplemental description or illustration is based. It is also known as a hypotype.

7. Genotype: A species that is defined as the type species of the genus it is based on.

8. Lectotype: The type of a species is a specimen chosen from a group of syntypes after the description has been published.

9. Neotype: When a species’ designated type (holotype, syntypes, neotype, or lectotype) is previously designated but then lost or damaged beyond recognition, a neotype is a new specimen recognized as the type.

10. Isotype: A specimen acquired at the same time as the holotype, paratypes, or syntypes, but not from the same location [11, 13].

11. Monotype: A monotype occurs when the holotype of a species is the only specimen known to science [13].

12. Morphotype: A specimen depicting a species’ morphological variation [11, 13].

6. Synonymy

Synonymy is a term used to describe two or more names that belong to the same taxon. The Law of Priority states that when a species has multiple synonyms, only the oldest one is valid (ICZN) [11]. The oldest is treated as the proper name and is referred to as a senior synonym, whereas the others are referred to as junior synonyms. Synonyms are a major tricky for taxonomists. These are made owing to a lack of awareness of the available research or the amount of variation that a species can have. Many times, the same species is reported by two or more writers under multiple names without the authors being aware of the species differences (Table 3).

Order	Suborder	Superfamily	Family	Genus
			Hollinidae Swartz, 1936	Anticostiella; Copeland, 1973
			Tetradellidae; Swartz, 1936	Foramenella; Stumbur, 1956
				Tetradella Ulrich, 1890
	Palaeocopina Henningsmoen, 1953	Hollinoidea; Swartz, 1936	Oepikellidae; Jaanusson, 1957	Platybolbina Henningsmoen, 1953
				Eographiodactylus Kraft, 1962
			Tvaerenellidae Jaanusson, 1957	Tvaerenella; Jaanusson, 1957
		Eurychilinoidea Ulrich and Bassler, 1923	Eurychilinidae Ulrich and Bassler, 1923	Eurychilina; Ulrich, 1889
			Bolliidae Bouček, 1936	Jonesites Coryell, 1930
				Dicranella Ulrich, 1894
Beyrichiocopida Pokorný, 1954			Circulinidae Neckaja, 1966	Byrsolopsina Swain and Cornell, 1961
				Easchmidtella Schallreuter, 1967
	Binodicopina Schallreuter, 1972	Binodicopina Schallreuter, 1972	Aechminidae Swartz, 1936	Aechmina Jones and Holl, 1869
				Pseudohippula Schallreuter, 1975
			Spinigeritidae Schallreuter, 1980	Faurella; Copeland, 1973
				Spinigerites Schallreuter, 1980
			Schmidtellidae; Neckaja, 1966	Schmidtella Ulrich, 1892
	Paraparchitocopa Gramm, 1975		Jaanussoniidae Schallreuter, 1971	Hemiaechminoides Morris and Hill, 1952
				Hemeaschmidtella Schallreuter, 1971
	Leiocopina Schallreuter, 1973b	Aparchitoidea Jones (in Chapman), 1901	Aparchitidae Jones (in Chapman), 1901	Baltonotella; Sarv, 1959
	Eridostraca Adamczak, 1961		Eridoconchidae Henningsmoen, 1953	Cryptophyllus; Levinson, 1951
			Steusloffinidae Schallreuter, 1984	Medianella; Neckaja, 1966
				Longiscula; Neckaja, 1958
			Longisculidae; Neckaja, 1966	Aviacypris; Schallreuter, 1977
Podocopida Sars, 1866	Metacopina Sylvester-Bradley, 1961		Krausellidae Berdan, 1961	Krausella Ulrich, 1894
			Rectellidae Neckaja, 1966	Rectella Neckaja, 1958
		Bairdiocypridoidea Shaver, 1961	Bairdiocyprididae Shaver, 1981	Elliptocyprites; Swain, 1962
			Pachydomellidae Berdan and Sohn, 1961	Microcheilinella; Geis, 1933
		Thlipsuroidea; Ulrich, 1894	Thlipsuriidae Ulrich, 1894	Anticostus n. gen
	Cypridocopina; Jones, 1901	Bairdioidea; Sars, 1865	Macrocyprididae Muller, 1912	Macrocyproides; Spivey, 1939
	Cytherelliformes Skogsberg, 1920	Leperditelloidea Ulrich and Bassler, 1906	Leperditellidae Ulrich and Bassler, 1906	Leperditella; Ulrich, 1894
Platycopida Sars, 1866	Kloedenellocopina Scott, 1961	Kloedenelloidea Ulrich and Bassler, 1908	Kloedenellidae Ulrich and Bassler, 1908	Eokloedenella; Kraft, 1962

Table 3.

Taxonomic structure of late Ordovician ostracod [5].

7. Priority

This is a contentious aspect of zoological nomenclature, yet it is a principal ICZN rule that promotes stability. When two names for the same taxon are identified, the law of priority determines which one is valid. With few exceptions, the valid name is the oldest (as determined by published sources). The authority of a name in a family, genus, or species does not alter if its rank within the group rises or falls. According to Ref. [14] nomenclature of the Pentastomida with a list of species and used higher taxon, Pentastomida is a name that can be traced back to at least Huxley (1869). General taxonomical structure of the late Ordovician ostracod fauna of the Ellis Bay Formation, Anticosti Island, eastern Canada (see Table 1).

8. Classification of Crustacean Decapoda

Classification for the entire Crustacean Decapoda has been updated. There are 2725 genera and 17,635 species of decapods in the 233 families that make up the categorization (including both extant and fossil species Figure 4). The families in our taxonomy consist of 71 current species only, 109 fossil species, and 53 entirely fossil species. A total 14,756 species are now thought to be extant, while 2979 species are only known from fossils [11].

Figure 4.

Genera of Decapoda Crustaceans, both modern and extinct [10].