Atlas of Crustacean Larvae

46. Dendrobranchiata

general: The Dendrobranchiata contains the economically important penaeoid and sergestoid shrimps. Among other characters, members of this suborder are recognized by their caridoid facies (elongate shrimp-like shape), dendrobranchiate (highly branching) gills, typically chelate first three pairs of legs, a second abdominal somite with pleura that do not overlap those of the first somite, and eggs that are shed directly into the water and hatch at a naupliar stage (see PérezFarfante and Kensley 1997; Tavares et al. 2009; Tavares and Martin 2010). There are approximately 500 extant species, currently partitioned among 7 families in 2 superfamilies. Nearly all are marine, with species found from shallow tropical waters to depths of 1,000 m or more on the continental slopes. Almost half of the known species are members of the Penaeidae, which inhabit shallow and inshore tropical and subtropical waters; species in this group form the basis of massive seafood industries. The Aristeidae, Benthesicymidae, and Sergestidae are predominantly deep-water families and contain species that are either deep benthic dwellers or are members of the meso- and bathypelagic fauna; some species of Sergestidae, however, are found in fresh water. Most Solenoceridae occur in deeper offshore waters. Species of the Sicyoniidae inhabit coastal waters up to 200 m in depth. Species of the Luciferidae are all planktonic (Pérez-Farfante and Kensley 1997; Tavares and Martin 2010). The life cycle consists of a nauplius, a zoea (including protozoea and mysis stages), a decapodid, a juvenile , and an adult. All stages are free living. Larval development is regular anamorphic (Anger 2001), meaning that the appearance of characters and shape changes are gradual. larval types: Nearly all species shed their eggs directly into the water. Luciferids, which brood their eggs for a short time on the posterior thoracopods, are the exception. Nauplius: Dendrobranchiates are unique among decapods in having their eggs hatch as free-swimming nauplii; thus they are also the only decapods with three larval phases (a nauplius, a zoea, and a decapodid). Zoea (Protozoea, Mysis), Decapodid: Neither the transition from naupliar to zoeal stages, nor the transition from decapodid to early juvenile stages, is truly metamorphic. Nevertheless , larvae can be partitioned into a nauplius, a zoeal phase (subdivided into protozoea and mysis stages), and (usually) several decapodid stages (in this group, also called post-larvae). For most decapod groups, the term post-larva refers to any developmental stage beyond the decapodid, and especially to juveniles. In the Dendrobranchiata, however, the term post-larva has been used for the transitional phase between pelagic larvae and benthic juveniles, covering several decapodid stages. There are different substages within all of these stages; the number varies among and within the families . The Penaeidae usually have 5–6 naupliar, 6 zoeal (3 protozoea + 3 mysis), and several (1–9) decapodid stages before settlement (Dall et al. 1990). All described solenocerids have 5–6 nauplii and 5 zoeae (3 protozoeae + 2 mysis) (Calazans 2000). In the Benthesicymidae, the genus Gennadas exhibits 4 mysis stages (Rivera and Guzmán 2002). Although the pattern of appendage development in the 2 superfamilies is essentially identical, the gross morphology of the larvae in the two groups can be quite distinctive (Tavares and Martin 2010). Sergestoid larvae tend to be more spinous, to the extent that in the past, distinctive names have been applied to them, such as elaphocaris (for the protozoea) and acanthosoma (for the zoea or mysis stage). The bizarre “larval genera” Cerataspides and Cerataspis are widely thought to belong to the penaeiods; Cerataspis monstrosa recently was shown to be the larval stage of the aristeid shrimp Plesiopenaeus armatus (Bracken-Grissom et al. 2012), whereas Cerataspides has never been attributed with certainly to an adult genus (Heegaard 1966; S. Morgan et al. 1985; Bracken-Grissom et al. 2012). morphology Nauplius (fig. 46.1): Early nauplii are characterized by having three pairs of propulsive limbs (antennules, antennae, and mandibles) and a naupliar eye (not illustrated here; see 46 Joel W. Martin Maria M. Criales Antonina dos Santos Joel W. Martin, Maria M. Criales, and Antonina dos Santos Dendrobranchiata 236 Joel W. Martin, Maria M. Criales, and Antonina dos Santos chapter 2); these larvae are often called orthonauplii (D. Williamson 1982a). The antennules are always uniramous and lack a flagellum. The antennae are typically biramous. They may be unsegmented in early nauplii, but the peduncle always consists of two segments by the end of this stage. The endopod is always unsegmented, and the exopod is segmented throughout its length. The endopod and...